Mep 802a bogs down when a/c circuit interrupt

[tinz1722]

I’ve had this unit running great for a couple years in an off grid situation. Had a lighting storm the other day and thinking that may have caused this issue:

It starts and runs fine. When I go to flip the A/C circuit interruptor switch it bogs down and almost dies (good bit of black smoke). Produces power at terminal prior to flipping switch, but then no power anywhere once switch is flipped. I turned off the breaker to the camp thinking overload but it’s still happening?

 

[rickf]

I’ve had this unit running great for a couple years in an off grid situation. Had a lighting storm the other day and thinking that may have caused this issue:

It starts and runs fine. When I go to flip the A/C circuit interruptor switch it bogs down and almost dies (good bit of black smoke). Produces power at terminal prior to flipping switch, but then no power anywhere once switch is flipped. I turned off the breaker to the camp thinking overload but it’s still happening?

Sounds like a dead short to me, you might want to do some investigation before you let the magic smoke out! And make SURE your ground rod is planted well since it could be shooting power through the ground. If that ground is loose and there is a short to the frame YOU become the ground, it will not end well.

 

[tinz1722]

Sounds like a dead short to me, you might want to do some investigation before you let the magic smoke out! And make SURE your ground rod is planted well since it could be shooting power through the ground. If that ground is loose and there is a short to the frame YOU become the ground, it will not end well.

Anything to check for a dead short, not familiar with that term? I’ll check grounding rod

 

[2Pbfeet]

A dead short is a low resistance connection (short) between two conductors.

After a lightning strike, I think that going over every single electrical connections is prudent. I would bear in mind that relays, contractors, and breakers have all been known to weld contacts shut, and between contacts. So, just because something looks ok from the outside is not good enough. You need to test the connections and the function of each part. Yes, this is not a small, quick job, but you have at least one issue. That means to me that your unit got hit pretty hard with the strike, so I think that all bets are off on assuming that all parts save one are good.

I would start back at the generator head, and work out to the main AC interrupt or switch and relay. (After doing all of that, and fixing any issues, I would also double check the voltage coming out of the generator, without a load, and with a maximum load, before connecting anything else.)

Sorry for the bad news. With some luck it will only be one or two small items.

All the best,

2PbFeet

 

[rickf]

How familiar are you with electrical systems and wiring? I am not trying to be smart here but if you are not familiar with what a dead short is then you probably are not real familiar with electrical circuits. It only takes 1/4 of an amp to kill a person, touch the wrong thing here and it is 50 amps. This diagnosis is going to take a lot of circuit reading and meter checking.

 

[DieselAddict]

To add to what was said above, Do NOT run it again until you do some looking around inside the unit. You will need to remove the top covers to gain access to the places where the main wiring goes.

Also, since the term DEAD SHORT is a new one to you, I strongly suggest you "phone-a-friend" that has good basic electrical skills to help you. That should shorten the time to find the problem and reduce the risk of injury. As already stated, these thinks can and will kill you if you are not careful.

 

[Ray70]

I'd check the wires going from the K1 contactor to the power lugs. They typically touch the body of the generator is several places ( need to remove the top cover on the front part. Lightening may have burnt one of the main power wires, causing your short to ground.
You can also use an ohm meter and check resistance between the L1 L2 and L3 lugs to any metal chassis point.
Low resistance there means a dead short is present between that lug and the K1 contactor.

 

[Guyfang]

Was the set running when you had lightening strikes?

Second all the above. To add to Rays comment, also open the rear left side door and look to see if any of the load wires are shorted to the gen set side and control cube. To add to Diesel addict's comment, do remove the top and Inspect. Produces power at terminal prior to flipping switch, but then no power anywhere once switch is flipped. What terminal are you talking about?

Do this check first. If the set starts up, runs and makes power, then turn it off. Remove the out put side terminal cover of K1, (AC output contactor), then remove the three output wires, L1,L2 and L3. Tape the ends up. Start the set. check that its making power, with a DMM, (Multi meter) on the INPUT wires of K1. If you have power, then use the S5, (AC Interrupt switch) to turn on the K1. If it starts to act up, shut it off. The problem is in the K1. If it runs normally, then the problem is from the wires you took off from the K1 to your camp. So if it still acts up, hook the wires back up to the K1, and remove the cable from the gen set to the Camp. Redo the above test. Start it up, and push S5 up. If the set acts up, the problem is from the output wires on the K1 to the output load terminals. If it acts right, the problem is in the cable from the gen set to the cabin.

There is nothing wrong with the gen set making power. You said it doesn't act up until you push S5 up. So you do not have to troubleshoot the entire gen set. Just make damn SURE the ground is good to the set, and that its tight.

 

[rickf]

And DO NOT TOUCH ANYTHING BUT THAT SWITCH once it is running!!!!! There is a problem and you need to find it before poking around with it running, especially with open panels. The switch is plastic so no danger there. Just because the ground is good does not mean that if you touch a hot wire you will be safe, you will be toast.

 

[Digger556]

Check these wires behind the fuel/water separator. They connect the circuit interrupter contactor and the output lugs. Despite them being routed through a P-clamp, they can still rub on the edge of the sheet metal, which is compounded by how much an 802 shakes when running. Here is an example of an 802a I refurbished where one of the wires had rubbed through and was arcing on the chassis. (red circle)


Here is an image from someone else's unit with the top off. You can see where the wires exit the contactor and head down to the output lugs. (top). Plenty of places to rub against the sheet metal.

 

[2Pbfeet]

Check these wires behind the fuel/water separator. They connect the circuit interrupter contactor and the output lugs. Despite them being routed through a P-clamp, they can still rub on the edge of the sheet metal, which is compounded by how much an 802 shakes when running. Here is an example of an 802a I refurbished where one of the wires had rubbed through and was arcing on the chassis. (red circle)
View attachment 938178

Here is an image from someone else's unit with the top off. You can see where the wires exit the contactor and head down to the output lugs. (top). Plenty of places to rub against the sheet metal.

Great point! These wires are tough but sharp edges and wires are never a great combination in my experience.

There is a similar edge on the '803s as well, IIRC. I remember adding some additional wire management in that area on mine to get wires up and away from an edge.

All the best,

2Pbfeet

 

[Ray70]

Way back years ago, someone had posted a thread warning about this exact wire chaffing condition particularly on Tier2 reset machines.
The issue, if I recall was that many Tier2 machines were reassembled with the output wires from the K1 to terminal lugs incorrectly routed, causing them to rub on the corner's of the sheet metal in the areas Digger indicates above.

 

[Guyfang]

We always used inner tube material to make one wrap around the wires and zip tied them there. Same thing when you open the rear doors. Look up in there and you see places that would bother me. Especially in the Army. They use the sets for sometimes VERY extended time periods.

 

[rickf]

Inner tubes, conveyor belts and wire ties. How in the world did we get by without the wire ties! So much quicker and easier that baling wire. Wait, most people under the age of 70 will not know what baling wire is, so we will say Mechanics wire. LOL.
Wire ties don't last as long as baling wire though, I have worked on cars that have had baling wire repairs that are decades old.

The one repair item missing is tin cans, Baling wire and tin cans fixed a LOT of exhaust systems.

 

[Guyfang]

Do not forget lacing wire. I still have two lacing wire plyers. All the Aviation guy were masters with lacing wire!

 

[rickf]

Right, we called it Safety wire. Being into racing I did a lot of safety wiring tying. I was taught how to be efficient by an aviation mechanic.

 

[Digger556]

I have "safety wire" from my racing days, but I remember my grandfather always had two things on his person when we were out on the tractor, pliers and a roll of bailing wire.