Heat pump package with heater coils.

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dec

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A new central air/heat pump package list the minimum circuit ampacity @ 33 amps (240vac 1ph). The heater package minimum circuit ampacity is 75 amps. There is an existing cable which served the old unit marked SE style U Type XHHW-2. It also has markings AWG 6-1 & AWG 8. Can this cable be used for the new unit since it is XHHW-2 ?
ALSO....the AC/Heat pump part is listed at 33amps. The old feed used # 10 NM cable. Using the 60 deg column for NM cable would mean I have to use #8 for this feed....right ?
 

kwired

Electron manager
Location
NE Nebraska
NM cable does need to be 8AWG for reasons you mentioned.

SE cable used for interior wiring must also be sized per the 60Deg ampacity. 75 amps will require at least 3AWG copper for 60 deg conductor.
 

dec

Member
A new central air/heat pump package list the minimum circuit ampacity @ 33 amps (240vac 1ph). The heater package minimum circuit ampacity is 75 amps. There is an existing cable which served the old unit marked SE style U Type XHHW-2. It also has markings AWG 6-1 & AWG 8. Can this cable be used for the new unit since it is XHHW-2 ?
ALSO....the AC/Heat pump part is listed at 33amps. The old feed used # 10 NM cable. Using the 60 deg column for NM cable would mean I have to use #8 for this feed....right ?

Service panel is located just inside the back door and about 10 ft. from the outside unit. Can the 90 C rating be used in this case ?
 

kwired

Electron manager
Location
NE Nebraska
Service panel is located just inside the back door and about 10 ft. from the outside unit. Can the 90 C rating be used in this case ?

90 deg can not even be used for raceway and installed conductors. Terminal temp ratings will be either 60 or 75Deg. Almost all new equipment will be 75. 90 deg ampacities can only be used for a starting point for ambient temp/number of conductors in a raceway derations. Final conductor size must still be at least that of 60 or 75 deg column - which ever applies to the installation.
 
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