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Old 12-13-2010, 08:59 AM   #1
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Question About A/C Wiring


I recently had a new Condensor installed in the same location as my old Condensor. When the original unit was installed the electrical was run in rigid conduit along some joists in the basement to the panel. I am now finishing my basement and want to remove the portion of the conduit that hangs on the bottom of some of the joists. There are two juntion boxes (one that was used to pull and one that has splices in it) that I opened up and I noticed that the exiting wiring was either 8 gauge or 6 gauge. I checked the existing breaker and it was a 50 amp (which I believe is too large for my new condensor (should be 30 amp correct?)). My question is - can I install 10 gauge "romex" from a new 30 amp breaker to one of the junction boxes and splice the 10 gauge "romex" with the larger 8 gauge or 6 gauge wire? Is this acceptable?

Thanks in advance!

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Old 12-13-2010, 09:02 AM   #2
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Question About A/C Wiring


You should really verify the minimum circuit ampacity needed to determine the proper wire size. You can check the nameplate on the unit. Look for minimum circuit ampacity and also maximum breaker or fuse size.

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Old 12-13-2010, 09:33 AM   #3
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Ok, thanks, I will do that.

If it requires a maximum 30 amp breaker is it acceptable to wire it that way (i.e. have a 10 gauge wire (which from my understanding is the size needed for 30 amp) spliced with an 8 gauge or 6 gauge wire in a junction box that leads to the condensor?
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Old 12-13-2010, 09:36 AM   #4
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Question About A/C Wiring


As long as the splice is made properly, you can always use bigger wire than what is required.
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Old 12-13-2010, 09:45 AM   #5
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Question About A/C Wiring


Thanks. I checked the miniumum circuit ampacity and it is 17.1 amps
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Old 12-13-2010, 09:45 AM   #6
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Question About A/C Wiring


In addition to what Andy said, the splice must remain permanently accessible and be contained in a properly sized junction box. The box also needs to be grounded if metal.
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Old 12-13-2010, 09:46 AM   #7
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Question About A/C Wiring


You should also verify whether your jurisdiction allows the use of NM cable.
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Old 12-13-2010, 09:59 AM   #8
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Question About A/C Wiring


Quote:
Originally Posted by bengal21 View Post
Thanks. I checked the miniumum circuit ampacity and it is 17.1 amps
You also need to check the nameplate for the max breaker size.
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Old 12-13-2010, 10:40 AM   #9
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Question About A/C Wiring


Given the 17.1 MCA you could run #12.
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Old 12-13-2010, 11:52 AM   #10
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Question About A/C Wiring


The goodman site says that the unit has maximum overcurrent protection of 25.
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Old 12-13-2010, 12:32 PM   #11
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You will need to change the breaker to satisfy the 25 amp requirement.
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Old 12-13-2010, 12:45 PM   #12
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Can I still run #12 with changing the breaker to 25?
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Old 12-13-2010, 01:04 PM   #13
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Question About A/C Wiring


Yes, you can use the #12 with the 25 amp breaker. The sizing rules are different for motor loads like A/C.

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