generator issue very weird

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Sierrasparky

Sierrasparky

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Location
USA
Occupation
Electrician ,contractor
I ran a call the other day at a farm. They were on a generator no utility power at all.
They have two generators and a transfer switch so they can shut down one genset to be serviced and still have power.
The problem is that 40 plus old gernerator is rated at 120/240v three phase. 22kv.

The second generator only a couple of years old is a 120/208v. This is the genset that runs most the time. and was running at the time of the visit. The distribution panels are using all three legs at 120v with the exception of a couple of two pole motors and a 3 pole well pump.

my question is how can you use all three legs with the 120/208v genset and then shut down the 120/208v genset for service ( change oil ) and fire up the old genset that is 120/240v without having one "high leg"
Is there some way that 120/240v generator is wired to provide 120v to ground on all three legs? Otherwise every time they would do a oil change they would send 208v on anything that is connected to the stinger!

Could they have re-wired the generator and made it a WYE ? somehow capping off the center tap. and then grounding one end of each of the windings.
Is this possible?
 
My guess is there's something else in the loop somewhere or they double lugged one of the poles from the 240V genset.

Obviously creating an unbalance for the time that that unit is in use.

Feel free to ignore the above, the 3 pole well pump wouldn't work if that were the case. :-?
 
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Sierrasparky said:
I ran a call the other day at a farm. They were on a generator no utility power at all.
They have two generators and a transfer switch so they can shut down one genset to be serviced and still have power.
The problem is that 40 plus old gernerator is rated at 120/240v three phase. 22kv.

The second generator only a couple of years old is a 120/208v. This is the genset that runs most the time. and was running at the time of the visit. The distribution panels are using all three legs at 120v with the exception of a couple of two pole motors and a 3 pole well pump.

my question is how can you use all three legs with the 120/208v genset and then shut down the 120/208v genset for service ( change oil ) and fire up the old genset that is 120/240v without having one "high leg"
Is there some way that 120/240v generator is wired to provide 120v to ground on all three legs? Otherwise every time they would do a oil change they would send 208v on anything that is connected to the stinger!

Could they have re-wired the generator and made it a WYE ? somehow capping off the center tap. and then grounding one end of each of the windings.
Is this possible?
Click to expand...

Are you positive the 120/240 is 3 phase?

They may have simply doubled up a phase somewhere
 
RICK NAPIER said:
These voltges you're telling us did you get them from nameplates or from voltage testing? I would run a voltage test.
Click to expand...


the 120/208 is actual as it was in operation and thats the namplate.

The other unit was not running at the time of my visit. The nameplate is 120/240

There appers to be some modifications. to the 120/240.
 
mcclary's electrical said:
I didn't catch that. All I saw was double poles:grin:I need to read more thoroughly.


Unless, when it transfers it doesn't run that pump(through control wiring)
Click to expand...

So do you guys think that some hack got to the generator as I do?
I'll need them to run the thing and check the voltage.

This install is probable the very worst job I have ever seen in my life.

1) individual conductors #4 entering a panel without a bushing , not in conduit running across the wall.

2) load side terminals of the Genset terminate behind a workbench to a open buss terminal block . looks like it was something you'd see 30's era or pre war... Drop a wrench behind the bench an ploweeeeeeeeeee boom sparks .

3) indivudual condctors ran through drilled holes in rafters no insulators and caluked with silicone sealant.

4) # 12 wire on a 40 amp breaker.

5) # 10 on a 100 amp breaker I guess it's a fuse.

6) One single phase panel containing phase A and B a seperate panel just having phase C

7) panels not grounded

8) no covers on panels

it goes on and on

I live in the sticks but come on !
 
leftpanel.jpg
right3rdlegpanel.jpg
 
you have not see all of them... I'll post later.

You like the neutral block at the lower left outside the panel.
Well there is a similar terminal block with exposed lugs for all phase conductors also!
 
Wierd Gen issue

Wierd Gen issue

My take on this would first be, obviously, not installed/wired by an electrical professional. The person had enough knowledge to be real dangerous.
I would start by actually checking to see how the 120/240 volt generator is wired. With it't age I would think it is actually a single phase gen wired to the single phase panel. This being the original installation.
Check to be sure the pump is what it originally appears to be although I could see it is a 120 volt pump. If it is a 230/240 volt pump I wouldn't think it would run well on 208.
If the pump was a 120 Volt 3 wire pump it wouldn't care which generator it was running on. If the majority of the loads are 120volt they wouldn't care which phase to neut they were wired to they would run fine on either gen. It was said there are some two pole breakers. I would think any device other than maybe a heating element would be hard pressed to operate on 208 volts.
Just some thoughts.
Also be careful you may own this whole mess. It sounds like a quote to replace the whole install is in order.:roll:
 
Sierrasparky said:
you have not see all of them... I'll post later.

You like the neutral block at the lower left outside the panel.
Well there is a similar terminal block with exposed lugs for all phase conductors also!
Click to expand...

I can't believe this hasn't burned up, yet!!!!! What a mess.
Mark
 
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