Need Help with an Electrical Plan for Adding Heat Pump

[Stoopalini]

I've ordered an AquaCal SQ150VS heat pump, and will be doing a self install when it arrives. So in preparation of that, I'm taking a hard look at the electrical layout of my house and the pool equipment.

A coupe of years ago, when I added an EcoSmart 27kW tankless hot water heater during a master bath remodel, I called my local electric company and had them come out and advise me on if I needed a service upgrade to handle the tankless heater. They told me I did not, and should be fine adding it in. This required adding three 40Amp double throw breakers into my main panel, which is fed by a 200A service.

When the pool was installed last year, I repurposed a 50A breaker spot which was feeding a welder circuit in my garage (which I've only used once in 14 years) to make room for the 50A breaker for the EasyTouch load center.

So now I'm trying to determine if I can add the pool heat pump to the mix, or if I've finally gotten to the point where I need a service upgrade; which honestly, I think I should have done when I added the tankless.

If I do need a service upgrade ... what are my options are for doing so (complete main panel replacement for a 400A panel, or ... adding a 2nd 200A panel in parallel, or ... adding a 100A single cut-off breaker box in parallel to feed the EasyTouch sub-panel, or ... something I'm not considering?). I realize the answer to this is impacted by local code as well.

Here is what my main panel looks like today:




And below is how the EasyTouch is currently tied in, along with the loads running off the ET's panel

Note: The existing wiring between the main panel and the ET panel consists of four THHN 8AWG wires in conduit (not romex). My understanding is this type of install allows the 75*c table to be used for determining load capabilities; so I'm currently ok with 8AWG and a 50A breaker. But any increase in breaker size would require upgrading the 8AWG wires to the ET panel.




The heat pump's RLA (Rated Load Amps) spec is 36A, with minimum circuit ampacity of 47A and max breaker size of 60A. So I'm using 36A for load calc, and 50A for the circuit breaker.

I know the EasyTouch is a 150A capable sub-panel, so I wonder if I can upgrade my service to 320/400, keep my existing 200A panel, and add a 100A circuit breaker enclosure in parallel to feed the EasyTouch. I think this would be the most cost effective option, if it's an acceptable solution per code and the local electric company.




Option 2 is the most expensive, and would be upgrading to 320/400A service and replacing the 200A panel with a 400A main panel. Then run the heater from a dedicated CB in the main panel.




And I'm sure there's other options too, like upgrading the service to 320/400, upgrading the main panel to 400, and then installing a 100A breaker to feed the EasyTouch load center as a sub-panel, and adding a dedicated 50A breaker in the ET for the heater:




Or maybe I should just install a 2nd 200A panel, since I'm out of room?




Another option would be to go with the 2nd 200A panel in parallel, and run the ET from a 50A breaker, use a 2nd 50A breaker for the new heat pump, and then I could also move the tankless water heater breakers over as well to this new panel. This would probably give me the most flexibility, but again, would be a costly option.




The main panel and the EasyTouch panel are fairly close to each other, on the same exterior wall of the house. So any of these options should be fairly easy to implement, but I think replacing my main panel will be costly since every circuit will need to be rewired from the old panel to the new.



As you can probably tell, I may be over thinking this to some extent. I plan to call the electric company out here again, to consult with me on options ... but would like to get some input in the meantime.

Any advice here would be greatly appreciated!

 

[Stoopalini]

Hmm, just to add one more piece of info here. I have a sense Energy Monitor in my main panel, so I went and looked at the past months usage numbers to see what the max kW I have pulled at any given time. The peak was during the crazy winter storm we just had, and it was 37.1 kW. At 240v, that's 155A max draw.

I also looked back in my history, and this is the highest spike I've ever had, even through the summer months.



So based on this, maybe I would be ok to run the heat pump on my existing service? If I could replace the 50A breaker in the main panel with a 70A one, upgrade the wiring to the ET to handle this, and run the heatpump off of a 50A breaker in the ET sub-panel instead? Although I don't think that's an option, since 50A seems to be the largest miniature dual throw GE breaker which is made and I don't have room for a full size dual throw.

 

[Stoopalini]

So I spoke to a couple of electricians, and they agree I do not need a service upgrade to add the heat pump ... so that's great news.

My plan now is to install a 100A sub panel, right next to my 200A main panel. Then move enough breakers out of the main panel into the sub, to free up enough space to add a 100A breaker to feed the sub. Then add a 50A breaker into the sub for the heater.




The reason I have to move circuits is because the main panel is out of space.


But ... after reading the following from @JamesW , I'm wondering if I even need the sub-panel anymore?

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.

The wire feeding the EasyTouch subpanel is #8 THHN, which I think is good to 55A (90c column) or 50A (75c column).

Here are the details of the heater I am installing. So RLA of 36A on a variable speed compressor, which AquaCal tells me will typically pull somewhere around 26-28A max continuously when operating in high speed.



So given these details, I'm now wondering if I'd be ok to put a 50A breaker in the EasyTouch panel, and run the heater directly off of that.

The path would be 50A breaker in 200A main panel, #8 THHN in conduit to the EasyTouch panel, a 50A breaker in the EasyTouch sub panel feeding the SQ150 heat pump using #8 THHN in conduit.



I realize the max ratings are just that, max limit ratings and not what the devices will pull on a continual basis. So given what I quoted from James above, am I ok to use option 7 here?

I do plan to discuss this with my electrician, just hoping to learn as much as possible before hand. Obvious installing the 100A sub panel, and moving the circuits over, is costly and I'd prefer not to if not needed.

 

[ajw22]

NEC says no circuit shall be loaded to more then 80% capacity. Maximum load on a 50 amp breaker is 40 amps.

That is why your HP that draws 36A specifies a 50 amp circuit. A 40 amp circuit would not meet code.

 

[Stoopalini]

NEC says no circuit shall be loaded to more then 80% capacity. Maximum load on a 50 amp breaker is 40 amps.

That is why your HP that draws 36A specifies a 50 amp circuit. A 40 amp circuit would not meet code.

That makes sense, but is that referring to actual load? Meaning the amount of current being demanded at any given point cannot exceed 80% of the capacity? The heat pump actually draws around 26-28A when running at the highest speed, according to AquaCa ... and of course none of the other devices are drawing the name plate rating. My lighting trasformers are rated at 2.5A each, and the easyTouch panel is also rated at 2.5A. But none of these are drawing that much.

Another example, is that my pump has a rating of 13.8A, but doesn't pull that even at max speed. I run it at 1200 and 2500 RPM for high and low speed, and it pulls 0.5A and 4.4A respectively. At the pump's max speed (3450 RPM), it pulls 10.8A.



So for calculating the 80% rule, would I use the name plate (13.8), the actual max load I run it at (4.4A), or the actual load it is capable of (10.8)?

When looking at all the devices running off the EasyTouch, and adding in the heater ... I'm more around 35A continuous load when everything is turned on and running at max. But if NEC requires the name plate ratings to be used, then I'm at 60.55A.

 

[Stoopalini]

I guess another way I'm thinking about this is .... if I added up all the name plates of everything in my house, I'm sure I would exceed 160A (80% of my 200A main breaker) ... but it's still ok to connect it all to breakers in the panel, since the continuous load is never actually 160A or more.

Can I use that same approach here, on the sub panel?

 

[ajw22]

For design purposes on any one circuit you use max load.

The fact that continuous load is less then max load makes the loading more conservative.

Electrical load calculations for a panel take into account the type of devices on the circuit and the time of day they may be used. That is why all the breakers on a panel can add up to more then the panel service amperage. It recognizes that not all circuits are used simultaneously.

Electrical Load Calculations For Residential Panel-EET-2021

Electrical Load Calculation. Online Interactive Residential Electrical Load Calculator. residential-electrical-panel-calculations. Summary: Residential Ele

electricengineer13.com

You can ask your electrician if your planned panel loading meets your local codes.

 

[Stoopalini]

Ok, so I'm back to something like Option 6 then, with an additional sub panel to create some space.

Thanks for the input!