Fix False GFCI Tripping in 240V AC Circuit

[tjpoc]

Hello, I have installed a 240 Volt AC circuit with neutral. I am having false tripping on the GFCI breaker due to the installation of a set of 75 watt lights (on one of the hot legs and neutral for 120 volts). When I turn on the lights, the GFCI will sometimes trip I believe due to the inductance in the lights (because the GFCI picks up on inductance as a possible fault). I would like to prevent this false tripping by offsetting with capacitance but I don't have a clue how to begin or if this is even possible. The circuit in which the light is connected is through a step-down tranformer from 120 to 12 Volts AC. If I were to put a capacitor in series with the bulb and transformer winding, would that "surpress" the line to keep the voltage and current in step with each other? Also, how would I calculate the type and size of capacitance needed?

Thanks in advance for any assistance!

TJ

 

[berkeman]

No disrespect intended, but are you an electrician? Have you contacted the manufacturer of the lights? IMO, hacking into this may create a serious safety hazard. Please start with the light manufacturer.

 

[DaveC426913]

Hello, I have installed a 240 Volt AC circuit with neutral. I am having false tripping on the GFCI breaker due to the installation of a set of 75 watt lights (on one of the hot legs and neutral for 120 volts). When I turn on the lights, the GFCI will sometimes trip I believe due to the inductance in the lights (because the GFCI picks up on inductance as a possible fault). I would like to prevent this false tripping by offsetting with capacitance but I don't have a clue how to begin or if this is even possible.
TJ

I installed a GFCI too and had the same problem. I too thought the loads I was putting on it were tripping it. Turns out I hadn't adequately isolated the line from shorts such as water (it was outdoors, and I guess older wiring).

Are you positive you've installed the lights and wiring flawlessly? Pinch a wire with a connector somewhere?

 

[tjpoc]

I'm extremely certain all wiring is good. All fresh wiring from the main box to a new GFCI box and all new wiring in fresh PVC cable. The wiring is connected to a spa where the majority of the circuits are 240 volt. However, there are other 120 volt circuits within the cabinet which are working fine (i.e.: blower, prime pump, stereo, etc...). These all run off the same 120 volt circuit. It is a random thing...it's not consistent. I did remove the light housing, disassembled it, isolated everything and found that when I remove the bulbs, no tripping occurs. As soon as I put the bulbs back in, it trips. I went to lower wattage bulbs and it only trips sometimes, but still too often than desired. Thus, my thinking is the sudden current draw sends a signal to the GFCI that there is leakage current, but in my opinion it's just that the GFCI is too sensitive.

To the first gentleman's point, no, I am not a certified electricion. However, I've been working in the electrical industry for a number of years dealing with capacitance / reactance in high-voltage systems. I have contacted the manufacturer...then even sent someone out, and all they do is replace parts...not troubleshoot the issue. I'll admit, it's not likely this setup was intended for a spa, however this manufacturer (I'll not mention names to protect their privacy) is on the leading edge of providing features and functions maybe a little ahead of their time. So, with that said, they haven't been much help. As mentioed earlier, I did isolate everything, checked for ground leakages, shorts, etc., and found nothing.

 

[dahlungril]

have you tried hooking it up to the other 120v lead?

 

[Averagesupernova]

A normal GFCI breaker in the 120 volt (single pole) variety comare the difference between current in the hot and neutral. In the event that those 2 currents are not exactly the same it is assumed that there is a ground fault and the breaker trips off. I am not familiar with a 240 volt GFCI breaker (if that's what you have) but I would assume that it would compare current in both hot wires. If this is the case you should NOT be hooking into one side of the line to run 120 volt devices because naturally the currents between the hot wires will be unbalanced which would indicate a fault. A true 240 volt device such as a water heater does not have or need a neutral. There will be a third wire run but it is ground which is often confused with neutral. It is not meant to carry any current except during a fault condition.
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So, the question is, what type of GFCI breaker(s) do you have? I would rule out any inductance in the bulb. That's the absolute last thing I would suspect.

 

[turbo]

A normal GFCI breaker in the 120 volt (single pole) variety comare the difference between current in the hot and neutral. In the event that those 2 currents are not exactly the same it is assumed that there is a ground fault and the breaker trips off. I am not familiar with a 240 volt GFCI breaker (if that's what you have) but I would assume that it would compare current in both hot wires. If this is the case you should NOT be hooking into one side of the line to run 120 volt devices because naturally the currents between the hot wires will be unbalanced which would indicate a fault. A true 240 volt device such as a water heater does not have or need a neutral. There will be a third wire run but it is ground which is often confused with neutral. It is not meant to carry any current except during a fault condition.
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So, the question is, what type of GFCI breaker(s) do you have? I would rule out any inductance in the bulb. That's the absolute last thing I would suspect.

Yes. A 120V GFCI breaker would probably interpret any shift in the ground reference of the neutral as a "ground fault" so that any sudden load on either 120V leg could trip it. Sounds reasonable.

 

[nikola-tesla]

GFCI breaker doesn't trip bcs of the load and its purpose is to trip bcs of the leakage=insulation is very bad and/or moisture.
GFCI breaker would trip if the load is very high same like any other regular breaker but I am sensing in your case; or you didn't connect it properly that white coiled wire and white neutral wire. If you misplaced those 2 wires breaker will trip. But, the main thing that I am suspecting is something related to the spa, water, moisture makes GFCI do what they are supposed to do.

*** try to install regular 120V, 15 Amps breaker and see is it tripping. That way you will know for sure is the load or moisture.

 

[tjpoc]

Thanks all for the feedback. The breaker is a 240 volt GFCI. These types of breakers are intended for motors, etc. near wet areas. In a spa, some devices use the 120 volt circuit for basic items. The breaker is designed to check for zero balance current flow in all legs. Thus, a significant inductive shift could cause the breaker to think the flow doesn't zero out for that momentary shift. Unfortunately, I don't have the ability to shift circuits as all feed is done at the spa circuit board. I have switched hots, but no difference. I did try some smaller wattage bulbs and it seems to be holding. I've done some research about the manufacturer of this breaker (cuttler hammer) and had read that it has given many people these types of false trips. I may just replace the breaker with a different type (although they are very expensive...about $90). So, I'd much rather see if my theory is true by adding capacitance to the light to see if it would offset the initial startup surge.

Quoting nikola-tesla:
"GFCI breaker doesn't trip bcs of the load and its purpose is to trip bcs of the leakage=insulation is very bad and/or moisture.
GFCI breaker would trip if the load is very high same like any other regular breaker but I am sensing in your case; or you didn't connect it properly that white coiled wire and white neutral wire. If you misplaced those 2 wires breaker will trip. But, the main thing that I am suspecting is something related to the spa, water, moisture makes GFCI do what they are supposed to do."

Not always the case. It is possible that a surge, phase shift, or any differential in current flow (for a short burst) can simulate a ground fault. Since these breakers trip on current differential (i.e.: leakage current to ground, one circuit lags for a short time, etc.) the breaker will trip. I don't believe it's the "load" that's causing the trip...I'm pretty sure it's the initial startup differential in the circuit.

 

[Averagesupernova]

Ok, so the breaker in question compares current in both hots and the neutral? That makes sense. An electric motor is WAY more of an inductive load than a light bulb. Have you put another load on the transformer in place of the lights?

 

[berkeman]

GFCI breaker would trip if the load is very high same like any other regular breaker

Not true. Please don't say things like that. GFCIs trip only on unbalance, not on overload.


EDIT -- Oops, I missed that you were talking about a GFCI *breaker*. You are correct, and I apologize for my comment. I've just run across several people with dangerous ideas of what GFCI outlets do, so I'm a bit sensitive about that.

 

[Averagesupernova]

Not true. Please don't say things like that. GFCIs trip only on unbalance, not on overload.

Read it again berkeman. A GFCI outlet will only trip on unbalance, but a GFCI breaker is a regular breaker with GFCI protection built in.

 

[berkeman]

Read it again berkeman. A GFCI outlet will only trip on unbalance, but a GFCI breaker is a regular breaker with GFCI protection built in.

Oh gosh, you're right! Thanks for the correction, ASN. I'll edit my post to point out my error.

 

[nikola-tesla]

Read it again berkeman. A GFCI outlet will only trip on unbalance, but a GFCI breaker is a regular breaker with GFCI protection built in.

It's me again; let's make sure we understand one another; GFCI breaker is installed to trip the power on all receptacles that get power from that GFCI breaker. GFCI outlet will disable just the appliance that is plugged into that particular GFCI outlet. Again: GFCI breaker WILL trip on the appliance that has amperage higher than rated amperage of the GFCI breaker and on the ground leakage. And , the same thing applies for the GFCI outlet; it WILL trip on the ground leakage and on the power consumption higher than the rated amperage of the GFCI outlet.

 

[tjpoc]

Ok, so the breaker in question compares current in both hots and the neutral? That makes sense. An electric motor is WAY more of an inductive load than a light bulb. Have you put another load on the transformer in place of the lights?

That's a good point of trying a different device in place of the lights. I'll give that a try. I did lower the wattage bulb significantly and it seems to be holding. But I do like your idea of testing a different load.

The only thing I can think of with the motor being more inductive is that is uses both hot's and no neutral. I "believe" the GFCI breaker senses leakage current on the neutral, so with the nuetral not being in the motor curcuit, it's not as sensitive to the inductive difference. Just guessing here...completely speculation on my part.

However, since I lowered the wattage bulbs (almost half of what was originally in there), wouldn't that indicate something with the shock to the system when the lights are turned on?

 

[fhhunt]

When a GFCI trips inadvertently look at the load side. One thing I found, and it took a while to think it out, is surge suppressors on the load side. I needed more connections than a standard duplex receptacle provided so I used an over plug 2 by 6. These are the plugins that you buy at Wal-Mart and plug into the duplex receptacle. It provides 6 connectors on a duplex receptacle. If you have one of these on the load side of a GFCI remove it and look at the reverse side. It is most probably a surge suppressor as well as a connector. These things use Metal Oxide Varistors (MOVs) to move any surge to the common line. That connects the high side to the common thru a variable resistor. It doesn’t take much for it to bleed 5 ma to the common line. These things can react to transients as well as surges on the line. I would think that any surge suppressor, no matter its design, would cause a problem with GFCIs. That is one thing to consider when GFCIs trip for no reason.

 

[Proton Soup]

you might want to clear up some confusion by posting the part number of the "GFCI breaker" you're using, and the wattage of all items on its circuit.

 

[stewartcs]

This thread is over 2 years old, he's probably bought a new one by now!

CS

 

[Proton Soup]

ah, thanks, wasn't paying attention