Tech Support

Need some questions answered? Below are some of the most common questions we receive. Click below to view the answers to each of these questions. If your question isn’t answered here, please feel free to contact us.

Questions

 

No Power From the Outlets On the Rear Panel of an Equi=Tech Rack or Shelf Mounted Unit (This is the #1 question that we have received over the years from people seeking technical assistance.) Question:  All of the outlets on the rear panel of my Equi=Tech system are dead.  I’ve tried everything I can think of and still nothing.  What is happening?  Do I need to send my unit in for repair?

Electrical and Architectural Specifications — A complete set of engineering specifications and drawings for use in designing and planning an engineered balanced power electrical installation.  System specifiers and engineers will find this MICROSOFT WORD document a very useful cut and paste resource tool when drawing up plans and specifications for a project where balanced power is specified.  (Download approximately 184K)

2002 National Electric Code Article 647 — The official text of Article 647 that authorizes and defines legally acceptable wiring methods for balanced power applications as of the year 2002.  This article replaces and supercedes Article 530 Part G in the 1999 National Electrical Code.  The text is written in a new NEC code format that includes references to the latest tables and sections in the 2002 Code.  The most significant difference between Article 647 and the 1999 Code version is the widening of the scope of application of balanced power to include ANY type of sensitive electronics.  Balanced power is no longer restricted to A/V equipment.  The article also includes a provision for electronic lighting fixtures such as fluorescent lights and other extreme noise-producing types of commercial lighting equipment.

1996/1999 National Electric Code Article 530 Part “G” — Official text of the 1996/1999 NEC Article that authorized and defined required wiring methods for balanced power applications.

World Power Standards — A comprehensive information table of power standards in foreign principalities that include voltage, frequency and common plug types used in every country.

Audio Wiring and Grounding — A technically in depth article that explains how to optimize equipment interconnections in audio and video facilities supplied with balanced technical power. Discussion of methods used by audio engineers and technicians to route signal between balanced and unbalanced inputs and outputs under varying conditions — suggestions for handling problems with noisy equipment.

How to Do an Audio System Noise Floor Test — This document provides a step by step method for determining relative noise levels in a production area and comparing before and after results when either changing or adding audio equipment or changing the AC system over to balanced power.

The “Dirty Chassis” Condition — When balanced power has been applied and all of the electronic gear is properly interconnected, sometimes there will still be objectionable noise in the grounding system. Very often, the noise is caused by one or more pieces of equipment with a dirty chassis condition. This document describes in detail how to locate the offending piece of equipment and suggests what may be done to correct the problem.

How to Double the Amount of Available Power in a Room — This step-by-step procedure provides a simple and cost effective method of dealing with the problem of not enough available power in a room. Instead of wiring in more circuits, the power available from an pre-existing wall outlet can safely be doubled. By increasing the outlet’s voltage from 120 Volts to 240 Volts, a larger Equi=Tech system with double the capacity (but still having a balanced 120-volt output) can be plugged in to the original outlet location. This document provides a step-by-step code-worthy procedure for changing the outlet’s voltage — doubling the amount of power available for equipment without running any new lines.

Installing a Technical Grounding System — One of the most frequently asked questions is: “How do I ground the studio?” This document outlines an electrically approved and safe method that works very well with all types of A/V equipment.

Technical Power Budget — One of the most often asked questions by the non-electrically minded is: “How much power do I need and where?” The answer depends on how big and how spread out is the facility. This technical support bulletin will help determine power requirements and assist in selecting the right system(s). This material can be applied to any facility, no matter how large or how small.

 

Answers

No Power From the Outlets On the Rear Panel of an Equi=Tech Rack or Shelf Mounted Unit (This is the #1 question that we have received over the years from people seeking technical assistance.) Question:  All of the outlets on the rear panel of my Equi=Tech system are dead.  I’ve tried everything I can think of and still nothing.  What is happening?  Do I need to send my unit in for repair?

Answer:

We hope not. In fact we are happy to inform you that you are the lucky person who has asked this very
question for the 10,000th time. Congratulations! It is you for whom this question is being asked and answered because
we are thoroughly worn out from handling all of the email and phone traffic that deals with the very same issue. The
odds that the solution shown below will not work for you are almost zero.

Note: Sometimes this problem occurs right out of the box when first received. This is usually due to some jostling and
bumping around during shipment. The same solution applies in that situation.

The solution to the problem rests with the GFCI device on the rear panel.

Here is what one of these looks like:

 

You have probably seen one of these in your bathroom or near your patio or deck outside.

There are two buttons, red and black as shown. One is a “test” button and one is a “reset” button.
Someimes there are no colors such as the red and black buttons shown above but there will still be 2
buttons that are used for test and reset purposes.

Here is the tip that you didn’t know about or you would probably not be looking for assistance.

When resetting a GFCI device, it must be done under power. That means the Equi=Tech unit is plugged
in and all of the switches and breakers on both the front and rear panels are in the “on” (up) position. If
this is not the case, the GFCI won’t reset. GFCI’s must be under power to reset.

Try it. There has never been a single instance where there was no power and “everything” imaginable was
attempted to fix the problem where this “tip” failed.

 

2002 National Electric Code Article 647 — The official text of Article 647 that authorizes and defines legally acceptable wiring methods for balanced power applications as of the year 2002.  This article replaces and supercedes Article 530 Part G in the 1999 National Electrical Code.  The text is written in a new NEC code format that includes references to the latest tables and sections in the 2002 Code.  The most significant difference between Article 647 and the 1999 Code version is the widening of the scope of application of balanced power to include ANY type of sensitive electronics.  Balanced power is no longer restricted to A/V equipment.  The article also includes a provision for electronic lighting fixtures such as fluorescent lights and other extreme noise-producing types of commercial lighting equipment.

Answer:
ARTICLE 647 — SENSITIVE ELECTRONIC EQUIPMENT

647.1 Scope. This article covers the installation and wiring of seperately derived systems operating at 120 volts line-to-line and 60 volts to ground for sensitive electronic equipment.

647.3 General. Use of a separately derived 120-volt single-phase 3-wire system with 60 volts on each of two ungrounded conductors to a grounded neutral conductor shall be permitted for the purpose of reducing objectionable noise in sensitive electronic equipment locations provided that the following conditions apply.
(1) The system is installed only in commercial or industrial occupancies.
(2) The system’s use is restricted to areas under close supervision by qualified personnel.
(3) All of the requirements in 647.4 through 647.8 are met.

647.4 Wiring Methods

(A) Panelboards and Overcurrent Protection. Use of standard single-phase panelboards and distribution equipment with a higher voltage rating shall be permitted. The system shall be clearly marked on the face of the panel or on the inside of the panel doors. Common-trip two-pole circuit breakers that are identified for operation at the system voltage shall be provided for both ungrounded conductors in all feeders and branch circuits.

(B) Junction Boxes. All junction box covers shall be clearly marked to indicate the distribution panel and the system voltage.

(C) Color Coding. All feeders and branch-circuit conductors installed under this section shall be identified as to system at all splices and terminations by color, marking, tagging or equally effective means. The means of identification shall be posted at each branch-circuit panelboard and at the disconnecting means for the building.

(D) Voltage Drop. The voltage drop on any branch circuit shall not exceed 1.5 percent. The combined voltage drop of feeder and branch-circuit conductors shall not exceed 2.5 percent.
(1) Fixed Equipment. The voltage drop on branch circuits supplying equipment connected using wiring methods in Chapter 3 shall not exceed 1.5 percent. The combined voltage drop of feeder and branch-circuit conductors shall not exceed 2.5 percent.
(2) Cord-Connected Equipment. The voltage drop on branch circuits supplying receptacle outlets shall not exceed 1 percent. For the purposes of making this calculation, the load connected to the receptacle outlet shall be considered to be 50 percent of the branch circuit rating. The combined voltage drop of feeder and branch-circuit conductors shall not exceed 2.0 percent.

(FPN): The purpose of this provision is to limit voltage drop to 1.5 percent where portable cords may be used as a means of connecting equipment.
647.5 3-phase Systems. Where 3-phase power is supplied, a separately derived 6-phase “Wye” system with 60 volts to ground installed under this article shall be configured as three separately derived 120-volt single-phase systems having a combined total of no more than six main disconnects.
647.6 Grounding.

(A) General. The system shall be grounded as provided in Section 250.30 as a separately derived single-phase 3-wire system.

(B) Grounding Conductors Required. Permanently wired utilization equipment and receptacles shall be grounded by means of an equipment grounding conductor run with the circuit conductors to an equipment grounding bus prominently marked “Technical Equipment Ground” in the originating branch-circuit panelboard. The grounding bus shall be connected to the grounded conductor on the line side of the separately derived system’s disconnecting means. The grounding conductor shall not be smaller than that specified in Table 250.122 and run with the feeder conductors. The technical equipment grounding bus need not be bonded to the panelboard enclosure. Other grounding methods authorized elsewhere in this Code shall be permitted where the impedance of the grounding return path does not exceed the impedance of equipment grounding conductors sized and installed in accordance with this article.

FPN No. 1: See Section 250.122 for equipment grounding conductor sizing requirements where circuit conductors are adjusted in size to compensate for voltage drop.

FPN No. 2: These requirements limit the impedance of the ground fault path where only 60 volts applies to a fault condition instead of the usual 120 volts..
647.7 Receptacles.

(A) General. Where receptacles are used as a means of connecting equipment, the following conditions shall be met:
(1) All 15- and 20-ampere receptacles shall be GFCI protected.
(2) All outlet strips, adapters, receptacle covers and faceplates shall be marked with the following words or equivalent:

WARNING – TECHNICAL POWER
Do not connect to lighting equipment.
For electronic equipment use only.
60/120 V. 1-phase AC
GFCI protected.

(3) A 125-volt, single-phase, 15- or 20-ampere-rated receptacle outlet having one of its current carrying poles connected to a grounded circuit conductor shall be located within 1.8 m (6 ft.) of all permanently installed 15- or 20-ampere-rated 60/120-volt technical power-system receptacles.
(4) All 125-volt receptacles used for 60/120-volt technical power shall have a unique configuration and be identified for use with this class of system. 125-Volt, single phase, 15- or 20-ampere-rated receptacle outlets and attachment plugs that are identified for use with grounded circuit conductors shall be permitted in machine rooms, control rooms, equipment rooms, equipment racks and other similar locations that are restricted to use by qualified personnel..
(B) Isolated ground receptacles. Isolated ground receptacles shall be permitted as described in Section 250.146(D), however, the branch circuit equipment grounding conductor shall be terminated as required in Section 647.6(B).

647.8 Lighting Equipment. Lighting equipment installed under this article for the purpose of reducing electrical noise originating from lighting equipment shall meet the following conditions (A) through (C).

(A) Disconnecting Means. All lighting equipment, luminaires and associated control equipment if provided shall have a disconnecting means that simultaneously opens all ungrounded conductors that shall be located within sight of the luminaire or be capable of being locked in the open position.

(B) Luminaires. All luminaires shall be permanently installed, listed and ballast operated.

(C) Screw-shell. Lighting fixtures installed under this section shall not have an exposed lamp screw-shell.

 

 
Question1996/1999 National Electric Code Article 530 Part “G” — Official text of the 1996/1999 NEC Article that authorized and defined required wiring methods for balanced power applications.

Answer:

Article 530 — MOTION PICTURE AND TELEVISION STUDIOS AND SIMILAR LOCATIONS

G. Separately Derived Systems with 60 Volts to Ground

530-70.General. Use of a separately derived 120-volt single-phase 3-wire system with 60 volts on each of two ungrounded conductors to a grounded neutral conductor shall be permitted for the purpose of reducing objectionable noise in audio/video production or other similar sensitive electronic equipment locations provided that its use is restricted to electronic equipment only and that all of the requirements in Sections 530-71 through 530-73 are met.530-71. Wiring Methods.

(a) Panelboards and Overcurrent Protection. Use of standard single-phase panelboards and distribution equipment with a higher voltage rating shall be permitted. The system shall be clearly marked on the face of the panel or on the inside of the panel doors. Common-trip two-pole circuit breakers that are identified for operation at the system voltage shall be provided for both ungrounded conductors in all feeders and branch circuits.

(b) Junction Boxes. All junction box covers shall be clearly marked to indicate the distribution panel and the system voltage.

(c) Color Coding. All feeders and branch-circuit conductors installed under this section shall be identified as to system at all splices and terminations by color, marking, tagging or equally effective means. The means of identification shall be posted at each branch-circuit panelboard and at the disconnecting means for the building.

(d) Voltage Drop. The voltage drop on any branch circuit shall not exceed 1.5 percent. The combined voltage drop of feeder and branch circuit conductors shall not exceed 2.5 percent.

530-72. Grounding.

(a) General. The system shall be grounded as provided in Section 250-26 as a separately derived single-phase 3-wire system.

(b) Grounding Conductors Required. Permanently wired utilization equipment and receptacles shall be grounded by means of an equipment grounding conductor run with the circuit conductors to an equipment grounding bus prominently marked “Technical Equipment Ground” in the originating branch-circuit panelboard. The grounding bus shall be connected to the grounded conductor on the line side of the separately derived system’s disconnecting means. The grounding conductor shall not be smaller than that specified in Table 250-95 and run with the feeder conductors. The technical equipment grounding bus need not be bonded to the panelboard enclosure.

Exception: Other grounding methods authorized elsewhere in this Code shall be permitted where the impedance of the grounding return path does not exceed the impedance of equipment grounding conductors sized and installed in accordance with Part G of this article.

(FPN No. 1): See Section 250-95 for equipment grounding conductor sizing requirements where circuit conductors are adjusted in size to compensate for voltage drop.

(FPN No. 2): These requirements limit the impedance of the ground fault path where only 60 volts applies to a fault condition instead of the usual 120 volts.

530-73. Receptacles.

(a) General. Where receptacles are used as a means of connecting equipment, the following conditions shall be met:

(1) All 15- and 20-amp receptacles shall be GFCI protected.

(2) All outlet strips, adapters, receptacle covers and faceplates shall be marked as follows:

WARNING – TECHNICAL POWER
Do not connect to lighting equipment.
For electronic equipment use only.
60/120 V. 1ø AC
GFCI protected

(3) A 125-volt, single-phase, 15- or 20-ampere-rated receptacle outlet having one of its current carrying poles connected to a grounded circuit conductor shall be located witnin 6 feet of all permanently installed 15- or 20-ampere rated 60/120-volt technical power-system receptacles.(4) All 125-volt receptacles used for 60/120-volt technical power shall have a unique configuration and be identified for use with this class of system.

Exception: 125-Volt, single phase, 15- or 20-ampere-rated receptacle outlets and attachment plugs that are identified for use with grounded circuit conductors shall be permitted in machine rooms, control rooms, equipment rooms, equipment racks and other similar locations that are restricted to use by qualified personnel.

(b) Isolated ground receptacles. Isolated ground receptacles shall be permitted as described in Section 250-74 Exception No. 4, however, the branch circuit equipment grounding conductor shall be terminated as required in Section 530-72(b).

 

World Power Standards
  COUNTRY  VOLTAGE  FREQ..(Hz)  PLUG.TYPE COMMENTS
Afghanistan 220V 50
Hz
D Charikar -60
Hz
Algeria 127/220V 50
Hz
C  F  
Angola 220V 50
Hz
C  
Antigua 230V 60
Hz
A
 
Argentina 220V 50
Hz
C   Neutral and
line reversed
Aruba 127V 60
Hz
A  B  F Lago Colony
-115V
Australia 240V 50
Hz
 I
Switched outlets
Austria 230V 50
Hz
F  
Azores 220V 50
Hz
B  C  F Ponta Delgada
-110V
Bahamas 120V 60
Hz
A  B  
Bahrain 230V 50
Hz
G Awali -110V
60 Hz
Balearic Islands 127/220V 50
Hz
C  E  
Bangladesh 220V 50
Hz
A  C  D  G  K  
Barbados 115V 50
Hz
A  B  F  
Belgium 230V 50
Hz
C  E  
Belize 110/220V 60
Hz
B  G  
Benin 220V 50
Hz
D  
Bermuda 120V 60
Hz
A  B  
Bolivia 220/230V 50
Hz
A  C La Paz, Viacha
-115V
Bosnia-Hertzegovenia 220V 50
Hz
C   F
J
 
Botswana 231V 50
Hz
D  G  
Brazil 110/220V 60
Hz
A  B
C
220V in some
areas
Virgin Islands (British) British Virgin Islands 120V 60
Hz
A  B  
Brunei 240V 50
Hz
G  
Bulgaria 220V 50
Hz
C  F  
Burkina Faso 220V 50
Hz
C  E  
Burma (Myanmar) 230V 50
Hz
C  D
F
 
Burundi 220V 50
Hz
C  E  
Cambodia 120V 50
Hz
A  C
G
 
Cameroon 220V 50
Hz
C  D
E  G
K
127V in some
areas
Canada 120V 60
Hz
A  B  
Canary Islands 127V 50
Hz
C  E  
Cape Verde 220V 50
Hz
C  F  
Cayman Islands 120V 60
Hz
A  B  
Central African
Republic
220V 50
Hz
C  E  
Chad 220V 50
Hz
D  E
F
 
Channel Islands 240V 50
Hz
C  G Guernsey -230V
Chile 220V 50
Hz
C  L
 
China 220V 50
Hz
 I
 
Colombia 110V 60
Hz
A  B Parts of Bogota
-150V
Comoros 220V 50
Hz
C  E  
Congo 220V 50
Hz
C  E  
Congo,
Democratic Republic
220V 50 Hz C  D
E
 
Cook Islands Cook
Islands
240V 50
Hz
 I   
Costa Rica 120V 60
Hz
A  B  
Côte d’Ivoire 220V 50
Hz
C  E  
Croatia 220V 50
Hz
C   F
J
 
Cyprus 240V 50
Hz
C  G  
Czech Republic 220V 50
Hz
E  
Denmark 220V 50
Hz
C  K  
Djibouti 220V 50
Hz
C  E  
Dominica 230V 50
Hz
D  G  
Dominican Republic 110V 60
Hz
A  
Ecuador 120-127V 60
Hz
A  B
C  D
120/240V in
rural areas
Egypt 220V 50
Hz
C  
El Salvador 115V 60
Hz
 A  B
C  D
E  F
G 
L  
 
England  230V  50
Hz
 G
 
Equatorial Guinea 220V 50
Hz
C  E Varies from
150V-175V
Estonia 220V 50
Hz
C  F  
Ethiopia 220V 50
Hz
C  D  J  L
 
Faeroe Islands 220V 50
Hz
C  K  
Falkland Islands 240V 50
Hz
G  
Fiji 240V 50
Hz
 I
 
Finland  230V 50
Hz
C  F  
France 230V 50
Hz
C  E
F
 
French Guiana 220V 50
Hz
C  D
E
 
Gabon 220V 50
Hz
C  
Gambia 220V 50
Hz
G  
Germany 230V 50
Hz
F  
Ghana 230V 50
Hz
D  G  
Gibraltar 240V 50
Hz
C  G  
Great Britain  230V  
50 Hz
 G
 
Greece 220V 50
Hz
C  D  E
F
 
Greenland 220V 50
Hz
C  K  
Grenada (Windward
Is.)
230V 50
Hz
G  
Guadeloupe 220V 50
Hz
C  D
E
 
Guam 110V 60
Hz
A  B  
Guatemala 120V 60
Hz
A  B
G
 
Guinea 220V 50
Hz
C  F
K
 
Guinea-Bissau 220V 50
Hz
C  
Guyana 110V 60
Hz
A  B
D  G
Georgetown -50
Hz
Haiti 110V 60
Hz
A  B
 
Honduras 110V 60
Hz
A  B  
Hong Kong 220V 50
Hz
D  G Converting to 230V
Hungary 220V 50
Hz
C  F  
Iceland 220V 50
Hz
C  F  
India 230V 50
Hz
C  D DC in some areas
Indonesia 127/220V 50 Hz C  E  F  
Iran 220 50
Hz
 C   F  

Iraq 220V 50
Hz
C  D
G
 
Ireland 230V 50
Hz
G  
Isle of Man 240V 50
Hz
C  G  
Israel 230V 50
Hz
C  H
M
 
Italy 127/220V 50
Hz
F  L
 
Ivory Coast   220V  50
Hz
 C  E  
Jamaica 110V 50
Hz
A  B  
Japan 100V 50/60
Hz
A  B E.Japan 50HzW Japan 60Hz
Jerusalem 220V 50
Hz
C  D
H  M
 
Jordan Jordan 220V 50
Hz
C  D  F
G  J
 
Kenya Kenya 240V 50
Hz
D  G  
Kazakhistan Khazakistan 220V 50
Hz
C  F  
Kiribati Kiribati 240V 50
Hz
 I   
North Korea Korea (North) 110/220V 50/60
Hz
A  C  F 110V 60 Hz   220V 50 Hz
South Korea Korea
(South)
110/220V 60
Hz
A  B
C  D
G 
K
 
Kosovo 220V 50
Hz
C   F
J
 
Kuwait Kuwait 240V 50
Hz
C  G  
Laos Laos 220V 50
Hz
A  B
C  E
F
 
Latvia Latvia 220V 50
Hz
C  F  
Lebanon Lebanon 110/220V 50
Hz
A  B  C
D  G
 
Lesotho 220V 50
Hz
M  
Liberia Liberia 120V 60
Hz
A  G  
Libya Libya 127V 50
Hz
D 230V Barce, Benghazi,
Derna,
Sebha, Tobruk
Lithuania Lithuania 220V 50
Hz
C  F  
Luxembourg Luxembourg 220V 50
Hz
C  F  
Macau Macau 200V 50
Hz
C  D  
Madagascar Madagascar 127/220V 50
Hz
C  D  E  J  K  
Madeira Madeira 220V 50
Hz
C  F  
Malawi Malawi 230V 50
Hz
G  
Malaysia Malaysia 240V 50
Hz
G Penang -230V
Maldives Maldives 230V 50
Hz
A  D
G  J
K  L
 
Mali Mali 220V 50
Hz
C  E  
Malta Malta 240V 50
Hz
G  
Martinique Martinique 220V 50
Hz
C  D
E
 
Mauritania Mauritania 220V 50
Hz
C  
Mauritius Mauritius 230V 50
Hz
C  G  
Mexico Mexico 127V 60
Hz
A  
Micronesia Micronesia 120V 60Hz A  B  
Monaco 127/220V 50
Hz
C  D
E  F
 
Montserrat Montserrat
(Leeward
Is.)
230V 60
Hz
A  B  
Morocco Morocco 127/220V 50
Hz
C  E  
Mozambique Mozambique 220V 50
Hz
C  F  
Myanmar (Burma) 230V 50
Hz
C  D
F
 
Namibia Namibia 220V 50
Hz
D Keetmanshoop
-230V
Nauru Nauru 240V 50
Hz
 I   
Nepal Nepal 220V 50
Hz
C  D  
Netherlands Netherlands 230V 50
Hz
C  F  
Netherlands Antilles Netherlands
Antilles
127/220V 50
Hz
A  B
F
St. Martin -120V
60 Hz
New Caledonia New Caledonia 220V 50
Hz
F  
New Zealand New Zealand 240V 50
Hz
 I   
Nicaragua Nicaragua 120V 60
Hz
A  
Niger Niger 220V 50
Hz
A  B
C  D
E  F
 
Nigeria Nigeria 230V 50
Hz
D  G  
Northern Ireland Northern Ireland  230V  50
Hz
 G
 
Norway Norway 230V 50
Hz
C  F  
Okinawa Okinawa 100V 60
Hz
A  B   I
Military facilities
-120V
Oman Oman 240V 50
Hz
C  G Many voltage
variations
Pakistan Pakistan 220V 50
Hz
C  D  
Panama Panama 110V 60
Hz
A  B   I
Panama City
-120V
Papua New Guinea Papua New Guinea 240V 50
Hz
 I   
Paraguay Paraguay 220V 50
Hz
C  
Peru Peru 220V 60
Hz
A  C Talara-110/220V
Arequipa
50Hz
Philippines 110/220V 60
Hz
A  B  C  E  F   Manila -115/230V
Poland Poland 220V 50
Hz
C  E  
Portugal Portugal 220V 50
Hz
C  F  
Puerto Rico Puerto Rico 120V 60
Hz
A  B  
Qatar Qatar 240V 50
Hz
D  G  
Reunion Is. Reunion Is. 230V 50
Hz
C  E
F
 
Romania Romania 220V 50
Hz
C  F  
Russia Russia 220V 50
Hz
C  F  
Rwanda Rwanda 220V 50
Hz
C   J
 
Samoa (US) Samoa
(U.S.)
120V 60
Hz
A  B
F   I
 
Western Samoa Samoa
(Western)
230V 50
Hz
A  B
F   I 
 
San Marino San
Marino
230V 50
Hz
C
F
L
 
Sao Tome Sao
Tome & Principe
220V 50
Hz
C   F  
Saudi Arabia Saudi Arabia 127V 60
Hz
A  B
G
 
Scotland 230V  50
Hz
 G
 
Senegal Senegal 127V 60
Hz
C  D
E  K
 
Serbia Serbia 220V 50
Hz
C   F
J
 
Seychelles Seychelles 240V 50
Hz
C  D  E  K  
Sierra Leone Sierra Leone 230V 50
Hz
D  G  
Singapore Singapore 230V 50
Hz
D  G  
Slovakia 220V 50
Hz
E  
Slovenia 220V 50
Hz
E  
Solomon Islands Soloman
Islands
220V 50
Hz
 I   G  
Somalia 220V 50
Hz
C Berbera-230V
Merca-110/220V
South Africa 220/230V 50
Hz
C  D  M  N
250V -Grahamstad, Port Elizabeth,
King Williams
South Sudan 240V 50
Hz
C
D
 
Spain 127/220V 50
Hz
C  E  
Sri Lanka Sri Lanka 230V 50
Hz
D  
Saint Kitts & Nevis St.
Kitts & Nevis

(Leeward Is.)
230V 60
Hz
D  G  
Saint Lucia St.
Lucia
(Windward
Is.)
240V 50
Hz
G  
Saint Vincent St.
Vincent

(Windward Is.)
230V 50
Hz
A  C
E  G  I   K
 
Sudan Sudan 240V 50
Hz
C  D  
Suriname Surinam 127V 60
Hz
C  F  
Swaziland Swaziland 230V 50
Hz
M  
Sweden Sweden 230V 50
Hz
C  F  
Switzerland Switzerland 220V 50
Hz
C  E  J
 
Syria Syria 220V 50
Hz
C  E  L
 
Tahiti Tahiti (French
Polynesia)
127V 60
Hz
A  
Taiwan Taiwan 120V 60
Hz
A  B  

Tajikistan Tajikistan 220V 50
Hz
C  F  I
 
Tanzania Tanzania 230V 50
Hz
D  G  
Thailand Thailand 220V 50
Hz
C  
Tibet Tibet 220V 50
Hz
 I   
Timor-Leste 220V 50 Hz C  E  F   
Togo Togo 220V 50
Hz
C Lome -127V
Tonga Tonga 240V 50
Hz
 I   
Trinadad Trinidad &
Tobago
115V 60
Hz
B  
Tunisia Tunisia 127/220V 50
Hz
C  E
F  K
L
 
Tuvalu Tuvalu 220V 50
Hz
 I   
Turkey 220V 50
Hz
C  F  
Uganda Uganda 240V 50
Hz
G Many voltage
variations
United Arab
Emirates
220V 50
Hz
D  G Ajman, Sharjah
-230V
United Kingdom United Kingdom 230V 50
Hz
G Switched outlets 
USA United States 120V 60
Hz
A  B  
Uruguay Uruguay 220V 50
Hz
C  F   I   L
 
Uzbekistan Uzbekistan 220V 50
Hz
C    
Vanuatu Vanuatu 220V 50Hz C  G   I   
Venezuela 120V 60
Hz
A  B Maracay,Valencia
-50 Hz
Vietnam 127/220V 50
Hz
A  C Converting to
220V
Virgin Islands (British) Virgin
Islands (British)
110V 60
Hz
A
B
 
Virgin Islands [US] Virgin
Islands
(US)
120V 60
Hz
A  B  
Wales Wales
 230V
 50
Hz
 G
 
Yemen
220/230V 50
Hz
A  D
G
 
Yugoslavia 220V 50
Hz
C  F  J
 
Zaire 220V 50
Hz
C  D  
Zambia 220V 50
Hz
C  D
G
 
Zimbabwe 220V 50
Hz
D  G  

 

 

 

Audio Wiring and Grounding — A technically in depth article that explains how to optimize equipment interconnections in audio and video facilities supplied with balanced technical power. Discussion of methods used by audio engineers and technicians to route signal between balanced and unbalanced inputs and outputs under varying conditions — suggestions for handling problems with noisy equipment.

Answer:

Two basic techniques of audio wiring and grounding will be discussed — standard methods used in
facilities with conventional AC power and new methods used in facilities with balanced AC power.  There are some grounding techniques that apply to both types of AC systems but there are a few important differences.

Most every system utilizing standard wiring and grounding methods will exhibit significant improvement in the system’s background noise level when balanced power is applied.  Usually, noise can be attenuated still further when some additional grounding methods are used.  Under a globally applied balanced power grid, these grounding methods may be used which were otherwise impossible under normal circumstances without increasing background noise.  This is due primarily to a unity potential (zero-crossing AC ground reference) that is equally present in every equipment chassis in the studio.  Removing most AC ground-lift adapters and reconnecting the majority of shields that were previously telescoped or lifted at one end are some of the grounding techniques possible in a balanced power based a/v system.

A general rule which applies to audio wiring with balanced power is: ground everything, lift nothing and connect all shields (at both ends.) There are a few exceptions which will be described later in detail.  If audio interconnections are unbalanced, balance them.  If audio is already balanced keep it balanced.

Audio Ground References

Standard Methods:

All audio interconnections utilize a ground reference.  In unbalanced audio interconnections, there is a direct signal mode between one signal conductor and the audio ground.  In a balanced audio circuit, there is a common mode signal between two conductors that are inversely phased to audio ground.  In both cases the audio ground is part of an audio signal reference that is commonly connected the equipment chassis, which itself is normally referenced to earth ground.

When connecting the audio ground between two pieces of audio equipment, a grounding path is created.  If there is an increased potential in any chassis, reactive current (noise) will be introduced into the signal reference of which the audio ground is also a part.  This is often called a “ground loop” — but this is a misnomer.  A “ground loop” is not really a loop but an indication of current flow into signal circuits resulting from objectionable voltage potentials traversing the grounding reference.  Many techniques have been developed over the years in an attempt to deal with this problem.  Some of these methods include using short audio cables, audio isolation transformers, single-point grounding, linear signal reference grids, star grounding, lifting audio grounds from chassis and lifting or telescoping shields.  Another common practice involves the use of AC ground-lift adapters on gear with 3-prong AC power cords — indeed a very dangerous technique.  If any component were to short to chassis ground, touching that chassis could place one’s body in the grounding path, a typical scenario for electrocution.  (Especially if one were to be holding something that is grounded like for example a balanced mike.)

New Methods Used with Balanced Power:

The “ground loop” phenomenon has not been clearly defined until the advent of balanced AC power.  The technology provides a new reference point and a new understanding of grounding.

When chassis and audio grounds are connected to the center tap of a balanced AC isolation transformer, they are referenced to the mean AC voltage differential which is equivalent to the zero crossing point of the AC sine wave.  There is no current or voltage on the center tap — here is a clean single-point ground reference for audio.  Virtually all chassis, audio grounds and shields can be referenced back to this single point.  The center tap of the transformer is then grounded to earth for safety and to shunt any electromagnetic and radio frequency interference away from shields and chassis.

In almost every case, AC ground lift adapters can be removed from gear with 3-prong AC power cords and the chassis of gear with a 2-prong AC power cords can now be grounded without introducing hum and noise into system as may be the case with unbalanced AC power.  Most shields that were telescoped or lifted at one end can now be connected and grounded at both ends because there is no longer any difference in potential between the audio chassis.  The audio grounds can be connected to a single point at the AC system.  Generally as more gear is grounded and shields are reconnected, the system gets quieter.

Occasionally there will be a piece of equipment that has a “dirty” or noisy chassis because of a substandard power supply, internal grounding problems or for other reasons.  In many cases this equipment is semi-professional unbalanced audio gear with a two-prong AC power cord.  The best way to deal with this equipment is to leave the two prong cord on it, isolate that chassis from any rack rails or other chassis, balance the audio with a direct box or audio isolation transformer and connect it to the console or other device’s balanced connections.  Then lift the audio ground/shield of the balanced line at the inputs so you do not contaminate your “clean” audio ground with this “dirty” chassis ground.

Unbalanced Audio Connections

Standard methods:

In a standard unbalanced interconnection there is a one signal conductor and a shield.  The shield is commonly an integral part of the signal reference.  (Fig.1) One thing that has been done to alter this standard unbalanced wiring configuration is to use balanced audio cable with two conductors and a shield.  (Fig.2) Use the one conductor for the signal and the other for the ground.  The shield is sometimes lifted at one end of the cable, usually at the input.  Often upgrading from unbalanced cables to balanced cables with a good quality shield will yield positive results.

Another approach has been to insert various types of filters into the cable, including putting capacitors in place of a part of the ground wire, in an attempt to remove unwanted hum and noise from the system.  This has worked to varying degrees, depending on the nature of the application.  However, filters in the audio chain can alter or colorize the signal and capacitors in the ground path are dangerous and could result in a shock hazard.

New methods used with balanced power:

In most cases when using balanced power, unbalanced audio can be interconnected in a standard way.  Using balanced cable with a good quality shield is still a sound practice, just connect the shield at both ends.  The only exception is when there is a “dirty” chassis (see section above.)

Balancing unbalanced audio at the source with a direct box or audio isolation transformer and running it balanced will lower the overall system noise floor.  An example would be using a direct box at the output of a keyboard to balance the signal and sending it into a balanced preamp at the console.  Balanced audio is highly compatible with balanced power — perhaps more than unbalanced audio.  General rule: if it’s unbalanced, balance it if possible and keep it that way.  Remember balanced power and balanced audio both reject common mode noise better than their unbalanced versions.

Balanced Audio Connections

Standard methods:

In a standard balanced interconnection there are two signal conductors and a shield.  (Fig. 3) The shield is normally referenced to ground at one or both ends.  Many times the shield is lifted at one end, usually at the input to eliminate “ground loops” or noise.  (Fig. 4) The problem with this approach is that while it may reduce hum, the shields act as radio antennas and pickup radio frequency interference from the environment.  This can be a serious problem in an environment that has computers, MIDI gear and other digital systems.

Top engineers, as of late 1996, still have not agreed on which end of the shield to connect on balanced interconnections.  Though most will tell you if it must be lifted, do it at the input, that way the shield (which now has an impedance across it like a radio antenna) is connected to the audio ground of the output device where EMI/RFI is less likely to be picked up by the input.

The degree to which a cable is balanced from each conductor to ground, as well as it’s overall impedance and capacitance, seem to be critical factors in a cable’s overall performance.  Some manufacturers have even built balanced cables with filters in them to filter out unwanted noise and to deal with the cable as a component in the audio system.

New methods used with balanced power:

In virtually every case, with balanced power, balanced audio can be interconnected in a standard way with the shield hooked up at both ends.  The only exception is when a piece of gear has a “dirty” chassis which requires isolation away from the rest of the grounding system.  This can usually be accomplished by lifting the audio ground at the input and isolating the offending chassis from other chassis with insulators.  A “dirty” chassis condition is rare in professional audio equipment and it often is the result of a substandard power supply or the audio ground not being connected to the chassis.  These problems can often be fixed with some effort. In general, wiring and grounding techniques are far simpler with balanced power and it is easier to identify and deal with any offending piece of equipment.

 

How to do an audio system noise floor test:

Answer:

Be certain that all test equipment with a three-prong AC power cord is plugged in to a properly grounded AC outlet, check the outlet with an outlet tester or an AC voltmeter to be sure. If possible, use dedicated circuits with isolated grounds to power all equipment involved in the test. This will insure that you have a true earth ground as a reference for your measurements. Unplug all equipment in the facility that is not being tested to avoid possible sources of stray interference.

Turn on all equipment involved in the test and let it warm up for at least 30 minutes.

Create a signal path and a gain structure that represents a typical working situation as if one were doing a session.

In a multi-track facility, send audio from the console or pre-amps to the tape machine or digital workstation at unity gain and return it to the console. Assign the multi-track outputs to the stereo buss and send the console’s stereo output at unity gain to the DAT machine or other two track. You can also assign effects to the stereo buss. Monitor the DAT’s or other two track’s output through the console and studio monitor system. Listen to the stereo output with studio monitors and headphones. Connect audio test instruments to the output of the DAT or other two track.

If a tone generator is available it can be used to establish a unity gain structure throughout the system. Set it at 1 khz and +4 db or -10 db, depending on your system reference level and run a tone through the entire system. Then, set all inputs and outputs at unity gain — all the way through and out to the test equipment. Proper gain structure is an essential part of accurate noise floor testing.

Measurements can now be made without signal present — but with all audio paths at unity gain. Record some blank audio then play it back checking the noise level on both the multi-tracks and the two tracks. Also, A/B testing can be done this way. Various different types of wiring, grounding and AC power sources can be evaluated accurately.

Listen critically to the system, increase the gain on the DAT’s or the two track’s input to raise the level of background noise until it is both audible and visible on the meters. In a typical project studio with 24 to 32 tracks of MDM and an inexpensive console the noise floor is visible at about -40 db on the meters of the DAT machine when the input of the DAT is turned all the way up. The noise floor will be audible long before that. With the DAT or two track gain up, A/B test various wiring, grounding and AC power systems by listening as well as measuring.

When A/B testing balanced AC power with unbalanced AC power the use of an isolated ground outlet to power the system under test is highly recommended, be certain that all equipment with a three-wire AC cord is properly grounded and most importantly, make sure that all interconnected equipment involved in the test, including the test instruments are running on balanced power.

 

The “Dirty Chassis” Condition — When balanced power has been applied and all of the electronic gear is properly interconnected, sometimes there will still be objectionable noise in the grounding system. Very often, the noise is caused by one or more pieces of equipment with a dirty chassis condition. This document describes in detail how to locate the offending piece of equipment and suggests what may be done to correct the problem.

Answer:

A “dirty chassis” condition occurs when a piece of equipment has voltage or ground noise present on its chassis and/or its signal ground reference even after balanced power has been applied. This technical bulletin outlines the various types of dirty chassis conditions and the techniques used to solve these problems.
Locating a dirty chassis
To locate a specific piece of equipment that has a dirty chassis leave all audio/video connections intact then plug in and turn on all of the equipment one piece at a time. When objectionable noise becomes audible, visible or measurable, the last unit turned on has a dirty chassis condition.

4 Types of “Dirty Chassis” Conditions:
1. Noise is present with signal ground and chassis ground not connected

When the signal ground (pin 1 in a balanced audio system or the sleeve in an unbalanced audio or video connection) is not connected to the chassis ground, it is probably because the manufacturer has determined that the chassis power supply has made the chassis too dirty to reference to the signal ground. Often, manufacturers or technicians lift pin 1 from the chassis in this manner to avoid noise which is often the case when unbalanced power is used. It is easy to check for this condition with an ohm meter — simply test for continuity from the signal ground to chassis. For balanced power applications there should be continuity. If there is no continuity, try jumping from the signal ground to chassis. The device should get quieter. If it doesn’t, another type of dirty chassis condition may be present that requires a different solution.

2. Noise is present when chassis ground is not referenced to AC ground

When an equipment chassis is not referenced to the AC ground, it is often because the unit has an ungrounded 2-prong AC cord. In order to avoid grounding noise, some manufacturers avoid referencing the chassis to the AC ground altogether. The solution is to connect the equipment chassis to the AC ground with a #12 ga. or #14 ga. copper wire. Often the simplest way to ground a chassis is to strip the paint off of the inside of the rack ears and off one side of the rack rails with a grinding stone and a drill. Then, sandwich a ring terminal between the stripped rack ear and rack rail and run a copper wire from the ring terminal to the AC ground.

Occasionally, some equipment does not have continuity between the chassis and the AC ground even if it has a grounded 3-prong AC cord. It is easy to check this with an ohm meter. Simply test for continuity between the chassis and the ground prong on the AC plug. For balanced power applications there should be continuity. If there is no continuity, run a jumper wire from the chassis to the AC ground and the device should become quieter. If it does not become quieter, this is an indication that a different approach to the noise problem is needed.

3. Noise is present with audio ground, chassis and AC ground connected

When a device has continuity from signal ground to chassis ground and AC ground but there is still voltage or noise present, there are simple procedures to follow that should correct the noise problem. If the unit has unbalanced audio signal connections the best approach is to balance and isolate the unbalanced audio with an audio isolation transformer or direct box and route balanced signal to a balanced audio input connection. An alternative approach when using unbalanced audio or video is to use an unbalanced to unbalanced isolation transformer. Both of these techniques serve to isolate the ground of a unit with a dirty chassis from the ground of the rest of the system thereby eliminating ground noise contamination.

Often, CATV lines exhibit a dirty chassis condition, the dirty chassis in this case being the CATV company’s equipment. Similar to the above situation with noisy a/v equipment, this problem readily resolves with an RF isolation transformer. One can be built by soldering two balun transformers back to back and connecting the coax cables at the unbalanced ends.

4. Noise is present with audio ground, chassis and AC ground connected and an audio isolation transformer is being used for interconnecting to the system.

When a piece of equipment has so much voltage or noise on the chassis and/or signal ground, it needs to be insulated from the rack rail with plastic insulators. In some rare cases, an AC ground lift adapter is also required to cure the condition.

There are also a few units that radiate so much EMI/RFI that other equipment will pickup noise from the stray field generated by the device with the dirty chassis, particularly if there is an unshielded patch bay or other unshielded gear nearby. These units need to removed from the rack completely or the sensitive gear that is picking up the noise needs to be moved away from the source of EMI/RFI. Fortunately, these seriously affected chassis are quite rare. Often replacement is the most logical course of action to take.

 

 

How to Double the Amount of Available Power in a Room — This step-by-step procedure provides a simple and cost effective method of dealing with the problem of not enough available power in a room. Instead of wiring in more circuits, the power available from an pre-existing wall outlet can safely be doubled. By increasing the outlet’s voltage from 120 Volts to 240 Volts, a larger Equi=Tech system with double the capacity (but still having a balanced 120-volt output) can be plugged in to the original outlet location. This document provides a step-by-step code-worthy procedure for changing the outlet’s voltage — doubling the amount of power available for equipment without running any new lines.

Answer:

Often the question is asked: “How can I get more power into my room?” This bulletin offers a simple, safe and highly cost effective solution that is ideal in many situations and it is not necessary to change or to add more circuit wires to get more power. — “How to upgrade a 120-volt outlet to 240-volts.”
Note: This procedure is not to be used with “Edison” type circuits (typically where a red and black pair of circuit wires feeding outlets share a single white neutral.) Check inside the circuit breaker panel to verify the circuit type. Check to see that only a black (or other colored wire) and white wire are present that feed the outlet to be changed. A green or bare wire should also be present for proper grounding. Presence of another colored wire (often red) run with a black and a white generally indicates and Edison circuit. However, if there is one white wire for each line conductor in the run between the breaker panel and the plug, this is not an Edison circuit and it is OK to use the following procedure.

1.) Under ideal conditions, one would select an existing dedicated outlet that is fed from a single circuit breaker. There should be three wires feeding this outlet: a black, white and green wire (sometimes the green wire is bare copper). The color of the hot wire is not important as long as there is a “hot” (120 Volts), a neutral (zero Volts) and a ground wire present. If the selected outlet is dedicated (one outlet on the circuit-breaker) skip to step 3.

2.) If there is a chain of outlets on a circuit, select an outlet that is conveniently located, remove it and the rest of the receptacles on the same circuit in the following manner:

Turn off the power.
Remove all of the outlets on the circuit and disconnect all of the wires. Check the stripped wire ends for damage or the possibility of wire stress and restrip the wire ends if necessary.
Put red tape around all of the white (neutral) wires for safety. Red tape indicates that 240-volts may be present and white is not to be regarded as a neutral to anyone who later might open the outlet box.
Using wire-nuts, reconnect by color all of the wires removed from the receptacles– white to white, black to black, etc. If there are no wires to connect with wire nuts at a particular location, cap off the wires anyway.
Cover all of the non-essential outlet boxes with an appropriate blank plate, leaving the selected outlet unfinished for now.

3.) At the selected outlet location, using the black white wires for power, install a 20-amp 250-volt receptacle (NEMA 6-20R). First inspect the wires first for physical damage or stress and restrip if necessary. Be sure to properly ground the receptacle.

4.) Locate the appropriate circuit wires in the breaker-panel and disconnect both the hot wire from the circuit-breaker and the white wire from the neutral buss. Put red tape on the neutral wire.

5.) Install a 2-pole circuit breaker in the panel with the ampacity rating that is appropriate for the circuit wires (15-amp for #14 gauge, 20-amp for #12 gauge.)

6.) Attach the black and white circuit wires to the 2-pole breaker, one wire per pole. Restore power to the circuit.

7.) Replace the breaker panel’s cover.

This completes the upgrade installation of a 240-volt 15- or 20-amp receptacle outlet with enough power capacity to run an ET3R or ET4R Equi=Tech rack system (capacity of 30- or 40-amps @ 120 Volts.)

 

Installing a Technical Grounding System — One of the most frequently asked questions is: “How do I ground the studio?” This document outlines an electrically approved and safe method that works very well with all types of A/V equipment.

Answer:

1.) Drive two copper-clad 8-foot x 5/8” (or larger) ground rods, a minimum distance of 6 feet apart into the Earth. As an option, a ring ground, plate ground or other low impedance grounding electrode such as a chemical ground may be used. Consult with a qualified electrical installer if you choose one of the alternatives. Using an alternate grounding electrode for a technical ground is usually unnecessary with balanced power unless there is poor soil conductivity or very high RF levels in your area.

2.) Run a #6ga. copper wire between the two ground rods passing through a UL listed brass acorn clamp on one of the rods and terminating the run at the main grounding electrode of the building’s AC system. It is essential to bond together all of the grounding electrodes in a building for safety. NEVER use a separate grounding electrode system for the technical ground that is not bonded to the building ground. With balanced power under normal conditions, bonding the ground rods to the building’s main grounding electrode in this manner will not have an adverse effect on noise levels in the studio.

3.) From the technical ground buss in the studio power panel, run a #6ga. copper wire to one of the copper-clad ground rods and connect it to the ground rod with a UL listed brass acorn clamp. Using a brass clamp will provide resistance to corrosion in damp environments and insure longevity of the termination. Brass acorn clamps may be buried in the soil however it is recommended that they remain visible and above ground for occasional inspection. If another type of grounding electrode is used, such as a chemical grounding electrode, a ground ring or euffer ground, a larger grounding conductor may well serve to lower the grounding impedance. This is especially true where there is a long distance to the grounding electrode from the studio ground buss. Larger grounding conductors will also have a wider bandwidth of RF noise attenuation because of their larger surface area of copper. This phenomenon is called skin effect. However, it is best to use some judgment when deciding if a wider bandwidth of RF noise attenuation is needed in your area. Often the problem of high-frequency RF is very localized and the cost of a large copper ground wire will yeild only marginal returns. But one area where a large conductor would yeild benefit would be high up in an office building in a large city where RF transmissions are thick like mud. So consider your locale when making this decision. Just for your information, the most sophisticated grounding electrodes short of chemical systems are often used at radio transmission tower sites. The most popular method is the ground ring which consists of a 4/0 or larger bare copper wire burried in a circle around the building about 2ft. – 3ft. deep. All “joints” and connections to the tower and electrical system are cadwelded. Often, the grounding conductors used inside of the ring are 6 inch wide copper ribbons, or at least very large copper conductors.

4.) When using an Equi=Tech isolation transformer (in a permanent, hard-wired balanced power system,) the isolated ground buss in the primary tech power panel must also connect to the center tap terminal on the output of the isolation transformer. This wire must occupy the same raceway as the main power feeder wires that feed from the isolation transformer to the tech power panel. Minimum sizing requirements for this conductor are contained in Table 250-95 in the National Electrical Code.

5.) The (isolated) technical ground buss in the studio technical power panel is where all technical branch circuit ground wires are to be terminated. The technical ground buss is the “single-point” ground source of the studio. From the isolated ground buss in the panel, sharing the same conduit (or cable) with the branch circuit conductors, run an insulated ground wire and connect it to the grounding screw on each receptacle that is fed by that circuit. In a balanced power system, multiple receptacles on the same circuit may share a single ground wire in daisy-chain fashion without inducing noise. Radial or star grounding has little impact where there is no noise in the ground however there is nothing wrong with employing radial or “star” grounding.

6.) If metal conduit or metal clad (MC) cable and metal outlet boxes are used in construction, isolated ground (IG) receptacles must be used. Be sure that the ground wire in the conduit or cable is insulated. If you are using a section of flexible conduit or MC cable longer than 6 feet, a FOURTH wire called an electrical equipment ground (dirty ground) may be required in EACH CABLE to ground the metal outlet boxes. Be very aware of this ELECTRICAL CODE REQUIREMENT if you want true isolated grounding. The additional electrical equipment ground wire may be a bare conductor. Another common term for this conductor is “bonding wire”. The function and purpose of this “bonding wire” is to make sure that the entire metal conduit system and all metal outlet boxes, J-boxes and panelboards are grounded. Often this requirement is forgotton or neglected and this can spell trouble later. Isolated ground wires should not be used to ground metal outlet boxes especially where flex, metal conduit, metal clad cable or steel wall studs are used in construction. So remember the bonding conductor requirement. The additional bonding wire is only necessary if the conduit system is OTHER than rigid aluminum or steel conduit, intermediate metal conduit (IMC), or electrical metal tubing (EMT). If romex is used in construction, the bare wire in the romex cable may serve as the isolated ground. Isolated ground receptacles are unnecessary when using romex and plastic boxes.

Studio equipment with a 3-prong plug is grounded via its AC cord. Equipment with a two prong cord may be grounded with a supplemental ground wire. This is accomplished by connecting the bare metal of the equipment chassis to the technical ground (isolated ground) with a #12ga. or #14ga. green copper wire. A simple means of accessing the technical ground electrically is to use a male cord plug having only a ground wire connected to it and plugged into an isolated ground receptacle. When using an Equi=Tech rack system, use the grounding terminal on the back of the unit as a supplemental means of grounding studio equipment chassis or racks.

NEVER use an AC ground lift adapter on equipment that has a grounded 3-prong AC cord. This is a very dangerous practice. When using unbalanced power, chassis and/or signal grounds are often lifted from the AC ground to reduce noise. When balanced power is used, all chassis and audio/video signal grounds can be referenced to the AC ground without adding interference. The only exception to this is the rare occasion when a piece of equipment has a “dirty chassis” condition.

 

 

Technical Power Budget — One of the most often asked questions by the non-electrically minded is: “How much power do I need and where?” The answer depends on how big and how spread out is the facility. This technical support bulletin will help determine power requirements and assist in selecting the right system(s). This material can be applied to any facility, no matter how large or how small.

Answer:

What is a technical power budget?
A technical power budget is an electrical power distribution plan that is tailored to meet the power needs of a facility where technical power is to be supplied. There are two basic questions to answer in order to create an effective and realistic technical power budget.

First, how much power is required to handle the anticipated power needs of the facility? Second, how many separate ac systems are required to provide power where needed?

The second question is easy. Decide first if it is practical or desired to hard wire the AC power in the room(s) where technical power is needed. If yes, the answer is probably one. If the facility is huge or spread out making it difficult to route power to all areas from a single location, more than one system may be the most practical approach.

If it is determined that more than one system is needed, calculate each area (referred to herein as “task area”) for a separate system. The systems may consist of any combination of rack or wall cabinet models or if the facility is exceptionally large, an engineered AC distribution system with a large isolation transformer is likely the proper course to consider.

To determine the amount of power required for a task area (or entire facility), fill out all of the attached lists and add up all of the equipment for each voltage used (typically 120 volts and sometimes 230 volts — i.e. European locations). Once the net load (in amps) is determined, multiply that number by the appropriate voltage to get volt-amperes (VA). Electrical systems are rated in size by KVA. All Equi=Tech system model numbers and isolation transformers correspond to power output capacity in KVA.

A separate system is required for each voltage. Often this a single 120 Volt system.

An additional system is required for each UPS because UPS outputs are unbalanced. The only exception to this rule is where a single large UPS is used to cover an entire facility. In this instance, one equally large balanced power system is connected to the UPS output. This is the simplest way to cover all bases.

In new construction, a wall-cabinet style Symmetrical Power System is the most economical in many cases because it is simple to install and it completely blankets a studio or production facility. But, there are other options that may better suit the specific needs of the studio. Pre-existing facilities may be difficult to rewire making it hard to install a centralized wall-cabinet system.

Rack-mount systems can be used anywhere and are an easy way to retrofit an existing facility with balanced ac. The physical placement of the equipment in a room or in a group of rooms is a major factor in determining how many rack-mount ac systems to use and where. For example, 3 side-by-side equipment racks in a machine room could be powered by one rack system with enough capacity to run all three racks. A 24-track tape machine with rack-mount Dolby™ units could be considered a “roll-around task area” by itself. The same could be said about a roll-around effects rack. The amount of power needed in a task area determines the size of the system for that area. Once one has determined how many task areas exist and how many systems are needed, proceed to calculate the required power for each area’s system.

Use the attached work sheets to determine the overall power requirements and the distribution breakdown per task area of the power needed for your facility. These worksheets will aid you in determining your power budget and which Equi=Tech system(s) will best suit your needs.