Subpanel Load Question

[TopherM]

I have a subpanel in my backyard for my pool pump that's fed from my main box by a 40a 240v breaker. The pool pump and an salt water clorination system runs off a single 20a 120v circuit at the subpanel.

I want to add a 30a GFCI breaker to the subpanel for my eBIAB build. Will I be able to run the pool pump and the eBIAB at the same time without tripping breakers, or will I need to be sure to always have one or the other circuit off?

I measured the draw from the pool pump circuit with everything running, and it read 15.6a at 120v, which I think would represent 7.8a of the total 240v feed, leaving a suitable 32.2a to run everything simultaneously, if needed? Any flaws in this logic? I'm a novice with electric, and might be oversimplifying the calculations.

Thanks for any help!

 

[ColeBeer78]

I'm not an electrician but the 15.6amp draw at 120v is just that. 15.6 amps on one phase. It doesn't divide the amperage. It only allows you at 16.4amps left on that phase to run at 80% of that 40amp breaker. It doesn't look like your gonna be able to. How much do you plan on drawing with your eBIAB?

 

[TopherM]

I have no idea. I did read, however, that I can still run my 30a 240v circuit off my subpanel, I just will have to keep the other circuit off (i.e., manually trip the breaker) whenever I'm using it. Would that be correct?

 

[ColeBeer78]

Yes... Correct.

 

[John53189]

Some pool pumps are dual voltage, check the motor rating plate. If so you may be able to rewire 240 and reduce amp draw.

 

[sennister]

I'm not an electrician but the 15.6amp draw at 120v is just that. 15.6 amps on one phase. It doesn't divide the amperage. It only allows you at 16.4amps left on that phase to run at 80% of that 40amp breaker. It doesn't look like your gonna be able to. How much do you plan on drawing with your eBIAB?

Yep, can't divide it if it is a 120 device on one leg of a 240 circuit.

I have no idea. I did read, however, that I can still run my 30a 240v circuit off my subpanel, I just will have to keep the other circuit off (i.e., manually trip the breaker) whenever I'm using it. Would that be correct?

Yep, if it isn't on it isn't pulling a load. Not sure how the pool stuff is powered. On all the time or on a timer. No need to flip the breaker unless you really want to make sure a timer doesn't turn something on.

On a side note. I am not there and don't know how you are wiring this. If I were to guess, I would imagine the pool has a GFCI. Any reason you can't just tie into that for your brewery and save from buying another spa panel with GFCI? Like I said, I don't know where you are trying to tie into this. Normally for a build like this it works like this. Lets say your main panel has a 40 amp breaker which feeds the subpanel. The sub panel also has a 40 amp breaker but this one is a GFCI because of the water (pool) and being outdoors. Are you trying to tie into the pool's sub panel for your power. If so and it is a GFCI no need for another one but it also means you can't flip the breaker to ensure the pool stays off. You would have to have a switch or change the timer that may control it. If you are trying to tap into the 40 amp breaker in the main panel to add a second sub (spa) panel, you may have some issues. While you are right that by throwing the breaker on the pool you know you won't overload the 40 amp breaker in the main panel and the 30 amp brewery is not going to overload it, my concern is the wires. I don't know that you will physically be able to hook up those wires to the breaker in the main panel unless you were to come out of the main panel into another sub. Well I guess you could put the spa in the middle and it would work but it would be a pain. You would be better off adding another 240v breaker to the main panel to do a dedicated circuit for the brewery if you have room. Again, I don't know your layout so this is speculation on options.

I kind of have a similar issue. We have an older house built in 1963. It only has 150 amp service. We also live in the country so we have some big items like a 220v 30A well. My main panel doesn't have much for room. Then add in multiple outbuildings with 220v runs and things can get tight. For instance I have a 220v 60A circuit to the pole barn/shop/brewery. That goes into a 60 amp subpanel. But then there is a 40 amp 220v feed that runs to the back part of the pole barn/shop/brewery where I have a 200Amp panel. Well might as well call it a sub panel. It is only that big because we got a smokin deal on it. Even though the panel is rated for 200A, it wouldn't ever be able to run that since the input wires and the breakers are rated to 40 amps. The only thing that makes it a 200A panel is the number of slots for breakers. Off the 200A sub-sub panel there is a run to the back yard where there is a 40 amp 220v panel (GFCI) for the 5th wheel camper. It is nice to have full power out there if needed but it doesn't pull 40A. Sure if we were to try and really load things down we would blow breakers, but it really has never been an issue.

The point is that it can get messy and you have to keep in mind that you need to work within the limitations of your weakest link. Breakers are there to protect the wires to prevent fires and protect the equipment. Not you. GFCIs will protect you. It may be cleaner to do a dedicated run.

 

[TopherM]

Thanks for the info.

I have the same issue. My house was build in 1959, and I have a 150a main panel with 140a worth of breakers spoken for.

I don't think my pool subpanel has a GFCI breaker, but I could be mistaken. I'll check and report back!