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Discussion Starter · #1 ·
Hello.. I have a Generac 5550 generator that I use during hurricane season here in Florida.
I use the 240v outlet on the generator to my dryer plug so it back feeds to my panel.
For the few times I had to use it I didn't have any issues, but now its not working.
At the generator, I checked the 110v outlets with a volt meter and they are working, but I am not sure how to test the 240v round outlet on the generator. Can someone please tell me where to put the leads of the volt meter to test that 240v outlet on the generator, its a 4 pin configuration.
Thanks !!

9669


 

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I’ll get the PSA out of the way, back feeding the panel without an interlock is a bad move. Potential dangerous for you, but particularly dangerous for the linesman working to restore power. Interlocks are cheap and easy to install.

With your multimeter you should have 240v probing the terminals marked line1 and line 2.

You should have 120v probing between line1 or line2 and ground and neutral.

9670
 

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Agree with the above post...get an interlock and a proper input box and generator breaker. Make sure your generator switch (if your model has one) is set to 120/240 and not 120V only and also check the generator breaker/reset for that outlet.
 

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I used to back feed through a dryer plug also. We have 2 sets of hook ups here for washer/dryer. The build spec was in the mud room right off the garage. That wasn't desirable at the time of build so a 2nd set was put in the basement. The house was still built with the original set off the garage = never used. The dryer plug is a 14-30 (non-locking) and made an easy hook up for feeding welders etc in the garage - and easy hook up for back up power.

I agree an interlock set up is by far the best way to do it. Electrically speaking, there is no difference between back feeding a dryer plug vs an actual inlet box. Each feeds through a breaker to the main panel. The catch is in order to back feed through an existing outlet at some point in the circuit you need to have a male plug hot from the generator - usually that is the one that plugs in to the dryer plug. Having a "hot male plug" is dangerous - and why inlet boxes exist. They have the pins for the connection buried down inside the box to make it very difficult to get to, and with the interlock set up in place the inlet box can not be hot with the utility feed on - the interlock is there to make it impossible for the inlet box to be hot when the utility feed is on. Only when you turn off the utility feed does that free up the breaker for the inlet box to turn on.

The pinout diagram of the L14-30 posted earlier is a good place to start. My guess is the breaker that feeds that outlet is bad. To add to the troubleshooting - unless you have a switch on the generator that lets you select "120v only" then the 2 duplex sets of 120v outlets should be on each pole of the alternator. So if you measure across both hot pins (the small blades) between each set of duplex outlets (not within the set, one outlet from EACH set) then you should have 240v. If you have 120v out of them then you would have to have 240v. So if the power is there - but not on the L14-30 - then the alternator side of the circuit is fine - the breaker is likely the weak link.

If you find the breaker is bad and have trouble sourcing parts check Blue Sea Systems for a double pole breaker of the ampacity you need. They are stand-alone breakers with screw terminals. Ring terminals on your wires from the alternator and the feeder pigtails to the outlet on the generator would be good to use. You could use fork terminals - these will let you connect the wires to the breakers without removing the screws, but they don't hold should the screws get loose (they will pop off).

Good luck with it!
 

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Feeding through a dryer plug is just BAD. Dangerous to line crews, Illegal, dangerous to you as you'll use a "suicide cord" to connect it. Also, if there's every a fire or other loss your insurance company will be very interested in any electrical issues that were going on. Spend a couple hundred (material) and put in a lockout and generator inlet box and be legal and safe.

Agree that the issue is probably the breaker or a bad connection, particularly if both 120V outlets are working.
 

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Discussion Starter · #6 ·
I did some testing today. The 4 120v outlets work correctly. On the L14-30 here's what I get....when I probe (per the illustration)
Line 1 to Line 2 = 0v
Line 1 to Ground = 120v
Line 1 to Neutral = 120v
Same results when I probe Line 2 to those.
 

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I did some testing today. The 4 120v outlets work correctly. On the L14-30 here's what I get....when I probe (per the illustration)
Line 1 to Line 2 = 0v
Line 1 to Ground = 120v
Line 1 to Neutral = 120v
Same results when I probe Line 2 to those.
Does your generator have a 120v or 120/240v selector switch?
 

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was this a new gen set for a second hand set you picked up?
did it work ok for you at some point or has it always been this way??

if it was second hand...
check your wiring behind that panel on the gen set.
they could to have set it up for 120 vac only!
 

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I did some testing today. The 4 120v outlets work correctly. On the L14-30 here's what I get....when I probe (per the illustration)
Line 1 to Line 2 = 0v
Line 1 to Ground = 120v
Line 1 to Neutral = 120v
Same results when I probe Line 2 to those.
That partially makes sense.

Ground and neutral are bonded - so when you test voltage between L1 and L2 to ground or neutral you get the same result.

This test would also debunk having a voltage switch because you can't parallel poles on a rotary alternator that has bonded neutral. The only way to parallel poles is to move what was neutral on the 2nd pole to what was hot, and vice versa - that gives you the alignment of the poles so the AC power lies in-phase. If the neutral of the alternator is hard bonded to ground it is impossible to align the poles right.

What doesn't make sense is that your 120 volts is there but you are not getting 240 volts. The way you wrote the supposed "test results" doesn't make sense because the voltage test from the hots to neutral and ground shows voltage but between the hots does not.

Did you work on the L14-30 connector/electrical box at all?

This might be a good learning experience on how to use a multimeter. I suggest you do some wiring tracing with continuity through the electrical box. Check breakers, terminals, etc.
 

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if it was second hand...
check your wiring behind that panel on the gen set.
they could to have set it up for 120 vac only!
Point.

However, if it doesn't have a voltage selector switch I am not sure how it is possible to do so as unless an alternator is built with a true split pole alternator (4 wires, not 3) you can't parallel the 2nd pole with the first and "double the amperage" at 120v. You need to flip the phasing of the 2nd pole and to do that you have to have a split pole alternator. I'm not suggesting this generator isn't built that way - but if the generator doesn't have a voltage switch it wouldn't make sense to me why they would put a split phase alternator in it and tie the 2 middle wires together to bond that to ground? Doesn't make sense.
 

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I got 120v across the two.
For the few times it was back fed, the mains were always in the off position.
That’s very odd. Like flyfisher stated it should have been 0 or 240v… what’s the voltage reading between hot and neutral on each of the duplexes.
9679


Ground and neutral are bonded - so when you test voltage between L1 and L2 to ground or neutral you get the same result.

This test would also debunk having a voltage switch because you can't parallel poles on a rotary alternator that has bonded neutral. The only way to parallel poles is to move what was neutral on the 2nd pole to what was hot, and vice versa - that gives you the alignment of the poles so the AC power lies in-phase. If the neutral of the alternator is hard bonded to ground it is impossible to align the poles right.
Voltage selector switch, and neutral bonded.
 

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Did anybody work on this generator. If you numbers are correct, both sides of the 120V outlets could of been wired to one side of the alternator (was one side previously damaged?) and that would limit the generator output to 2,800 watts total. You would have to open the panel and trace the wires coming from the alternator and test them.
 

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Voltage selector switch, and neutral bonded.
See last picture and text around it in the thread/post I had here a few weeks back:

The neutral would have to be one of the many pole positions of the voltage selector switch where "neutral" (which ever configuration it is in - see crude schematics in the referenced post/thread also) is tied to ground through the switch.

Otherwise, if neutral, directly off the alternator, is actually 100% "bonded" to ground with no switching or jumpering then you can't stack the poles of the alternator in parallel which that is where you get the full wattage on 120v, and not half of it as in loading only 1 of the 2 poles.
 

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See last picture and text around it in the thread/post I had here a few weeks back:

The neutral would have to be one of the many pole positions of the voltage selector switch where "neutral" (which ever configuration it is in - see crude schematics in the referenced post/thread also) is tied to ground through the switch.

Otherwise, if neutral, directly off the alternator, is actually 100% "bonded" to ground with no switching or jumpering then you can't stack the poles of the alternator in parallel which that is where you get the full wattage on 120v, and not half of it as in loading only 1 of the 2 poles.
Good stuff, Informative.

Honda’s EB generators have a jumper right at the alternator going from neutral to ground, and are 120v - 120/240v selectable. Just sayin, How this is accomplished s over my head.
 

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Good stuff, Informative.

Honda’s EB generators have a jumper right at the alternator going from neutral to ground, and are 120v - 120/240v selectable. Just sayin, How this is accomplished s over my head.
Electrically they would have to have the poles wired as below:
9687


If you look at the top coil - blue and first gray lead pair - you could conceivably have that neutral bonded straight to ground, but not the 2nd one. You need what was neutral on the bottom coil to go to hot on the first coil and what was hot on the 2nd coil to go to neutral on the 1st coil. Thats how you stack the AC waves. If you leave neutral as-is and take the 2nd hot and connect it to the 1st hot you blow up the generator. Kaboom. Reason being - the AC waves are directly opposing and canceling each other out = dead short. Think of tug-a-war with equal forces. The rope doesn't move. Then flip one side so one side pulls and one side pushes. Now you have twice the force in 1 direction. Of course, AC is an oscillation so the tug-of-war analogy doesn't match perfectly, but the point is the "force" being either opposing or directly in-line. Same with the AC power. You need to align it so it is together, not opposing.
 
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