What color of neutral to use

[wireman]

I'm designing a control panel fed with 120VAC/20A power that will power a small UPS w/120VAC output. The UPS will power everything else in the panel. Using #12 THHN. The neutrals are both grounded.

Questions:
1) Section 200.6(A) applies so the neutrals need to be different colors, yes/no?

2) Can one neutral can be white per 200.6(A)(1) and the other can be gray per 200.6(A)(1)? Any other sections that apply (besides Art. 409)?

It seems straight forward but I just wanted to check.

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Thanks in advance for any answers

 

[infinity]

You can mix white and gray in this application. I see no reason why you couldn't just use all white.

 

[wireman]

You can mix white and gray in this application. I see no reason why you couldn't just use all white.

Using all white is easier, but I don't understand.

From reading 200.6(D), it seems like the panel will have grounded conductors from two different systems so they would be required to be different colors. Isn't the "normal" power neutral considered a different "system" from the UPS neutral?

If you had a 120V neutral & a 277V neutral in the same enclosure would they need to be different colors.

Thanks.

 

[PEDRO ESCOVILLA]

NEC says white or natural grey. it is not req'd to differentiate , however, from working with different systems, any time i installed 277/480, i always used grey for a grounded conductor. when it is 120/240 it was white. the NESC (national electrical safety code) (not the NEC) discusses the phase colors for different voltages, this, I was taught, is where we get Brown , Orange and Yellow, and Grey for 277/480 systems. it is so one can differentiate from one system to another when woerking on multiple systems in the same enclosure.( if you've ever cut into a 277 nuetral that was under load, that was NOT identified as 277, you'll grasp it in a hurry! )if any of this info is incorrect, it is what i was taught coming up through the trades, so i took it for "what it was". i ihope this is helpful

 

[billsnuff]

Does this control panel fall under industrial machinery for NFPA 79 ?

 

[wireman]

Does this control panel fall under industrial machinery for NFPA 79 ?

Yes, it does come under NFPA 79.
When the main disconnect is OFF the UPS output power is disconnected too, so I don't believe NFPA79 13.2.3.2(2) applies regarding white w/org stripe. All wires will have wire #'s as shown on the drawings (see exception #2 of same article).

At this point I'm going to submit the drawings with WHITE wire for the "normal" power's neutral and GRAY for the UPS power neutral, then let the consulting engineers tell me if it's OK or not.

 

[pfalcon]

Yes, it does come under NFPA 79.

I am sooooo happy to hear someone is paying attention to the 79! :happyyes:

When the main disconnect is OFF the UPS output power is disconnected too,

Really? What does the UPS protect if not power loss?

 

[infinity]

Since both the UPS and the normal power are 120 volts I see no reason why you would need a different colored neutral.

 

[kbsparky]

NEC says white or natural grey....

I've often wondered what an un-natural gray would look like? Is it any more or less gray than a natural gray? And is there any difference between grey and gray?

Would it look like this?
Or this?
Or even this?

But it appears that the loons who write the codes figured it out anyways, since the "natural" wording in the NEC was last seen in the 1999 edition.

What edition of the Code are you using?

 

[don_resqcapt19]

I've often wondered what an un-natural gray would look like? Is it any more or less gray than a natural gray? And is there any difference between grey and gray?

Would it look like this?
Or this?
Or even this?

But it appears that the loons who write the codes figured it out anyways, since the "natural" wording in the NEC was last seen in the 1999 edition.

What edition of the Code are you using?

Natural gray was really just white, but many years ago, it did not look white. It looked gray. It had to do with the technology that was available to make colored insulation. Natural gray insulation has not been made in over 40 years. The code issue is that prior to the 1999 code, you could use the color gray as an ungrounded conductor. In fact you were not permitted to use it as a grounded conductor. The 1999 code caught up to the real world and made the use of the color gray legal as a grounded conductor.

 

[don_resqcapt19]

Since both the UPS and the normal power are 120 volts I see no reason why you would need a different colored neutral.

If the installation is covered by the NEC, I would see the normal power and the UPS power as being different systems and 200.6(D) would require that the neutrals be identified as to system.

 

[infinity]

If the installation is covered by the NEC, I would see the normal power and the UPS power as being different systems and 200.6(D) would require that the neutrals be identified as to system.

I guess it comes down to what they're implying by the word system. It's not uncommon to have multiple UPS systems and normal systems all of the same voltage in a building. How would you differentiate multiple system neutrals?

 

[don_resqcapt19]

I guess it comes down to what they're implying by the word system. It's not uncommon to have multiple UPS systems and normal systems all of the same voltage in a building. How would you differentiate multiple system neutrals?

It is only required when the grounded conductors from different systems are in the same raceway or enclosure. 200.6(D) permits a number of methods as long as you document what you are using to identify the conductors.

Your system question is a good one as 200.6 uses the word system and not the words "voltage system" as are used in 210.5. If you have two 208/120Y systems and their grounded conductors are in the same raceway, it is my opinion that 200.6(D) requires them to be identified as to which transformer they are associated with.

 

[wireman]

I am sooooo happy to hear someone is paying attention to the 79! :happyyes:



Really? What does the UPS protect if not power loss?

Good question. The control panel is fed from a lighting panel's 20A CB. There are 3 different scenarios of how the control panel's main disconnect could be wired:
1) The main could only shut off the feed from the lighting panel, allowing the UPS to kick in & the UPS output power will remain on.

2) The main could only shut off the UPS power, but then there would still be a few "normal power" circuits in the control panel that would still be hot.

3) The main could shut off both the incoming power and the UPS' output power and then everything in the panel would be off (except for the line side terminals & UPS output line side terminals).

Our customer chose option #3. Their choice.

 

[pfalcon]

I've often wondered what an un-natural gray would look like?

It looks exactly like your Avatar

Good question. The control panel is fed from a lighting panel's 20A CB. There are 3 different scenarios of how the control panel's main disconnect could be wired:
1) The main could only shut off the feed from the lighting panel, allowing the UPS to kick in & the UPS output power will remain on.

2) The main could only shut off the UPS power, but then there would still be a few "normal power" circuits in the control panel that would still be hot.

3) The main could shut off both the incoming power and the UPS' output power and then everything in the panel would be off (except for the line side terminals & UPS output line side terminals).

Our customer chose option #3. Their choice.

Okay, so from a 20A CB on the wall we come into the panel with 120Vac through the disconnect to the UPS and then:
Out from the UPS back through the disconnect to the rest of the panel?

How about running the loopback in sealtite to provide separation from the other portions of the circuit? Grey sealtite from the disconnect to the UPS and orange for the return trip?

Essentially you'd be dodging 200.6(D) by providing separate raceways for the loopback. You fulfill the 79 with the orange sealtite on the return loop.

 

[wireman]

It looks exactly like your Avatar

How about running the loopback in sealtite to provide separation from the other portions of the circuit? Grey sealtite from the disconnect to the UPS and orange for the return trip?

Essentially you'd be dodging 200.6(D) by providing separate raceways for the loopback. You fulfill the 79 with the orange sealtite on the return loop.

I'm not sure exactly how the different sealtites will satisfy the requirements we're discussing. Both system's neutrals would emerge from the sealtites and land on separate terminal strips inside the panel so the wires will be visible at that point.


In light of all the good info I've received here and since all of the wires will all have wire labels I'm going to use white on ALL of the neutrals. Thanks for all the help.