Adding a heat pump is my wiring/breaker sufficient?

Spinachetr

Active member
Jun 8, 2014
30
Walkersville, MD
#1
I'll start off by saying that I will have a qualified electrician & pool service professional do the installation of the heat pump. I'm just doing research for costs involved which include possibly beefing up the existing pool wiring.

I'm looking at the Pentair UltraTemp 120k btu heat/cool heat pump (recommended 50amp breaker)
http://images.inyopools.com/cloud/documents/ultrafloom.pdf

The breaker in my house that supplies the subpanel at the pool equipment has a 60amp breaker. I have a pool light, 1hp FloPro pump (less than 8 amp draw) , and an AquaPure E1 SWG (less than 2 amp draw) hooked up to that panel. There are still slots available in the sub-panel.

Would the 60 amp breaker in the main panel be enough for the new heater and existing equipment? Or should I expect that I'll need to go bigger? Thanks in advance.
 

AftonJeeper

Bronze Supporter
May 11, 2017
1,147
Twin Cities, MN
#2
Yes. Technically you can add a 100 amp sub panel off of a 100 amp panel. So as long as you install a 50 amp breaker/fuse out at the equipment you will be fine.

Only issue you might run into is if everything pulls it max amps at once, that could trip the 60 amp breaker.
 

CJadamec

TFP Expert
Apr 29, 2016
2,194
Quaker Hill, CT
#3
You need more information to answer that question. You need to know the length of the wire run and what gauge and type of wire was used for the run to your pool panel. My first guess is to say no your 60 amp panel probably isn't enough. The last thing you want to do is under-volt your heat pump or pool motor because you don't have enough power available.
 

Spinachetr

Active member
Jun 8, 2014
30
Walkersville, MD
#5
Hi, thanks for the replies. The total run is about 50 feet and yes I have 6agw wire. At the subpanel there are 2 20amp breakers. 1 for the pool light and the other one for the SWG and pump. Thoughts now? Thanks again
 

CJadamec

TFP Expert
Apr 29, 2016
2,194
Quaker Hill, CT
#8
If you run the voltage drop calculations on that run at 60 amps draw you actually need #4 wire. Your current wiring run is borderline acceptable at 50amps. Just looking at the maximum current for the wire is not all there is to a circuit like this one. Following opinions and not calculations is how you burn out motors and fry control boards.
 

The dog

Well-known member
Apr 17, 2017
147
sacramento CA
#9
I did say to double check with your electrician.

I just looked at the specs on your heat pump. Looks like they want a 70 amp fuse. Or 50 amp breaker. So it must pull 45 or so amps at startup. I guess it is borderline like CJ said. (Depending not real loads from your other equipment).

Here's the ampacity chart. You may indeed need larger wire from your main panel to your sub panel. What's your main panel look like?

And I disagree with you CJ. You can run 50 amps all day long with 3-#6 and a #8 ground.

 

CJadamec

TFP Expert
Apr 29, 2016
2,194
Quaker Hill, CT
#10
It's called voltage drop calculations. The longer the wire run with high amp draw the bigger the wire you need. 3% voltage, or 6 volts for 230v, drop is the max acceptable for this type of circuit. At 50 amps and 50 feet your #6 wire has a voltage drop of 2.3%. I also assumed your wire run is in conduit and not direct burial. Direct burial cable has a lower allowed ampacity.
The net effect is that everytime the heat pump turns on you will drop voltage on your wire which is very damaging to equipment. Like I said before the wire ampacity chart is only the starting point when designing a circuit you aren't allowed to exceed those numbers on wire it's not what that wire can carry all the time.
 

jza1736

Silver Supporter
Apr 21, 2017
536
Greenlawn, NY
#12
The breakers are designed with a tolerance. If you pull 65 amps from a 60 amp breaker it would trip in a minute or two, or maybe even longer. If it was 70 amps it would be a minute or less. If it was 100 amps, a second or less. They are designed that way for the in rush current when you turn things on. Motors especially.
 

JamesW

TFP Expert
Mar 2, 2011
12,840
#14
A 60 amp breaker has an allowable trip time of up to 6 minutes at 120 amps (200% of rated current).

It does not have to trip until the current hits 81 amps (135% of its rated current.). For breakers up to 50 amps, the allowable trip time is up to 1 hour at 135%.

http://goodsonengineering.com/wp-content/uploads/2011/08/CircuitBreakerMyths_web.pdf

At 100% of rated amps, the breaker should not trip. The breaker can trip between 100% and 135%, but it doesn't have to. It has to trip at 135%. It can trip between 0 seconds and 1 hour at 135%, but it can take up to 1 hour.

Different manufacturers have different trip times for the 135% and 200% limits that are usually less than the maximum allowable trip times.
 

Spinachetr

Active member
Jun 8, 2014
30
Walkersville, MD
#17
Just wanted to provide an update to close this out. I did order the heat pump I indicated and had a professional pool installer/electrician do the install. There were no changes to the wire size or breaker from my main panel. Knock on wood, but the heat pump has been running without issues (no tripped breakers) for the past week. The first day it ran for about 8 hours straight to bring the pool temp up from 75 to 86 degrees.