Using white wires for I/Os in a UL electrical board

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Gonen

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Israel
Hello,

I would like to if there are restrictions in the UL regulations on using white wire (or other colors) for wiring I/Os (24VDC, 4-20 mA)?

Thanks a lot,
Gonen
 
Gonen said:
Hello,

I would like to if there are restrictions in the UL regulations on using white wire (or other colors) for wiring I/Os (24VDC, 4-20 mA)?

Thanks a lot,
Gonen
Click to expand...
What kind of "board". What UL standard?

For UL508a industrial control panels:

4-20mA signals are not normally "wire". They are normally shielded cables. I don't know that this is required though. I would have to look. The color coding of conductors within cables is allowed to be different than for single conductors, but without looking I don't recall what differences are allowed.

DC single conductors are required to be blue for ungrounded conductors and white with a blue stripe for grounded conductors.
 
Thanks Bob

It's an electrical & control board, 460 & 110V feed, Class1,Div2 (equipped with Type Z purging unit).
My problem is that my board manufacturer encountered shortage of grey wires for wiring the IO, from the controller to the wiring terminals...
Therefore, I would like to know if he can replace the grey wires with white ones.
It's only for wiring the 24VDC, 4-20 mA signals.
All the transmitters (110V) are properly wired.

Gonen
 
Gonen said:
Thanks Bob

It's an electrical & control board, 460 & 110V feed, Class1,Div2 (equipped with Type Z purging unit).
My problem is that my board manufacturer encountered shortage of grey wires for wiring the IO, from the controller to the wiring terminals...
Therefore, I would like to know if he can replace the grey wires with white ones.
It's only for wiring the 24VDC, 4-20 mA signals.
All the transmitters (110V) are properly wired.

Gonen
Click to expand...

The supplier will know if there is a UL issue. The fact that he is suggesting either white or gray wire suggests it may not end up being a listed assembly anyway.
 
And...

"Just because you can, doesn't mean you should."

I always like to think about the NEXT guy who has to work on that panel. What if he looks at those white wires and assumes they are all Neutrals?
 
Only thing white should be for is AC neutrals. The grey DC wires should be blue per UL508A. Your panel would not get listed
as wired. As pointed out the whites may cause some confusion in the field. But unless you plan on having it listed it really doesn't
matter and in fact we have some older panels at work that use white for all kinds of stuff. I would advise using a different color.
 
Aleman said:
Only thing white should be for is AC neutrals. The grey DC wires should be blue per UL508A. Your panel would not get listed
as wired. As pointed out the whites may cause some confusion in the field. But unless you plan on having it listed it really doesn't
matter and in fact we have some older panels at work that use white for all kinds of stuff. I would advise using a different color.
Click to expand...

It cannot be listed under UL508a.

It appears to me that the type of equipment the OP is talking about is more properly part of a switchboard or panelboard and probably should be listed under that category. IIRC, switchboard control circuits can use gray wire (think about all that gray SIS wire used in switchboards over the last 100 years or so). I don't know about white wire. Just don't know enough about the UL requirements for such things.
 
Aleman said:
... As pointed out the whites may cause some confusion in the field. ...
Click to expand...
Most 4-20mA field wiring is black and white twisted pair. I fail to see how it would be any more confusing than connecting black and white to blue and white/blue.
 
Smart $ said:
OP lists Israel as location... so it really comes down to what standards are in effect where the installation is located.
Click to expand...
From the OP.

restrictions in the UL regulations on using white wire
Click to expand...

Since he specifically asked about UL requirements, I tried to respond to his actual question and not speculate about what standard it "should" be built to.
 
Smart $ said:
Most 4-20mA field wiring is black and white twisted pair. I fail to see how it would be any more confusing than connecting black and white to blue and white/blue.
Click to expand...

Maybe it is "most" in your experience but I have seen just about every color code under the sun used with that kind of wiring, and often it is not consistent within the plant, or even within the wiring going into a single enclosure.

Besides, 2 wire, 3 wire, and 4 wire 4-20 mA circuits get wired differently anyway.

UL equipment rules do not extend beyond the equipment, so there is no UL standard for color coding of field wiring.
 
petersonra said:
What kind of "board". What UL standard?

For UL508a industrial control panels:

4-20mA signals are not normally "wire". They are normally shielded cables. I don't know that this is required though. I would have to look. The color coding of conductors within cables is allowed to be different than for single conductors, but without looking I don't recall what differences are allowed.

DC single conductors are required to be blue for ungrounded conductors and white with a blue stripe for grounded conductors.
Click to expand...

What if you have ungrounded DC? Both can't be blue....or you couldn't identify polarity. Hmmmmm.....
 
meternerd said:
What if you have ungrounded DC? Both can't be blue....or you couldn't identify polarity. Hmmmmm.....
Click to expand...

UL508a does not generally allow ungrounded DC control circuits. But, if it is ungrounded, it would be blue, regardless of polarity. The white is to indicate a grounded conductor, not polarity. It is analogous to all three phase wires being black regardless of which phase it is.
 
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