What’s that buzz? 2019 Vista LX 35F

[John Vista]

Hey all, lately I’ve noticed an electrical buzz/hum sound while plugged into our 30A circuit at our camp. Sounds like it’s coming from the drivers side, towards the rear wheel area (where the RV cord is)……haven’t really noticed it in the past, at least not as loud as it currently is. Should I be worried or just tune it out?

[Morich]

First, I would mention that many of us do not have good ears when it comes to locating sounds! So we hear things wrong!
But I might think first of what kind of "buzz" it might be?
Is it a pretty steady, uniform sound or come and go?
There is a thing called 60 cycle hum that can come from things like transformers when thin metal plates are stamped out and glued together to make the center of transformers.
The thin metal plates can come unglued and begin to do a "dance" at 60 cycles. A pretty consistent hummm! You can sometimes hear it near load centers or converters or lots of things that hum. Solenoids and things on furnaces often make a noise and it is nothing to worry until it gets loud enough to bother.

But there is another noise that might be called a hum and it might need checked to avoid damage. Maybe take a good listen at the transfer switch where it chooses generator or cord?
There are somewhat often reports of the connections getting a bit loose inside the transfer switch. That would likely be more of an intermitant on/off frying noise as it arced. But it would need work quicker to avoid the arcing getting hot enough to burn the connections or ruin the transfer switch!
Possible the transfer switch itself making a hum but not a problem? It does have relays that pull and might tend to make a smallish hum!

[creativepart]

IF, and that's if, you have a ATS Automatic Transfer Switch that is very likely the Buzzing sound you hear. I know some 30-amp Vista's don't have a transfer switch, but I'd "guess" that the Vista LX does even if it's a 30-amp coach.

How do you know? When using the generator do you have to manually plug the 30-amp cord into a receptacle in the power compartment? If the answer is yes, then you don't have an ATS.

My Adventurer has a very loud noticeable buzzing in the last driver's side compartment that comes from my ATS. I know everyone says that's a sign of loose wiring or a device that's on the verge of failure. However, I opened mine up and tested every connection and they are all tight as can be. But buzzzzz it does.

I considered buying a replacement ATS to carry for that day real soon when the buzzing thing finale broke. But after talking to others with the same issue decided against it. It's now been 3-buzzing years since I held off on that spare part plan.

[Morich]

Thought that might be the case and whether it is a bother or something to worry is related to what type buzzing!
A steady buzz like I described for a 60 cycle hum is nothing to worry about as they are relays in the transfer and thye certainly could be the cause of a hum.
I have not looked in one to study what type relay they have but many will have a coil wrapped around the stack of thin metal plates.
So how much noise and after how long is certain to be different in different RV.If we imagine a stack of thin metal held together when built, and then wire wrapped around them to form the magnetic coil, it's easy to see they may vibrate as the current flows.
How much vibration and resulting noise, depends on lots of small points.
How thing, how many, how good the adhesive, etc. etc. etc.!
A shift in tone of the hum is likely as weather and current flow changes but the steady hum is normally quiet different than arcing is expected to make!

[creativepart]

Originally Posted by Morich

I have not looked in one to study what type relay they have but many will have a coil wrapped around the stack of thin metal plates.

Richard, inside the ATS are two Contactors. One for shore power and another for generator power.

They look pretty much like an A/C contactor inside an air conditioning evaporator outside of your home.

It is a typical relay.

Here's one:

[Blastvalve]

If it helps, I have a 2015 Vista 35B which shares a lot of similarities to the 35F. In mine, that’s exactly where the ATS is located (in the bay for the shore power cable, just behind the rear tire and under the master bed). It is known to buzz from time to time.

Assuming the 2019 didn’t have significant chages, I’m guessing we are on the right path.

I’ve found that the connections in the ATS can need a slight tightening from time to time which reduces the buzz. If not familiar with a ATS, it’s an easy job, make sure all power is disconnected, remove the cover and you will have easy access. Snug up the connections and replace the cover.