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Bloodyhell · 04-18-2016, 10:15 AM

Somebody told me this was a no no. I realize there isn't usually a need, but I'd like to know if it's death to anything if it happens.

Charlie

Spk64 · 04-18-2016, 10:23 AM

I have done it several times when doing maintenance on the generator while still hooked to shore power. Ours is set such that Generator has priority over shore power. So once started and breaker not tripped on genset the transfer switch transfers power to the generator.

Sky_Boss · 04-18-2016, 10:27 AM

Quote:

Originally Posted by Bloodyhell

Somebody told me this was a no no. I realize there isn't usually a need, but I'd like to know if it's death to anything if it happens.

Charlie

It shouldn't be a problem but...

One popular opinion is to avoid this practice especially with big loads. The idea is to protect the ATS from problems it SHOULD be able to handle.

My normal pattern is to turn off high load items like the air conditioners and such when transferring between shore and generator power. I'm certain some folks don't worry much about it and let the ATS do its thing.

YMMV

Selah · 04-18-2016, 10:45 AM

+1 for SkyBoss. As long as there is a minimal electrical load when starting the generator it is not a problem. The idea is to prevent arcing of the transfer switch contacts when the switch is energized. Same goes for when first connecting to shore power. Turn off any high loads.

Patti Brown · 04-18-2016, 12:52 PM

Starting the generator while plugged into shore power is safe enough, but you will get a tiny double voltage spike at the point of changeover. It is enough to blow an appliance. Know of someone who destroyed 2 Keurigs doing that. So we try to be off shore power before we turn on generator.

CJ7365 · 04-18-2016, 01:02 PM

I would just turn everything off, unplug shore, start gen set turn on what you turned off.

Not sure why people are so lazy

HicksRA · 04-18-2016, 02:00 PM

I do it all the time when I exercise the genny while plugged in at storage. I make sure there are no loads present. No problem.

Spk64 · 04-18-2016, 02:05 PM

Yes. Should have clarified my post. No loads present when this is done.

When heading out for a trip and cooling things down then switching to Gen. We do the full power down switch then power up.

Wayne M · 04-18-2016, 02:43 PM

FYI Cummins Onan Literature

Dutch Star Don · 04-18-2016, 03:09 PM

Theoretically, there should be no issue, but that means your transfer has to be working properly and doesn't momentarily glitch. I had it happen once on my Diplomat and blew some circuit breakers. I try never to do it now.

SteveByrum · 03-16-2020, 10:27 AM

Just had tiffin electrical guy tell me that if when the transfer switch changes from shore power to generator there is a possibility that if the neutral line disconnects first, there is a possibility that 220 volts can be sent to the system momentarily while it searches for a neutral.
I have lost 2 coffee pots and a space heater. It’s the only thing I can think of that could be causing this..
Thoughts?

twinboat · 03-16-2020, 10:42 AM

More likely you have a MSW inverter.

Their output can cause havoc on sensitive electronics.

TXTiger · 03-16-2020, 12:09 PM

When my transfer switch went out, the mobil tech doing the repair and installation of my new transfer switch said it is not supposed be a problem but for insurance sake you should always unplug from shore power before starting the generator and not plug back in until, you turn off the generator

Domo · 03-16-2020, 01:35 PM

Quote:

Originally Posted by Patti Brown

Starting the generator while plugged into shore power is safe enough, but you will get a tiny double voltage spike at the point of changeover. It is enough to blow an appliance. Know of someone who destroyed 2 Keurigs doing that. So we try to be off shore power before we turn on generator.

Sorry for your friend. He obviously has something wrong with his system. Sad he can't rely on automatic gen start and transfer switch.

You could suggest he buy a few <$10 surge suppressors that can plug directly into an outlet and then protect the device that is subsequently plugged into the suppressor. They are in bubble packs in the electronics section of Home Depot.

As an electrical engineer, with surge suppression on-board and un understanding of transient spikes, I use these for all our "computer-based" appliances (you have to buy the appliance rated suppressor - it'll say that on the package) such as the microwave, washer, computer power station, TV, multimedia, etc.