Rooftop AC unit wiring

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woodduder

Senior Member
Location
West Central FL.
We have typical 5 ton RTU's on the roof of an office building. We will be installing a disconnect on the outside of the unit. We are coming up through the 3" x 5" raised area on the bottom pan.

My field foreman wants to bring the wiring up though the pan via a flex connector he has put into the raised area, but after that he wants to free wire (next to the condensor coil) approx. 30" over to the disconnect. I said "you cannot free wire here", he said "yes I can....the manufacturer did when he ran from the control box to the compressor".

What do you think? I think the manufacturer is OK since it is a listed product, but we must keep our wiring in conduit until we reach the terminal box.
 
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gotmud

Senior Member
Location
some place cold
it is not acceptable to wire through the unit...It has to be in conduit because the temp rating on the factory wiring is rated higher for the difference in temperature on a rooftop. Your THHN is not rated as high. That's what my inspector has told me...If you look at the insulation rating on the factory wiring it is rated to higher temps. I want to say it's 105 degree
 
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chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
gotmud said:
it is not acceptable to wire through the unit...It has to be in conduit because the temp rating on the factory wiring is rated higher for the difference in temperature on a rooftop.
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Where can I find some of this "conductor cooling conduit"?

IMO once I enter the enclosure (see Art. 100 definition) it would be up to me as to whether I use conduit or not. I often free wire in RTU's.
 
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www.assuredelectric.net

Member
Location
long beach ca
If its done in the enclosed control cabinet portion of the unit I don't see why it would be a problem. However if he has wires sleeved through a knockout and spanning over to the compressor I would let him know that that is pretty shabby craftsmanship. IMO.
 
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woodduder

Senior Member
Location
West Central FL.
Well, I guess the opinions are split somewhat down the middle. Thanks for all the comments. Since I am the boss man, he will be putting it in (my way) liquidtite conduit. I just feel better if it is.
 
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woodduder

Senior Member
Location
West Central FL.
chris kennedy said:
Where can I find some of this "conductor cooling conduit"?

IMO once I enter the enclosure (see Art. 100 definition) it would be up to me as to whether I use conduit or not. I often free wire in RTU's.
Click to expand...

What enclosure are you refering to? The condenser coil area insn't in much of an enclosure. It is wide open to the elements.
 
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gotmud

Senior Member
Location
some place cold
chris kennedy said:
Where can I find some of this "conductor cooling conduit"?

IMO once I enter the enclosure (see Art. 100 definition) it would be up to me as to whether I use conduit or not. I often free wire in RTU's.
Click to expand...

you know your right!...That's what my inspector has always told me and I just said "OK" never really thinking about it. Now that you said that it's GAME ON with my inspector.;)
 
chris kennedy

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
woodduder said:
What enclosure are you refering to? The condenser coil area insn't in much of an enclosure. It is wide open to the elements.
Click to expand...

So is a fence. You didn't read the definition of enclosure did you?:roll::grin:


Enclosure. The case or housing of apparatus, or the fence or walls surrounding an installation to prevent personnel from accidentally contacting energized parts or to protect the equipment from physical damage.
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gotmud said:
you know your right!...That's what my inspector has always told me and I just said "OK" never really thinking about it. Now that you said that it's GAME ON with my inspector.;)
Click to expand...

Tell your inspector that the conduit would trap the heat produced by the conductors themselves and be added to the ambient temperature in the enclosure.
 
B

benaround

Senior Member
Location
Arizona
The fpn after 'Enclosure' says see Table 430.91 for examples of enclosures. As long as we

are in 'definitions' take a look at Exposed ( as applied to wiring methods ).
 
augie47

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
woodduder said:
What do you think? I think the manufacturer is OK since it is a listed product, but we must keep our wiring in conduit until we reach the terminal box.
Click to expand...

So only wiring in conduit is permitted by Code ? I have to take down that overhead span to my garage ? :)
My opinion would be the only argument preventing the open wiring in the unit would be Jim W's that the space might be considered an air plenum.
 
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woodduder

Senior Member
Location
West Central FL.
Thanks again for all the opinions. Some of the things that we all do are done a certain way because we feel it is safe. I can definately see that both sides have a valid point. I will sleep better knowing that I did it my way.

Happy Thanksgiving to all the Mike Holt community. I hear a beer calling my name.
 
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