AC unit

[DARUSA]

The name plate require a MCA of 27amps (#10 THHN) and MCB of 40 amps, how the nameplate allow me to use a CB I will install a non-fuse DS at the unit.My question is Can I use a 30 amps DS or due to the 40amps MCB this have to be a 60amps DS? It is a indoor unit.

 

[augie47]

I this case I would say you would have to use a 60 amp based on 440.32 which requires a rating of 115% of the nameplate branch circuit selection.
However there is an exception that you might check out.

 

[infinity]

I this case I would say you would have to use a 60 amp based on 440.32 which requires a rating of 115% of the nameplate branch circuit selection.
However there is an exception that you might check out.

Is that the correct code section?

 

[DARUSA]

Is that the correct code section?

yes,It is.
440.32 Single Motor-Compressor.
Branch-circuit conductors supplying a single motor-compressor shall have an ampacity not less than 125 percent of either the motor-compressor rated-load current or the branch-circuit selection current, whichever is greater.
For a wye-start, delta-run connected motor-compressor, the selection of branch-circuit conductors between the controller and the motor-compressor shall be permitted to be based on 72 percent of either the motor-compressor rated-load current or the branch-circuit selection current, whichever is greater.
FPN: The individual motor circuit conductors of wye-start, delta-run connected motor-compressors carry 58 percent of the rated load current. The multiplier of 72 percent is obtained by multiplying 58 percent by 1.25.

 

[augie47]

Is that the correct code section?

No. I should have proof read better 440.12

Thanks

 

[DARUSA]

No. I should have proof read better 440.12

Thanks

I can't understand 440.12. Can you explain!!!

 

[DARUSA]

Name-Plate

Name-Plate

This is one of the units nameplate

 

[augie47]

The way i read it, the disconnecting means must have a rating of 115% of the nameplate rated load current or branch circuit selection current, which in your case is 27 amps (in my opinion). In your situation, I don't know the "rated load current", but since the branch circuit current takes us beyond 30 amps and the next level is 60, I would think you would be covered.

The exception might let you use the 30amp if it has a high enough horsepower rating, but as you can see from 440.12(A)(3) making that determination is a tedious procedure, but a qucik look at that data looks like the switch would need a 5HP rating to qualify.

 

[DARUSA]

This picture is better.
Shows 28.1 MCA and 45amps MCB

 

[curt swartz]

DARUSA

This unit is not a single motor compressor, it is has multiple motors (1-compressor and 1-fan). The 28.1 is the minimum branch circuit rating not the nameplate rating. The name plate ratings are 18.3 for the compressor and 5.3 for the fan. The branch circuit rating includes both of these loads plus 25% of the largest motor. The disconnect is sized to according to 440.12(B). I agree with the answer Gus came up with.