Loud Banging From Surge Guard 40250

[Keith Duner]

Hello:  Our 2005 Monterey has a built in Surge Guard Transfer Switch Model 40250 installed in the power bay.  Today I was exercising the generator (by using the heat strip features of both A/Cs) and noticed a loud banging coming from the Transfer Switch.  Happened over and over, maybe 5 to 20 second intervals and severe enough that I could see the Transfer Switch enclosure shake when the noise occurred.  I had normal power inside the coach and both A/Cs were running and producing heat during this time, so aside from the loud banging, all else seemed normal.  I shut the A/Cs off and with the Gen set still running, the noise continued.  I shut off the gen set and plugged the coach into the 30Amp service I have in the barn and the noise stopped (I don't have 50A available, just 30A).  I've seen something about this issue here before but when I searched the forum I didn't find anything that would point to resolution (I'm not the sharpest pencil in the box when it comes to electricity).  Can someone point me in the right direction to existing posts or offer some ideas?  Are there any serviceable components inside this Surge Guard Transfer Switch Model 40250?  Thanks

[Edward Buker]

Keith,

The only thing that comes to mind is momentary voltages from the genset not meeting the surge guard spec and relays are slapping on and off quickly. Not sure but a call to surgeguard may shed some light. I would turn on an incandescent 120V light (not the 12V puck lights) and see if it flickers or modulates with the noise you hear.

later Ed

[Keith Duner]

Update.  Still chasing a banging coming from the Surge Guard 40250.  All loads inside seem to be working fine on Generator power only, TV, microwave, AC W/Heat strips.  Removed Surge Guard cover and I can see the contactor connected to the Generator input vibrating consistent with the audible bang.  I can put an insulated screw driver on the visible portion of the vibrating contactor and stop the vibration and noise.  No visible indication of problem, no burn marks or loose pieces, connections are all tight.  However, when running the generator and looking at the Aladdin screen I see "AC LEG1 123 VAC AMP 0.0 FRQ 60, AC LEG2 122 VAC AMP 20.0 FRQ 60 Gen-Set Power Selected.  QUESTION, should I see Amperage on both legs?  Sorry if this is a dumb question, I'm a rookie at electrical problems.    

[Edward Buker]

Keith,

You should see current if you have something turned on that is on that leg. Start turning on 120V loads, if everything works it is the monitor that is not working. At some point you should see current on that leg also.

Later Ed

[Keith Duner]

Ed:  Thanks for the information, greatly appreciated.  I just ran the generator with both ACs w/heat strips, TV, microwave AND a small 110 V space heater plugged in and saw the following:  AC LEG1 121 VAC 9 AMP 60 FRQ and AC LEG2 121 VAC 34 AMP 60 FRQ.  I'm beginning to think that the generator output is OK and that I simply have a failing contactor inside the Surge Guard.  I've trolled the internet and can't find a replacement for the Cutler-Hammer C65FNF360 contactor so I think it's time to face the music and pop for a new Surge Guard 40250.  Just another one of those $1000 repairs  .  Thanks again for the guidance Ed.

[Edward Buker]

Keith,

Seems like the voltage is good and the current output is in order from the genset. Do you get this relay chatter when using a campground power post feed or just from the genset? If just the genset you might call the Surge Guard company and see if some generator waveforms cause their circuitry to sense an issue that causes the relay to chatter. Let them know the model of your generator. If you find this to only be an issue with the genset and the Surge Guard is fine otherwise you may want to consider moving the surge guard wiring so that it just protects the power pole feed coming into the transfer switch. If your generator is not used all that much and you are typically there when it does run there is little risk in not having a surge guard inline with the generator.

Later Ed