Wiring heat pump questions, and surge protection

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J

Juggernaut1103

0
Jul 24, 2015
54
STAMFORD, CT
Im having trouble finding the correct info on my heat pump through search on the web. I bought a used Aqua Comfort LS MBP-125 for $200 from a friends friend, it was used twice before they switched to propane. The manual provides little information. Im trying to plan ahead and get everything figured out in my head. I am an avid DIYer, I think i have all the correct info but i wanted to double check with the pros on TFP. From what i understand, this heat pump requires a 70amp breaker (does not have to be GFCI) RLA is 30.1 multiplied by 225%=67.725+(FLA)2.8= 70.525. I was really hoping i only needed a 50 or 60amp breaker. I have a 100amp sub panel in the shed next to the pad, i literally just ran all the wire and everything lasy fall and im in the middle of getting that all hooke dup as well. This does not need a seoerate disconnect is that correct? the panel only holds 6 breakers, so no disconnect is needed there, but i was curious if the heat pump still required a seperate disconnect outside by the pad? It looks like i also need to use #8 wire based on the MCA of 40.4. Needing a 70amp breaker really sucks, doesn't leave much room for much else, then i have the pool pump which will need a 20amp break, and i ran extra pipe to run power to a pool bar, but that only leaves me room for a 10amp break, which i cant do much with.

Also, if i had to use a 70amp break, then a 20 for the heat pump, is it a problem using a surge protector that requires a 20 amp dual pole breaker, its not pulling any amperage if i understand correctly. using the 20amp breaker doesnt need to be counted towards the 100amps being supplied to the panel does it?

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I am getting ready to install a used heatpump myself. The manual I found for mine online says a max of 70amp but 60amp is preferred. I just did a full overhaul on my electrical last spring and only ran a 60amp for my sub panel. Now I have to figure out what I will do as this heatpump was not in my original plans. I believe a switched disconnect is required to be installed at the heatpump for emergency disconnect. They are only $15 at my local big box store so I am planning to install one even if it isnt required. Also, from my understanding, you will need minimum of #6 wire for a 60amp breaker. I am not an electrician just an avid DIYer like yourself.
 
Im seeing lots of equations online for figuring it out, but i continue to just confuse myself. I know needing a bigger breaker has to do with start up. there are different reasons, and i think you either multiply by 225% or 125% of the FLA, but again, im not sure. Im really hoping someone can chime in and make my life easier. Im just really upset i did 100amp, i would have done 125 if i had known i needed such a big breaker. my run was 115feet and not easy to pull the wire through with all the turns (also not cheap). if i only need a 60 amp, i will feel much beter.

I think the wire size is based on the minimum circuit amp, which on my pump is 40, which only requires #8. i dont think the wire size has to be matched to the actual breaker since its a pump, the wiring requirements for pumps are different.
 
You can exceed the rating of the line coming to your subpanel with all of the devices you connect to the subpanel. The subpanel protects each of its own branch circuits and your main panel protects the subpanel circuit. Now will you blow your main panel breaker? Probably not unless everything starts at once.
 
I just spoke to aqua comfort and they told me a 40amp breaker is the minimum, and 70amp is the largest. So im going to put in a 50amp and go from there. Hopefully it works. From reading online it seemed like i would need something bigger than the 40 minimum due to start up, but maybe since the breaker is going to be time delayed it wont blow the breaker right away. Well, fingers crossed.
 
Juggernaut1103 said:
I just spoke to aqua comfort and they told me a 40amp breaker is the minimum, and 70amp is the largest. So im going to put in a 50amp and go from there. Hopefully it works. From reading online it seemed like i would need something bigger than the 40 minimum due to start up, but maybe since the breaker is going to be time delayed it wont blow the breaker right away. Well, fingers crossed.
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Don't forget that your circuit breaker protects the wire. That is what needs to match. So if you are going with a 50 amp breaker, you must have at least 6 gauge copper wire.
 
I thought since its a heat pump with a motor, that you only have to match to the minimum circuit amp?

Only reason i asked is because there are lots of situations where pumps with motors may have #8 and also have a 70amp breaker.

All this heat pump reading is going to give me an ulcer. LOL
 
Wire has to be sized for the breaker. You have to also size the wire to limit voltage drop based on expected circuit ampacity. Which might mean you need a bigger wire depending on circuit voltage and length.

Do not under volt your heat pump you will not like the results.
 

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joshua5438 said:
Per code, heat pump motors can have a smaller wire than what the breaker requires. I will see if I can find it for you...
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Could you find the section in the NEC code that says this is true? I would like to read that over. There is a link in my signature to the NEC website where you can get free access to the current 2017 code book.
 
I will have to get my head back into it but this is from when I was researching last year...

240.4(D) says, "Unless specifically permitted in 240.4(E) or (G). 240.4(G)"

240.4(G) says, "Overcurrent protection for the specific conductors shall be permitted to be provided as referenced in Table 240.4(G).

Then you read the table and it takes you to 440, 430, and a few other places where you can use smaller wires than usually allowed like 630.
 
I haven't looked through the code book, but i've read a lot about it online through other forums and i think i saw that on TFP too. At the end of the day i will probably just wire it using #6. this way its guaranteed to pass inspection for the cost of a few extra dollars per wire.
 
Hey Guys, i stumbled upon the post in another forum that also lists code sections in regards to the wire size and breaker size. Air Condition and Heat Pump over current protection and wire sizes. Chelan County Real Estate Inspections | NCW Home Inspections, LLC I believe heat pumps are clumped in with refrigerating and air conditioning.

I ended up buying a 50amp breaker, but after doing the math it looks like i would have been fine with a 40 if needed. I still plan to match the wire to the breaker size, but it also looks like I could use #8 THHN wire in place of #6 because THHN/THWN is rated at 75*C
 
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