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Electrical Code - USA Commercial or Residential 1999 / 2002 / 2005 versions - for UNITED STATES

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  #1   IP: 207.193.21.25
Old May 10th, 2005, 07:43 PM
paul paul is offline
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Default HVAC recepticle

Does anyone see a problem with feeding a 120V 20A HVAC service receptacle (REQD by 210.63) from the 240V 20A HVAC feeder, provided of course, a neutral is pulled as well. Granted this opportunity wouldn't arise often, but the air conditioner compressor nameplate says to OCPD at 20A. Since Residential receptacles can be on 20A branch circuits wouldn't this be acceptable?

Breaker size =20A
Wire = THHN #12

440.34 AC unit with other loads must be of sufficient ampacity to supply both.
220.3(B)(9) receptacle load is not applicable, but I'll pad it to be 180VA.
210.63 would be met by placing the receptacle before the AC disconnect.
210.4 (C) EX2 is met by the 240V 20A listed breaker.


I can't see why this wouldn't work as described, being field installed from separately listed parts. But my concern is that the listed combo disconnect / service recept units do not allow this scenario. They say the recept must be on a seperate branch cir. What am I missing?
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  #2   IP: 24.16.225.236
Old May 10th, 2005, 08:30 PM
suemarkp suemarkp is offline
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If I was NEC King, I would allow it since it is a limited use receptacle and typically used when the AC is off. However, I don't think you can do this because of 210.23(A)(2) which disallows general use receptacles on circuits that have fastened-in-place equipment that draws more than 50% of the circuit ampacity. If the AC has an MCA of 9.9 amps or less, you can do it.

Now a silly alternative, which would be compliant, would be to use a 3R 4 slot enclosure for your AC disconnect and put a 20A double pole in slots 1 and 2 (for the airconditioner) and a 20A single pole breaker in the 3rd slot. This would be for your required branch circuit. This even passes the 215.2(A)(2) rule, subrule (1) if you don't install a breaker in the 4th slot.

Seems like a lot of work for little gain though, so you may want to ask the inspector if he's going to force you to jump through those hoops.
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  #3   IP: 68.193.88.245
Old May 11th, 2005, 04:40 AM
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Ron Ron is offline
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Since it is not a general use receptacle (used for HVAC servicing), how about a UL list disconnect with a receptacle built in?

http://www.bussmann.com/library/bifs/1143.PDF#search='hvac%20disconnect%20receptacle'
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  #4   IP: 24.16.225.236
Old May 11th, 2005, 11:27 AM
suemarkp suemarkp is offline
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The "general use receptacle" wording was mine and not the NEC. What the code says is "cord-and-plug-connected utilization equipment not fastened in
place".

I think the intent is you don't put receptacles on heavily loaded circuits unless that receptacle is already used up serving a known load (i.e. fastened in place).
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  #5   IP: 66.59.122.233
Old May 11th, 2005, 02:52 PM
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There was a thread almost identical to this one on another site yesterday, but in that scenario it was a 240 volt, 20 amp pool pump receptacle with a 120 volt duplex convenience rec jumped off that same circuit. It was resolved that if it didn't violate 210.23(A)(2), then it's okay. Very darned seldom will you run into a 20 amp condensing unit. Many evaporative coolers are 20 amp, but they're used in a limited geographic area. My personal preference is to wire all the house's outside receptacles on one circuit expressly for outdoor recs, and I catch the rec in the combo HVAC disco with the outdoor rec circuit.
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  #6   IP: 148.78.243.24
Old May 12th, 2005, 03:29 PM
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Wgoodrich Wgoodrich is offline
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The receptacle to serve as the required HVAC unit area is forbidden to be connected to the load side of that unit disconnect. It is not forbidden to install a sub panel then two branch circuits one for the HVAC and one for the receptacle. Install a 4 circuit disconnect by the HVAC unit within sight to serve as both a subpanel and a unit disconnect.

210.63 Heating, Air-Conditioning, and Refrigeration Equipment Outlet
A 125-volt, single-phase, 15- or 20-ampere-rated receptacle outlet shall be installed at an accessible location for the servicing of heating, air-conditioning, and refrigeration equipment. The receptacle shall be located on the same level and within 7.5 m (25 ft) of the heating, air-conditioning, and refrigeration equipment. The receptacle outlet shall not be connected to the load side of the equipment disconnecting means.Section 210.63 is intended to prevent makeshift methods of obtaining 125-volt power for servicing and troubleshooting heating, air-conditioning, and refrigeration (HACR) equipment. The reference to 210.8 in the fine print note to 210.63 reminds the Code user of the GFCI requirements for these receptacle outlets. The requirements in 210.52(E) for outdoor dwelling unit receptacles located within 25 ft of HACR equipment meet the requirements of 210.63.
The requirements of 210.63 were expanded in the 2002 Code to improve worker safety. As a result, a receptacle outlet is now required for troubleshooting HACR equipment at grade-accessible outdoor equipment and at rooftop units associated with one- and two-family dwelling units. A new exception added in the 2005 Code exempts evaporative coolers (commonly referred to as ``swamp coolers'') from the receptacle requirement where the cooler is installed at a one- or two-family dwelling. It should be noted that although this type of cooling equipment is exempt from 210.63, one- and two-family dwellings are required to have outdoor receptacle outlets at the front and the back of the structure in accordance with 210.52(E).

Just an idea

Wg
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  #7   IP: 66.59.122.134
Old May 12th, 2005, 03:36 PM
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But it can be installed on the LINE SIDE of the disco if it is a 15 or 20 amp circuit.
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