Automatic transfer switch

[kmad1999]

I had one of the 40 amp contactors go bad in my transfer switch. I swapped it out with a new one (identical) and when I plug the motorhome in, I get a LOUD buzz. I took pictures before I unhooked the old one to verify proper wiring of the replacement. Ideas?

 

[BGMAC]

Does it sound like a transformer buzz? If so it may not be secured tightly. I have had transformers buzz because they were kind of loose.

 

[Kevin D Pem]

You took before pic's! So where are the before and after pics.

Don't forget the pictures of the labels on new and old contractors. Without that I can only guess!

 

[Chuggs]

I have a different rating…but if you got all the wiring 100% correct…there may be an issue with the mechanical interlock. The little module that is situated between the two relays. If the pins are not indexed correctly, it may be giving you an issue.

If you accidentally got the field line to the Shore power relay, properly routed thru the switching terminals in the generator relay…it could be an issue if they both have power. That switch disconnect the shore relay as the generator relay begins to close…. The combination of field switching and the mechanical interconnect are what allows the switch to have generator priority, and break connection before make connection preventing a phase issue….