Community Forums

djhinds · 12-04-2010, 07:38 AM

The transfer switch on my 04 Monaco Sig hums when on shore power or on the gen. power. It has an Esco Power 50 switch and I found the manufacture's web site trouble shooting page. It says I need to remove the contacts as they have dust on them

and clean them. DUST ON THEM YOU SAY, I guess the DW has 1 more thing to dust now... Has anybody else had this problem and what did you do to fix it? Is this an indication of switch failure in the future? I would not think dust would make a difference. Also should I put Dielectric Grease on the contacts for better contections.

Dave

Robi.1014 · 12-04-2010, 07:55 AM

Dave,
My experience is that if the main (high amperage) contacts in your ATS (automatic transfer switch) were doing the "humming", they would fail quickly....especially when running onboard a/c units (high-amperage drawing devices).

The "throw" of the ATS contacts from shore to genset and back again is accomplished by a/c -powered solenoids that are momentarily energized, and once the "throw" is complete, there is no more power to the solenoid that caused the "throw" to happen. But if the solenoid is REMAINING energized, that would cause the humming.

I have a drawing in Microsoft PowerPoint that explains how my home-based ATS works (to attach my portable generator...out back). Accompanying text explains how it works....thus it should give you a good background on how to troubleshoot yours. Send me an email and I'll forward you a copy. robi.robison@verizon.net

Mike Canter · 12-04-2010, 09:09 AM

Dave, I agree with Robi. I just went out to my Sig and it hums on shore power and gen power as did my last MH. There is a big difference between a 60 HZ AC hum and relay chatter. If it had relay chatter then maybe the contacts need cleaning. That transfer switch is closed up tight and I doubt that much dust can get in there. If yours hums like mine hums then I would say it is normal and you should leave it alone.

Midniteoyl · 12-04-2010, 09:19 AM

Pretty sure they meant simply that the contacts are dirty.. little emery cloth and grease, as it looks like you did.

Mike Canter · 12-04-2010, 10:17 AM

If you are ever going to clean high amperage electrical contacts then you should only use 1000 or 1500 emery cloth or even better is crocus cloth to polish the contacts. If you use to coarse of a grade of emery paper then you will rough up the contacts and increase the resistance of the two contacts joining together and will burn out faster. If they are really pitted then use just coarse enough emery paper to clean them then polish them with real fine paper to make them smooth again. And NO do not use any dielectric grease on those contacts unless specified by the manufacture

Midniteoyl · 12-04-2010, 10:34 AM

Agree.. the grease is not to be on the contact pads themselves. Should have clarified.

The other thing to look for is that the contact pad faces are parallel to each other - as parallel, flat, and smooth as you can get without removing too much material.

nodine · 12-05-2010, 04:09 AM

Quote:

Originally Posted by djhinds

The transfer switch on my 04 Monaco Sig hums when on shore power or on the gen. power. It has an Esco Power 50 switch and I found the manufacture's web site trouble shooting page. It says I need to remove the contacts as they have dust on them

and clean them. DUST ON THEM YOU SAY, I guess the DW has 1 more thing to dust now... Has anybody else had this problem and what did you do to fix it? Is this an indication of switch failure in the future? I would not think dust would make a difference. Also should I put Dielectric Grease on the contacts for better contections.

Dave

There is not much that can be done about the hum. The transfer switch uses a contactor to connect the shore power to the coach 110 VAC system. By default, when shore power is lost the contactor de-energizes and connects the coach 110 VAC system to the generator. This is because the electromagnet that pulls the contacts and connects the shore power is powered by the shore power. The hum is due to the electromagnetic field in the coil changing polarity at the rate of 60 Hz. High quality contactors usual do not hum so noticeably unless the manufacturer of the transfer switch did a poor job of mounting it.

Bob