GENERAC GFCI's

[ptonsparky]

We connected 8KW diesel generators in a trailer for insulators. Set up a small panel with CBs and the whole thing. Units worked great but were a little small when the temp went down and the connected equipment was harder to start. These sets were hardwired to a panel and we bonded the neutral to the frame of the trailer. No rods required.

The customer bought two 15KW gas Generac units to replace the 8s and set them in the back of crew cab pickups. The units have recepts on the gen. OK. Just install a 4wire 50 amp cord to my trailer mounted panel/equipment and be done. The guys checked operation of GFCIs both on the gen and in the trailer. The "test" buttons trip the GFCI but a Fluke T Pro will not. We bonded the gen frames to the bed of the truck. The neutral of the gens float. How are these GFCIs going to function? As I see it they will not operate on the first ground fault but will on a subsequent. Not sure what will happen if/when the first fault is L1 and the second is L2.

 

[tom baker]

We connected 8KW diesel generators in a trailer for insulators. Set up a small panel with CBs and the whole thing. Units worked great but were a little small when the temp went down and the connected equipment was harder to start. These sets were hardwired to a panel and we bonded the neutral to the frame of the trailer. No rods required.
.

I'll answer your question next.
Why do state "no rods required"? If you hardwired then you don't meet the allowance for a portable or vehicle generator to not have ground rods.

 

[tom baker]

Do your 15 KW generators have a system bonding jumper?

 

[ptonsparky]

The 8 KWs were mounted in a trailer that moves from job to job and only served the items in the trailer or cord & plug connected hand tools. We used conduit inside the trailer to load center, lights, recepts and insulation blower.

The 15s have no system bonding jumper although I could certainly make one.

 

[nakulak]

....... These sets were hardwired to a panel and we bonded the neutral to the frame of the trailer. .....

?? .

 

[gndrod]

We connected 8KW diesel generators in a trailer for insulators. Set up a small panel with CBs and the whole thing. Units worked great but were a little small when the temp went down and the connected equipment was harder to start.

Are crankcase heaters available?

 

[ptonsparky]

The 8KW Gens started and ran beautifully, whenever they were used. I never heard any complaints about them. Offbrand name that were made in China, what isn't, but still impressive little units. They were just a bit undersized when winter came around and the insultion blowers had to be started when cold. Voltage sine wave would flat top and the holding circuit on the blower would not stay in. Plus the motors protested loudly.

Yes, neutral bonded to frame of trailer then EG pulled everywhere. The trailer mounted gen is never connected to a building of any sort. The whole concept is to provide the workers with power not connected to the POCO. They can shut off the power to the house while working and not have to worry about getting tangled up in DIY'r wiring that killed one of them a couple years ago.

Now back to the new 15kw gens and the GFCIs not tripping. I understand that GFCIs sense a current imbalance but unless they current flow to charge up the frame of the gen, plus truck & trailer combined, is high enough, then the GFCI won't trip. The current thru a TPro GFCI test button wasn't enough. I will try good old test lights come Monday and record the current.

 

[don_resqcapt19]

...
Now back to the new 15kw gens and the GFCIs not tripping. I understand that GFCIs sense a current imbalance but unless they current flow to charge up the frame of the gen, plus truck & trailer combined, is high enough, then the GFCI won't trip. The current thru a TPro GFCI test button wasn't enough. I will try good old test lights come Monday and record the current.

However if the current flow is not high enough because there the system is not a grounded system (neutral not bonded to frame) there is not the type of shock hazard that a GFCI is designed to provide protection from.

 

[ptonsparky]

However if the current flow is not high enough because there the system is not a grounded system (neutral not bonded to frame) there is not the type of shock hazard that a GFCI is designed to provide protection from.

Kind of makes a guy wonder why they are required on portable generators.

 

[suemarkp]

I'm not so sure there is a way to shock a person easily when the neutral floats. If the system neutral floats, why would a GFCI matter since a person standing on the ground isn't in the fault path? It would take two failures of two separate circuits to trip the GFCI, and even then those failures would have to have someone touching the exposed failures simultaneously or they'd need to both touch a common piece of metal.

Perhaps you could get a static shock if voltage is building up in the spinning generator rotor and it can't dissipate out. If you're getting static shocks, consider hanging one of those static discharge strips from the vehicle frame to the earth.

I believe the GFCI receptacle on the generator shorts to the incoming neutral, so no neutral-ground bond is required for its TEST button to work. An external tester is going to short from neutral to ground, but the ground is floating and there is no current path. So no trip of the GFCI. I don't think putting a bigger load between neutral and ground is ever going to trip the GFCI.

 

[don_resqcapt19]

Kind of makes a guy wonder why they are required on portable generators.

Some generators have the neutral bonded and others don't. If the generator supplies a "premises wiring system" (see Article 100 as the definition of a premises wiring system is very broad) then 250.20(B) requires the neutral to be bonded.