markz528
Hot Rolled
- Joined
- Sep 25, 2012
- Location
- Cincinnati
And when I say remove the load from the breakers that trip, that means pulling the plugs out or even better pull the hot leads off the breaker.
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It's there at the start: "All 3 breakers are new Homeline tandem GFIC breakers (HOM 220GFIC and HOM 250GFIC)"
So there is no neutral involved. Sorta blows my theory out of the water. One thing for sure is there's going to be a pretty big spike from the start current.
Altrernate test: disconnect wires from one of the 20 amp ckts, one at a time. When it stops tripping off, the last wire was it!
When dealing with issues like this, I like to make sure that the basics are covered. Usually capacitive coupling is playing a role and circulating currents can bite you too.
I like the idea of disconnecting the load on the breakers that trip and seeing what happens.
But circulating currents can be nasty. Remember that the neutral gets bonded to ground at only one point! And only at one point! It is usually at the service disconnect which is usually the first electrical panel. From there, any sub panel(s) must have the neutral and grounds separate - this means that the sub panel cannot be only service entrance rated - must have the capability to remove the neutral to ground bonding jumper and have separate ground and neutral rails.
As stated earlier, you must use a 4 wire (2 hots, neutral and a ground) from the service entrance electrical panel to the sub panel, and from that sub panel to the next sub panel. From there, make 100% sure that the neutral and ground are separate in both sub panels and that you have not crossed a neutral and a ground. Grounds must go the the ground bar and neutrals go to the neutral bar!
I can't tell you how many times I have seen this violated in the industrial world and sometimes it causes nasty electrical gremlins.
Its not a surprise you are have trouble. A 15 hp 3 phase 240 volt motor (rpc) has a three phase locked rotor amps of 232, as you are feeding it 240 volt single phase the amps could go up by 173% to 401 amps on starting. The time it takes to get up to speed is quite slow compared to 3 phase, so the inrush amps are there longer. It is a mystery to me why you are [not] blowing the fuse,s out on the pole, let alone your inside breakers. But the induced current is what is tripping your gfi,s. I would add a pony motor to run the rpc up to speed before you entertain to start it. And the down side you do not a big enough service to run 15 hp.....Phil
I might be getting behind the times here, but is there a code requirement for GFCI breakers in this application?
Its not a surprise you are have trouble. A 15 hp 3 phase 240 volt motor (rpc) has a three phase locked rotor amps of 232,...
Phil... the breaker-trip in question isn't the breaker feeding the machine...
When he starts the machine, the breakers NEXT to the breakers feeding the machine trip.
The magnetic field of the big breakers' rush load, is causing the ones beside it (laden or not) to chunk-out. It's like the guy who put a 5" marine speaker on the dashboard of his boat, and wondered why his compass was always wrong...
Phil... the breaker-trip in question isn't the breaker feeding the machine...
When he starts the machine, the breakers NEXT to the breakers feeding the machine trip.
The magnetic field of the big breakers' rush load, is causing the ones beside it (laden or not) to chunk-out. It's like the guy who put a 5" marine speaker on the dashboard of his boat, and wondered why his compass was always wrong...
'Ceptin it is NOT next to it. I figured it was, but look at the slots he states they are in.
The probability is that there is a machine or a load of some sort out on those circuits. If it happens, when "off", to have a different capacitance to ground on each line, there is the imbalance.
If the noise is common mode, there does not even have to be an imbalance, just some capacitance out there. The CM current does not cancel, so it is all effective in tripping the GFCI.
So that is why we want him to unplug everything from those and see if they still trip.
Won't help.Or put in a decent panel.
So be careful, please.
Totally agree but not sure sure about the common mode. Definition of common mode is voltage between neutral and ground. Don't think that has to be the case here. A difference in capacitive coupling to neutral or ground from each leg can cause it.
Still not ruling out circulating currents unless his panels 100% for sure have no crossed grounds and neutrals......
ALL GFCIs have sensitivity problems. Q0 are better than Homeline, does not mean they are perfect.
Issues with machinery and GFCIs are usually due to trying to use a type A consumer GFCI that is intended to handle household loads, in the shop, where all sorts of loads with higher leakage currents are present. The type A GFCI trips on just a few mA current, and is unsuited to machinery with large motors and so forth.
"common mode" definition is actually a current (or voltage) common to all wires of a circuit..... differential is between wires, as per normal.
So in these breakers, which have 3 wires (2 hots and a neutral), a current common to all would clearly trip the GFCI, since it would be not returning on any of the sensed wires.
For a 230V load, voltages common to both hot wires (neutral is not used) would be "common mode".
Yes, capacitances out on the various wires would be a cause for such a current. It would likely have a differential component since the capacitances are likely not all equal.
Disconnecting the loads, which the OP seems resistant to doing, would determine this.
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