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Old 05-21-2011, 01:44 PM   #1
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Condensor Unit Wiring issues with Square D QO Breaker


I have a question about what to do with Condensor unit wiring. The system I have specifies a minimum circuit ampacity of 30 amps. The unit also states that the minimum HACR circuit breaker should be 40 amps. I understand that this is permitted by article 440 in the NEC.

The unit is wired using 10 guage copper UF wire all the way from the breaker to the disconnect switch outside. The breaker is a Square D QO240 (40 AMP, 2 pole) unit. These are rated as per Square D litterature for use as an HACR breaker. At issue is that the Square D litterature also states that this breaker can accomodate wire sizes 8-2 AL/CU. This appears to be a violation of the breaker's wire termination capacity.

How should this be addressed? Should a short "pigtail" of #8 wire be used at the breaker, then wire-nutted to the 10 gauge wire? Should the breaker be wired using the #10 wire anyway? Should the #10 wire be supplemented by another piece of wire to make it fill the breaker to the range specified, if so how is this determined? Is there a #10 to #8 ferrule which could be used to correct this issue?

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Old 05-21-2011, 02:35 PM   #2
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Condensor Unit Wiring issues with Square D QO Breaker


Check the side of the breaker for the proper wire size range. I suspect a misprint.

You should not need to pigtail. You especially do not want to add filler material to the wire clamp.

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Old 05-21-2011, 05:38 PM   #3
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Condensor Unit Wiring issues with Square D QO Breaker


Same wire range listed on breaker as on website and materials furnished with new breaker. Does this mean I have to upgrade entire cable now to #8?
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Old 05-21-2011, 09:42 PM   #4
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Condensor Unit Wiring issues with Square D QO Breaker


The listing is the max size wire the termals will allow on the breaker.
The #10 is fine.
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Old 05-22-2011, 12:59 AM   #5
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Condensor Unit Wiring issues with Square D QO Breaker


Quote:
Originally Posted by jbfan View Post
The listing is the max size wire the termals will allow on the breaker.
The #10 is fine.
listed for #8-2, could this mean that it won't accept smaller than 8?
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Old 05-22-2011, 01:04 AM   #6
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Condensor Unit Wiring issues with Square D QO Breaker


if it makes you feel better pigtail a short piece of larger (8) wire to make transition
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Old 05-22-2011, 01:16 AM   #7
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Condensor Unit Wiring issues with Square D QO Breaker


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if it makes you feel better pigtail a short piece of larger (8) wire to make transition
I thought my question was a bit more valid than that answer, SatC.
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Old 05-22-2011, 01:59 AM   #8
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Condensor Unit Wiring issues with Square D QO Breaker


apologies, I was addressing my comments to the OP.
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Old 05-22-2011, 06:29 AM   #9
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Condensor Unit Wiring issues with Square D QO Breaker


Take another look at the codenser label. It might say 30 amp min and 40 amp max. The #10 would be fine for this installation.
You can size the circuit based on the min amp requirement.
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Old 06-04-2011, 10:39 PM   #10
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Condensor Unit Wiring issues with Square D QO Breaker


Sorry to hit on this again, but I did some more research, and it appears my initial assumption about the 40 Amp QO 2 pole breakers was right and others may want to avoid this situation using either a different brand of breaker or by using larger than required wire sizes.

In summary -- I had a question about the Air Conditioning Condensor unit wiring. The system I have specifies, on a stamped nameplate, a minimum circuit ampacity of 30 amps. The unit also states that the minimum HACR circuit breaker should be 40 amps. I understand that this is permitted by Article 440 in the 2008 NEC.

The unit is wired using 10 guage copper, again this is acceptable by Article 440. The breaker is a Square D QO240 (40 AMP, 2 pole) unit which is rated as an HACR breaker. Square D litterature states that this breaker can accomodate wire sizes 8-2 AL/CU.

Use of a #10 wire on this breaker appears to be a violation of the breaker's wire termination capacity.

Quote:
Originally Posted by Jim Port View Post
Check the side of the breaker for the proper wire size range. I suspect a misprint.

You should not need to pigtail...
Quote:
Originally Posted by sirsparksalot View Post
listed for #8-2, could this mean that it won't accept smaller than 8?
Quote:
Originally Posted by jbfan View Post
The listing is the max size wire the termals will allow on the breaker.
The #10 is fine.
The breaker says the wire range is #8-2, The website says the wire range is #8-2, and I emailed Square D (Sherry Glass, Schneider Electric, North America, Senior Product Support Specialist - Distribution Equipment) who confirmed the wire range is #8-2 and that a #10 wire can not be legally used with this breaker. She stated that I needed to install a pigtail or preferably a #8 cable to a transition outside the circuit breaker box.

Quote:
Originally Posted by Saturday Cowboy View Post
if it makes you feel better pigtail a short piece of larger (8) wire to make transition
Yes, it does make me feel better to do the job right -- to follow the code requirements. But this should be done with a transition even if I really didn't want to do it since it is a code issue!

An inside pigtail might look like "sloppy" workmanship, and be "corrected" by a future workman by eliminating the pigtail. An outside connection at a new junction box might cause an inspector to wonder "Who's this clown trying to fool -- running a legal wire from the breaker to this box then changing over to a smaller wire that is undersized for the size of the breaker?"

I think that either way, I should make up a laminated label with something like "Refer to Article 440, 2008 NEC for information on this wire transition." or something like that, then attach it to or near the junction box (or near the internal connection) where the transition is made.

Obviously there are a few other less than desirable options:
1. Change the entire circuit wiring over to #8 (expensive and unnecessary).
2. Use a different brand 40 Amp HACR rated breaker that is legal to use with #10 wire. (Too late to change without changing everything or installing an unnecessary sub-panel)

So my question now is should a short pigtail be used within the electrical panel (discouraged by Square D) or should a longer piece of #8 cable be run to a junction box outside the panel where the transition should be made?
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Old 06-04-2011, 11:55 PM   #11
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Condensor Unit Wiring issues with Square D QO Breaker


Quote:
Originally Posted by Perry401 View Post
So my question now is should a short pigtail be used within the electrical panel (discouraged by Square D) or should a longer piece of #8 cable be run to a junction box outside the panel where the transition should be made?
I'd recommend about a 6-8" pigtail and wire-nut it inside the panel. This is easier to install and also allows for easy inspection of the wire nuts at a later date. Adding a box when splicing in the panel is perfectly allowable seems like a waste of time and money.

Personally, I would not install pigtails. I would double the stripped conductor back on itself tightly and land it on the breaker. That would be a minor listing violation, but in my (scientifically very well informed, but entirely unofficial and empirically unsubstantiated) opinion is less likely to fail eventually. Adding connections to a circuit always increases the chances of a failure, and wire nuts are not even a particularly reliable means of connection.
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Old 06-05-2011, 01:13 PM   #12
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Condensor Unit Wiring issues with Square D QO Breaker


Quote:
Originally Posted by Perry401 View Post
Sorry to hit on this again, but I did some more research, and it appears my initial assumption about the 40 Amp QO 2 pole breakers was right and others may want to avoid this situation using either a different brand of breaker or by using larger than required wire sizes.

In summary -- I had a question about the Air Conditioning Condensor unit wiring. The system I have specifies, on a stamped nameplate, a minimum circuit ampacity of 30 amps. The unit also states that the minimum HACR circuit breaker should be 40 amps. I understand that this is permitted by Article 440 in the 2008 NEC.

The unit is wired using 10 guage copper, again this is acceptable by Article 440. The breaker is a Square D QO240 (40 AMP, 2 pole) unit which is rated as an HACR breaker. Square D litterature states that this breaker can accomodate wire sizes 8-2 AL/CU.

Use of a #10 wire on this breaker appears to be a violation of the breaker's wire termination capacity.







The breaker says the wire range is #8-2, The website says the wire range is #8-2, and I emailed Square D (Sherry Glass, Schneider Electric, North America, Senior Product Support Specialist - Distribution Equipment) who confirmed the wire range is #8-2 and that a #10 wire can not be legally used with this breaker. She stated that I needed to install a pigtail or preferably a #8 cable to a transition outside the circuit breaker box.



Yes, it does make me feel better to do the job right -- to follow the code requirements. But this should be done with a transition even if I really didn't want to do it since it is a code issue!

An inside pigtail might look like "sloppy" workmanship, and be "corrected" by a future workman by eliminating the pigtail. An outside connection at a new junction box might cause an inspector to wonder "Who's this clown trying to fool -- running a legal wire from the breaker to this box then changing over to a smaller wire that is undersized for the size of the breaker?"

I think that either way, I should make up a laminated label with something like "Refer to Article 440, 2008 NEC for information on this wire transition." or something like that, then attach it to or near the junction box (or near the internal connection) where the transition is made.

Obviously there are a few other less than desirable options:
1. Change the entire circuit wiring over to #8 (expensive and unnecessary).
2. Use a different brand 40 Amp HACR rated breaker that is legal to use with #10 wire. (Too late to change without changing everything or installing an unnecessary sub-panel)

So my question now is should a short pigtail be used within the electrical panel (discouraged by Square D) or should a longer piece of #8 cable be run to a junction box outside the panel where the transition should be made?
Are you sure the nameplate didn't indicate minimum circuit ampacity 30A and not maximum HACR breaker 40A? I have never seen a nameplate where it states minimum breaker size. If infact it indicates maximum HACR breaker 40A, then install a 30A and see if it holds. Otherwise the wire will have to be replaced.

Is the breaker in the disco or in the panel? Is the disco a knife switch?
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Old 06-05-2011, 02:45 PM   #13
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Condensor Unit Wiring issues with Square D QO Breaker


Quote:
Originally Posted by electures View Post
Are you sure the nameplate didn't indicate minimum circuit ampacity 30A and not maximum HACR breaker 40A? I have never seen a nameplate where it states minimum breaker size. If infact it indicates maximum HACR breaker 40A, then install a 30A and see if it holds. Otherwise the wire will have to be replaced.

Is the breaker in the disco or in the panel? Is the disco a knife switch?
I have to agree with this reply. I just looked at the compressor I installed and it says Min Amps 23 and Max Breaker 30 Amps
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Old 06-05-2011, 03:08 PM   #14
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Condensor Unit Wiring issues with Square D QO Breaker


Many units state min and max cb size. It is not necceary to install a cb disconnect out by the condenser. You can use a nonfused disconnect providing your area allows it. If the 30 amp does not hold you can install a 40 without changing wire size.
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Old 06-05-2011, 03:22 PM   #15
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Condensor Unit Wiring issues with Square D QO Breaker


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Are you sure the nameplate didn't indicate minimum circuit ampacity 30A and not maximum HACR breaker 40A? I have never seen a nameplate where it states minimum breaker size.
Correct, the circuit ampacity sets the minimum wire size. The other (mca) sets the overcurrent protection size to allow the motor to start without tripping.

I guess you could infer that the breaker size is stated due to the minimum circuit size being specified.

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