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PFDG3 11-21-2012 06:06 PM

Fried my generator
 
I installed a generator interlock on my garage GE load center, with a new 30A double breaker, 10-3w/g romex, to a Reliance 30A inlet box.

My generator is a Powermate BlackMax 5250/6560 that I've used once, and fire up every 6 months or so. I connected the generator's 20A receptable with a 20A cable, a 20A/30A adapter and 30A cable to the inlet box.

To test, I shut off the mains and all breakers, fired up the generator, flipped on the generator breaker and one circuit that controlled a few house lights and the light in the garage. The light in the garage went on, and everything was fine for 30-60 seconds. Then the generator coughed,the garage light went off and the generator started smoking.

After shutting down the generator, I noticed the wires were very warm right up to the load center. I took off the end of the generator and the windings on one side of the stator were burnt black. Also, plastic around the ground prong on the 20A cable had melted.

Any thoughts before I call a pro.

Thanks

bobelectric 11-21-2012 06:42 PM

Wired the plug wrong?

PFDG3 11-21-2012 06:45 PM

Quote:

Originally Posted by bobelectric (Post 1057928)
Wired the plug wrong?

Afterward, I tested at the inlet, by removing the breaker cover and flipping on the generator breaker. All seems OK.

frenchelectrican 11-21-2012 09:09 PM

Quote:

Originally Posted by PFDG3 (Post 1057914)
I installed a generator interlock on my garage GE load center, with a new 30A double breaker, 10-3w/g romex, to a Reliance 30A inlet box.

Cool., this is pretty common one., However you mention GE load centre so read my comment below there are few thing you may want to check it out.

My generator is a Powermate BlackMax 5250/6560 that I've used once, and fire up every 6 months or so. I connected the generator's 20A receptable with a 20A cable, a 20A/30A adapter and 30A cable to the inlet box.

Are you useing both 120/240 volts or straight 120 volts ?? that will make the differnce on how you did hook it up and was the adpaitor is correct conferation for that pupose.

Did you get the factory "generatour " cord or a local made type cord ?


To test, I shut off the mains and all breakers, fired up the generator, flipped on the generator breaker and one circuit that controlled a few house lights and the light in the garage. The light in the garage went on, and everything was fine for 30-60 seconds. Then the generator coughed,the garage light went off and the generator started smoking.

Most likey you did have a short in the generator head or the cord itself one of the two.


After shutting down the generator, I noticed the wires were very warm right up to the load center. I took off the end of the generator and the windings on one side of the stator were burnt black. Also, plastic around the ground prong on the 20A cable had melted.

Any thoughts before I call a pro.

Thanks

Burnt black is useally indecated that you have serious overload or short circuit one of the two and the other thing that the ground prong is melted that mean you may have mismatched wiring connection.

You will have to get the ohm meter to see if the cord is connected wrong and I know you say 10-3 NM and are you using two pole breaker if so then you have connection or the adpatour hooked up wrong.

Which inlet recpetale you did use the straight 120 volts or 120/240 volts ?? that will make the differnce ( straight voltage <120 ou 240 volts> type will only have three blades while 120/240 volts single phase verison will have 4 blade )

The 4 blade verison should be L14-20R if so let us know if you are using this one if so you may have one of the " line / netural " reversed so you will need to test it out carefully.

As far for repair the generator itself the only way you can fix is replace the stator ( main winding ) or rewinded at one of the motour shop they can rewinded for ya.

I did take a look at specs and that kinda ring the bell I have work on those skunkers ( don't ask why but they are good to blow the 12 volt coil out ) and the stator replacement cost from factory is over 300+ Euros sometime it cheaper just get a whole new unit unless it a malfunction from factory then it can be done under warranty if you still have it.

Merci,
Marc

AllanJ 11-21-2012 09:23 PM

Did it work properly before? Did you make any changes since it last worked?

Suggest that at the generator, connect up or plug in a small (as little as 25 watt) incandescent light (two, one on each side of the line for 120/240 volts). Then when you fire up the generator and these light(s) do not (both) come on properly that is a sign of trouble and you should shut off the generator quickly.

For a generator with a 4 prong receptacle for nearly the full output into a 120/240 volt house feed and also two 120 volt receptacles, one on each side of the line, the latter receptacles can be used to plug in the small test lights.

Incandescent lights immediately reveal problems with overly high or overly low voltage. Compact fluorescents might seem to come on properly even if there is a severe overload which is almost always accompanied by low voltage.

gregzoll 11-21-2012 09:23 PM

Usually when you do this, you hear the words "Hey, hold my beer." Now of course, if you did a dead short, you could also have killed the resistor & diode on the generator.

Billy_Bob 11-22-2012 12:29 PM

In all the many many years I have been reading DIY electrical stuff on the internet, this is the FIRST time I have ever read about anyone frying a generator!

You would think this this would happen more often with the various ways people connect these!

Anyway it sounds like a hot to ground (instead of neutral) overload and the generator should have a circuit breaker which should have tripped.

The manufacturer may be interested in this problem as there may be a problem with this generator's circuit breaker(s).

frenchelectrican 11-22-2012 06:26 PM

Quote:

Originally Posted by Billy_Bob (Post 1058337)
In all the many many years I have been reading DIY electrical stuff on the internet, this is the FIRST time I have ever read about anyone frying a generator!

You would think this this would happen more often with the various ways people connect these!

Anyway it sounds like a hot to ground (instead of neutral) overload and the generator should have a circuit breaker which should have tripped.

The manufacturer may be interested in this problem as there may be a problem with this generator's circuit breaker(s).

Billy Bob.,

I have see quite few fried generators from simple small portable units to large industrail sized generatour.

Speaking of circuit breakers some of the small portable generator never really work very well but the breaker will not protect the interal short circuit inside of the generator head itself you will able hear odd sound like knocking or deep moaning sound like turbine engine try to spool up fast and the primemover ( engine ) will have to run pretty hard to keep up with it unless you have serious overload or serious short circuit that can stall the unit.

The most common way to destory the generatour itself is misconnection that useally is the most common one.

Second most common mistake is use the wrong voltage receptale ( I have see it happend from time to time when someone try to rig up something to get full wattage of that unit)

Third most common but pretty much mort ( death ) for generatours is backfeed connection if not set up for parallel connection ( this is not for faint of heart and only cerifited generator tech or electrician can do this on larger unit if they are designed for it )

This one is semi common but not widespread is overspeed when the primemover govonver is stuck or have broken coupling. ( some case with larger unit when they dump the load very fast you can expect the speed ramp up a bit then slow down to back normal speed )

There are few other parts I can see the damage but it is not in the scope in here.

Merci,
Marc

PFDG3 11-27-2012 05:46 PM

Quote:

Originally Posted by frenchelectrican (Post 1058020)
Burnt black is useally indecated that you have serious overload or short circuit one of the two and the other thing that the ground prong is melted that mean you may have mismatched wiring connection.

You will have to get the ohm meter to see if the cord is connected wrong and I know you say 10-3 NM and are you using two pole breaker if so then you have connection or the adpatour hooked up wrong.

Which inlet recpetale you did use the straight 120 volts or 120/240 volts ?? that will make the differnce ( straight voltage <120 ou 240 volts> type will only have three blades while 120/240 volts single phase verison will have 4 blade )

The 4 blade verison should be L14-20R if so let us know if you are using this one if so you may have one of the " line / netural " reversed so you will need to test it out carefully.

As far for repair the generator itself the only way you can fix is replace the stator ( main winding ) or rewinded at one of the motour shop they can rewinded for ya.

I did take a look at specs and that kinda ring the bell I have work on those skunkers ( don't ask why but they are good to blow the 12 volt coil out ) and the stator replacement cost from factory is over 300+ Euros sometime it cheaper just get a whole new unit unless it a malfunction from factory then it can be done under warranty if you still have it.

Merci,
Marc


I'm using a 4-blade L14-30R inlet. I'm getting 120v at W-X, W-Y, G-X, and G-Y, with the backfeed breaker closed. Should I be testing it some other way additionally?

Thanks

Oso954 11-27-2012 06:42 PM

2 Attachment(s)
Are you saying that you connected one of the receptacles in the orange rectangle to the inlet box ?

If yes, what 20a/30a adapter did you use

PFDG3 11-27-2012 07:17 PM

Quote:

Originally Posted by Oso954 (Post 1061933)
Are you saying that you connected one of the receptacles in the orange rectangle to the inlet box ?

If yes, what 20a/30a adapter did you use

No, to the 120/240 twistlock.

frenchelectrican 11-27-2012 10:59 PM

I will post the wiring diagram what it supposed to be.

http://www.doityourself.com/forum/at...ingdiagram.png

This is the correct pattern. The netural and ground should be oppostie side of each other then 1/4 turn around the lines are each other as it posted.

The plug will be reversed what it will show on the diagram.


Merci,
Marc

PFDG3 11-28-2012 04:11 PM

Quote:

Originally Posted by frenchelectrican (Post 1062095)
I will post the wiring diagram what it supposed to be.

http://www.doityourself.com/forum/at...ingdiagram.png

This is the correct pattern. The netural and ground should be oppostie side of each other then 1/4 turn around the lines are each other as it posted.

The plug will be reversed what it will show on the diagram.


Merci,
Marc


Marc, yes, that's how the inlet is wired.

micromind 11-28-2012 07:19 PM

Here's what I suspect happened;

The gen was supplying some sort of load, likely not very much. Somehow, it became paralleled with the utility. But even worse, the burned winding (120 volt) was being backfed with 240 from the utility.

If a small gen like this one is paralleled with a larger source, it will almost certainly be out of synch. The larger source will snap it into synch, but the gen is not big enough to be damaged, especially if it was close to synch when the larger source was applied.

If 240 was applied to one of the 120 windings, the speed would not change at all. The current would be fairly high, though not as high as a 120 motor with 240 applied. It should have tripped a 30 amp breaker, but we do not know the condition of said breaker. Once in a while, I'm asked to test branch circuit breakers. I have absolutely seen brand new breakers that would not trip no matter how much current is applied. Very rare, but it does happen.

The gen ran smoothly even with severe overcurrent applied to one of its windings until the insulation began to break down from excessive heat. Then, as the winding began to short out, the load on the engine suddenly increased (hence the 'cough').

This would explain the heated #10 wire. This gen does not have the ability to heat up a #10 in a short time, even if the other end was a bolted fault (short circuit). And even if it could heat up the wire, it'd lug the engine down.

I could easily be wrong, but in my mind, there had to be another source of power besides the gen to cause this much damage in this short of a time.

Rob

frenchelectrican 11-28-2012 11:54 PM

Quote:

Originally Posted by PFDG3 (Post 1062503)
Marc, yes, that's how the inlet is wired.

Ok then what you will have to do is test the cord and the adpatour to make sure they are on the same sequince so you will have to use the DVM and run this on Ohm scale or Ohms input ( make sure this cord is 100% unplugged please ) and test the probe neddle to see it that will swing to zero or very low numbers.

Start with the ground slot first ( the L shaped ) on both end including the adpatour then do the netural then the line either side first then other one it should be all the same all the way thru if not then you have issue right there.

This simple test should take about less than 5 minuites so you will rule the cord and the adpatour out to make sure then if clear on that part then you can focus on the generatour head.

That generatour head itself is the excat the same as standard Coleman units so very easy to get into the head with out issue there will be 4 bolts holding the unit up ( you may want to find a scrap wood to block up the engine due the generatour head is supported by one bracket.) unplug the harness and slide the stator out that part is outside of the generatour unit and you can able tell by the winding to see where the short start.

To pop rotor off ( armture ) there will be a very long bolt holding this and the shaft is tapered so you may want to give a quick rap then it will pop off but somecase gear puller will do the trick as well, But becarefull not to nick the windings on the rotor.

But before you do that check with your Coleman generator rep to see if they can do something related to the warranty work due you have pretty new unit.

Bon Chance.

Merci,
Marc


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