Is their no-hum tranfer switches out there?

richard5933 · October 28, 2018, 01:52:31 PM

An ATS is used to transfer between AC feed sources. By definition you will have AC available from one of the sources, maybe multiple sources. Otherwise, there is no need for the ATS to S.

DC is not typically involved in an ATS because it is irrelevant. When our old bus was under renovation, I went for a few months without a working DC system. An ATS that relied on DC would have been useless.

On that bus we went with a Blue Sea rotary manual switch rated at 65 amps per leg. Never had a problem with it. Our current bus has the OEM Kohler transfer switch, and it too works without fail. There are times I would appreciate an ATS, but not enough to make it worth the effort to convert.

Jim Blackwood · October 28, 2018, 05:09:38 PM

ATS=automatic transfer switch huh? Good to know. You could still use an industrial contactor with a DC coil and a small AC operated control relay. That'd get rid of your hummmmmmm. But I guess if you pulled the batteries out of the bus it might need to be bypassed. Or you could hook up a small DC power supply to it. Like a left over phone charger or something. None of that is hard to do.

Jim

dtcerrato · October 28, 2018, 07:06:04 PM

We have the ESCO ES50M-65N, it has AC contactors. While researching ATSs we found out that ESCO recently came out with the LPT50BRD LYGHT 50 Amp unit that utilizes DC coils to reduce the AC hum. DC coils also prevent low voltage drop out which is the other issue our unit has. Sometimes when we start the aux. electric air compressor - if it starts with 100+ PSI - our current ATS kicks out due to voltage drop - a real PITA. The only reason we went with the ATS was for the 30 second delay which is nice when starting the genny from the drivers seat on the go with a high load - the ATS gives the genny time to warm & stabilize before loading it. On another board a bus nut has a tutorial he's going to post that is a "fix" for the AC coils the hhhuuuuummmmm. That would be great so we can keep our unit. We'll see because with the current hum, it's out of here. Thanks for the feedback.

Frank @ TX · October 29, 2018, 04:29:57 PM

The big relays hum because they are NOT fully home. The problem is not with the contacts it's with the solenoid not coming to rest against the electro magnet. Clean the dust from both surfaces and the thing will be quiet until dust builds up again. Just maintenance.
Frank

dtcerrato · October 29, 2018, 08:03:47 PM

Interesting Frank - I'll look into that, thanks

luvrbus · October 31, 2018, 08:18:29 PM

I opened my ATS today the reason it is so quite they used 50 amp solid state relays instead of the mechanical type

thomasinnv · November 01, 2018, 08:03:00 AM

My solenoids only have power applied when the generator is running, and nobody is going to be able to hear a hum then. The standard, most common wiring configuration for an ATS is for shore power to be connected to the NC contacts, and generator input wired to the NO, so the relays are only energized while generator is running. Should be no hum on shore power.

Geoff · November 01, 2018, 08:35:42 AM

Quote from: thomasinnv on November 01, 2018, 08:03:00 AM
My solenoids only have power applied when the generator is running, and nobody is going to be able to hear a hum then. The standard, most common wiring configuration for an ATS is for shore power to be connected to the NC contacts, and generator input wired to the NO, so the relays are only energized while generator is running. Should be no hum on shore power.

They can be set up nc like you describe above, or some use contact relays that are on with shore power, and use another contact when the generator starts and disconnects the shore power if left on.

dtcerrato · November 01, 2018, 07:06:01 PM

I wish I knew then what I know now! That's an understatement - huh? Kinda like "hindsight" being 20/20 hah! We try & do things right the 1st time but when one invests $100s in a product that creates inconvenience or even worse – a nuisance – it definitely wasn't done right the 1st time, was it? It's unbelievable the variables in the various ATS's on the market. What's even more unbelievable is the lack of information up front when these beasties are marketed as Buswarrior mentioned more than once...
I will get it right the 2nd time around due to the collective knowledge & the willingness to share it on this & other forums like it.
So far in the last few days – researching what I can find & what others on the boards do find & bring forward there are many variables for selecting an ATS (automatic transfer switch) that were found & many more unknowns.
Some make noise (EMR-Electro Mechanical Relay) & some don't (SSR-Solid State Relay) EMRs are more economical, SSRs are more pricey but to say one is better than the other is inaccurate because both have their advantages & disadvantages.
Frank@TX made suggestion on how to decrease the AC noise; Luvrbus didn't have any noise because he had SSRs
Of the EMRs some make more noise (AC coil) than others (DC coils) Jim Blackwood & Richard5933 were hitting some points referring to AC vs DC coils when in fact both types are very successfully marketed. The DC current used in DC coils is not relevant to the coach's dc batteries but originates from the pole/ shore power or Genny AC then converted.
Also of the EMRs some are NO (normally open) & some are NC (normally closed) Thomasinnv has NC ATS so hum wouldn't be heard (if there was any) over the running generator ambient. Derrick please post a link of what ATS you're running! Thanks
Unfortunately in our situation our EMR NO AC coil ATS sets at the interior base of the living room console & if the roof air was running everything would be fine but if it is quiet (which it never is due to the hhhhuuuuuuummmmmm) the wife can't take the hhhhuuuuuuummmmmm, soooo hence this post.

sixtyseven · November 01, 2018, 10:30:53 PM

Hey Dan, looks like you're getting an ear full over here ! I like Derrick's solution the best even though it might be quite a task on yours with your circuit board control. Absolutely 0 noise that way ! I wish I would have thought of that when I was building my ATS. Thanks Derrick....now I am going to be thinking about rebuilding my ATS when it doesn't even need it

dtcerrato · November 02, 2018, 04:09:41 AM

Hi Joe, yes I was going to give Derrick's suggestion a shot. I need to throw this in the mix. Somewhere I read that when an AC coil contactor can "fully" find home, the coil runs much hotter reducing it's life span - thus in that same reading lots of mfgers prevent the contactor from bottoming out which increases the life span & also the hum. I really like the idea Thomasinnv mentioned about using a NC contactor. I was thinking on approaching Esco on my ATS & ask if it's possible to switch the shore power contactor from NO to NC. Really swimming in deep water in this one!

thomasinnv · November 02, 2018, 08:08:18 AM

Quote from: dtcerrato on November 02, 2018, 04:09:41 AM
. I was thinking on approaching Esco on my ATS & ask if it's possible to switch the shore power contactor from NO to NC. Really swimming in deep water in this one!

If your ats is in fact nc on generator side without relay coils being energised, there is no reason you couldn't switch the shore and generator connections and eliminate the hum on shore power. The only caviat may be if it has a delay for the generator side. I have worked on and replaced a lot of ats's in a lot of rv's over the years and every one of them (with the exception of a few that were replaced by the customer and improperly wired) were always wired with shore on nc. The ones that have a generator delay have the delay mechanism wired into the relay coil circuit.

Of coarse I realize these are all designed and manufactured for rv use, and whatever you might find in a bus conversion could have come from anywhere, and have been designed for who knows what actual purpose. All bets are off then.

dtcerrato · November 03, 2018, 06:10:01 PM

I received a reply from ESCO, the mfger of my ATS (ES50M-65N). They said with my transfer switch you have to live with hum because they're magnetic AC contactors. They have a unit out now (that I have been pondering on, the LPT50BRD) that utilizes DC relays and is totally silent. Live & learn, sometimes the hard way.

Geoff · November 04, 2018, 12:21:10 PM

Quote from: dtcerrato on November 03, 2018, 06:10:01 PM
I received a reply from ESCO, the mfger of my ATS (ES50M-65N). They said with my transfer switch you have to live with hum because they're magnetic AC contactors. They have a unit out now (that I have been pondering on, the LPT50BRD) that utilizes DC relays and is totally silent. Live & learn, sometimes the hard way.

What the manufacturer told you is B.S. The magnetic relays don't necessary buzz. Plus you can replace just the coil instead of the whole switch. They are simple to work on. Did you ever open the box and get the number off the switch that humms?

dtcerrato · November 04, 2018, 09:45:08 PM

Yes, the shoreline contactor is a GE CR353ADY39APAK. What complicates matters (at least for me) is both contactors (the shoreline I mentioned & the generator contactor) are both connected to a circuit board with a delay for generator switchover. It would be great if the shoreline contactor was NC, then it would be inoperative until the genny is running at which point we wouldn't be able to here the audible hummmm. Please keep in mind that this ATS has hummed since day one. We've tried everything just short of replacing anything.