Wire Inside Condensing Units

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Fitzdrew516

Senior Member
Location
Cincinnati, OH
Working on a fairly large job right now. Here's the set up for this particular question.

Wire feeds to the roof for condensing unit, then hits the disconnect, and then, inside the unit, feeds a control panel on the backside of the unit. The way it was installed the wires that are feeding the control panel are not in conduit.

The question was posed to me by my construction manager whether or not that wire should be in conduit. I've never run across this before, but my initial gut feeling is no. I don't see any reason why it would need to be. All the other wires inside the unit (from manufacturer) aren't in conduit. I've never seen another piece of equipment that had conduit inside of it.

Anyway, like I said, I can't see any reason why this would be needed, but he said the refrigeration guy on site said something to him about it. Are there any code references, or anything else that I'm missing here?

Thanks,
-Drew
 
steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Fitzdrew516 said:
Working on a fairly large job right now. Here's the set up for this particular question.

Wire feeds to the roof for condensing unit, then hits the disconnect, and then, inside the unit, feeds a control panel on the backside of the unit. The way it was installed the wires that are feeding the control panel are not in conduit.

The question was posed to me by my construction manager whether or not that wire should be in conduit. I've never run across this before, but my initial gut feeling is no. I don't see any reason why it would need to be. All the other wires inside the unit (from manufacturer) aren't in conduit. I've never seen another piece of equipment that had conduit inside of it.

Anyway, like I said, I can't see any reason why this would be needed, but he said the refrigeration guy on site said something to him about it. Are there any code references, or anything else that I'm missing here?

Thanks,
-Drew
Click to expand...

I'm a little confused, because normally the field wiring just terminates in a control panel?

Are these field installed wires, or were they part of the condensing unit? And exactly what do you mean by "inside the unit"? As in the wires run across inside the unit, so you can look down and see them through the fan? Why would they be ran like that?

I believe most of the factory wiring you can see inside the unit is low voltage. And the 120V power wiring to the fan is normally done through sealtight. So just because you can see factory wires inside the unit doesn't mean its OK to run field power wiring through the unit?
 
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Fitzdrew516

Senior Member
Location
Cincinnati, OH
steve66 said:
I'm a little confused, because normally the field wiring just terminates in a control panel?

Are these field installed wires, or were they part of the condensing unit? And exactly what do you mean by "inside the unit"? As in the wires run across inside the unit, so you can look down and see them through the fan? Why would they be ran like that?

I believe most of the factory wiring you can see inside the unit is low voltage. And the 120V power wiring to the fan is normally done through sealtight. So just because you can see factory wires inside the unit doesn't mean its OK to run field power wiring through the unit?
Click to expand...

How it was explained to me is that it is field wired from the disconnect, through the unit to the control panel on the opposite side of the unit (inside the unit).
 
Smart $

Smart $

Esteemed Member
Location
Ohio
You are under the NEC up to the supply terminals. You can't use what the manufacturer did as an example. They are not under NEC purview.

Typical units have an electrical supply compartment or one that includes control devices. I believe we must use NEC wiring methods all the way to that compartment, even where the supply conductors are routed through the inside of the unit itself. In many cases, inside the unit, electrical compartment excluded, is an environmental air plenum. Codes for such must be enforced.
 
steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
It needs to be in conduit or some type of chapter 3 wiring method (maybe liquid tight flexible metal conduit).

Normally, the wiring enters directly into the control panel. I'm having a hard time understanding why it would go through the CU before going into the control panel. Seems like the installer would have to drill 2 extra holes (one in the side of the CU, and one in the control panel) to install it like that.

As mentioned before, the factory wiring that is exposed is covered by the units listing (and factory testing), and that wiring is probably low voltage anyway.

Smart $ said:
You are under the NEC up to the supply terminals. You can't use what the manufacturer did as an example. They are not under NEC purview.

Typical units have an electrical supply compartment or one that includes control devices. I believe we must use NEC wiring methods all the way to that compartment, even where the supply conductors are routed through the inside of the unit itself. In many cases, inside the unit, electrical compartment excluded, is an environmental air plenum. Codes for such must be enforced.
Click to expand...

I agree, except its a condensing unit, not a roof top unit, so there wouldn't be any plenum areas.
 
I

Ingenieur

Senior Member
Location
Earth
Did the control unit come as part of the factory unit?
the disconnect? Was it an option?
are you sure the wire from disconnect to cntl pnl is not factory?
 
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jusme123

Senior Member
Location
NY
Occupation
JW
Fitzdrew516 said:
How it was explained to me is that it is field wired from the disconnect, through the unit to the control panel on the opposite side of the unit (inside the unit).
Click to expand...

It needs to be in conduit or some type of chapter 3 wiring method
 
Smart $

Smart $

Esteemed Member
Location
Ohio
steve66 said:
...
I agree, except its a condensing unit, not a roof top unit, so there wouldn't be any plenum areas.
Click to expand...
That's a valid counterpoint to single conductors passing through a plenum.

BTW, it is a roof top unit per OP's drawing... just not an [environmental] air handling unit.

What does the installation manual say about the electrical connection? Citing 110.3(B) here.
 
brantmacga

brantmacga

Señor Member
Location
Georgia
Occupation
Former Child
I think the OP is talking about factory wiring inside the unit; in that case, there is nothing for OP to do. I've never seen conduit inside a condensing unit. Typically just bushings between compartments and open air conductors running inside.


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petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Smart $ said:
IMO, yes. But...

Is the unit listed, labeled, or identified as an electrical raceway or enclosure?
Click to expand...

I am not sure it has to be as long as the unit is listed as a whole.

UL allows all kinds of things to enclose conductors in listed equipment that are not listed raceways or listed enclosures.

Look at the wiring inside of a drill or an electric chain saw for example.
 
Smart $

Smart $

Esteemed Member
Location
Ohio
petersonra said:
I am not sure it has to be as long as the unit is listed as a whole.

UL allows all kinds of things to enclose conductors in listed equipment that are not listed raceways or listed enclosures.

Look at the wiring inside of a drill or an electric chain saw for example.
Click to expand...
Wiring under UL, yes. But as I said earlier, wiring up to the equipment supply terminals is under NEC purview. Then combine that with 110.3(B)...
 
I

Ingenieur

Senior Member
Location
Earth
Smart $ said:
Wiring under UL, yes. But as I said earlier, wiring up to the equipment supply terminals is under NEC purview. Then combine that with 110.3(B)...
Click to expand...

if the disconnect, cntl pnl and interconnect wiring is factory installed then the disconnect is the supply point

we lack information
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Ingenieur said:
if the disconnect, cntl pnl and interconnect wiring is factory installed then the disconnect is the supply point

we lack information
Click to expand...
Fair point. I have been assuming the disconnect was field installed, being on the opposite end of the unit. IME no units had externally mounted disconnects from the manufacturer.
 
steve66

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Ingenieur said:
if the disconnect, cntl pnl and interconnect wiring is factory installed then the disconnect is the supply point

we lack information
Click to expand...

I asked that in the first post, and it looks to me like its been answered:


Fitzdrew516 said:
How it was explained to me is that it is field wired from the disconnect, through the unit to the control panel on the opposite side of the unit (inside the unit).
Click to expand...
 
F

Fitzdrew516

Senior Member
Location
Cincinnati, OH
Again, as it was explained to me, the wire from the disconnect to the control panel is field wired. I also have my doubts about that so I'm going to follow up with my CM on it.
 
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