breaker/wire info/heat pump

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floatr

Member
Location
tn
if i have a 5 ton 2 stage unit what size on the disconnect/fuses and the breaker is required..(ita a double 100 amp breaker going to disconnect )and can i go with 2 sets of 60 amp fuses -one set for heat and other for air-even if its 100/100 ?
i know wiring to heat and air can be a bit different to home wiring/breakers .

-any additional info is appreciated.

thanks
 

kwired

Electron manager
Location
NE Nebraska
if i have a 5 ton 2 stage unit what size on the disconnect/fuses and the breaker is required..(ita a double 100 amp breaker going to disconnect )and can i go with 2 sets of 60 amp fuses -one set for heat and other for air-even if its 100/100 ?
i know wiring to heat and air can be a bit different to home wiring/breakers .

-any additional info is appreciated.

thanks
In order to more accurately answer your questions we need to know name plate data from your unit(s). In particular MCA and MOCPD. Also clarification on exactly what you mean when you say double 100 amp - do you mean it is a two pole breaker or that there are 2 breakers?
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
The one for heat, one for air statement can be interpreted several ways.
Usually a heat pump will have one circuit for the compressor and air handler, which will both heat and cool, and a separate circuit (or circuits) for electric resistance heating which is mainly used when the outside air temperature is so low that the heat pump is no longer effective.
The sizes of both types of circuit will be part of the nameplate and installation instructions and may not be the same for both circuits.
Just knowing 5 ton is not enough.
 

floatr

Member
Location
tn
it says mca-43.4 and mop-70
total unit amps-36.6

the set up at disconnect has a side for ac compressor with 1 100 amp and 2 slots for fuses

the other side also has same set up for 2 fuses ,supply is 1 100 amp ...is for heat /strip--9.7 kw its mca on chart says 80 and mop 90(says 9.7 kw/32.4 btu)
 

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kwired

Electron manager
Location
NE Nebraska
it says mca-43.4 and mop-70
total unit amps-36.6

the set up at disconnect has a side for ac compressor with 1 100 amp and 2 slots for fuses

the other side also has same set up for 2 fuses ,supply is 1 100 amp ...is for heat /strip--9.7 kw its mca on chart says 80 and mop 90(says 9.7 kw/32.4 btu)
Heat pump info seems reasonable, but 80 MCA for a 9.7kW heat strip doesn't make any sense, unless there is other loads besides a fractional to 1 hp motor involved. 9.7kW @240 volts is only 40.4 amps would likely work out on a 50 amp breaker but they may go up one more step to 60 amp only because of the extra .4 amps (if it were exactly 40 amps the 125% factor puts you right at 50 amps for overcurrent protection).

How do you intend to put 70 or 90 amp fuses if needed into a 60 amp fuseholder?;)

I take it you are saying this dual circuit fuse unit has a 100 amp feeder to it?
 

floatr

Member
Location
tn
There are 2 seperate 100 amps ,one to each side..
On chart I see also ..mca 43/49 and mop 45/50..at hkr 10 charts for heat kit
 
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Smart $

Esteemed Member
Location
Ohio
There are 2 seperate 100 amps ,one to each side..
On chart I see also ..mca 43/49 and mop 45/50..at hkr 10 charts for heat kit
Those appear to be 2-pole 60A fused disconnects. Being fused disconnects, the only bearing the supply circuit rating has is that it is rated not less than the size fuses you put in the disconnects.

Even though the MOCP of the compressor is 70A, the max fuse you can put in there is 60A.

The slash ratings for the heater lit are 240/208. Assuming a 120/240 system, you use the left rating. The load side wires appear to be too small... but required minimum wire size will depend on termination temperature ratings on both ends.... 60 or 75?C???
 

floatr

Member
Location
tn
its the 6/2 copper wire after fuses and the al #2 coming in.had 60s in from last unit-1 was time delayed for ac
 

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floatr

Member
Location
tn
will the 2 pairs of 60 amps with the # 6 wire be ok since it doesnt continually pull 70 but for a moment if that?
 

Smart $

Esteemed Member
Location
Ohio
its the 6/2 copper wire after fuses and the al #2 coming in.had 60s in from last unit-1 was time delayed for ac
Pictures, lacking 3-dimensional perspective, make it hard to gauge wire size. Only appear to be #8 at best to me, which is good for 50A if terminations at both ends are rated for 75?C and ambient doesn't ampacity to less than MCA.

Time delay fuses (TDFs) for motor applications cannot typically be rated as high as non-time delay, but I don't know of any Code provision for "derating" TDFs used in an MOCPD scenario. Given your MOCPD is 70A, you may want to consider putting in a second... provided no one points out a restriction I'm not aware of.
 

kwired

Electron manager
Location
NE Nebraska
will the 2 pairs of 60 amps with the # 6 wire be ok since it doesnt continually pull 70 but for a moment if that?
Unless your nameplate specifies a minimum, it will be fine if it allows the unit to start. The unit likely pulls more then 70 amps - with a unit amps of 36 I wouldn't be surprised if it draws over 150 amps - but only for a "moment" when starting, 70 is just one with trip curve they have determined would likely hold in worst case conditions.
 

floatr

Member
Location
tn
And I am 100% sure both are 6/2-- I bought/ ran the new wire to hook up heat kit an the other is identicle,I compared before reattatching both .

I'll keep time delay for Ac side only .
 
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floatr

Member
Location
tn
i did a amp draw test(clamp meter) after installing the heater kit ,when running it was a 45 on each line. -is 45 a normal draw for the circuit to it ,i ran 6/2 and heater is 9.5kw..also do i need to stay with the 60 amp fuses ?

i also oddly wasnt able to get a reading off the main 6/2 incoming to A/C off the other set of 60s,i was trying to measure amp draw -any ideas as to why during the run it didnt pick up much as to amps(was 1.5 maybe 3.0)?

any info is appreciated
 
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kwired

Electron manager
Location
NE Nebraska
i did a amp draw test(clamp meter) after installing the heater kit ,when running it was a 45 on each line. -is 45 a normal draw for the circuit to it ,i ran 6/2 and heater is 9.5kw..also do i need to stay with the 60 amp fuses ?

i also oddly wasnt able to get a reading off the main 6/2 incoming to A/C off the other set of 60s,i was trying to measure amp draw -any ideas as to why during the run it didnt pick up much as to amps(was 1.5 maybe 3.0)?

any info is appreciated
9.5kW = 9500W. 9500W / 240 V = 39.58 A. You possibly have a blower pulling some current as well, but 5 amps seems a little on the high side for a blower in most applications. Otherwise the general rule would be 125% the load for overcurrent protection. So if the load is 45 amps add another 25% and you have 56.25 round up to next standard size device of 60 amps.

As for the other circuit with the compressor - the compressor was not fully loaded. If this were a heat pump 3.0 amps could be possible especially in heat mode with low ambient temp. The compressor is loaded more when it is moving more heat, in low ambient temp it is not moving as much heat as it is designed to move at full load rating. Seems a little low of a reading but I don't know what capacity of unit you have or if it is multi stage, variable speed, etc.
 

floatr

Member
Location
tn
its a 2 stage-since i had heat in aux mode before any wire was run to heater kit.im going by the paper inside since nameplate is difficult to read.

what else besides the compressor can i look at to tell exact size of unit..

here is a check out paper i saw inside..

i want to be 100% sure on size as to fuses for ac side 60s in it now.
i guess it would also be wise to have both ac side fuses as delayed to protect better - only 1 is the delayed in earlier pic
 

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GeorgeB

ElectroHydraulics engineer (retired)
Location
Greenville SC
Occupation
Retired
its a 2 stage-since i had heat in aux mode before any wire was run to heater kit.im going by the paper inside since nameplate is difficult to read.

what else besides the compressor can i look at to tell exact size of unit..

here is a check out paper i saw inside..

i want to be 100% sure on size as to fuses for ac side 60s in it now.
i guess it would also be wise to have both ac side fuses as delayed to protect better - only 1 is the delayed in earlier pic

Google is your friend. With that part number, I found it to be an Amana labeled package unit. Their website was easy to traverse, and I find that it is a 15SEER 60,000BTU unit, 36.6 total unit amps, 43.4 MCA, 70 max circuit.

Link to the manual, http://www.amana-hac.com/Portals/1/pdf/SS/SS-APH15M.pdf
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Google is your friend. With that part number, I found it to be an Amana labeled package unit. Their website was easy to traverse, and I find that it is a 15SEER 60,000BTU unit, 36.6 total unit amps, 43.4 MCA, 70 max circuit.

Link to the manual, http://www.amana-hac.com/Portals/1/pdf/SS/SS-APH15M.pdf

George:
From what I can tell, that addressees the unit without taking any auxiliary heat into account.
Am I correct ?
 

suemarkp

Senior Member
Location
Kent, WA
Occupation
Retired Engineer
It would have to be. This is a package unit, where the compressor and aux heat are in the same box (has giant air duct inlets and outlets on it, but the unit goes outside). The instructions say the heat kit has the instructions for wiring and wire size. I'm thinking they have their own sets of wire lugs and are fed by a second circuit. They offer 4 or 5 different heat kits, and each will require a different size circuit.

But I don't see why he'd be getting more than 40A on a meter with a 10KW kit. Perhaps the fan gets it power from this same circuit, but the wiring diagram isn't clear. There are both Evaporator motor and Condensor motor on the wiring diagram for the unit (no heat strips are shown on that diagram).
 

floatr

Member
Location
tn
Thanks for the suggestions.
if i change out the fuses on the main ac side(currently 60s also) ,not the 2 for the heat side, over to the 40s -that the 3 ton calls for will that pop them if its a 5 ton?-there for telling me its a 5..

here are the specs the unit pulls if 5 ton

min circuit ampacity 43.4

max overcurrent protection 70

total unit amps 36.6


-any info is appreciated
 
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