MEP-802a Power on only 1 leg?

[Billy2642]

I have an 802a with only 34 hours with an issue I’ve never seen. Searched the TM and didn’t find an answer either. Got the generator all serviced up and it purrs like a kitten. I have power on all lugs it’s supposed to on 3 phase but when I have it set for single phase 240v, I only have power on the L3 lug. On single phase, I can’t get but 12 volts if that off the L1 leg. 3 phase works perfect though. Any ideas?

 

[Scoobyshep]

If i had to guess (and this is a generator physics guess), reconnection switch or winding failure. Other place check is meyer it before the overcurrent protection device (output breaker or contactor)

Sent from my SM-G973U using Tapatalk

 

[Andyrv6av8r]

Did you check your settings behind the panel?

 

[Billy2642]

Did you check your settings behind the panel?

yes settings on the back panel and front panel are correct

 

[Dieselmeister]

3 phase works perfect though. Any ideas?

Since 3 phase works good, it is not a generator problem. Did this generator ever work correctly on single phase? Sounds like a wiring or switch problem. Based on how single phase is derived, it could be that one of the windings is reversed or disconnected when the switch is set to single phase. Check all the wiring from and to the selector switch. Check for any evidence of "rewiring" by previous personnel.

 

[Billy2642]

Since 3 phase works good, it is not a generator problem. Did this generator ever work correctly on single phase? Sounds like a wiring or switch problem. Based on how single phase is derived, it could be that one of the windings is reversed when the switch is set to single phase. Check all the wiring from and to the selector switch. Check for any evidence of "rewiring" by previous personnel.

Just picked it up so previous history is unknown. This is the first I’ve had it running. I’ll recheck both selector switches. I didn’t take the top off to check the contacts of the rear selector switch under the control panel so I’ll probably start there and check the circuit interrupter as well.

 

[Daybreak]

OK, with the system off.
Get some contact cleaner.
Spray the 120v, 120/240, 3 phase selector well, and turn it back and forth lots of times to clean up the contacts. And then turn the switch back and forth some more.
Start your unit, and have a meter ready and check duplex rececptacle, turn on the a/c circuit interrupter, and check the lugs.

 

[Billy2642]

OK, with the system off.
Get some contact cleaner.
Spray the 120v, 120/240, 3 phase selector well, and turn it back and forth lots of times to clean up the contacts. And then turn the switch back and forth some more.
Start your unit, and have a meter ready and check duplex rececptacle, turn on the a/c circuit interrupter, and check the lugs.

Got out there again today to mess with it. Nothing on the machine appears to have been tampered with. Cleaned all the electrical components with cleaner and worked the S8 switch a bunch and no change. Started it up and the gauge shows 120v when it should be at 240. What I found interesting though is when set on 240v single phase, I have 120v on legs L3 and L2 instead of what it should be on L1 and L3. I found this kind of odd so I went to my 803a which even though bigger, the operation of them is the same. On that machine, when set for 240v single phase, I have 120v on L1 and L3 and nothing on L2. So the question is on this 802, why do I have voltage on the L2 leg and not the L1 leg?

 

[Ray70]

the 802 should be no different than the 803. Having power on L2 while in 240V single phase mode leads me to suspect something is wired incorrectly. It could even just be the wires crossed at the K1 relay.
If it appears to be working correctly other than sending power to L2 instead of L1 I would check the wiring on L1 and L2. It sounds like they are reversed somewhere, most likely at the K1 relay.

 

[Billy2642]

the 802 should be no different than the 803. Having power on L2 while in 240V single phase mode leads me to suspect something is wired incorrectly. It could even just be the wires crossed at the K1 relay.
If it appears to be working correctly other than sending power to L2 instead of L1 I would check the wiring on L1 and L2. It sounds like they are reversed somewhere, most likely at the K1 relay.

I’m not as well versed in the labeling of the parts but which one is the K1 relay? Is that also know as the circuit interrupter?

 

[Ray70]

Correct, K1 is the circuit interruptor, buried back in the left corner behind the inner control panel back wall.
Have to remove the top cover to access it.

 

[Dieselmeister]

If it appears to be working correctly other than sending power to L2 instead of L1 I would check the wiring on L1 and L2. It sounds like they are reversed somewhere, most likely at the K1 relay.

I agree with the reversed wires. Your generator meter reading 120V instead of 240V, makes sense, because it is reading L1 and L3. Since you have no power on L3, the meter is only getting 1/2 of the voltage. If the schematic is correct, the meter is connected between between K1, and the power selector switch S8. Once you get the top off your machine, carefully check the wire numbers that go from the Power Selector switch, to the K1, and compare them to the schematic. Specifically, you need to look at the thick power wires ( L1, L2, L3, L0), and their connection locations between K1 and S8.