Since we installed our upgrade 50 amp shore power along with a 50 amp transfer switch - the constant hum of the transfer switch is really getting on the wife's nerves. It's going to have to go weather or not I can find one without the hhhhhhuuuuuummmmm.... Are there transfer switches with DC contactors without the annoying hum? If so can anyone comment on them. That's another $150 clams wasted. Not all our decisions are good ones but we must keep keeping on.
Can you cover it with a thin sheet lead box? Is the hum noticeable because of rigid mounting? Can you mount it on rubber isolators?
I have the same problem with mine. I tried to isolate with rubber,clean it,nothing work.
There are some that claim to be silent, but more expensive.
Tried everything to quiet it down but the hum is still very noticeable. We found a couple of different brands with DC contactors but would really like to hear from someone that has experienced them. Best pricing I found was $165-$175. Only no-hum would make it worth it otherwise we're doing away with the current one. Too annoying.
I have a TRC Surge Guard it makes no noise been installed now going on 3 years and it's still quite
If it is new, take it back. If it is out of warranty, open the cover and see which relay is humming (if it has two relays). Once you know that, you can safely remove the box and change out the relay that hums. With the part number off the relay you can look on eBay and get the exact replacement. I had one ATS that didn't start humming for a few years, so I did what I am advising you to do.
can't help ya because I replaced the old one that had a hhhhhhhhhhhuuuuuuuuuuuuummmmm with a new one and the instructions said to make sure it was mounted vertically and the old one was mounted on its side so I assumed that was the problem .
NOPE ! after about 6-8 months this one started to hum but it is still
ok ish
https://www.amazon.ca/gp/product/B003VAWNVK/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
this is the one I have now crap unless you like the hum
good luck . if you find one let me know
dave
I'm confused, wouldn't transfer contactors be DC operated? Otherwise if your inverter went down it seems like you wouldn't be able to operate your transfer switch? What am I missing here?
Jim
The ATS relays are AC, not DC. When they start to hum you can try cleaning the contracts, of course when it is turned off (added for the nit-pickers).
But why would you ever use AC for that? You always have DC on the bus, and it can't hum unless the contacts are really dirty.
Here's why it doesn't make sense to me. OTR you are on DC and inverter power. No DC, no inverter. When you plug in, until the transfer switch closes you're still on DC and inverter. Again, no DC, no AC. If the bus is completely dead you have no AC to actuate the transfer switch unless you bypass the transfer switch somehow. And if you do that won't your inverter charge the DC circuits? So how does it make any sense at all to use an AC contactor for your transfer switch?
Jim
If the coach is completely dead, how can dc relays actuate once you plug in till charger turns on to provide enough power to actuate relays. I guess what the default is on the transfer switch depends also.
Yeah, that's right too. Maybe what would make sense is a contactor with a manual operator, those are common enough. Push the button to engage the contactor and power up the system. Should work either way.
Still, an AC contactor just seems backwards to me.
Jim
Maybe it would make sense for the battery charger to be hard wired to the shore line? What would be the down side to that? Maybe an inline breaker or switch so you could isolate it if you want.
I realize these days the highly sophisticated inverter/charger units are very popular and for good reason, and I guess some of the better ones have the transfer relays built in, so not a whole lot you can do with that I guess. I just wonder if maybe separate units don't make a little more sense. In which case any generic industrial contactor of the proper rating would do the job just fine. If you want it to turn off or on automatically under certain conditions it's not that hard to do.
Jim
Quote from: Jim Blackwood on October 28, 2018, 11:59:28 AM
But why would you ever use AC for that? You always have DC on the bus, and it can't hum unless the contacts are really dirty.
Here's why it doesn't make sense to me. OTR you are on DC and inverter power. No DC, no inverter. When you plug in, until the transfer switch closes you're still on DC and inverter. Again, no DC, no AC. If the bus is completely dead you have no AC to actuate the transfer switch unless you bypass the transfer switch somehow. And if you do that won't your inverter charge the DC circuits? So how does it make any sense at all to use an AC contactor for your transfer switch?
Jim
I'm not sure how DC relays got into the picture. I've never seen a DC relay in a 30 or 50 amp ATS. They are activated by AC relays that switch when you plug into shore power or start the generator. The inverter can work independently with dedicated 120 outlets, have a pass-through, or be a hybrid.
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.
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
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.
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
Interesting Frank - I'll look into that, thanks
I opened my ATS today the reason it is so quite they used 50 amp solid state relays instead of the mechanical type
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.
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.
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. ;)
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 ;D
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!
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.
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.
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?
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.
Mechanical AC contactors hum. There is just no getting around it. Sometimes it is more, sometimes it is less, but it is always there. Usually other running equipment covers up the sound. There is no easy way to know if a contactor is going to hum more, or less except to try it.
The way I see it you have 3 choices.
-Rewire the contactor to NC
-Replace the contactor with solid state or DC
-Replace the entire unit.
Or, I suppose more drastic measures could have to do with ignoring certain things... not a happy solution.
Jim
I can give you the part number for a magnetic relay that doesn't hum, but you would have to figure out how to wire it in. Especially with a circuit board that delays the generator feed.
My SW Trace delays the generator feed, so I don't have to worry about it. I don't have the relay part number handy, so if you want it I'll find it for you.
--Geoff
I appreciate it Geoff but don't bother. I'm not comfortable modifying a piece of equipment like that. I could maybe use it for an ATS on the house for Genny power during hurricanes - so at least it's not a total waste. Thanks
Dan - I only skimmed the comments, so someone may have said the same thing already. As you have found most ATS' are built with "normally open" relays, if you don't want the huuuuummmmmm, you need to find one with normally closed relays on the shore side. With the normally closed on the shore side, the relay is energized by the generator, so you always hear the generator over the relay buzzing. Each type of setup has it's advantages and disadvantages as usual. Good Luck.
Solardude
solardude - 10-4 on NC relays. The lack of information given when shopping for ATSs is ominous! Does anyone on the board know a manufacturer & model no. of an ATS with a NC relay on the shore power side?! That was my first choice but can't nail one down. Was considering a purchase of an ATS with DC coil relays that advertise "silence". IE: the WFCO WF-T57 or the ESCO LPT 50 BRD. Comments please!
Is there any reason why you can't wire the shore power to the Gen input and vice-versa? Would it make any difference to the ATS where the power comes from and are there any functions available from it on shore power that are not available on generator power?
Jim
Don't think so Jim, its more involved than that. There's a delay circuit board on the Generator contactor - but what do I know? I got a call into ESCO to talk to one of their techs. If I learn more I'll post it. Thanks
Here is an ATS that is NC for shore power:. Power Max PMTS-50. Available on eBay.
Thanks Goeff. Was curious how you know this unit has a normally closed shorline contactor. I'm not questioning your response but heck I can't find nothing stating that and this unit is so much lower in $$ than what I've been serching for. Uninformed bus nut wondering how you guys find your info. Thanks.
I know this unit because I installed one in a customer's bus recently. I have the installation instructions which details that it is NC to shore power and has a generator delay switch. No problems with the unit, it is well made.
Thanks Geoff. Sorry for all the questions but you seem to be the go to guy for my transfer switch issues. One other issue that I'm having (besides the annoying hum) with my current transfer switch that I'd like to steer away from (maybe with your help). The AC contactor for the Genny "drops out" with low voltage. Specifically when we're on genny power and I start up the auxiliary electric air compressor, if the compressor starts at high PSI (90 or higher) the transfer switch "drops out" & goes through another delay cycle. The only way I can get around that is to exhaust the compressor air down to below 50 psi before trying to energize it. Okay, with that in mind - while ATS shopping there is language stating with only the DC coiled "relay" ATSs (that I mentioned this morning on this post) that the DC coils have reduced (if any) hum and "don't drop out" during low voltage. With all this being said I'm thinking I may need to stay away from the AC magnetic contactor & go with the DC coil relays. Please give me your take on that. Thanks
Quote from: dtcerrato on November 07, 2018, 06:50:31 PM
Thanks Geoff. Sorry for all the questions but you seem to be the go to guy for my transfer switch issues. One other issue that I'm having (besides the annoying hum) with my current transfer switch that I'd like to steer away from (maybe with your help). The AC contactor for the Genny "drops out" with low voltage. Specifically when we're on genny power and I start up the auxiliary electric air compressor, if the compressor starts at high PSI (90 or higher) the transfer switch "drops out" & goes through another delay cycle. The only way I can get around that is to exhaust the compressor air down to below 50 psi before trying to energize it. Okay, with that in mind - while ATS shopping there is language stating with only the DC coiled "relay" ATSs (that I mentioned this morning on this post) that the DC coils have reduced (if any) hum and "don't drop out" during low voltage. With all this being said I'm thinking I may need to stay away from the AC magnetic contactor & go with the DC coil relays. Please give me your take on that. Thanks
Your compressor is out of spec/worn/under size cord...lots of possibles for start amps. The contactor "falls out" at 105v.
Check the unloader first. It should drain pressure from compressor pump so it starts unloaded. You can usually hear a slight hiss as comp. shuts off. It is usually part of the pressure switch assembly.Also check one way check valve between pump and tank. It could be leaking back keeping pressure on pump head.Finally, compressor should be fed with 12 gauge wire.
Thanks for the quick response eagle & chessie. I must admit you gents caught me by surprise when you mention the compressor. I have to admit it is a forever running old Craftsman compressor but a real gem. It doesn't give me any problem when on shore power, only when transferring to genny power through the ATS. It is wired with 12 gauge copper. I do hear the hiss as comp. shuts off. I will check for the check valve. I was asking the question about drop out because the only mention of "eliminates drop out" is on ATSs advertised with DC coil relays. More important than drop out for us is eliminating the hum which can be done with a NC shoreline contactor &/or DC coil relays. Thanks
If all else fails, is it possible to use a soft start capacitor for the air compressor, same as done for air conditioners?
wrestle this beast to the ground!!!
happy coaching!
buswarrior
BW how does one determine how to size a soft start capacitor? Where would it hook in at. The compressor is a 1HP motor. It's wired for 110vac & is convertible to 220vac. It would probably be better on 220vac for the ATS but hate to have to be on 50 amp shore power to run it that's why we like it on 110vac. Gotta check the check valve, wonder if the motor capacitor(s) are getting tired. Damned ATS issue is kicking my butt.
Check voltage at motor when starting. If you have a clamp meter, check amperage draw when trying to start. Instead of soft start, maybe a booster capacitor kit, if it turns out motor starting capacitors are ok.
Do you have an electric motor repair company near by you could take motor to to have it checked?
Quote from: chessie4905 on November 08, 2018, 05:18:56 AM... Do you have an electric motor repair company near by you could take motor to to have it checked?
Yeah, if there's an underlying problem with the (not-so-new) motor, it would be better to fix that before it shows up in other issues besides just with the ATS.
(PS - If the motor is OK, "Sure Start" and "Micro-Air" both recommend their soft-start kits for large-start-current motors like compressors. If the motor is working correctly and needs the help with an ATS, a kit might also be of benefit when of shore power, too; you never know when you're going to get a worn or tricky breaker on a shore power panel.)
Let's make this simple. If it starts OK under 50psi then inertia isn't a problem but high pressure is. Sounds like you do have a functioning unloader. So what you need is more volume between your head and check valve. Possibly an accumulator tank of some sort. Your unloader reduces the pressure in that tank to ambient so that on startup there is no pressure resistance. You need to size your accumulator so that it stays under 50psi until after the compressor has reached full speed. There will be a larger and longer "hiss" when it stops but that will do the job for you.
Jim
Well I finally ordered a transfer switch that should make wifey (& me) happy with no hhhuuuummmmmmm. Same manufacturer - ESCO because its in the identical enclosure so will make changeout easier. The shore power relay is NC (not activated) and the coils are DC & the drop out voltage is 90 compared to 107 on the current AC contactors. We'll see how it works - if it doesn't it's going back. We will also be looking into the items that were mentioned of the electric air compressor. Thanks for the input.
Got the new transfer switch installed today. Works great, no hum, actually no nothing. The DC coil contactors are normally closed on the shore power side so the unit is dead silent. Wished I knew then what I know now about auto transfer switches when I purchased the 1st unit. Same company just designed differently. Thanks for all the input. Sometimes we learn the hard drive way...
Quote from: dtcerrato on December 03, 2018, 06:53:12 PMGot the new transfer switch installed today. Works great, no hum, ...
Great, Dan, glad it worked out for you. Do you have a manufacturer and part number - sounds like an ATS I need. Thanks, BH
Bill the unit we bought was the Esco LPT50BRD Lyght. It was the most expensive of the three units ($165.39 from RVUpgrades.) that satisfied our needs. I stayed with the same manufacturer for a simpler reinstall because the enclosure was exactly the same as the one it was replacing. The following units were also compatible in every aspect we were looking for: Power Max PMTS-50 (Burnstine's Distributors @ $155) and the WFCO T-57 50 amp ($143.29 from RVUpgrades.com). All three of these units mentioned are quiet instead of the annoying hum from AC contactors. The Esco is the only one I can vouch for - installation complete & very happy with it.
Quote from: dtcerrato on December 04, 2018, 06:23:54 PMBill the unit we bought was the Esco LPT50BRD Lyght. ... I can vouch for - installation complete & very happy with it.
Thanks - nothing like personal experience! Appreciate the effort. BH
Didn't mean to call you Bill - Bruce, good luck.
Quote from: dtcerrato on December 05, 2018, 07:32:36 PMDidn't mean to call you Bill - Bruce, good luck.
Not a bit of upset from me, Dan. I just appreciate that you took the time to answer my question in the most helpful way. Y'all have a good day now!