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First time question asker, here. I have read several threads on this site, which is a great resource. I am still unsure if what I'd like to do is safely possible, so here I am asking about my specific situation.

I have a dead pool heater (electric heat pump) that I'm not going to replace. It is serviced with 8/2 wire (white, black, and bare ground) and already has a 50A two pole breaker on the main panel. The service on the back of the house is a great location for me to convert the circuit for either of the following uses, both of which would be better than having an unused circuit.

Option 1. Install a twist lock inlet (L14-20P) so that I can backfeed the panel via a 5,000 watt generator for occasional use. I would use an interlock kit to do this correctly. My question is, as the generator has a 4 prong outlet (L14-20R), is it possible to safely connect to the 3 wire? What to do with the ground and neutral? My generator has a floating neutral. The neutral vs ground - and where that all occurs - is what makes my head spin.

Option 2. Install a 50A RV service, which would also be for occasional, short-term use. Same question, since the NEMA 14-50R is designed for 4 wire (X,Y,neutral, and ground,) can I safely make this work with the 3 wire?

Other details that might matter. There is a manual disconnect box in line for the heat pump that I could either keep or remove. I am in FL.

Any help is appreciated. Thanks!

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  • Are you planning to pull the neutral bond from your generator? What make and model is your generator for that matter, and can you post photos of your existing electrical panel please? – ThreePhaseEel Aug 18 '20 at 23:44
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Nope, this isn't going to work.

The lack of a seaparate neutral/ground is a deal-killer here on both applications.

Further, that 8/2 cable is not allowable to 50A.

Neutral is not ground

There's really nothing confusing about it, except that you bit fruit from the tree of knowledge when you noticed neutrals and grounds go to the same place in the main panel. Disregard this: that isn't what you think.

Electric current flows in loops - you kinda know that. It wants to return to source (not ground by the way; source).

Neutral is the ordinary, everyday current return path, and it has current flowing on it all the time. Neutral "works for a living". Because of this it can be hot under certain conditions, and that's why we insulate it. Using a bare neutral would be dangerous.

However, trouble can happen. Equipment safety ground is a protective shield. Current NEVER flows on safety ground except during a fault condition. Safety ground returns fault current to source: So for natural electricity (lightning, ESD) that is the earth. For human-generated electricity, that is back to the neutral and the supply transformer. (and now, you know what that neutral-ground connection in the panel is for). If it wasn't for safety ground, the equipment would sit there energized.

Your pool heat pump ran on 240V only, and did not need neutral (which is in the middle). The original installer saved a tiny bit of money by using /2 cable instead of /3 cable, which unfortunately ruined your ability to reuse it for your generator.

Your options

Since you need to pull new cable anyway, you might as well pull both of them - a 6/3 for the RV, and at least a 10/3 for the generator. (A 12/3 would suffice for now, but there's a lesson here and I'm assuming you've learned it :)

The existing 8/2 could be used for a 120V feed to a generator, hot-neutral-ground, of up to 40A. However, if your house is wired in "Multi-Wire Branch Circuits", that could introduce a danger.

The 8/2 could also be used for a 120V/30A RV connection called a "TT30" found on smaller RVs. If your larger RV has the adapters to work on a TT30 connection, that is an option.

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  • Thanks for that Harper. My RV is actually 30A, so at least this circuit won't go to waste. I was going to the do the 50A since I already have the adapter, the breaker was already there, and to allow for a bigger RV down the line if we ever go that route. My panel doesn't have much room left, but I'll put in a 30A single pole, move this 8/2 wire to the new breaker and let it be dedicated for the RV. – Ryan Aug 18 '20 at 17:50
  • Sounds good @Ryan. You can stay with a 30A double-pole and just use half of it; 30A 2-poles are useful for lots of things but 30A single-poles are only useful for TT30 RV circuits, so I avoid buying them. – Harper - Reinstate Monica Aug 18 '20 at 19:22

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