Minimum Wire Size for OCPD to Motor

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ken44

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I have a stand-alone A/C unit(Liebert) it has a minimum OCPD requirement of 25.4 amps but the unit itself has a built in 100 amp OCPD which is itself fed from a 30 amp circuit(from the panelboard) and is fed with #10 AWG. The main fan motor has an FLA of 11.0 amps. There are two other identical units which have # 4 AWG and #6 AWG.
The unit tag says (maximum 50 amp OCPD.)
What size wire is correct for this application?
 
Re: Minimum Wire Size for OCPD to Motor

Originally posted by ken44:
I have a stand-alone A/C unit(Liebert) it has a minimum OCPD requirement of 25.4 amps
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I think you may be reading the tag wrong or it has been made wrong.

Most unit tags have a "Minimum Circuit Ampacity" (MCA) Rating and a "Maximum Overcurrent Device" rating.

25.4 sounds like a MCA rating and that would mean a 12 AWG would be acceptable.

You need to look at the tag to find the overcurrent device type and size.
 
Re: Minimum Wire Size for OCPD to Motor

Wire for the minimum, protect at the maximum.

So, if the minimum branch circuit rating is 25.4-ampere, Table 310.16 permits #10, 75 degree conductors. The OCPD can be nameplate or in this case 50-ampere. :)

I have no clue what the 100-ampere breaker is all about? :confused:
 
Re: Minimum Wire Size for OCPD to Motor

Oops :eek: I read that as 24.5 not 25.4, use 10 AWG minimum as Bryan has said.

[ April 26, 2004, 06:50 PM: Message edited by: iwire ]
 
Re: Minimum Wire Size for OCPD to Motor

I can only assume that the 100 amp breaker has to do with in-rush current to prevent nuisance tripping. Other than that, I have no clue myself but all the units come that way from factory for some unknown reason.
 
Re: Minimum Wire Size for OCPD to Motor

Ken44,

If you could provide the exact model & serial number, I could obtain the proper factory requirements for you.

SBE
 
Re: Minimum Wire Size for OCPD to Motor

SBE
That is the one thing I didnt write down! I have made my decision, I am going to reuse the #10 and install a grounding conductor.
 
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