voltage to ground
- Thread starter jonaslc
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Re: voltage to ground
If you are dealing with the ?02 code there is a new section 647 covering sensitive electronic equipment. It used to be covered in part G of article 530 in the ?99 & ?96 codes. It was new to the ?96. It deals with 60/120 V systems which have a L-L voltage of 120V and a L-G voltage of 60V. This is probably what the question is referring to.
If you are dealing with the ?02 code there is a new section 647 covering sensitive electronic equipment. It used to be covered in part G of article 530 in the ?99 & ?96 codes. It was new to the ?96. It deals with 60/120 V systems which have a L-L voltage of 120V and a L-G voltage of 60V. This is probably what the question is referring to.
mikeames
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Re: voltage to ground
I think this is the Art in reference.
ARTICLE 647 Sensitive Electronic Equipment
647.1 Scope.
This article covers the installation and wiring of separately derived systems operating at 120 volts line-to-line and 60 volts to ground for senstitive electronic equipment.
The use of this type of supply system as a means to reduce objectionable noise and its adverse effect on the performance of electronic audio and video equipment has been recognized since the 1996 edition of the Code. Until the 2002 NEC, the use of separately derived, three-wire, 120-volt line-to-line, 60-volt-to-ground technical power systems was limited to motion picture and television studios. This new article expands the permitted use of this type of supply system to all commercial and industrial applications where sensitive audio/video or similar electronic equipment is used. This system can be used only under the close supervision of qualified individuals.
Unlike electrical distribution systems that supply lighting and appliance branch circuits, the supply systems covered by Article 647 are subject to mandatory voltage-drop requirements. The voltage-drop requirements are needed to ensure the operation of overcurrent devices to protect conductors and equipment supplied by these systems. Because the use of standard overcurrent devices and distribution equipment with higher voltage ratings is permitted, the impedance in circuits supplied by these systems under fault conditions is a primary concern, hence the mandatory voltage-drop requirement.
I think this is the Art in reference.
ARTICLE 647 Sensitive Electronic Equipment
647.1 Scope.
This article covers the installation and wiring of separately derived systems operating at 120 volts line-to-line and 60 volts to ground for senstitive electronic equipment.
The use of this type of supply system as a means to reduce objectionable noise and its adverse effect on the performance of electronic audio and video equipment has been recognized since the 1996 edition of the Code. Until the 2002 NEC, the use of separately derived, three-wire, 120-volt line-to-line, 60-volt-to-ground technical power systems was limited to motion picture and television studios. This new article expands the permitted use of this type of supply system to all commercial and industrial applications where sensitive audio/video or similar electronic equipment is used. This system can be used only under the close supervision of qualified individuals.
Unlike electrical distribution systems that supply lighting and appliance branch circuits, the supply systems covered by Article 647 are subject to mandatory voltage-drop requirements. The voltage-drop requirements are needed to ensure the operation of overcurrent devices to protect conductors and equipment supplied by these systems. Because the use of standard overcurrent devices and distribution equipment with higher voltage ratings is permitted, the impedance in circuits supplied by these systems under fault conditions is a primary concern, hence the mandatory voltage-drop requirement.
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