NEC 110.4

[mark24]

Can we use 277/480V 1200 Amp MDP for 240V 1200 Amp service? Same way can we use 277/480V 1200 Amp CT for 240V 1200 Amp service?

 

[JoeStillman]

Welcome to the forum! See NEC 110.16(B), 230.66, and 408.4(B).

A current transformer shouldn't be affected by the operating voltage.

It's best to consult your AHJ before making a commitment to such an expensive purchase.

 

[drktmplr12]

3-Phase Panel Used as Single-Phase

A few issues here: I was asked to look over some inspection hits on a 3-phase, 208Y/120V sub-panel that an inspector had instructed should have feeders phase-taped black, orange (high-leg) and blue. My guess is he had the deadfront removed and saw that it was a 3-phase panel, and noticing phase...

forums.mikeholt.com

you open a host of complicating factors by trying to use a three-phase panel for single-phase power.

phase tape
neutral bus size
labels

to name a few

you want to check with AHJ

 

[Dennis Alwon]

you open a host of complicating factors by trying to use a three-phase panel for single-phase power.

phase tape
neutral bus size
labels

to name a few

you want to check with AHJ

It could be a delta 3 phase--- 120/240

 

[jim dungar]

Can we use 277/480V 1200 Amp MDP for 240V 1200 Amp service? Same way can we use 277/480V 1200 Amp CT for 240V 1200 Amp service?

Yes, probably.
What voltage do you actually have?
120/240 1 phase 3 wire
240/120 3 phase 4 wire
240 3 phase 3 wire

 

[mark24]

Yes, probably.
What voltage do you actually have?
120/240 1 phase 3 wire
240/120 3 phase 4 wire
240 3 phase 3 wire

Incoming service is 120/240V 3 Phase -4 wire 1200 Amp and the MDP is rated 480Y/277 3 Phase 4 wire 1200 Amp. Is there any NEC reference I can provide to the Village inspector to allow us to use this existing MDP?

 

[mark24]

Welcome to the forum! See NEC 110.16(B), 230.66, and 408.4(B).

A current transformer shouldn't be affected by the operating voltage.

It's best to consult your AHJ before making a commitment to such an expensive purchase.

Here is the situation, the existing main distribution panel is rated at 480Y/270 3 Phase 4 wire 1200 Amp and the existing incoming service is 120/240 V 3 Phase 4 wire 600 Amp, we want to increase it to 1200 Amp.
so now when we apply for the permit to increase the amp to 1200, they are saying existing MDP can not be used since it is rated for 480V.
NEC code 110.4 says lower voltage shall not be used. Isn't that mean we can use 480v rated MDP for 240V incoming service?

 

[Dennis Alwon]

Here is the situation, the existing main distribution panel is rated at 480Y/270 3 Phase 4 wire 1200 Amp and the existing incoming service is 120/240 V 3 Phase 4 wire 600 Amp, we want to increase it to 1200 Amp.
so now when we apply for the permit to increase the amp to 1200, they are saying existing MDP can not be used since it is rated for 480V.
NEC code 110.4 says lower voltage shall not be used. Isn't that mean we can use 480v rated MDP for 240V incoming service?

I don't see why not but getting an inspector to agree may be an issue.

 

[infinity]

There is no code reason why you cannot use 480 volt equipment on a 240 volt system. Ask them for a code reference.

 

[mark24]

There is no code reason why you cannot use 480 volt equipment on a 240 volt system. Ask them for a code reference.

I asked, they said NEC Code 110.4

 

[infinity]

I asked, they said NEC Code 110.4

If that's what they're hanging their hat on they need a refresher course in reading.

110.4 Voltages.
Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.

 

[jim dungar]

Manufacturers regularly apply 480 and 600V labeled equipment at lower voltages, for example Square D I-Line panels.

How do they feel about using 600V THHN conductors on 240V circuits?

 

[drktmplr12]

How do they feel about using 600V THHN conductors on 240V circuits?

that can't be right

 

[steve66]

Here is the situation, the existing main distribution panel is rated at 480Y/270 3 Phase 4 wire 1200 Amp and the existing incoming service is 120/240 V 3 Phase 4 wire 600 Amp, we want to increase it to 1200 Amp.
so now when we apply for the permit to increase the amp to 1200, they are saying existing MDP can not be used since it is rated for 480V.
NEC code 110.4 says lower voltage shall not be used. Isn't that mean we can use 480v rated MDP for 240V incoming service?

Panels usually specifically list the voltages they are rated for. Look at page 6 for example.

Square D I-Line Circuit Breaker Panelboards Catalog - Class 2110 | Schneider Electric USA

This document contains the product description and information on features, accessories, application, dimensions, and replacement parts for I-Line™ Circuit Breaker Panelboards.

www.se.com

 

[infinity]

We often use 480/277 volt panels for 208/120 systems when we need a higher breaker aic rating.