Generator tripping 240v circuit breaker

[hammick]

I am rehabbing a Coleman Powermate 3500w Generator (new carb, fuel lines, plug, air filter, valves adjusted, etc). It's running great. 120v outlets work fine and it has idle control which is working.

There is a problem with the 240v circuit. The generator is tripping the circuit breaker with no loads attached. When I reset the 240v circuit breaker on the Genny it tries to rev up and bogs down like it is overloaded even though nothing is plugged in.

With the generator off I am getting continuity between L1 and L2 and also between L1 and neutral and L2 and neutral. Is my continuity test normal? If so, what else should I be looking for?

FYI neutral is not bonded to ground on this Generator.

Thanks for any help.

[Sunking]

You cannot test the generator windings with an Ohmeter. You should see continuity, very low reading However you might get a clue. Take a reading between L1/Neutral and L2/Neutral. They should be equal.

First thing I would look for with an Ohmmeter is continuity From L1 and L2 to the generator frame aka ground. Should be open circuit. Sounds like you might have a winding shorted out to the generator frame.

What you really need to test with is a Megar aka high voltage ohmmeter.

[inetdog]

My take is that since the generator runs and delivers power on all of the 120V outlets (probably half on L1 and half on L2) but blows the 240V breaker immediately on resetting it, even with no load:
The problem is not in the generator windings, or else the two 120V circuits would not be working.
The problem is not in the generator windings because that would not blow a breaker connected to the output ends of those windings.
The only place left, if the breaker itself is not defective, is in the wiring between the breaker and the 240V output connector.
Careful inspection of that wiring should show the problem. If not, the disconnect both hot leads at the receptacle and at the breaker and get out the ordinary ohmmeter again. If no fault is found with the 1-9 volts that the ohmmeter uses, then you will need to megger those wires and the connector.

[hammick]

Thanks for the great info guys but i'm 99.9% sure I know the problem. I replaced the 120v duplex outlet because it was cracked. Didn't realize the duplex tab needed to be broken on the hot screws. I dug the old outlet out of the trash and sure enough the tab was broken on it. So when I reset the 240v circuit breaker L1 and L2 were shorting together.

Looks like I got a sweat deal on a nice generator with a Honda GX160 motor and idle control. I have never seen a carburetor and fuel lines so clogged (I think I'll give up bacon). I spent 40 minutes unclogging the carburetor and then realized the main jet was corroded in. Had I know a new carb was only $10 on Amazon I would have started there first.

I don't know how they can produce and sell carbs for $10. Damn Chinese. Love em and hate em.

[Sunking]

Thanks for the great info guys but i'm 99.9% sure I know the problem. I replaced the 120v duplex outlet because it was cracked. Didn't realize the duplex tab needed to be broken on the hot screws. I dug the old outlet out of the trash and sure enough the tab was broken on it. So when I reset the 240v circuit breaker L1 and L2 were shorting together..

That would do it but means you wired it incorrectly.

When you buy a receptacle it can either be used as a standard 120 VAC receptacles or Multi-Wire Branch receptacle. They are wired differently. Using them as Multi-Wire is rare.

In a standard connection you just run 3-wires, L-N-G and leave the Tab in connecting the two halves together.

Multi-Wire you must use a Ganged Breaker, and Remove the Tab connecting th etwo halves together. You run 4-wires (L1-L2-N-G) L1 supplies power to 1/2, and L2 to the other half. If you do not remove the tab, you get BANG.

So here is the BIG QUESTION. WHY DID YOU RUN L1 and L2 to the Receptacle? All it needed was one of them and leave the TAB in.

[Logan005]

I am guessing to maximize the output capacity, most generators I have seen run specific power to each plug.

[inetdog]

T

So here is the BIG QUESTION. WHY DID YOU RUN L1 and L2 to the Receptacle? All it needed was one of them and leave the TAB in.

it is commonly done on small generators to provide two full current 120V outlets using one receptacle device.

[Sunstar]

Heard Honda Gens are really good and at a pretty decent price for what its worth. awesommeeeee!

[Sunking]

I am guessing to maximize the output capacity, most generators I have seen run specific power to each plug.

Not in a house premises wiring. Multi-wire outlets are very rare and have very strict rules.

[inetdog]

Not in a house premises wiring. Multi-wire outlets are very rare and have very strict rules.

Would you call a duplex receptacle mounted on the genny house wiring? If the OP is talking about a house outlet cord connected to the 240V out of the genny, I agree with you.
My genny has one 30A 120 twist lock, two 20A duplex receptacles on opposite phases, and one 20A 240 twist lock.
All have their own compact CBs.

[Sunking]

Would you call a duplex receptacle mounted on the genny house wiring?.

I would call that factory wiring that is done properly.

Multiwire receptacles are permitted but seldom used. Hammick indicated he found the problem to be the TAB that connects both halves of the duplex receptacle together. That tells me he had to wire it himself and ran 4-wire circuit to it. If the LINK as it is technically called had been removed it would have worked. But with the LINK in I would certainly hope the genny breaker operated. as it had a Bolted Line to Line fault.

NEC is very specific about Multiwire circuits as they requires special attention. It is covered in 210.4 and 240.15 (B)(1). In short requires that a Ganged Dual Circuit breaker used, and can serve only Line to Neutral loads.

Having said all that, I am happy Hammick found the problem and I hope he understands what happened. So Hammic if you want to use a Multiwire circuit you need a special circuit breaker for them and labeled as Multwire. They require 4-wires L1, L2, N, & G. Don't forget to TAKE THE DAMN LINK OUT OR BOOM as you discovered.

[inetdog]

I would call that factory wiring that is done properly.
Multiwire receptacles are permitted but seldom used. Hammick indicated he found the problem to be the TAB that connects both halves of the duplex receptacle together. That tells me he had to wire it himself and ran 4-wire circuit to it. If the LINK as it is technically called had been removed it would have worked. But with the LINK in I would certainly hope the genny breaker operated. as it had a Bolted Line to Line fault.

Keep reading the posts Dereck.
He replaced a broken duplex on the genny he was reconditioning.

PS: It is possible that there was a blown single pole CB that he did not tell us about that allowed one phase to successfully power the two receptacles with the link still in place.
Still some wiring details missing.

[Sunking]

Keep reading the posts Dereck.
He replaced a broken duplex on the genny he was reconditioning.

DOH! OK does not change much, he did not know how to wire a Multiwire. more specifically to break the LINK.

[hammick]

I replaced the cracked 120v outlet with a 120v outlet I bought at Lowes. I kept the wiring exactly as it was. Just didn't know I needed to remove the tab. Above my pay grade to know why the 240v breaker was the only circuit tripping.

I won't be able to remove the tab and start it up until Sunday but I suspect it will work just fine.

Lesson learned and I didn't get lit up.

[Sunking]

I kept the wiring exactly as it was. Just didn't know I needed to remove the tab. .

Unless you have experience working with it, you would likely not know unless someone with experience pointed it out. You are lucky you got recept with a Link.

Let it be a lesson and remember when you are running a circuit with both L1 and L2 something is different about it you need to pay attention too. Generally speaking a circuit with both L1 and L2 are 240 volt circuits.

240 VAC circuits comes in 2-Flavors, 3-wire and 4-wire.

• 3-Wire circuits are L1, L2, and G and strictly for 240 loads only.
• 4-Wire Circuits are L1, L2, N, & G The load is both 240 volt and 120 volt. Good examples are Ovens, Cooktops, and Dryers. For example a electric dryer heating elements are 240 volts, while the motors and controls are 120 volt.

Tip for anyone when you need to run a 240 VAC circuit, run 4-wires. Your device may only need L1, L2, and G initially, but some time in the future you may need a Neutral to derive 120 volts. Nothing prevents you from running the 4th wire, just tape it up so it cannot short anything out. If for some reason in the future if you need the 4th wire is a lot easier to run it now vs later. Only down side is the 4th wire cost more initially, but is an Ace in the hole if needed.