GFCI BREAKERS TRIPPING?

[elevate]

Hello great forum. 20 amp gfci breaker feeds heat trace on the roof. 277 volts. works well until once a month the transfer unit switches for testing,
then it trips. There is a tiny transformer that sends signal to fire panel which tells us when its off. I have switched breakers and checked all
connections :?

 

[hillbilly1]

Three pole or four pole transfer switch on the generator?

 

[elevate]

4 pole. Or switched neutral.

 

[don_resqcapt19]

Is the transfer switch the closed transition type?

 

[Devilace8]

Are there settings on the breaker? I had a similiar issue(not a gfi breaker) at a pump station where the main feeding the MCC would trip as soon as the transfer switch transferred power to Generator power. Had to get the GE guy to come out and change a setting on the breaker.