Propane VS Diesel in ~20-30kW generator ranges.

[hornetd]

Ask any OTR driver to answer your question.

I'm not trying to be a Pain In The A.. (PITA) but sometimes I succeed without trying. I think it is worth pointing out that you used an acronym in your first post without first spelling the phrase out to identify the acronym. I would be willing to wager that there are a fair number of people in the electrical craft that know very little about Over The Road trucking.

 

[tortuga]

... if you use a 4 wire plug to connect your portable genset to power the structure (i.e. just the two Hot legs, Neutral & Ground), you must remove the bonding jumper on the genset.

Easy rule of thumb...there can only be ONE bond in an electrical system!

View attachment 2553789

Good point so most consumer market portables are the "Separately Derived System" type I gather ? Every residential generator 'inlet' and manual lockout/transfer switch I have seen does not switch a noodle.
So the diligent electrical contractor installing one of those inlets manual/lockout kits needs to read the manual on their customers portable and unbond that ECG before plugging it in I gather, (as a typical homeowner will probably never do that).

 

[tortuga]

What happened when the 20kw overload?

Nothing really it just shuts down then our phone rings with a customer wanting a larger generator, I look into the prices for 25-30 kW generators, cant believe the price per kW double's above 20kW, And a thread gets started on here LOL.
I'll probably use some load management relays instead of the larger generator.

 

[hornetd]

Wow...looks like that was a mess! And yes, in those cases, larger sets come into high demand pretty quickly.



As far as the bonding jumper question, Mike Holt has a great guide on generators located here: NEC Genset Requirements

If you look at page 4, you'll see that the generator can only be bonded when it is a "Separately Derived System" meaning the neutral would need to be switched by the transfer switch. If your transfer switch does not do this OR if you use a 4 wire plug to connect your portable genset to power the structure (i.e. just the two Hot legs, Neutral & Ground), you must remove the bonding jumper on the genset.

Easy rule of thumb...there can only be ONE bond in an electrical system!

View attachment 2553789

I do understand why a permanent installation has to differentiate between transferred and non-transferred neutrals. but I would think that distinction is only important in cases were the generator only carries the load from a feeder supplied panel or a larger but electrically similar system. In those cases the generator bonding jumper is a bond to ground of the Grounded Current Carrying Conductor on the load side of the Service Disconnecting Means (SDM) which could cause real problems, and even danger.

But when a permanently installed generator supplies the entire building, and the generator connection is prior to or in the enclosure of the Service Disconnecting Means what is the real hazard which the code is trying to address. Under utility power I have a Grounded Current Carrying Conductor connection to Ground at the transformer which is bonded to the transformer case and the Utility's Multi Grounded Neutral and I have a ground connection at the SDM. In the case of the generator carrying the load with the connection at or before the SDM we have an electrically identical situation. There is a ground connection at the generator and one at the SDM. Both arrangements connect the grounded current carrying conductor at the source of supply and at the SDM.

With transportable generators the situation gets even more bizarre because the requirement for having the Grounded Current Carrying Conductor bonded to the frame or not makes no actual difference in current flow as long as the connection to the building's wiring system is prior to or at the SDM.

I repeat my earlier question. What is the hazard the code is trying to prevent.