Amp Load for 4 Ton Heat Pump

[pamike]

I need to finish up some wiring in my new shop. I need to install a subpanel where the 4 Ton heat pump/AC unit will go. I may actually go with a hot air gas furnace but I want to size electric for the highest load, which would be a heat pump. Buddy said he needs 60 amps for outdoor unit and 60 amps for the air handler...?? Does that should right? All the info I see online says much less for air handler. Any input? I have a 3/4" conduit free but that's not going to fit 120 amps worth of electric...

 

[yeldogt]

Will it have backup heat strips? that's the high load.

 

[bonneyman]

For your locale the typical heat pump will need 2 or 3 strips. Each strip needs 20 amps. Do the math.

Most often the breaker for the heat pump/compressor section will be less than breaker feeding the strips. You can determine the breaker size for your unit by looking at the nameplate. It'll list the max fuse size for the unit. That's the amperage of the breaker you need to install.

 

[zmaxmotorsports]

You won't be running g the heat strip and heat pump at same time.
The heat strips are closer to 60a depending on what size you run,the heat pump shouldn't pull more than 20-30 amps when its running.

 

[Stuff]

You won't be running g the heat strip and heat pump at same time.

OP is in PA so likely will run both at same time. Also depending on how it is set up defrost mode turns on some of the coils.

 

[zmaxmotorsports]

OP is in PA so likely will run both at same time. Also depending on how it is set up defrost mode turns on some of the coils.

When do you run a heat pump and heat strips at same time?
If it's cold enough to need to heat strips you're generally past the point where the heat pump is of any use.

 

[yeldogt]

You want to get any BTU's out of the HP .. even if it can't satisfy the heat load. The heat strips are the auxiliary heat. The HP's BTU's are less expensive vs the resistance. So both run to satisfy the heat load at lower temps.

The output of early HP's dropped off at mild temps -- sometimes in the 40's -- vs what is possible today down past 0 degrees. Also, the earlier units did not have all the needed options to run in freezing temps.

My new unit does not have back up heat strips.

 

[eddieK]

When do you run a heat pump and heat strips at same time?
If it's cold enough to need to heat strips you're generally past the point where the heat pump is of any use.

There are two purposes for the heat strips -

The first is secondary or second stage heat.

The second is more important.

It is to energize the heat strips when the outdoor unit goes into defrost, this accomplishes two goals. When a heat pump goes into defrost it reverts to A/C...the indoor coil evaporates refrigerant (removes heat from the air) the strips provide heat during this time so you do not get cooling when you are calling for heat. The outdoor coil condenses refrigerant (it gets hot and evaporates the icing on the outdoor coil).

While the heat strips add heat to the indoor air it also adds heat to the refrigerant, to assist defrost, this dramatically speeds up defrost.

Typical 4 ton capacity system needs minimum 40 amp circuit to outdoor unit and max 60...

Indoor without strips (we have that sometimes in the right climate) 20 amp

With heat strips it can be as high as 70 amp...depending on what kilowatt strips you have installed.

 

[yeldogt]

There are two purposes for the heat strips -

The first is secondary or second stage heat.

The second is more important.

It is to energize the heat strips when the outdoor unit goes into defrost, this accomplishes two goals. When a heat pump goes into defrost it reverts to A/C...the indoor coil evaporates refrigerant (removes heat from the air) the strips provide heat during this time so you do not get cooling when you are calling for heat. The outdoor coil condenses refrigerant (it gets hot and evaporates the icing on the outdoor coil).

While the heat strips add heat to the indoor air it also adds heat to the refrigerant, to assist defrost, this dramatically speeds up defrost.

Typical 4 ton capacity system needs minimum 40 amp circuit to outdoor unit and max 60...

Indoor without strips (we have that sometimes in the right climate) 20 amp

With heat strips it can be as high as 70 amp...depending on what kilowatt strips you have installed.

This is another benefit with the newer units -- since they only go into defrost when needed vs the old style of timed defrost ... this is often very infrequent. Mine was spinning away in freezing rain and never had a problem -- they also are able to defrost very quickly.

 

[Brian_WK]

There are two purposes for the heat strips -

The first is secondary or second stage heat.

The second is more important.

It is to energize the heat strips when the outdoor unit goes into defrost, this accomplishes two goals. When a heat pump goes into defrost it reverts to A/C...the indoor coil evaporates refrigerant (removes heat from the air) the strips provide heat during this time so you do not get cooling when you are calling for heat. The outdoor coil condenses refrigerant (it gets hot and evaporates the icing on the outdoor coil).

While the heat strips add heat to the indoor air it also adds heat to the refrigerant, to assist defrost, this dramatically speeds up defrost.

Typical 4 ton capacity system needs minimum 40 amp circuit to outdoor unit and max 60...

Indoor without strips (we have that sometimes in the right climate) 20 amp

With heat strips it can be as high as 70 amp...depending on what kilowatt strips you have installed.

I support this statement.

Brian