Air conditioner service

[nickelec]

Im looking at a potential job and never had to do the calcs my self as of yet.

When you need to determine the size of a feeder for multiple split unit air conditioners. Do you just add up all the MCA's or are there demand factors I would assume not

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[LarryFine]

Gotta look at Art. 440.

 

[Coppersmith]

There might be a demand factor, but odds are all units will be on simultaneously. Do you want to have to redo the job because of an overloaded circuit?

 

[don_resqcapt19]

Since Article 440 does not directly address feeder circuits and and 440.3(A) says the rules in 430 apply unless modified by a rule in 440, you can use 430.62(A) for this.

 

[curt swartz]

The isn't a demand factor but you don't need to use the MCA's for all units. You can use the largest motor * 1.25 then add all the remaining FLA's to it.

Simple way is to use the MCA of the largest unit then get the FLA's from all the remaining motors that will be connected to the feeder.

 

[nickelec]

All units are the same size with mca of 37

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[curt swartz]

All units are the same size with mca of 37

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So........look at the nameplate of the units. Take the MCA of the first unit and add all the motor FLA's of the other units. This will be your minimum feeder size.