Adding sub panel but using existing cable from generator.

[EdB210]

Hello everyone. New to the forum. Thanks for being here.
I apologize for the lengthiness of my write up but I wanted to provide as much info as possible. I appreciate any help or guidance.

I am not an electrician by trade so I may be a little dangerous. I have been reviewing NEC 2017 and many articles online but still have uncertainties and need some help.

I removed a generator that was too small for my current needs (no pun intended). I wish to use the existing generator cable to feed a 140,000 btu 240v pool heat pump and hopefully some additional 120v circuits.

The cable is an aluminum SER 2–2-2-4. The heat pump requires a minimum 50 and max 70 amp double pole breaker per manufacturer. They recommend not using a GFI.

One end of the cable is about 4 feet from my main panel inside my garage so I plan on splicing a piece of the same cable type between my main panel and the original cable using an 8”x 8”x 4”deep pvc junction box (I assumed 1.25” trade size conduit to size the box but no conduit will be used since the run is within a wall).

The cable run is about 40-45 feet.

The other end of the cable is outside. At that end, I wish to put a local panel board to power the heat pump. The panel board will be located within 5 feet of, and in sight of, the panel board and will have a 2 pole breaker for the heat pump and a hopefully a couple of 20 amp 120 volt circuit for future work (non continuous). The heat pump will be a continuous load.



Using the existing SER 2-2-2-4 aluminum cable,

1. What size breakers will I need at the main panel to feed the local panel board? I m thinking 90 amp 2 pole.

1. What size breaker will I need at the local panel board? I’m thinking (1) 70 amp 2 pole (1.25x50 rounded up to 70 from 62.5) for the heat pump
2. I would also like to be able to add (1) or if possible (2) 20 amp 120v breakers for future (non continuous loads). What am I limited to?
3. Is my junction box sizes correctly?

I will be using a local panel board with no more than 6 spaces which will serve as my disconnect, so it will be a main lug.



I believe my plans should be permitted per NEC but I’m not certain and I don’t know if I need to take any penalty because of the cable run length. I can’t find what 2 awg cable lengths require a penalty (require use of next larger conductor or derate of the existing conductor).



Thank you for any insight you may provide.

 

[nadogail]

Welcome to the Forum from Southwestern California.

Will the 2 AWG Cable handle the full output of the generator that will be feeding it? Or will the feed to 2 AWG be limited by an over current protection to within the capability of the cable?

If the answer to either of those two questions is YES, I think you will be able to use the cable.

 

[bronc076]

Only one reply and he told you that the wire will work fine for the generator you removed.

It sounds like you want to put a sub panel outside, can you provide a link to the panel you plan to use? The existing wires are large enough for your 70 amp load plus the occasional blender or hedge trimmer. I'd do the 90 amp breaker in your main panel and the 70 at the sub panel, remember the breaker protects the wiring down stream, so follow the recommendations from the pool heater manufacture. The ground and the neutral must be isolated at the sub panel, and you will need ground rods. Search around this section, there are tons of questions about sub panels and everyone pretty much gets the same advice.

If you have to get a permit and pass an inspection talk to the the inspector and let him know what you are doing so he can guide you in the direction he wants to see. If you live in the wild west like me where you can run fence wire through a garden hose to heat the chicken house, still do it correctly anyway so no one gets hurt and you don't have to fix stuff done wrong if you ever sell the place. No one wants kids playing in the pool and running around poorly installed electrical equipment.

If you are uncomfortable with any of it, hire an electrician.

 

[EdB210]

nadogail - thank you for the welcome and the response. The cable was for a generator but I wish to use it to feed a heat pump pool heater I wish to install a save some money by not having to run a new cable. I plan on using a 90 amp breaker at my main panel as boronc076 has recommended

bronc076 - thank you for your response. I will attempt to supply a link to the outside panel when I have access to the panel I purchased. It’s a 125 amp main lug with 6 spaces. Do you think given the cable size I can also install 20 amp sp or 15 amp sp breaker and circuit for future needs in the outside panel? If it looks like I can’t, then I don’t really need a panel outside and may be able to just put a mean’s of disconnect similar to what you typically see at air conditioning condenser units but I don’t understand the NEC requirements. I will run it by the inspector. Thanks again.

 

[PCustoms]

Welcome to the Forum from Southwestern California.

Will the 2 AWG Cable handle the full output of the generator that will be feeding it? Or will the feed to 2 AWG be limited by an over current protection to within the capability of the cable?

If the answer to either of those two questions is YES, I think you will be able to use the cable.

Would you read before responding?

 

[bronc076]

Sure you can put breakers in there and feed outlets, outside lights, whatever you want. Remember the outlets will need to be GFCI and observe requirements for outdoors and wired correctly. Not sure how close to the pool you can go. Ask your planning guys when you get your permit.

When I built my shop in AZ I found the building inspectors were very helpful to homeowners who wanted to do things right. But if you want to do it wrong they will comedown on you pretty hard. Better to ask then have to redo it.

 

[EdB210]

Thank you again bronc076.That’s good news.
I’ve met my inspector and established a good rapport with him. I’m trying to figure out what is permissible per NEC so I can run my plans by him and not overload him with questions. My project is pretty big for a DIY. Includes installing 26 kw generator and lp tank.

 

[wyliesdiesels]

does this SER cable run underground?

 

[EdB210]

No. It runs in a 2x6 wall cavity.