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Old 10-31-2020, 07:55 AM   #1
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Buzzing noise from Transfer Switch when hooked to shore power

Can anyone tell what a pretty loud buzzing noise is on my transfer switch when hooked up to 50A shore power, did it just get bad? This is the first time I've heard that noise. It is at my home 50A outlet I've used numerous times this fall. My phone records on MP4 and I can't upload the file here.
The unit is "Elkhart Automatic Transfer Switch - 50 Amp Service - Es50m-65n" on a 2004 HR Imperial.
To my knowledge there is nothing electrical hooked up but my Progressive Industries EMS is showing like 6 amps on L1, 0 amps on L2. Flipped all the circuit breakers off and on that I could find, but no change on the noise.
Both the house and chassis batteries are around 13.1V.
It did get to the 30s yesterday but I don't think there is any kind of heater hooked up anywhere that I can find.
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Old 10-31-2020, 08:10 AM   #2
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It can be somewhat normal depending on type of transfer switch.
But loose connections can also make it worse. It is best to check the connections inside the transfer switch annually.
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Old 10-31-2020, 08:14 AM   #3
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Lowflyer,
It could be dust on the contacts. They. Can be cleaned with some compressed air. Remove shore and generator when doing so.
I had the same unit in our 04 Intrigue and the buzzing got worse over time and could not rectify by cleaning so I installed a DC contact relay ESCO LPT50BRD coach is like a library now, never been this quiet
Good luck and let us know what you find out,
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Old 10-31-2020, 08:21 AM   #4
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Nothing likes to be hit. A slap on the wall directly outside of the switch stopped it for awhile but eventually you have to get inside & tighten down all of the connections.
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Old 10-31-2020, 08:43 AM   #5
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Agree with all posts, typical transfer switch issue. Remedies suggested should be tried. Older units tend to get noisier with age. Not a safety or proper function issue, just a nuisance. Replacement with a DC powered contact switch will solve the problem if you can't live with it.
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Old 10-31-2020, 09:54 AM   #6
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Thank you all for a quick response. I checked all the connections and they were tight. Just to be sure the connections are clean, I backed them all out and re-tightened. No Help. The current on L1 actually varies and sometimes shows 10 or 11 amps and that does not make sense but worries me where is it going.

Couple of good bangs on the contactors and the noise stopped and current went to 0 amps. But maybe 30 sec later the noise is back and current back to like 11 amps. Tried that couple times with same results.
Since there appears to be a circuit board and a smaller box below also, I probably need a new transfer switch, not just a contactor?
I was hoping to find an identical unit so I can swap without any extra mounting or wiring effort.
Is there anything close to my current unit or would the ESCO LPT50BRD be a simple swap? The pics on line are blurry but look like the connections are quite a bit different.
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Old 11-01-2020, 06:03 AM   #7
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The unit you have is similar to the ESCO ES50M-65N. The major difference between the two transfer switches is The LPT50BRD is a Relay Base unit that is much quieter. The ES50M-65N has Mechanical Contacts that make a hum when running.

https://www.pplmotorhomes.com/parts/...atic_ES50M-65N

https://www.pplmotorhomes.com/parts/...-50amp_49-1749
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Old 11-01-2020, 06:12 AM   #8
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...2x on the DC contactor model, Lyght/Esco is a very good product -- no issues.
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Old 11-01-2020, 06:31 AM   #9
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10 or 11 amps could be the block heater if you have a diesel.
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Old 11-01-2020, 07:25 AM   #10
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Thank you all for the feedback.
I did not even think about unplugging the block heater the second time around as I only unplugged it the fist time when I was trying to figure out the noise. So that's probably the current draw. Now the bus is back in storage and I can't work on it until next weekend earliest and depending Michigan weather, might be next spring.
One comment I saw on Amazon for Esco LPT50BRD: "While it is rated for 50A I don't like that it is wired with #10 wire. My 50A power cord uses #6 wire to the RV receptacle. #6 wire from receptacle to transfer switch and #6 wire from transfer switch to circuit breaker panel. My last transfer switch failed when the #10 internal wires over heated and melted into the ground...."
Is that a concern or did they have some other problems?
Also, there were comments that there were no installation instructions. I've done relay swaps in the past but those have been identical units and just follow pin to pin. Due to the real confined space (my unit is in behind the water heater), there is not much room to do anything.
Are the diagrams clear enough on the Esco LPT50BRD to follow from the old ES50M-65N?
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Old 11-01-2020, 07:55 AM   #11
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Last year my Esco ES50M-65N developed an internal short that prevented me from using shore power. I decided to replace with an identical unit to avoid having to make wiring changes. Getting to mine requires that you crawl into the "basement" and the working space is very limited. Total time to replace was less than an hour.

The new one came from with a note that "this device could make some noise" but I don't hear any, particularly with it tucked away underneath. My original switch lasted ~19 years; if I get anywhere close to that with this one I'll be happy.
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Old 11-01-2020, 09:26 AM   #12
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Quote:
Originally Posted by Lowflyer1 View Post
Thank you all for the feedback.
I did not even think about unplugging the block heater the second time around as I only unplugged it the fist time when I was trying to figure out the noise. So that's probably the current draw. Now the bus is back in storage and I can't work on it until next weekend earliest and depending Michigan weather, might be next spring.
One comment I saw on Amazon for Esco LPT50BRD: "While it is rated for 50A I don't like that it is wired with #10 wire. My 50A power cord uses #6 wire to the RV receptacle. #6 wire from receptacle to transfer switch and #6 wire from transfer switch to circuit breaker panel. My last transfer switch failed when the #10 internal wires over heated and melted into the ground...."
Is that a concern or did they have some other problems?
Also, there were comments that there were no installation instructions. I've done relay swaps in the past but those have been identical units and just follow pin to pin. Due to the real confined space (my unit is in behind the water heater), there is not much room to do anything.
Are the diagrams clear enough on the Esco LPT50BRD to follow from the old ES50M-65N?
I believe the #10 wiring is for the DC relays and does not carry the loads to/from shore power or generator. Why the poster's wires failed is unknown, but loose connection at the relays could account for his wiring meltdown.
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Old 11-01-2020, 09:43 AM   #13
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Quote:
Originally Posted by Ljwt330 View Post
I believe the #10 wiring is for the DC relays and does not carry the loads to/from shore power or generator. Why the poster's wires failed is unknown, but loose connection at the relays could account for his wiring meltdown.
They may be able to use individual 10 gauge wire, on the short jumpers, inside the ATS inclosure.

Amp rating is based on the type of wire or cable.
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Old 11-01-2020, 10:11 AM   #14
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In my experience working in the field the relay contractors in the transfer switch are similar to what we used in the sign and lighting industry. Typically the hum is created by the magnetic coil that pulls the contractor open or closed depending on type. Generally when this happens the coil is getting weak or there is something obstructing the contractor from opening or closing completely. It can still work but eventually like most everything will fail. If I were in your shoes I would consider replacement. I have seen contractors fail in months and then some last 20 years or more. But quality units aren’t cheap.
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