Buzzing Automatic Transfer Switch

Cocoa Rebel · 12-17-2022, 06:38 PM

Hi Everyone!

We have a 2022 Winnebago Vista 29V and just love it!

I notice that when I am hooked up to shore power at an RV park, there is a noticeable buzzing sound, and it is originating from a Southwire Model 40101 Automatic Transfer Switch. I always use a Southwire Surge Guard 50A Model 34951 when hooking up at an RV park pedestal, which indicates everything is normal.

I have researched this and have been told different things....."it's normal with a newer model" to "no, it shouldn't be doing that." Is it dangerous and indicates some sort of problem coming?

Any suggestions or anyone else's experiences or guidance would be appreciated. I am not looking to work on it myself but can certainly give the information to a local guy here.

Thank you and Happy Holidays!

**creativepart** · 12-17-2022, 09:28 PM

My 5-year old Adventurer has the same ATS and it has always made a loud hum, more of a buzzing actually. I worried about it and everyone said to open it up and check for loose connections. Which I did and found nothing loose. In fact, it was super tight in there. Folks told me that it was probably going to fail soon. I was even thinking of buying a replacement to carry with me for when it failed. That was two years ago and it’s still working and still loudly buzzing away.

I’ve learned to ignore it.

I’m not suggesting you do the same, just relating my experience.

TravatoJohn · 12-18-2022, 07:56 AM

My 2017 Winn. Travato has a slight buzz also when plugged in. It is directly underneath passenger side bed. Has been making hum ever since new. It is not loud but noticeable when quiet at night. I put extra insulation under 3/4 inch board under mattress which helped some. Has been doing same hum for 5 years so must be symptom of that model. Travato John

Morich · 12-18-2022, 08:06 AM

I have not worked with that transfer switch but they do have relays that stay operated and relay do have a common complaint of humming. I might guess that it is normal.

If you've been around things like a furnace that has a gas solenoid, it is common to hear a slight hum from the coil of the solenoid. Same basic item.
There are coils of wire wrapped around many thin layers of metal stampings to make the electromagnet. As the 60 cycle AC passes through this wire, the thin layers of metal can try to do a little 60 cycle "dance" that is fast enough that we call it a hum!
Just think of it as the electrons having a party?

**macnut** · 12-18-2022, 01:52 PM

I had the same transfer switch as CreativePart and it also buzzed. I always thought it was normal, which I guess it is, but it's always a good idea to ask this group, like you did!

jerichorick · 12-25-2022, 05:03 PM

Quote:

Originally Posted by Cocoa Rebel

Hi Everyone!

We have a 2022 Winnebago Vista 29V and just love it!

I notice that when I am hooked up to shore power at an RV park, there is a noticeable buzzing sound, and it is originating from a Southwire Model 40101 Automatic Transfer Switch. I always use a Southwire Surge Guard 50A Model 34951 when hooking up at an RV park pedestal, which indicates everything is normal.

I have researched this and have been told different things....."it's normal with a newer model" to "no, it shouldn't be doing that." Is it dangerous and indicates some sort of problem coming?

Any suggestions or anyone else's experiences or guidance would be appreciated. I am not looking to work on it myself but can certainly give the information to a local guy here.

Thank you and Happy Holidays!

The relays are always energized when on shore power. The coils in the relays are not made with the greatest care and the windings could vibrate as the AC changes polarity.

It would not be a bad idea to check for loose connections in any case. You won't get a humming from a loose connection that I know of at our power ratings but you will get burnt terminals. Out of 3 coaches I have had loose connections in 2 of them.

Merry Christmas and Happy New Year.
Rick

JimBec1putt · 12-26-2022, 01:23 PM

I had same issue on 2013 Sightseer 35g..

Repaced with an Elkhart LPT0BRD.

50 amp unit, They also make a 30 amp version.

It only has one relay for generator power, Has a delay to get generator up to speed before putting load on.

On shore power no relay. So no no noise and DW happy!

Happy Holidays

JimPutt1

Anyone interested in a 2013 Sightseer 35g.. 45000 miles very clean and no issues??

powercat_ras · 12-26-2022, 02:02 PM

What is strange to me is that all the RV transfer switches I have used have a 20 second delay before allowing generator power to cut thru to the load center, to give the engine of the generator a few seconds to stabilize. The contractors are de-energized cutting thru shore power and energize (after the 20 second delay) to connect to the generator power instead of shore power.

So there should be no power to the transfer switch contactor coils to generate a coil buzz sound when connected to shore power.

Maybe the generator and shore power connections are reversed. It would still work but the 20 second delay would be when connecting to shore power. If you connect to shore power and about 20 seconds later you hear the "clunk" of the transfer switch contactors closing it may not be wired the way the manufacturer recommended.

Note: some transfer switches have a setting on their control board that enables or disables the 20 second delay if the delay is set to off then you won't get the 20 second delay either way.

jerichorick · 12-27-2022, 05:51 AM

Quote:

Originally Posted by JimBec1putt

I had same issue on 2013 Sightseer 35g..

Repaced with an Elkhart LPT0BRD.

50 amp unit, They also make a 30 amp version.

It only has one relay for generator power, Has a delay to get generator up to speed before putting load on.

On shore power no relay. So no no noise and DW happy!

Happy Holidays

JimPutt1

Anyone interested in a 2013 Sightseer 35g.. 45000 miles very clean and no issues??

I found this manual on your ATS: https://www.manualslib.com/manual/17...?page=2#manual
Looks like it has 2 relays or contactors. Nice, simple design.
We used contactors in the phone company power control systems. On occasion we would have to replace the coil because of noise or it would fail. If this ATS uses relays such as what we used, repair parts are available for rebuilding them.

Happy New Year,
Rick

DustyDude · 01-06-2023, 12:07 PM

My ATS started making a louder hum than usual so I checked the lugs with a torque screw driver and found one of the lugs had become loose. After tightening it to 45 inch/pounds the hum is back to normal. I had hoped it would go away, but not today. Martin at RV Street has a good video about checking these things once a year, I guess he is right.