Service Receptacle inside HVAC control panel - allowable?

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lost_aussie

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On a greenfield construction project we have a HVAC vendor who is proposing to install a service receptacle inside the RTU control panel. These are fairly large RTU's (FLA 60A, 480V)

210.63 requires that the service receptacle not be connected to the load side of the disconnecting means. My question - if we power the service receptacle from a separate 120V circuit, does it violate the requirements for disconnecting means. As proposed, the disconnect can be opened and locked out and there would still be live wires (the receptacle, powered by a separate 120V supply) inside the control panel. It seems counter intuitive to allow it but my manager is insisting it's fine.

ps. First post, please be nice!
 
Think of it this way: The purpose of that receptacle is to give the maintenance technician some place to plug in his or her portable tools, while working on the RTU. That should answer your question.

Welcome to the forum.
 
charlie b said:
Think of it this way: The purpose of that receptacle is to give the maintenance technician some place to plug in his or her portable tools, while working on the RTU. That should answer your question.
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But isn't the purpose of the disconnecting means to indicate to the maintenance crew that it's safe to stick their fingers inside the control panel (once they've disconnected and tested for dead). I can't find a NEC requirement for this. I'd be much more comfortable with the receptacle on the outside of the equipment rather than inside the panel.
 
Wouldn't the receptacle be inside a standard outlet box, with that outlet box located inside the control panel? In other words, wouldn't the screws on the sides of the receptacle (where power is connected, and which constitute the "exposed live parts") be guarded from contact by the worker? If not, if the screws are just in the open, then I agree that this is a bad idea. But if they are installed by the RTU manufacturer, and thus are included in the listing, then they lie outside the scope of the NEC.
 
I work on 5-ton RTUs almost every day, and have been inside a few 10-ton machines. I've never seen the receptacle inside. Is the purpose of doing so to avoid the weatherproof box and cover?

Additionally, many times machines are located next to one another and a single receptacle mounted on one of them can serve as the required receptacle for two or three machines, but definitely not handy if inside of one I'm not already inside of, though I'm sure he wouldn't do that.

Is in-house maintenance using them, or hired contractors, when servicing the equipment? I'd be a little annoyed if I looked around the roof and then drug up a big extension cord with my stuff and then found the receptacle inside the machine after all that.

All in all, as an HVAC guy, I think it would needlessly be in my way.

As for safe, if in its own box, as I'm assuming you mean, that part wouldn't bother me. I do frequently see the live wires run through a machine when both the disconnect and the weatherproof receptacle box are each mounted to the side of the unit.
 
MAC702 said:
I work on 5-ton RTUs almost every day, and have been inside a few 10-ton machines. I've never seen the receptacle inside. Is the purpose of doing so to avoid the weatherproof box and cover?

Additionally, many times machines are located next to one another and a single receptacle mounted on one of them can serve as the required receptacle for two or three machines, but definitely not handy if inside of one I'm not already inside of, though I'm sure he wouldn't do that.

Is in-house maintenance using them, or hired contractors, when servicing the equipment? I'd be a little annoyed if I looked around the roof and then drug up a big extension cord with my stuff and then found the receptacle inside the machine after all that.

All in all, as an HVAC guy, I think it would needlessly be in my way.

As for safe, if in its own box, as I'm assuming you mean, that part wouldn't bother me. I do frequently see the live wires run through a machine when both the disconnect and the weatherproof receptacle box are each mounted to the side of the unit.
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You make some good points. Maintenance will likely be by hired contractors. I believe the purpose was to avoid field installation and a separate equipment stand for the receptacle. Is it common to see the box mounted directly to the side of the unit (on the unit itself)?
 
lost_aussie said:
On a greenfield construction project we have a HVAC vendor who is proposing to install a service receptacle inside the RTU control panel. These are fairly large RTU's (FLA 60A, 480V)

210.63 requires that the service receptacle not be connected to the load side of the disconnecting means. My question - if we power the service receptacle from a separate 120V circuit, does it violate the requirements for disconnecting means. As proposed, the disconnect can be opened and locked out and there would still be live wires (the receptacle, powered by a separate 120V supply) inside the control panel. It seems counter intuitive to allow it but my manager is insisting it's fine.

ps. First post, please be nice!
Click to expand...

In short..... I'm with you, for all the reasons you just mentioned.

JAP>
 
MAC702 said:
I work on 5-ton RTUs almost every day, and have been inside a few 10-ton machines. I've never seen the receptacle inside. Is the purpose of doing so to avoid the weatherproof box and cover?..
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Can’t remember the last time we connected to an RTU that didn’t have a service receptacle inside. Now, I have worked on buildings that have 30-40+ RTU’s and they might have a recep in every other unit instead of every single one.

The purpose is to avoid another roof penetration.


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To me it's all about how the connection is made to the box and receptacle on or in the unit itself.

I don't have a problem with it if the receptacle circuit is flexed all the way to the box and kept separate from the loose unit wiring, but, if the receptacle circuit is run loose once it gets inside the unit and starts to mingle with the loose unit conductors I do have a problem with it.


JAP>
 
charlie b said:
Wouldn't the receptacle be inside a standard outlet box, with that outlet box located inside the control panel? In other words, wouldn't the screws on the sides of the receptacle (where power is connected, and which constitute the "exposed live parts") be guarded from contact by the worker? If not, if the screws are just in the open, then I agree that this is a bad idea. But if they are installed by the RTU manufacturer, and thus are included in the listing, then they lie outside the scope of the NEC.
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The conductors to the receptacle are where the danger is, not the exposed live parts of the screws on the receptacle in the box.
The receptacle in the box is the safest part of this whole setup.

You shut off the disconnect on the unit expecting all of the power is off inside to cut that burnt red control wire out of the loom of control wires where the contractor zip tied his receptacle circuit into and unknowingly cut into the live red receptacle circuit going to the receptacle.


Convenient Yes, Nema 1, More than likely if its inside, Less roof penetrations, depends on whether you ran the receptacle circuit with the feeder or not,
Having a service receptacle mounted inside of a unit, not so bad, having a receptacle mounted in the actual control cabinet with free wire to it like in hot tub wiring not so smart, having a receptacle in the control cabinet mounted in it's own box with flex separating it from the feeder and control wiring, not so bad.
a receptacle mounted on the outside of the unit with a separate penetration through the curb and kept separate from the power on the inside of the unit where a person can actually see it,,,, priceless.

JAP>
 
charlie b said:
Think of it this way: The purpose of that receptacle is to give the maintenance technician some place to plug in his or her portable tools, while working on the RTU. That should answer your question.

Welcome to the forum.
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Which is a conflict in itself.

When you work on a piece of equipment you shut the disconnect or group of disconnects off to assure power is off inside of it and he can work safely on the unit.

That stands to reason whether he's even using the receptacle outlet or not.

So by rights if the receptacle is inside the unit he should go and lock out that circuit also, since its coming from an external source, which renders it safe and also useless.

The solution is to use the receptacle power from a unit that is functioning properly to troubleshoot the units that are not. :)


JAP>
 
lost_aussie said:
You make some good points. Maintenance will likely be by hired contractors. I believe the purpose was to avoid field installation and a separate equipment stand for the receptacle. Is it common to see the box mounted directly to the side of the unit (on the unit itself)?
Click to expand...

It's not uncommon to see them mounted to the side of the unit. You find them every which way. I would rather see them outside than inside.
 
lost_aussie said:
You make some good points. Maintenance will likely be by hired contractors. I believe the purpose was to avoid field installation and a separate equipment stand for the receptacle. Is it common to see the box mounted directly to the side of the unit (on the unit itself)?
Click to expand...

It's very common to see the receptacle mounted to the exterior of the machine itself when in the middle of a commercial roof. Usually, it is fed from its own roof penetration and conduit, though I also see its power run through the disconnect from time to time, as a separate circuit that stays live when the disconnect is off. When these wires also go inside the machine, it's always, so far, been very obvious what wires are coming through just to go to the receptacle. But I also agree that, in principle if nothing else, when a disconnect is off to a machine, there should be NO LIVE WIRES in its interior.
 
MAC702 said:
But I also agree that, in principle if nothing else, when a disconnect is off to a machine, there should be NO LIVE WIRES in its interior.
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My experience is with industrial control systems, not HVAC. It was not unusual to have wiring in a control panel that was powered externally from a source other than the internal CPT. The convention was to always use yellow wires for these circuits and label the panel to warn about the situation.
 
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