Community Forums

mr300ce · 07-08-2012, 02:33 PM

Hi,

I have a 1994 32H Bounder with an Onan Marquis 7000 generator. I am plugged into a 30 amp shore power box right now. I just came back from a field trip, and forgot to leave my A/C on low.

It is 100*F outside, and it was 110*F inside when I went in.

Question is.....can I leave the shore power plugged in, and run the generator. Isn't there a auto switch to cut off the shore power if I do that. I just want to fire up genset to run both A/C's for about 30 minutes to cool it down in here, then go back to shore power.

Prior times I always got out and unplugged the shore power when I run the genset once a month to exercise it.

Immediate help would be appreciated. And if the answer is yes, it certainly will save me the hassle of unplug-plug back the shore power, and resetting the clocks (from short time power loss).

KIX · 07-08-2012, 02:38 PM

IF you have an automatic transfer switch it wil automatically switch to gen when you start it. However, you should not switch between power sources with heave loads (AC or water hearter) turned on. Also, you will probably lose clock setting during the switch anyway.

mr300ce · 07-08-2012, 03:36 PM

That's what I don't know, because none of my books & literature that came with the coach, (there is a whole giant plastic folder that has everything in it) says anyhting about an automatic transfer switch.

One time I forgot to unplug the shore power when I started the genset, and nothing weird or bad happened. I ran outside and unplugged it withing 30 seconds.

I don't know if the genset took over the power duties, or just didn't do anything.

Anyone out there that might know these mid '90's Bounders, and if it had an auto switch, wouldn't it be in a panel where I would see it, or a meter, or LEDs or something.

I have been over every inch of this Bounder, and have not seen it. But maybe, if it's an automatic thing, then it could be buried behind/inside the breaker box(s), which I have NOT removed the covers on.

KIX · 07-08-2012, 07:55 PM

Actually the answer may be pretty siimple. Turn all heavy loads off......batt charger/converter, AC's and water heater. Start gen leaving shore power plugged in. If you continue to have power to 120volt appliance like microwave or light inside microwave then your gen is supplying power. To verify this go unplug shore power (just turn power pole breaker off) and see if you still have 120volts in coach.
The ATS is likely very near where power enters the moho. It's "normally" a box that may be metal or plastic.....approx 8" square x 3 - 4" deep. It will have 3 cables attached to the box.....one from gen.......one from shore power.....one going to your 110v panel.
If you do not have an ATS then you likely have a female plug into which plugs either the gen or the shore cable ........only one at a time.
Hope this helps you out

mr300ce · 07-08-2012, 10:46 PM

Yes, what you say does make sense. But.....the shore power cord just goes into a regular electrical box, 4x4x2deep. Then a 1 1/4" conduit comes out of that box and disappears up into the wall, very nearly under the breaker box located in a cabinet inside above the booth. So likely the ATS is behind, or inside that breaker box.

It does make sense that if I started the generator while plugged into shore power that the genset would take over. I mean, the engineers had to realize that somebody would start the genset while plugged in, and they had to make sure things would not self destruct.

YAH ??? ESS ' NT DAT RITE ???

Wolfpack Fan · 07-09-2012, 06:07 AM

I don't know how much validity there is to this, but I read an article about surge protectors, why they're needed and what can cause surges. Here, quoted from the article is what it states. It's quoted so, please don't think I'm referring to you or anyone as a moron. That's not my style.

"Suppose some moron, without proper equipment, turns on his generator while still tied into commercial power? 120 volt AC generator power, totally out of phase when generator output is suddenly attached to commercial power, will produce the same effect as a major surge. There are supposed to be safety measures in an RV to prevent this like:

Manual plug-ins so generator can't be on-line at the same time as commercial power (or an inverter).
Manual transfer switches that accomplish the same thing.
Electronic-relay transfer switches (ditto).
But, we have no idea what any given RVer might have wired up on his own. We have no idea what some manufacturer might have done. We have no idea when an electronic transfer switch might decide to "seize up" with both power sources being connected together (this last defect, not uncommon, can set your rig on fire in moments)."

Here's a link to the article.

Surges and Surge Protection by phred

It's an older article, but makes some sense. I wouldn't fire up the generator without knowing absolutely and without a doubt that the mh has a working isolator to prevent such an occurence.

mr300ce · 07-09-2012, 08:18 AM

Thanks WPF. That's what I was wondering. The part about an ATS not working properly, on my 1994 rig, is enough to now cause me NOT to just fire up the genset while still plugged into the shore power.

RLKBOB · 07-10-2012, 10:56 AM

The ATS is probably mounted to the back of the breaker panel as you suspect, that's where it is on mine. I don't see how, if an ATS fails, it can cause both incoming power sources to be paralleled on line at the same time. If you look at the relay it has to physically move almost 1/4 inch to switch from one power source to the other, it can't touch both at the same time(if it does fail, it will fail stuck in one position or the other). I've had mine open and watched it switch many times when I was adding a second ATS for my inverter. I've had my inverter on powering the loads then plugged in shore power and watched the ATS switch after its 20 sec delay. Then I started the gen and watched the built in ATS switch to gen power after a 20 sec delay. That is how they are designed to work.
I don't understand the underlined statement about some moron starting his gen while hooked up to shore power. That's how the systems are designed to operate and I'm sure I'm not the only one that doesn't have a problem starting my gen while shore power is still hooked up.

Jim_HiTek · 07-10-2012, 12:01 PM

The ATS is behind the breaker/fuse panel in my '94 too.

They can fail where one contact welds itself closed and won't open while the other contact closes to the opposite side. That's why you should shut off any heavy loads before starting up the genset. I always just flip off the parks breaker then start the genset.

Dutch Star Don · 07-10-2012, 12:59 PM

Simple answer.....it's suppose to work seemlessly. The transfer switch should switch back and forth between power sources without unplugging..............but........it's not unusual for for one to lag behind the other or the system has a brain fart. It's just a GOOD practice to unplug the coach and then start the generator.