Was running on battery power and charging batteries at night during the aloted times.In the bedroom near the breaker area
you could hear a humming sound,crawled under the coach but could not pinpoint the source.Coach runs and everything works
fine,any ideas what the sound could be?Is only on battery power,when we are plugged in the sounds gone.
John,
That should be your ATS (automatic transfer switch) for under the foot of the bed. Bet you'll hear it even louder if you lift the bed up. At least the is what used to hum or my coach before I traded out my AC powered ATS for a DC powered ATS.
Jim
2002 U320
You are not the first to "notice" this IRRITATING noise (nor will you be the last). :help:
30 amp transfer switch HUMMING! (http://www.foreforums.com/index.php?topic=28806.msg241404#msg241404)
The AC relays in the ATS have tht wonderful 60 cycle hum.
Jim
Jim,
I would be interested in hearing more about your DC powered ATS... Links, experiences, all would be welcome. How much DC current required? Source from the house bank?
Don
Why would it hum on battery power? Does the inverter power the transfer switch? Seems like the ATS should default on battery and power when plugged in.
X2 Don
Hi Don and John,
DC transfer switches are readily available, you just have to search online and read the specs. In a store you might be able to find the schematic diagram in the package. Or just Google the product.
I think they may have the same relay coils but the AC signal to activate them is converted to DC by a full wave diode bridge (and maybe a capacitor to smooth out the ripples). No AC ripple in thre relay, no aggrivating hum at night. Extra current is not needed for these far more quiet transfer switches. I would hope most newer ATS boxes have this benefit. Maybe others will chime in to be more specific.
Jim
2020 U320
There are two transfer switches (ATS) in most coaches - the 50 amp unit switches between shore AC and generator AC power, and the 30 amp unit switches the
inverter powered circuits between shore/gen AC power and inverter AC power. So, when running on batteries (inverter), the 50 amp unit is "idle" while the 30 amp unit is energized and (in some cases) humming a tune.
I solved the problem by eliminating both of them. NO MORE HUM! ^.^d
Thanks for that explanation. One more parasitic drain I wasn't aware of.