MEP-803a overload circuit

[Guyfang]

I will take the time to warn everyone about shock loading. A little is OK, but not a lot. First of fits a strain the gen set doesn't really need. Second off. The only gen sets that should experance a sudden and dramatic loading, is Auto start gen sets. Normally, if the power goes out, and you have to manually start the back up generator, you should turn off your load. Or at least reduce it. Put the set on line, then turn on your load, step by step. What we always did was to turn off circuit breakers in the fuse box, then turned them on one at a time. Largest load first. Yes you can turn it all on at once. But if your set is for example wet stacked badly, then it's just going to kick back off. Step it up and you can listen to the engine. Often it will be telling you to slow things down until the set works the carbon out. I have had some CECOM LAR's tell me you can damage the gen set with shock loading. I have never seen it, but these guys do have access to failure information that I never did. So they may be right.

 

[novaman]

Good to know. Ill keep it to a minimum then. I always did it to check the condition of the govenor. I do have a nordic air 36000btu of cooling /31000 btu of heating unit now. How do i step on the heating coil. About 9kw of load?

 

[Guyfang]

If you cant step the load, ya cant step the load. It is, what it is.

 

[TNriverjet]

Im using a fluke mm to measure the voltage differential. The volt gauge showd the phenomenon too. Also all three of my units do it. Yes ill be using 2000 grit wet sand paper or even emery cloth. Problem with cycling is its not sweeping the contacts accros each other just opening and closing them doesnt brush off the corrosion, grit or spider carcass thats on the contactor. So im going to use deoxit and be really gentle with the cleaning one or two passes with emry cloth should be enouph. I think it a poor design being open to the outside like that. This unit was kinda sandy and dusty so om guessing theres a piece of grit/dust in there somewhere

Novaman, I am interested in hearing how this S8 abrasive cleaning process goes. I'm in the same boat, but do not have a spare S8 to test. I'd like to clean in place albeit very gently to see if I can better results than deoxit alone.

 

[jamawieb]

TNriverjet did you ever get the generator to not trip the overload?

 

[TNriverjet]

TNriverjet did you ever get the generator to not trip the overload?

No, I need to call you and enlist your vast experience to locate the issue. It still generates fine until the load goes over 50% then trips. I actually had the short circuit trip last time I ran it, but may have had the legs unequally loaded when a load suddenly came online.

 

[jamawieb]

I wanted to let you know that I just finished up on a 803a that had previous work completed by someone else and I was having overload and voltage gauge issues. Took me about a week but I used the wiring diagram and traced ever wire that ran from the burden resistors, K8, S8 and S6. Found that 2 wires were put back in the wrong location which caused all my problems. Since your unit was recently refurbished they may have gotten a wire or 2 backwards which is causing the problems.

 

[Guyfang]

I am working the wire diagrams right now. Found two mistakes. If my wife lets me have enough time, I will do some more work on them.

 

[Light in the Dark]

So I was testing an 803 this morning for an overload condition. I can flip the battle short on, and the light will illuminate after a few minutes... well then a few minutes later with the set still chugging and the light still on, it stopped making power. I was able to flip off the battle, rest light, and still pull power. I think this rules out the overload relay? Should I be looking at the burden resisters right behind it?

I just sprayed the crap out of the AM/VM switch, because the gauge was not reading properly... appears to be much closer to reality now.

 

[jamawieb]

Did you notice if the short circuit light came on when you lost power with the battle short on. With the battle short on it still passes through the overload relay so if something is going on inside the relay it could cause your problem. A short circuit is the only thing the battle short will not bypass, if it senses a short circuit it disconnects power.

 

[Light in the Dark]

No, the short circuit light did not come on.

 

[jamawieb]

I would look at the wiring diagram and make sure everything is hooked to S8, K1, and S5 correctly. I would first try to swap the overload relay first because the battle short bypasses that internally with a relay. Something is sending the signal for the overload and disconnecting the load at K1. If it was just a burden resistor or dirty connections on S8 than it would just send the signal that its overloaded not disconnect the load at K8. That's the interesting part of the problem, is that it's disconnecting the load with the battle short on. The only time it should disconnect load is when a short circuit is detected.

 

[Light in the Dark]

So this set has about 1400 hours since Tier Reset... so I guess its possible its had a wiring fault this whole time, but I would think that maybe thats not as likely?

It does seem perplexing that its still dumping the load with the battle short on, which is why I post here. I will look at the connections again on my next day off, and see. I might look into another overload relay (I see Suprman has one on that auction place). Thanks for your help Jimmy.

 

[jamawieb]

I'm here to help. Just because it has 1400 hours on it doesn't mean someone hasn't been monkeying around in there. I had a reverse connection on s8 one time, that was causing an overload fault and it had 2500 hours on it. I would swap the overload relay first just because that is the only common factor with battle short and disconnecting load.

 

[Light in the Dark]

Just grabbed one off that auction place. I hope to swap it out this week, and have it readily fix the problem. Been innundated with calls for gensets in the last 48 hours. Happens after every major storm.

 

[Guyfang]

Did you notice if the short circuit light came on when you lost power with the battle short on. With the battle short on it still passes through the overload relay so if something is going on inside the relay it could cause your problem. A short circuit is the only thing the battle short will not bypass, if it senses a short circuit it disconnects power.

Short circuit OR Overload.

Here is the K8. If you use two roach clips and a wire to jump it, you can get a better idea if its the relay.

View attachment Scan0003.pdf

 

[robson1015]

Short circuit OR Overload.

Here is the K8. If you use two roach clips and a wire to jump it, you can get a better idea if its the relay.

I find it humorous that you call alligator clips 'roach clips' - you old hippie !!!

View attachment 720733

Those are alligator clips you Old Hippie !!!!

 

[Guyfang]

Got to have your priorities.

 

[Light in the Dark]

I will check the wires when I have the new part in my hand, during reinstall. Will circle back on this. Thanks for everyone's help.

 

[Light in the Dark]

Ok, so before I go burn my garage down with everything in it....

So I swapped the K8. All of the wires appeared to be put in place correctly (and I believe I did my due diligence in putting them all back in position)...

So now I have NO power at the set at all. The dead crank works... but when I cycle the start switch, nothing. No panel lights either. No fuel pumps running. Nothing.

Might I just have a bad replacement? Any other thoughts? I've got a terrible case of laryngitis right now, and I've been out in the garage for like 3.5 hours now (should be relaxing).. so this is literally the last thing I need.