Ren24 & GFI Hell

[Mufassa]

Ok, Ill try and give all the info the first time and see if anyone else knows what is going on.

I am trying to use a Ren24 (Franks 3.3) using both sides of the board powered separately. I have 2 20 Amp GFI's that are on Different Hot legs but sharing a neutral. (12-3 wire) (Note: I have tried it on a different set of GFI's that dont share a neutral and it does the same thing.)

I have hooked both neutrals together in the REN and whenever I plug both sides in the GFI's pop. If I try hooking up with only 1 neutral connected to the REN it seems to work just fine. My question is: Is this safe to run with the extension cords (16 gauge)? I know they are on different legs but I dont want to overpower the neutral. Which I assume couldnt really happen but still doesnt seem right to me. I doubt I would have GFI protection on the second GFI?

I have searched and the best I could come up with was this thread http://www.doityourselfchristmas.com/forums/showthread.php?t=6743 Which seems to say to connect the neutrals together.

Lastly I plan on running less than 13 amps (max for my extension cable) on each side. I just cant get away with only 1 power input.

Thanks in advance,
--Greg

[pete]

Hmm.. With GFCI's the load side of the device should be a isolated circuit. How a GFCI works is a GFCI monitors the amount of current flowing from hot to neutral. If there is any imbalance, it trips the circuit. It is able to sense a mismatch as small as 4 or 5 milliamps, and it can react as quickly as one-thirtieth of a second. So combining the two circuits combines watch the GFCI's see for current.

You could hook one neutral to the buss to service the control power transformer and channels 1-12 and take the neutrals from 13-24 off the neutral and wirenut them directly to the other feeds wire. then the two circuits would be isolated.

pete

[Mufassa]

That is basically what I came up with after talking to an electrician. That is what I thought was going on but was hoping it was something different. I can also cut the trace on the top of the board that connects both neutral sides together and then just connect the right side neutral to the board. Basically the same thing big wirenut.. :)

Thanks if anyone else has ideas! I dont look forward to digging thru the mega tree trunk to get to the controllers!

--Greg

[RPM]

There is probably an imbalance between the AC two phases causing your GFCI's to trip, as WireWrap noted.
It may help if you connected power through different GFCI's that are on the same phase.

[WireWrap]

Ok, Ill try and give all the info the first time and see if anyone else knows what is going on.

I am trying to use a Ren24 (Franks 3.3) using both sides of the board powered separately. I have 2 20 Amp GFI's that are on Different Hot legs but sharing a neutral. (12-3 wire) (Note: I have tried it on a different set of GFI's that dont share a neutral and it does the same thing.)

I have hooked both neutrals together in the REN and whenever I plug both sides in the GFI's pop. If I try hooking up with only 1 neutral connected to the REN it seems to work just fine. My question is: Is this safe to run with the extension cords (16 gauge)? I know they are on different legs but I dont want to overpower the neutral. Which I assume couldnt really happen but still doesnt seem right to me. I doubt I would have GFI protection on the second GFI?

I have searched and the best I could come up with was this thread http://www.doityourselfchristmas.com/forums/showthread.php?t=6743 Which seems to say to connect the neutrals together.

Lastly I plan on running less than 13 amps (max for my extension cable) on each side. I just cant get away with only 1 power input.

Thanks in advance,
--Greg


The issue is how you are drawing current. With normal US service, you have essentially a 240 Volt, center-tapped transformer feeding your house, with the center-tap (Neutral) grounded at the main entrance panel.

GFCIs operate by measuring the difference between the currents in the hot and neutral legs. If more than a few milliamps, it will trip.

The problem you are seeing, is because you are essentially making the REN into a 240 V device, where the neutral only carries the difference between the two hot legs. (eg: if leg A is drawing 12 amps, and leg B is drawing 7 amps, then the neutral will only be passing 5 amps back to the panel).

The easiest solution would be to relocate the second hot circuit to another source on the same phase as the first. This will prevent the differential action of the opposite phase.

[DIY Guy]

The easiest solution would be to relocate the second hot circuit to another source on the same phase as the first. This will prevent the differential action of the opposite phase.

Also n.b. that you couldn't use 12-3 in that scenario, you would have to run (2) 12-2 or similar.

[D4rknessxkilla]

The GFCI is detecting the different amp draws.. like if its a 30 amp outlet and one side draws 12 ams and the other draws 8 it see the different amp draws and cuts off

[omzig]

Just remember that if you are using 2 circuits from the same leg of the service and are sharing a neutral, the neutral will carry the sum of the currents of the 2 circuits, so it needs to be sized accordingly.

[Mufassa]

double post

[Mufassa]

THANKS!!!

Ok, well after reading everyone's reply's I cut the neutral trace on the board and hooked the neutral for the right side power to that neutral bar. I figure if I need to connect it I can either scrape and solder it back together or just run a jumper wire. (prolly the latter). But Its always easy enough to use 2 plugs.

I figured this was the easiest as I didnt want to run another neutral and move breakers to get them on the same leg. I learn something new everyday!

Thanks again!

-Greg