Over 600 volts clearances and construction

[controlgenius]

Since the code just recently (2002 version) began addressing the over 600 volt applications, there have been more questions popping up. This is a new installation I am working on that highlights the need for further code clarifications. Any takers on these?

My installation concerns a electrical room in an industrial facility that contains both 120 volt control panels, 480 volt MCC, and 4160 volt MCC. The low voltage equipment does not serve the 4160 volt equipment. All conductors are both cables in cable tray and wiring in conduit. Both MCC?s are commercially available enclosed type with dead front panels, having no exposed parts during normal operation. Exposed parts are present only during maintenance operations by qualified personnel. During normal operation, the room is only available to qualified personnel.

Q1: Does this room have to meet the construction requirements of Article 110.31, part A ?

Q2: What is the definition of a ?vault? as mentioned in Article 110.31, part A ?

Q3: Does the 4160 volt equipment have to be separated from the (below 600V) equipment by a fence, partition or screen as described in Article 110.34, part B. ?

 

[BAHTAH]

Looking at 110-31 of the 1999 NEC article 110-31 states that if you install your 4160 equipment in a room it is considered to which access is controlled by a lock and key, it is considered to be accessible to qualified persons only. Article 110-31(a)(1) states that installations that are accessible to unqualified persons shall be in a vault or in a controlled access area or must be metal-enclosed switchgear. I would think since you have metal-enclosed switchgear, it can be locked and marked with the appropriate signage without having to build any special vault or room.
Article 110-34 gives you the working space required around this equipment.

 

[dlhoule]

Controlgenius:

I agree with Grant.

Now with the forum name. I looked at your profile and I think your name is an oxymoron. An engineer that is a control genius. Come on!

I like it though.

 

[controlgenius]

Grant,
I am inclined to agree with you also.
Still in a quandary about the construction of the room as the NEC does not define "vault". It is used elsewhere in the code as a "transformer vault", but there are other spaces that are used for other purposes, like switchgear, that are placed in "vaults".
And there are above ground "vaults" and below grade "vaults.
Seems like a NEC definition would be in order here.

 

[Pierre C Belarge]

You are correct in referencing Art 450 regarding vaults.

Yes to Q3

 

[controlgenius]

Formal answers to questions received from NFPA

Formal answers to questions received from NFPA

:shock: I had sent a formal inquiry to NFPA and they returned the following replies to the presented questions:


I am pleased to provide an answer to your questions.



Q1: According to the 2005 National Electrical Code, no, 110.31(A) does not dictate that all interior rooms, spaces, areas, etc. containing conductors and equipment over 600 volts be constructed as an Electrical Vault in accordance with this section. Only equipment specifically required elsewhere in the Code, such as Capacitors containing more than 11L (3 gal) of flammable liquid (460.2) are required in an Electrical Vault.

An interior room, according to the NEC, containing just 5 kV metal clad or metal enclosed switchgear, dry, would not require a fire resistance rating.

Q2: Vaults are a permitted method to enclose electrical equipment and conductors in several sections of the NEC and offer other advantages. However, rooms containing dry-type transformers per 450.21, nonflammable fluid-insulated transformers per 450.24, oil-insulated transformers per 450.26, capacitors per 460.2, and oil-filled equipment per 490.3, are specifically to have fire resistance ratings per the requirements for this equipment contained in these sections of the NEC.

Q3: Over 600 volt, nominal metal-enclosed equipment is not required to be separated from 600 volt nominal and below enclosed equipment such as a motor control center. Section 110.34(B) covers the situation where there are exposed live parts or exposed wiring operating over 600 volts, nominal in the same vault, room or enclosure as equipment, switches and cutouts operating at 600 volts, nominal or less. The exposed energized high voltage equipment is to be separated by a suitable partition, fence or screen from the 600 volts, nominal or less equipment.