Multiwire Branch Circuit

[mkgrady]

I have a customer that needs more power at a pool shed. Currently they have one 20 amp gfci protected circuit that powers a filter pump and a convenience outlet. The breaker is located at the main house panel. wiring is through buried conduit. They want to add a propane pool heater that draws 5.5 amps. The pump fla is 15. The existing circuit is too small to power both heater and pump. If I convert the circuit to 120/240, 20 amps and protect it with a two pole gfci breaker do I have a problem powering each appliance with 120? I know it will work if I feed each appliance with 240 but I need to keep the convenience outlet working. I’m thinking it will work without tripping the gfi breaker. Am I correct? I want to avoid having to add ground rods which is why I want to keep it to one circuit.

 

[roger]

A two pole GFCI will work fine. The key is that all the current leaving and returning is through the three conductors.

Roger

 

[Fred B]

Just a question, why do you feel that adding another circuit run out to the pool would make it necessary to add a ground rod? You're not adding a second panel, or are you thinking that you need to do that?

 

[mkgrady]

Just a question, why do you feel that adding another circuit run out to the pool would make it necessary to add a ground rod? You're not adding a second panel, or are you thinking that you need to do that?

I don’t think the code allows more than one circuit to a separate structure without adding the rods. I think having two circuits would require I install a subpanel that would need the electrode.

 

[mkgrady]

A two pole GFCI will work fine. The key is that all the current leaving and returning is through the three conductors.

Roger

Thanks. My first thought was that the current on both legs would have to be balanced. After thinking about I figured it was more about having no current flowing on the egc.

 

[infinity]

I don’t think the code allows more than one circuit to a separate structure without adding the rods. I think having two circuits would require I install a subpanel that would need the electrode.

That's true but for a 3-wire MWBC (2-120 volt circuits) to a separate structure that can be considered one circuit.

 

[tom baker]

I don’t think the code allows more than one circuit to a separate structure without adding the rods. I think having two circuits would require I install a subpanel that would need the electrode.

Please see definition of Branch Circuit, Multiwire, and 250.32 (A)
Looks like Infinity beat me to this