I have a 40 amp circuit previously used for spa in back yard. Breaker is in the main box and wire extends through house crawl space to back yard. I have gotten rid of the spa and now want a 20 amp circuit for new barbecue island, to power the rotisserie motor, lighting, etc. My problem is determining best way to reduce the 40 amp circuit to a 20 amp (or maybe to two 20 amp circuits as I may have additional electrical needs). Can I simply replace the 40 amp breaker with two 20s then go to back yard and splice into the old 40 amp circuit where it exits the crawl space (enclosing the splices in a junction box), and run 12-gauge wire to the new circuit locations? This way, I would not have to run any new wiring under the house. I know that each of the two "hot" wires in a 40 amp circuit provides 20 amps individually, and I am pretty comfortable that I know how to match up wire colors, etc., when making the splices. I want to do this conversion right, and would like to know if my approach sounds OK? Thanks.

 

The key question here is, "does that circuit have two insulated hot wires, one insulated neutral wire, and a separate grounding wire (insulated or bare)?"

Depending on the answer to that question, you can either make one 20-amp circuit (2400 watts), or one 20-amp multiwire circuit (4800 amps).

 

No, each wire does not provide 20 amps individually. Each wire provides 40 amps. This is why there is a 40 amp breaker installed.

Per John's instructions, tell us what wires are present.

 

In response to John's question, yes the existing 40 amp circuit has two "hot" insulated wires (black and red), a neutral insulated wire (white), and a bare ground wire. Would appreciate your further advice, with this information!

By the way, after I submitted my question, I found another thread from a few weeks ago that raised almost exactly the same question. There is some debate in that thread about whether the existing breaker should be replaced with a double-pole 20 amp breaker or two single-pole 20 amp breakers. I'm not sure that the parties reached agreement on that, so would appreciate your take on the "bottom line" here; that is, which type of breaker should I plan on using in my situation?

Finally, one more related question. The cable running through the crawl space is lying on the ground. Does code require this to be off of the ground, meaning that I should go under and clamp it the floor joists? Thanks.

 

Replace the 40-amp double-pole breaker with a 20-amp double-pole breaker. Wire it the same way (you won't need to touch the white or bare wires). Under certain circumstances, you could use two 20-amp single-pole breakers rather than one double-pole breaker. But the double-pole breaker is always okay.

At the other end, connect one 12/2 to black/white/bare, and the other 12/2 to a red/white/bare.

 

Thanks for the advice. I am moving ahead on this project and have have run into one more question:

I have 12/2 romex on hand and was thinking about using this for the new circuits (outdoor, all above ground). I would encase it in 1/2 inch PVC electrical conduit. I would like to know if 12/2 romex is acceptable in this situation. Also, if it is "only acceptable" and there is a preferred alternative, what is that alternative?

In short, I could use a little info on the pros and cons of using romex in this situation: 12/2 romex, 1/2 inch PVC conduit - outdoor circuit with none of it buried. The run will be about 15 meet with two 90 degree turns.

Thanks

 

I would use 12-2 UF wire. I would rely on the conduit to supply protection only.

 

Convert the existing 40-amp Branch-Circuit to a "Feeder" simply by terminating the conductors on the lugs of a "Main-Lugs" sub-panel. The S-P will povide maximum "flexibilty" for connecting circuits of different voltage and current ratings, and circuits that require GFI protection.

Also, the "Feeder" concept provides maximum power, 40 amps X 220 volts, which is a power-capacity double the power capacity of a 40 amp conductor protected by 20-amp C-B's

Good Luck & Enjoy the Experience!!!!!!!!!