Using 120v inside 240v control panel

[guillaume]

I'm wondering if it is possible to use 120v inside my 240v control panel without making the GFCI trip? A friend had a doubt on that since I said the gfci checks for inbalance.

I'll get all 3 wires (L1-N-L2) inside my control panel, but everything would run off 240v including the pids. I'll have 2 5550w elements controlled by my Ezboil and a 3-way switch (so only one be running at a time).

I've got two 12v pumps and I'm wondering if using L1+N to get 120v so I can use a 120v to 12v power supply plugged in won't make the GFCI trip. How is the GFCI working in that case? Since one live wire will "draw" more current than the other.

Or am I completely wrong?

Here's the plan, if you can make sense of it (it's in french): https://www.dropbox.com/s/rvuqemw5ntaqz3z/CRQ426-401-AH.pdf?dl=0

 

[mredge73]

You have it drawn the way power is used here in the US with 2x 120vac hot wires and a neutral.
A GFCI monitors current going to ground and will trip somewhere under 10ma.
Your neutral and ground will be tied together at your main utility panel so the GFCI will trip immediately if you try to use the neutral to provide 120vac.
Your best bet is to get a power supply that goes from 240vac to 12vdc to run your pumps. Luckily these are easy to find, many power supplies nowadays have a input power range of 100v-240v.

 

[guillaume]

You have it drawn the way power is used here in the US with 2x 120vac hot wires and a neutral.
A GFCI monitors current going to ground and will trip somewhere under 10ma.
Your neutral and ground will be tied together at your main utility panel so the GFCI will trip immediately if you try to use the neutral to provide 120vac.
Your best bet is to get a power supply that goes from 240vac to 12vdc to run your pumps. Luckily these are easy to find, many power supplies nowadays have a input power range of 100v-240v.

Yeah, found a few for under 12$.

Shouldn't the GFCI be wired to Neutral instead as per the specs (attached file)? Not that it matters if neutral and ground are connected back at the main panel...

View attachment siemens-qf250-specification.pdf

 

[MerlinWerks]

It's been a while since I wired mine so please verify with other sources, but I believe the way it works is the pigtail from the gfci must be connected to the panel neutral if you want to source both 240 and 120 or if you want the "test" button to work with a strictly 240V load. The neutral for the load is connected to the neutral terminal on the load side of the gfci breaker. That way the breaker monitors current from both 240 and 120 loads. I have both 240 and 120 loads in my control panel both through supplementary breakers which are supplied by the spa panel.

This may help explain how it works: https://www.nema.org/Products/Documents/NEMA-GFCI-2012-Field-Representative-Presentation.pdf

 

[mredge73]

That is a cool presentation, I learned something new. I suppose I have always been wiring them up wrong, never used the "load neutral" terminal.
I have always wired them like page 30, page 26 is correct.