30 amp breaker trips shore power - NEED HELP

[Mastercraft]

120v 30 amp main breaker on R29 2017 keeps tripping shore power even though all secondary 120v breakers are off. Shore power is fine until boats 120v 30 amp main is turned on, then shore power is tripped off. There should be no power useage by just turning on main and having all secondaries off, am I correct. It’s been down in low teens in Seattle for several days. Don’t know if cold caused it. ANY ADViCE? Could boat 30 amp breaker be bad?
Everything was fine until today. I hooked up a twin hornet 700 watt engine heater last week by just running the cord thru engine wall and plugging it in cave. That should not affect it.
I ran regular extension cord to keep semi warm.

 

[knotflying]

Well, nine times out of ten it is the last thing that you did that causes your issue. After you disconnect what you did and you still have the problem. I would do the following: Plug into a different pedestal. If it still happens, see if you can use a different shore power cord.

 

[marksandyham]

This will require troubleshooting with a multimeter, clamp on amp meter and a healthy respect for electricity. If you are not comfortable with line voltage get help. Safety first.

Just to clarify the CB on the boat is tripping not the CB on the shore power pedestal. If so the first thing to check is that the inverter is turned off. Next open the power panel, turn shore power at pedestal on and check for voltage on the line side of the breaker. It should be an ELCI (similar to a GFCI but higher trip point) Be careful its line voltage. From neutral to ground. It should be "0" volts. Next check from Hot to Neutral and Hot to Ground. Both voltages should be the same.

Next turn off shore power at pedestal and disconnect hot wire from the load side of the CB, Turn shore power at pedestal on and see if the CB will reset. If it will not than the CB has failed, if it does reset then you have a short somewhere between the CB and the other CB's. It could be the voltmeter but unlikely however disconnect it and see if that solves the problem.

 

[ohioan55]

It could be the breaker (could be). you need to divide and conquer. First, disconnect the shore power cable on the boat end. Secure the disconnected end so that it doesn't drop into the water. Cycle the shore power breaker on (with the power cable connected to the power pier but not the boat end). What happens? Cycle the breaker off.

 

[Mastercraft]

Problem fixed. Andrew Custis from Ranger responded right away and trouble shot it. I share a 30 amp shore power with another boat and they were drawing too much power in the cold weather. The 30 amp circuit breaker in my cabin still draws power if all the secondaries are off since Andrew says it turns on the battery charger.
A big thanks to Andrew!!! Amazing customer service!!!!!