HVAC conductor sizing

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nizak

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MCA of unit is 120A,MOCP is listed at 150A. This is a 2 stage cooling unit w/ 2 compressors.Am I correct in assuming that 1/0 CU (75C) listed at 150A would be the correct conductor size for this application? (120Ax125%=150A).Have done very little with HVAC equip in the past, thanks for any help.
 
augie47

augie47

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If the unit nameplate states 120 MCA, you could actually use a #1 75? conductor as long as neither termination calls for a 60? termination or there are other dertaing factors..
 
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nizak

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Does the 125% factor only apply if it is a single motor compressor?Would fuse size in disconnect be found in 440.12 (A) (1)?
 
Dennis Alwon

Dennis Alwon

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Unless the unit states max fuse then you can do not need fuses at the disconnect unless it is specified. The max OCPD is done for you at 150 amps. The unit has overload protection to protect the wire so that is not an issue. The breaker is for short circuit and ground fault.

440.12(A)(1) is for the disconnect. You need to look at section III in 440
 
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