Exercise genny while on shore power?

[J-R]

New to on board generators. Parked for the winter with 50 amp service, and it's time to exercise the genny. Do I have to disconnect first?

2006 Bounder, Onan 5500, ATS

[4x4van]

way2roll wrote:
Not just hearsay, I've heard of real cases of things getting screwed up when running the genny and shore power at the same time.

Ummmmm....isn't that the very definition of "heresay"?;)

Seriously, there is no need to disconnect, but it is a good idea to shut down any heavy loads (A/C, WH, etc) prior to firing up the generator. If the transfer switch works, it will simply switch over to generator power (after a short delay for warm up/rpm settling). If it doesn't, it will remain on shore power. There really is very little possibility for it to connect to both at the same time. The contacts can only be in one position at a time; it is a "break, then make" system.

[magicbus]

Is it COVID or do people normally worry this much? If you have to ask the question, just go out and flip the breaker on the pedestal to OFF.

Dave

[MEXICOWANDERER]

To ABSOLUTELY GUARANTEE the impossibility of mutual conduction I gave a 10 pound knife switch mounted on the kitchen wall 5' off the ground child safe. It is a 4 conductor 4 gauge knife switch. Even earth ground is isolated. The Scott connection 3 to single phase transformers in the generator shed do not need to be worried about. So when I isolate for warm up I charge batteries and allow 10 minutes after oil temp has reached 190°F to de moisturize the oil. The KATO has a CL750 Luberfiner bypass filter so it takes longer to exercise it. Bypass filters are a miracle de sooting gizmo for diesels especially for high sulfur fuel. They and RAcor S series fuel filters have saved my rear too many times to count.

[pianotuna]

This is close.

"So a few weeks ago i started up my generator without realizing that the power switch for my fridge was on still. The generator tripped and a small amount of smoke came out near my inverter/converter and fuse panel. I replaced both of those and power still was not coming from my generator. So after some troubleshooting and finding out that my generator was in fact producing power, I landed on a fault in my auto transfer switch. I just located the switch, and it is attached to the back of the housing of my inverter/converter and fuse panel and I can't even open it. Has anybody else run into this problem? and what did you have to do to fix it?"

http://www.rvforum.net/SMF_forum/index.php?topic=115268.0

[time2roll]

Find me a single post of such disaster.

[way2roll]

time2roll wrote:
Anytime you start the generator it is a hot transfer unless you turn everything off including the converter and electric water heater. You could use the main breakers to cut power and save the transfer switch but then someone will say the breakers should not be used as a switch either. As I said the list never ends.

You act as though no one has ever had a disaster when on shore power and started their genny. Like the possibility of this problem doesn't exist. And reducing loads is just plain common sense. It's a risk and an expensive one given the minimal level of effort to prevent it altogether. But we get it, you've planted your flag and dying on that hill. I think most agree it's bad advice not to unplug first.

[time2roll]

Anytime you start the generator it is a hot transfer unless you turn everything off including the converter and electric water heater. You could use the main breakers to cut power and save the transfer switch but then someone will say the breakers should not be used as a switch either. As I said the list never ends.

[Hurricaner]

RV transfer switches are not fail safe devices. Industrial transfer switches have mechanical interlocks along with the electrical. RV transfer switches are cheap by comparison and you're taking a chance doing a hot switchover, which I don't think any of the switch manufactures recommend.

Sam

[way2roll]

time2roll wrote:
The list of systems that could be connected wrong is endless.
Do you verify everything else before you turn stuff on?

Truthfully if something this important is wired wrong I would prefer to know sooner than later.

There is no rolling of the dice. Wires do not jump off terminals and rewire themselves.

Because nothing ever fails on an Rv right? Wheel chocks, supplemental braking, emergency breakaway, towing chains, etc. All things that prevent an issue should something fail. No difference here. Like I said, to each his own. If it's not worth it to you to take 15 seconds of prevention to mitigate the risk of a lot of damage then no skin off my nose. I unplug before exercising the genset. No possible chance of anything getting fried. It's really a no brainer. The strawman argument of having to verify everything before you turn stuff on really makes no sense. Good luck to you.

Op, it's good advice to take the few seconds to disconnect before running the genset. Albeit small odds, it's an ounce of prevention that could avoid an expensive disaster.

[time2roll]

The list of systems that could be connected wrong is endless.
Do you verify everything else before you turn stuff on?

Truthfully if something this important is wired wrong I would prefer to know sooner than later.

There is no rolling of the dice. Wires do not jump off terminals and rewire themselves.

[way2roll]

time2roll wrote:

MrWizard wrote:
"Transfer switch shouldgive priority to the generator"


Now that is the stickler, the word should , if it doesn't , bad things could happen, that is why you unplug first

Ok so if the generator does not have priority the worst case would be no load on the generator.

Nothing bad will happen either way. Otherwise get back into the manual and read about how a transfer switch works.

Rolling the dice is fine when things work as they should. Until they don't. Then your worst case becomes something completely different.

Not sure why this is even a debate. It literally takes seconds to mitigate any risk even if the risk is small. But the implications can be very large.

To each his own I guess. I'd rather be wrong and have nothing happen than be wrong a lot of bad things happen. Rv's aren't always wired they way they are supposed to be and every component on an RV is suspect in my opinion, especially given the lack of quality in the RV and the components themselves.

To the folks saying nothing will happen and it's fine to remain plugged in, when the OP doesn't unplug and something does get fried, will you chip in to help him fix it? Some advice can have dramatic consequences.

[wopachop]

We normally camp during the winter so for me the funny question is when do you exercise your AC units when it's a high of 40 degree temps outside?

I have my own ritual. First is turning the fridge off. I wonder if clicking the button allows the circuit board to perform a task that would not happen if the fridge was left on when I go flip the 50a breakers.

Next is pull the cover to the generator. Had a mouse living in there so now I have a sticky trap and a snap trap in the unit itself. I yank those out and prime. Hit the start button. Check for any mouse next debris to come shooting out.

Looks good the cover goes back on. My manual recommends an hour. I usually do 45 mins to 1 hour. Pull the cover off again and drain the carb. Put my mouse traps back and feel good my genny and ACs got a workout.

During winter I will use space heaters instead. Run the AC every other month. Or 3 months.

[time2roll]

MrWizard wrote:
"Transfer switch shouldgive priority to the generator"


Now that is the stickler, the word should , if it doesn't , bad things could happen, that is why you unplug first

Ok so if the generator does not have priority the worst case would be no load on the generator.

Nothing bad will happen either way. Otherwise get back into the manual and read about how a transfer switch works.

[Cummins12V98]

MFL wrote:

pianotuna wrote:
Hi,

Unplug.

Exerise.

Replug.

30 minutes @ 50% load, after a 3 minute warm up.

This is how I do it too. Always best to be safe.

Jerry

Agree!

Jerry Knows!!!

[Veebyes]

MrWizard wrote:
"Transfer switch shouldgive priority to the generator"


Now that is the stickler, the word should , if it doesn't , bad things could happen, that is why you unplug first

BINGO! Shore power should be the default. To be sure how much trouble is it to flip the breaker at the post, make sure the inverter is off, then start the genny? No risk of trying to backfeed anything that way.