Got to the trailer and started the genny its been over a month.Then plugged into shore power with an amp reader because i was curious if it would switch over. Started the A/C and let it run for awhile. Then turned off the genny with both A/Cs cranked full blast. Only hooked up to 15amp. Ran and killed the front bedroom manual hand dial. Then turned the main room thermostat to off. What damage can that cause to the electrical switch and the air conditioner?

You actually had 2 A/Cs running on 15A? I don't switch under heavy loads as a electrical transient may cause equipment to quit or cause some degree of stress to the equipment. And relays switching under heavier loads can cause arcing on the terminals and shorten their life.

No harm but I would not do it every day.

Whew thats good to hear thanks!!

one time only , you might not have done anythingbut this type of thing is what pits and burns the contacts in the TSafter repeated times, they become damaged enough to cause problemsthey only need to stick together one time to cause something like your generator to burn outshore power and generator don't mix, and the generator will lose the fight

Not recommended. Do not repeat the "experiment".

Switching from Genny to Shore Power under load----bad?

pianotuna
Nomad III
Jul 05, 2018
Hi,

Yes, but if it is working.....don't fix what is not broken.

Better to blow than suck.

wopachop wrote:
Can you open up the switch and clean the contacts?

I might open my converter. Freaking forest river cuts holes and leaves all the dust in the cabinets for the fans to suck into your electronics. Thinking i might pull the cover and gently shop vac it.
wopachop
Explorer
Jul 05, 2018
Correct was thinking something like 600 grit. Not for me personally as i just made a one time mistake.
CA_Traveler
Explorer III
Jul 05, 2018
wopachop wrote:
Can you open up the switch and clean the contacts?

A vacuum won't help pitted contacts. While they can be cleaned with a small file or sandpaper best to just replace the unit. Plus if the contacts are coated not much you can do. You might be able to replace the relays.

I might open my converter. Freaking forest river cuts holes and leaves all the dust in the cabinets for the fans to suck into your electronics. Thinking i might pull the cover and gently shop vac it.

Hidden dust and debris is an industry standard.
time2roll
Nomad
Jul 05, 2018
Most ATS seem to fail from loose connections far more often than burnt contacts.
wopachop
Explorer
Jul 05, 2018
Can you open up the switch and clean the contacts?

I might open my converter. Freaking forest river cuts holes and leaves all the dust in the cabinets for the fans to suck into your electronics. Thinking i might pull the cover and gently shop vac it.
wa8yxm
Explorer III
Jul 05, 2018
Well. Doing what you are doing and putting your money on the great big Wheel in Las vegas..... Have a lot in common.

Good chance you are going home from "Lost Wages" understanding why Los Vegas has that nickname.

There are two possible outcomes.. And it depends on two things
1: how fast the ATS transfers
2: Where in the power cycle it transfers.

The ATS is what is called a "Break before Make" switch this means it does not go from Genny to Shore.. It goes from Genny to OFF to Shore

When it goes to OFF, with big motors like the A/C running, there is something we call an inductive "kick".. Think of Induction like Inertia

As you know an object in motion tends to remain in motion in the same direction unless acted upon by an external force.. A LOT of force in many cases.

LIkewise have you ever shut off a water faucet and heard the pipes "Rattle".

These are both examples of "Inertia" (The water tries to keep flowing, the moving object tries to keep moving)

Electronics are like that. only we call it inductance. They want to keep moving. and what's worse is the motor has a form of inertia so it turns to a generator till it stops.. The result can easily be a thousand volts or more at the ATS Contactors (Solenoid or Relay) and this can jump the gap and weld the contacts closed..

Instant need for a new ATS.

Happened to me.. Thankfully under warranty.
MrWizard
Moderator
Jul 05, 2018
opening the generator circuit breakers will stop the Back EMF and 'wind down'
is doesn't help the the ATS switching to live shore power with the A/C unit running

still going to arc the contacts on the ATS

much safer & better choice to turn off the A/C, then turn off the genny
then plugin, then restart A/C
j-d
Explorer II
Jul 05, 2018
time2roll wrote:
How about cut the breaker on the generator before you shut it down?

That might just work. I think, though, that this discussion points to not asking the ATS to switch under load. Just better to discontinue that practice. Our chassis/dash A/C does a good job and that makes it a better idea to just let it run on MAX till I can get us plugged in. The E450 engine cooling system has no problem idling awhile.
time2roll
Nomad
Jul 05, 2018
How about cut the breaker on the generator before you shut it down?
j-d
Explorer II
Jul 05, 2018
I tried it too, and found it wasn't a good idea. What I wanted to do, was start the genny to cool the coach at check-in, then switch over to shore tie at our site. Doesn't work. The genny has to spool down to cause the switch to shore tie. By then, the A/C has stalled, and it won't start again till it's had a cooling down/pressure bleed down period. That takes away any advantage of doing it.

The opposite (shore tie TO genny) does work. The ONAN 4KY takes several seconds to decide that it's ready to accept the load, then it pops 120VAC to the ATS and the A/C will actually keep running. OK, so what. Now I know all this and along with the rest, don't recommend doing it. It's gotta be murder on the ATS contacts and maybe worse for A/C and the genny itself.