Wiring Two 1500W circuits, help needed....

[robertwhite]

OK, need some help from a real electrician, if there are any on the board.

I need to wire 2 1500W water de-icers (12.5 amp draw each?) in my cattle water tanks. Both tanks are in same spot.

Plan was to run a 12/3 (Hot/Hot/Neutral/Ground) from circuit breaker panel using 2 20A breakers out to separate 20A GFCI's on the other end. 2 hots go out, neutral goes to buss on panel end and common at heater end, along with bare ground.(panel buss and common ground at other end)

People have said this will not work because using the single White as a common neutral will send the same current that goes in, back out. If that is the case, the GFCI's will never trip as they will never see a current difference.

If that is all true, what is the easiest (and cheapest) way to run it? I figure that just running another 12/2 (one is already there from last year) would be simplest, no? I don't really want to run 2 lines which was the reason for the 12/3, but I will if I have to. Runs are approx 100' long.

 

[porcupine73]

That should work just fine. The current still passes through each GFCI. It is true that the neutral going back to the panel will carry only the current imbalance (which should be nearly zero if you have two 1500W 120VAC heaters out there). But each GFCI will still see the neutral current for its circuit.

-------L1----------|
                  GFCI #1
--------N----------|
                  GFCI #2
-------L2----------|


OR

 -------L1----------|
                  GFCI #1
|--------N----------|
|
|
|--------N----------|
                  GFCI #2
--------L2----------|

The top diagram I think is what you are proposing. The counter people saying it wouldn't work, what would be the difference if you ran two 2/c w/gnd to the panel, I mean the neutrals are still going to be tied together on the neutral bar.

 

[Stuart in MN]

Having a shared neutral on the line side of a GFCI is okay, it's when you try to share the neutral on the load side of a GFCI that it won't work.

 

[robertwhite]

-------L1----------|
                  GFCI #1
--------N----------|
                  GFCI #2
-------L2----------|

The top diagram I think is what you are proposing. The counter people saying it wouldn't work, what would be the difference if you ran two 2/c w/gnd to the panel, I mean the neutrals are still going to be tied together on the neutral bar.

That's just what I said, but was told I couldn't do that.

 

[mtne]

Like Stuart said. I'm sure whomever told you that was thinking you would be sharing the neutral after the GFI........

 

[porcupine73]

I don't know, the people who told you can't do that might not be understanding what you are trying to do, or think you are messing with the subfeed lug neutrals possibly.

If diagram #2 would work, how could diagram #1 possibly not work?

 

[jbs]

I wired two of my receptacle circuits in my barn like this. Works fine.

(If it was wired wrong (i.e. shared neutral AFTER (on the load side) of the GFI), the GFI would trip unnecessarily, not never.)

 

[robertwhite]

Thanks guys.

I wound up just running another separate 12/2 since one was already in place. But nice to know I was correct in my thinking and the other folks were wrong.

 

[mrb]

are you supposed to use GFCI with those or GFEP which has 30ma trip?