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Old 01-15-2012, 07:37 PM   #1
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Breakers, wire size and new heat pump


Hello all,

More than a year ago I had a new HE heat pump and air handler put in. The previous heat pump and air handler was wired with what I think is #2 wire connected to the main panel via a gang 100 amp breaker (100 amp on each leg).

The new air handler has a box on the side that has the #2 wire coming into it and it has 2 breaker, one is 30 amps, the other is 60 amps.

I think (not sure) the new air handler has a 15Kwatt electric auxiliary heating coil in it. I know the heat pump is 4.5 tons.

My questions:
Is #2 wire necessary?
Is the 100amp gang breaker necessary?

I am planning to finish my basement. The way the #2 wire is ran is creating a little problem with how I want the bulkhead around the heat ducts. I intend on getting an electrician in to have a look-see and relocate the wire accordingly and clean things up. I am asking here so I will know if the electrician is trying to up charge me.

Thank you,
Fred


Last edited by ACR_SCOUT; 01-15-2012 at 08:59 PM.
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Old 01-15-2012, 08:42 PM   #2
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Breakers, wire size and new heat pump


What does the manufacturer's literature say regarding breaker sizing? Usually they will specify exactly what breaker is required, and sometimes what wire size is required. How long is the run from the panel to the unit?

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Old 01-15-2012, 08:43 PM   #3
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Originally Posted by mpoulton View Post
What does the manufacturer's literature say regarding breaker sizing? Usually they will specify exactly what breaker is required, and sometimes what wire size is required. How long is the run from the panel to the unit?
I'd have to dig out the literature on that air handler.

The run is just around 30 to 35 feet.
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Old 01-15-2012, 08:54 PM   #4
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Breakers, wire size and new heat pump


Quote:
Originally Posted by ACR_SCOUT View Post
Hello all,

More than a year ago I had a new HE heat pump and air handler put in. The previous heat pump and air handler was wired with what I think is #2 wire connected to the main panel via a gang 100 amp breaker (100 amp on each leg).

The new air handler has a box on the side that has the #2 wire coming into it and it has 2 breaker, one is 30 amps, the other is 60 amps.

I think (not sure) the new air handler has a 15Kwatt electric auxiliary heating coil in it. I know the heat pump is 4.5 tons.

My questions:
Is #2 wire necessary?
Is the 100amp gang breaker necessary?

I am planning to finish my basement. The way the #2 wire is ran is creating a little problem with how I want the bulkhead around the heat ducks. I intend on getting an electrician in to have a look-see and relocate the wire accordingly and clean things up. I am asking here so I will know if the electrician is trying to up charge me.

Thank you,
Fred
Get those heat ducks out of there. They make a lot of noise. The heating ducts should stay.
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Old 01-15-2012, 09:00 PM   #5
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Get those heat ducks out of there. They make a lot of noise. The heating ducts should stay.
Cute. Thanks. Good thing it came from you and not my English teaching wife. (I'd hate being her student).
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Old 01-15-2012, 09:38 PM   #6
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Breakers, wire size and new heat pump


There should be a data plate right on the unit. Look for minimum circuit ampacity.
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Old 01-15-2012, 09:40 PM   #7
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There should be a data plate right on the unit. Look for minimum circuit ampacity.
There is however it is a table with a bunch of different models and configurations. I didn't take the time to see if there was a specific model number on the unit somewhere.

Once I figure this out, what is it telling me? Is it telling me the breaker for the main panel or the breakers for the panel on the side of the air handler?
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Old 01-16-2012, 12:54 AM   #8
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Breakers, wire size and new heat pump


Quote:
Originally Posted by ACR_SCOUT View Post
Hello all,

More than a year ago I had a new HE heat pump and air handler put in. The previous heat pump and air handler was wired with what I think is #2 wire connected to the main panel via a gang 100 amp breaker (100 amp on each leg).
The heat pump and the air handler are on the same circuit? Or is this circuit for the air handler only? The heat pump itself should be on its own circuit.

Quote:
The new air handler has a box on the side that has the #2 wire coming into it and it has 2 breaker, one is 30 amps, the other is 60 amps.

I think (not sure) the new air handler has a 15Kwatt electric auxiliary heating coil in it. I know the heat pump is 4.5 tons.
This box is part of the air handler, right? My guess is that, if it is in fact a 15 kW system (and it may be, with a heat pump of that size), it has a 10 kW heat strip and a 5 kW strip, perhaps staged in some fashion. The 10 kW strip would be on the 60A breaker, and probably everything else in the air handler -- the 5 kW strip, the blower, and the low voltage -- are on the 30A breaker.

Quote:
My questions:
Is #2 wire necessary?
I don't have a chart in front of me, but I think that is the right size. As other posters have said, if the data panel on the air handler gives a wire size, you have to use that size regardless.

Quote:
Is the 100amp gang breaker necessary?
Yes, absolutely. It protects the circuit between the panel and the air handler.
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Old 01-16-2012, 04:21 AM   #9
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Let me ask it a different way. Could the 100 amp gang breaker be a smaller amperage thereby affording a smaller wire from the main panel to the air handler?
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Old 01-16-2012, 04:40 AM   #10
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yes you are right. just keep in mind that you have to read the criteria on the air handler to have the right size breaker on it to small and its going to keep triping and to big and it will be a lot harder to trip. the legnth of the wire run is important to the longer the run the bigger the wire but that doesn't matter in your case. ask the electrcian about this and you will be ok
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Old 01-16-2012, 05:13 AM   #11
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Breakers, wire size and new heat pump


IF that #2 wire is copper, then a 100 Amp breaker on the feeder is fine.

IF it's aluminum, then you need to change the feeder breaker to a 90.
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Old 01-16-2012, 10:43 AM   #12
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Breakers, wire size and new heat pump


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Originally Posted by ACR_SCOUT View Post
Let me ask it a different way. Could the 100 amp gang breaker be a smaller amperage thereby affording a smaller wire from the main panel to the air handler?
Let's see... 15 kW @ 240V is about 62 amps. Add in a few amps for the blower and other circuitry, and you could breaker it at 75 amps. Unfortunately, that only gets you down to #4, which probably doesn't help your situation very much.

Presuming that your air handler does in fact have two heat strips, you might could get permission to run a smaller conductor if you disconnect one of them. I had to do this with an air handler in my house (two 5 kW strips) because the electrician who did the rough only pulled a #8 circuit, and it would have been far too much trouble to redo it. The inspector made me disconnect and remove the breaker for the un-powered strip.

Last edited by fa_f3_20; 01-16-2012 at 10:46 AM.
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Old 01-16-2012, 10:01 PM   #13
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Breakers, wire size and new heat pump


Watch out... the heatpump is a hermetic refrigerant motor compressor. NEC 440 applies. Please refer to that and the manufacturer's plate on the unit to verify that your branch circuit is correctly sized and also has the correct disconnecting means.
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Old 01-17-2012, 03:20 AM   #14
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Quote:
Originally Posted by fa_f3_20

Let's see... 15 kW @ 240V is about 62 amps. Add in a few amps for the blower and other circuitry, and you could breaker it at 75 amps. Unfortunately, that only gets you down to #4, which probably doesn't help your situation very much.

Presuming that your air handler does in fact have two heat strips, you might could get permission to run a smaller conductor if you disconnect one of them. I had to do this with an air handler in my house (two 5 kW strips) because the electrician who did the rough only pulled a #8 circuit, and it would have been far too much trouble to redo it. The inspector made me disconnect and remove the breaker for the un-powered strip.
Well it looks like I will need to run new #2 then. Other than the stiffness of the wire it should be fairly easy.

Thanks.
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Old 01-17-2012, 03:36 AM   #15
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Breakers, wire size and new heat pump


Quote:
Originally Posted by fa_f3_20

Let's see... 15 kW @ 240V is about 62 amps. Add in a few amps for the blower and other circuitry, and you could breaker it at 75 amps. Unfortunately, that only gets you down to #4, which probably doesn't help your situation very much.

Presuming that your air handler does in fact have two heat strips, you might could get permission to run a smaller conductor if you disconnect one of them. I had to do this with an air handler in my house (two 5 kW strips) because the electrician who did the rough only pulled a #8 circuit, and it would have been far too much trouble to redo it. The inspector made me disconnect and remove the breaker for the un-powered strip.
Well it looks like I will need to run new #2 then. Other than the stiffness of the wire it should be fairly easy.

Thanks.

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