Why does GFCI trip when running 110 and 220 through same conduit?

[lfoss0612]

I am currently working on wiring a hot tub. I currently have a 50a subpanel with 2 breakers(2 pole 30A and a 1 pole 20a). The wires I am using to run to the tub are THHN wires and are 10awg for the 220v, and 12awg for the 110v. The heater for the tub runs on 220v and the circulation pump, jet pump, and display run off of the 110v. When the tub is hooked up, everything works except that when I turn on the jet pump it trips the breaker. I did some troubleshooting and ran the 110v wires outside of the conduit, and everything works including the jets. Can someone explain to me why when I run the 110v in the same conduit as the 220v, and turn on the jets, that the gfci on the breaker trips?

 

[pc1966]

Assuming the wires are OK (no insulation damage that moved when the pump started) there is no obvious reason. Typically when you get odd trips like this when a big load starts (like motor switch-on surge) it can be down to a neutral to ground fault.

Can you isolate all supplies (both lives and the neutral) and do an insulation test to the ground/conduit?

 

[lfoss0612]

Assuming the wires are OK (no insulation damage that moved when the pump started) there is no obvious reason. Typically when you get odd trips like this when a big load starts (like motor switch-on surge) it can be down to a neutral to ground fault.

Can you isolate all supplies (both lives and the neutral) and do an insulation test to the ground/conduit?

The conduit is schedule 40. I have also done a test with the ground completely detached. I believe I am down to 2 possible issues. It is either the starter capacitor, or the new breaker i installed is bad.

 

[Pete999]

I am currently working on wiring a hot tub. I currently have a 50a subpanel with 2 breakers(2 pole 30A and a 1 pole 20a). The wires I am using to run to the tub are THHN wires and are 10awg for the 220v, and 12awg for the 110v. The heater for the tub runs on 220v and the circulation pump, jet pump, and display run off of the 110v. When the tub is hooked up, everything works except that when I turn on the jet pump it trips the breaker. I did some troubleshooting and ran the 110v wires outside of the conduit, and everything works including the jets. Can someone explain to me why when I run the 110v in the same conduit as the 220v, and turn on the jets, that the gfci on the breaker trips?

In the UK any cables of different voltages running in the same containment MUST be rated to the highest voltage present.

 

[scotsparky]

could you be picking up induced voltages on the 110 CPC caused by the 220v

the Ground fault device may be reading that.

I am in Uk and not 100% sure of US acronyms.
I am guessing the 220 is a 2 pole supply from 2 phases. (UK polyphase)
The 110 is centre tapped from transformer so a reduced low voltage of 50v on each cable. if they are parrallel they voltages may be induced.


then again i may be well out i am on my third beer and a bottle of rum is calling

 

[lfoss0612]

That was my thought at first also, but even with the 220 breaker off, it still trips.

 

[Pete999]

I am currently working on wiring a hot tub. I currently have a 50a subpanel with 2 breakers(2 pole 30A and a 1 pole 20a). The wires I am using to run to the tub are THHN wires and are 10awg for the 220v, and 12awg for the 110v. The heater for the tub runs on 220v and the circulation pump, jet pump, and display run off of the 110v. When the tub is hooked up, everything works except that when I turn on the jet pump it trips the breaker. I did some troubleshooting and ran the 110v wires outside of the conduit, and everything works including the jets. Can someone explain to me why when I run the 110v in the same conduit as the 220v, and turn on the jets, that the gfci on the breaker trips?

Induced EMF. .