ATS question(s)

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ATS question(s)

June 07, 2017, 09:58:17 am

I'm sure these questions have been answered but have not found the answer I'm looking for yet.

1. What is the most common cause of 'burnt out' ATS ?
2. Will low voltage 'shore power' damage the ATS ?

* 1994 U225 - 50Amp service - propane generator *
We had just spent 5 days in a camp ground with very low voltage. Did not run AC's. Used propane on the fridge. Used a couple of wal mart fans.
The weather was hot on the way home. Had generator running and both AC's on. Burnt out ATS...........
Have since replaced ATS ( one year ago ) and have not had any problems ( shore power or generator )
**Generator shows to be working properly, correct voltage and Hertz.

Thank You for your help........~JL~

Re: ATS question(s)

Reply #1 – June 07, 2017, 10:25:13 am

The majority of ATS failures is due to loose/poor connections. That causes heat, which further degrades the connection, leading to more heat.........

Re: ATS question(s)

Reply #2 – June 07, 2017, 10:41:15 am

Yes. Low shore voltage can burn out the ATS.

A few years ago, I had to leave the coach for a few days, and was offered a dry camp site plus a long extension cord.

I came back to no ac power through the ATS and needs to swap out the contractor. Totally burned out contacts.

I ha thought ac would be only powering the refrigerator and battery charger. Wrong, the air conditioner thermostat was left on. Way too much load. Tripped my low voltage protection, probably many times.

Re: ATS question(s)

Reply #3 – June 07, 2017, 10:54:57 am

What Brett said, X1. We took a hit that fried the ATS, scared the pucky out of me. No one copped to what caused it, we think it was the park pedestal. We replaced all connections on the SP cable, including the main connection in the wet bay. Ran new wire to the new ATS and bought a EMS. Michelle had a great suggestion of mounting a EMS between the wet bay connection and the ATS. Ours is pedestal-mount, which is a big help, though no help if the cables short-out.

Re: ATS question(s)

Reply #4 – June 07, 2017, 02:22:17 pm

The main reason for burnt points is disconnect and connect with high loads running. Especially quick connect & disconnect actions.

Re: ATS question(s)

Reply #5 – June 07, 2017, 03:02:24 pm

Barry is correct. Another common failure is for the points to burn/arc and then stick in one position. Basically "welded" there.

And indeed changing power sources under high 120 VAC load causes this.

Re: ATS question(s)

Reply #6 – June 07, 2017, 04:49:47 pm

Ok. I am a beginner. What is ATS?

Re: ATS question(s)

Reply #7 – June 07, 2017, 04:59:35 pm

Its the Automatic Transfer Switch, usually at the foot under the bed.
John

Re: ATS question(s)

Reply #8 – June 07, 2017, 05:17:03 pm

Thanks All
Loose connection(s) could very well have been the problem. Hard to tell after every thing was burnt up.

I do know to check them from time to time now.

Lots easier to check them in the cool shade than to jump around a burnt ATS in the hot summer time near a hot engine compartment (on a Sunday afternoon). * I do carry a few wire line clamps now !

P.S. I never plug or unplug shore power or start or stop generator with any load on !
The generator guy I use says: Shutting down the generator with a load on it is very hard on the electronics. He says they are still trying to keep up with the load while the RPM's are winding down.

Thanks Again........~JL~

Re: ATS question(s)

Reply #9 – June 07, 2017, 05:27:17 pm

[quote author=Johnnie & Susan Laird link=msg=275331 date=1496870 I never plug or unplug shore power or start or stop generator with any load on ! The generator guy I use says: Shutting down the generator with a load on it is very hard on the electronics. He says they are still trying to keep up with the load while the RPM's are winding down.[/quote]

It may be "old geezer talk", but I've always made a habit of shutting-down everything on board before pulling the plug on either shore power or the gen set. For max life, the gen set likes to be started with no load, then increased, slowly, for total load; I reverse the process for shut-down.

Re: ATS question(s)

Reply #10 – June 07, 2017, 05:36:50 pm

Quote from: mike leary – June 07, 2017, 05:27:17 pm

It may be "old geezer talk", but I've always made a habit of shutting-down everything on board before pulling the plug on either shore power or the gen set. For max life, the gen set likes to be started with no load, then increased, slowly, for total load; I reverse the process for shut-down.

Not "old geezer talk"...

The manuals for many generators explicitly state to start a generator with no load, and let it run for a few minutes before applying a load.

Chris

Re: ATS question(s)

Reply #11 – June 07, 2017, 09:42:51 pm

Other coaches long ago had the electric wiring run into a side eye level flush cabinet. All breakers. Big manual switch to change from gen to shore.

I always cautioned owners about plugging in coach with the pedestal breaker on as you could go in crookedly and the three top connections make contact but not the bottom ground

Re: ATS question(s)

Reply #12 – June 08, 2017, 01:54:35 pm

want to see what wire connection that is not tight looks like...

Replacing a Transfer Relay

Re: ATS question(s)

Reply #13 – June 08, 2017, 02:04:42 pm

Quote from: Barry & Cindy – June 08, 2017, 01:54:35 pm

want to see what wire connection that is not tight looks like...

There are many things in life I'd rather deal with than, "THAT SMELL"!

Re: ATS question(s)

Reply #14 – June 08, 2017, 02:14:35 pm

This is recent example of what can happen with a loose connection...

Re: ATS question(s)

Reply #15 – June 08, 2017, 03:32:37 pm

Yup, one with a loose neutral, one with a loose hot. MELT insulation and worse case-- start a fire. And possibly destroy appliances run on improper power.

Removing the lid and tightening all the connections (yes with shore power, generator and inverter OFF) is part of my annual "electrical tune-up"

Re: ATS question(s)

Reply #16 – June 08, 2017, 04:04:31 pm

I appreciate this discussion and the photos.

When talking about the location of the Automatic Transfer Switch, a little more information might be helpful for people who are new.

On our 1998 U-320 the base of our bed faces front/back. At the foot of the bed (under the bed skirt), on the exterior of the bed platform wall that is visible when you are inside the coach, are the breaker boxes for the 120 volt AC circuits, and the fuse box for the 12 volt DC circuits.

If you lift up the platform of the bed (the platform the mattress sits on) you see the engine, and on the engine side of the foot of the bed's platform wall you will see a solenoid and some relays.

No transfer switch is readily visible.

When the bed's platform is lifted, at the foot, there is a section about 8" deep between the engine bay wall, and the interior of the foot of the bed where the breaker and fuse boxes are mounted.

On our unit a piece of wood paneling is covering this 8" deep section, so you do not see any of the wires, electrical boxes, etc. Take this off and you should see the transfer switch, etc.

Chris

Re: ATS question(s)

Reply #17 – June 08, 2017, 05:50:54 pm

I remember the tech that replaced ours finding it in the stern from above, down low. We were looking at what had to happen, and he said, "could they have put it in a worse place?"

Re: ATS question(s)

Reply #18 – June 09, 2017, 12:33:52 pm

Does the loosen then re-tighten the screws on the wires still hold. The thought is that the screw might be stuck and "feel" tight when it really isn't.

Re: ATS question(s)

Reply #19 – June 09, 2017, 01:32:29 pm

Quote from: Numbers – June 08, 2017, 04:04:31 pm

When talking about the location of the Automatic Transfer Switch, a little more information might be helpful for people who are new.

Good point! Plus, in many coaches, there are 2 Automatic Transfer Switches. One for shore/generator and the other for shore/inverter. In your schematics, these might be labeled as "Switching Relay #1" and "Switching Relay #2" with text describing where they are located, e.g. in a 2003 U320 the main one (shore/generator) was the back wall of the driver side bay where the HWH compressor and inverter are located, the secondary one (for shore vs. inverter) under the bed.

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