BAC Forum
General Boards => Technical Support => Topic started by: Wayne Tull on March 06, 2011, 01:06:48 AM
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Has anyone found an effective method of eliminating the 60hz hum from the transfer switch relays. Since I'm not the original owner of this coach can you tell me if this problem existed when it was new (doesn't seem likely) or am I right to assume it has gotten worse with the passage time. This is a 94' Beaver Marquis so a lot of time has passed, but from looking at the posts it appears to be on others as well. Yes, my wife would appreciate any input you share.
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The AC coils in the relays will hum and it is the nature of the beast. You may try blowing out the contact area with compressed air. They will tend to vibrate more if the contacts do not mate well due to dirt.
I believe the best solution is to change the transfer switch to one that uses relays with DC coils. This is an example. I'm not endorsing this particular unit just letting you know that they make one with DC coil relays in order to avoid the hum.
http://rvpowerpartsplus.net/index.php?main_page=product_info&cPath=11&products_id=131
I did the following to reduce the hum of the relay AC coils in my unit and it reduced the noise by 30 to 40% in the coach which makes them still audible but usually not annoying. I cannot say where your unit would end up noise wise with this treatment given no two sets of these relays seem to produce the same noise intensity, nor does it stay constant.
I removed the relays by drilling out the rivets and mounted a furniture glide rubber pad under them and bolted them back down to the box. I did not torque them very tightly given that I was trying to isolate the noise. I also placed a rubber pad between the metal box and the "sounding board" the unit was mounted on in the coach. The project took about 4 hours and given that it reduced the noise but did not completely eliminate the issue I would probably opt to change the unit out if I was to do it again given what I know now.
You never know the outcome of an experiment until it is done.....hope this helps.
Later Ed
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Ed,
That helped a lot, I am going to switch to the DC based relays. That unit is at the head of the bed in the RV, and a 50% reduction in the sound level wouldn't be enough. Thanks again for sharing.
Stan
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Good luck with this. If I was going ahead with the change I would look at the wire configuration to the relays in your existing transfer switch and the location of the relays in the new one. The closer they are to your current configuration the easier time you will have of it. Hopefully you have enough wire slack available to make this work without too much trouble.
The configuration of the wires in my coach coming into and leaving the transfer switch box have almost no slack for modification so I would need an almost exact match to reduce the colorful language while doing that job....
later Ed