MEP-004A Non-standard wiring, Main AC Output Contactor (CB2)

[1800 Diesel]

Got another unit in the shop and started working the basic fuel, coolant and coolant checks and then got to the wiring.
First thing I noticed is that someone has connected the three load side cables to the line side terminals. (See photo.)


I have to assume that they either had a non-functioning CB2 or the S3 switch. As soon as I finish pre-start fuel, oil and coolant maintenance , I'll be
reconnecting the cables back to the load side. to verify CB2 and S3 function.

Has anyone seen this done on any units? This is the first for me.

(Edited to correct "SB2" to "CB2".)

 

[Scoobyshep]

No. And this is really dangerous as it bypasses all the overcurrent protection.

Sent from my SM-G950U using Tapatalk

 

[1800 Diesel]

No. And this is really dangerous as it bypasses all the overcurrent protection.

Sent from my SM-G950U using Tapatalk

Agree, not to mention an accidental contact with one of the output terminals and electrocution of someone expecting the main breaker to be open. Knowing we should always treat the load terminals as hot while a generator is running, but still a very dangerous arrangement.

This one came from a small town in the southeast--I expect someone thought they had a good reason to relocate the cables....I'll be switching them back to their correct positions tonight!

 

[Guyfang]

This is a classic non-op CB "fix". Yes I have done this twice in my life. Both times had a company grade officer sign a statement that he ordered me to do it. It works, but its a killer waiting to happen. Sometimes the mission comes first. Or that was the excuse used to justify the order. To test the coil on the CB, apply 24 VDC to pins A&B. I would first take it apart, to see if water is present, that the actuator moves smoothly, and that the load contacts are not melted closed or that the contacts are still good. Its really simple to test/repair.

EDIT: This is not a standard CB2 for this type gen set. I would say it was from a 60 or 100 KW gen set.

 

[1800 Diesel]

This is a classic non-op CB "fix". Yes I have done this twice in my life. Both times had a company grade officer sign a statement that he ordered me to do it. It works, but its a killer waiting to happen. Sometimes the mission comes first. Or that was the excuse used to justify the order. To test the coil on the CB, apply 24 VDC to pins A&B. I would first take it apart, to see if water is present, that the actuator moves smoothly, and that the load contacts are not melted closed or that the contacts are still good. Its really simple to test/repair.

EDIT: This is not a standard CB2 for this type gen set. I would say it was from a 60 or 100 KW gen set.

Guy,

Good to know about the breaker not being for the 15 or 30KW model. I'll check to see if it has an NSN. After spending a couple hours cleaning the fuel system and another hour or so verifying the connections (when I moved the cables back to the load side) I did a light-off and the CB2 closed the first time I hit the S3 switch. Cycled S3 several more times and CB2 closed promptly each time; also verified voltage on the output terminals. Doesn't make a bit of sense that someone would have moved the cables. I still need to do an extended load test, but I'm optimistic about this one. It's good to have a success to keep you going! Thanks for checking in. Be safe over there!

 

[Guyfang]

This is an interesting part. The very first NSN for it, and it sticks in my head after 40+ years, is 5945-00-007-1147. The Prime NSN in today's world is, is 5945-01-165-1065. Having said that, this relay has more NSN's and Part numbers then my wife has shoes.
5945-01-165-1065
5945-00-007-1147
5945-01-010-5911
5945-01-021-4122

Part #'s
30920-020
70-501
70-501-1
70-501-2
A3349918
A3349918-1
A3349918-2
B301EA
HB200A
HB200A1C4H
JCG-6001A
JCG6001A
SA105C
SD105C

Trying to be safe. Had to work today. But wasn't too bad.

 

[1800 Diesel]

This is an interesting part. The very first NSN for it, and it sticks in my head after 40+ years, is 5945-00-007-1147. The Prime NSN in today's world is, is 5945-01-165-1065. Having said that, this relay has more NSN's and Part numbers then my wife has shoes.
5945-01-165-1065
5945-00-007-1147
5945-01-010-5911
5945-01-021-4122

Part #'s
30920-020
70-501
70-501-1
70-501-2
A3349918
A3349918-1
A3349918-2
B301EA
HB200A
HB200A1C4H
JCG-6001A
JCG6001A
SA105C
SD105C

Trying to be safe. Had to work today. But wasn't too bad.

Didn't get much MEP work done today...rainy morning and I ended up running the roads today picking up some supplies and such. I didn't see any numbers on the CB2 though. Meant to ask if this one is possibly from an MEP-006A, does it have a higher interrupt rating and therefore I should swap it out asap with a known good one (15KW model) from my spares locker? BTW, get what you mean about the shoe situation ........

 

[Guyfang]

Sometimes, when looking at the MEP-004A and MEP-005A schematics, you find something like J51, or TB101, and think, "Where the heck is this thing?" This list will help with such things. It is probably not complete, so if you find something not listed, give me a shout.