ECN Forum Forums General Topics of the Trade General Discussion Area generator question

Maybe I am living in the 20th century but aren't these constant speed alternators? Who cares what the engine does at idle, how is it at half load and 3600 RPM (or whatever) and full working load?

Unlike motive power, motor-alternator sets swing up and down the power band without changing RPMs.

(Typically)

As I alluded to above, these units run so rarely that fuel economy is -- in every sense -- not a consideration.

Be that as it may, all Otto cycle engines will use about twice as much fuel per net kW as a Diesel cycle would.

As they 'unload' -- ie drop back to near idle -- their specific fuel consumption is about five times as much as a lean runnning Diesel.

Which means nothing. That relative performance advantage is not going to be seen in any real world application.

I'd entirely ignore fuel economy and focus on first cost... In which case, all smaller installations will end up being Otto cycle/ regular gasoline engines -- usually getting natural gas as the main fuel.

For one facing hurricanes -- gasoline fuel stability is an issue -- as is natural gas continuity.

I'm 3,000 miles too far west to be of any help on that.

I'd peek in on the local grocers. They'll almost always have a back-up gen-set on the roof -- just to hold their freezers steady. I'd follow whatever they deem to be best local practice.

wewire2...If we were to move the pin and sleeve outside for interconnection between the generators then 400.8 (1), (2), and (4) would not apply, IMO

I don't see anything in 400.7 and 400.8 that would specifically prohibit the pin and sleeve outside by the generators, IMO

The rubber cord we would use would be type "W" (PPC) which rates at 96amps...next size up rule allows 100amp OPD

Tesla, diesel as a fuel source is never considered for residential applications in my area.

As for fuel degradation, I was told that today's gasoline would start to go bad in 30-60 days and diesel in 6-12 months.

I agree that continuity of street gas would be an issue in a major disaster.

Propane would be less susceptible to a disaster. For that reason and because there is no street gas for this project, over 5000 gallons of propane will be underground for fuel supply for cooking,heating and the generators.

There will also be an 8KW solar PV system with storage batteries that will allow 24-48hrs of backup power independant of any generator power if need be.

If the pin/sleeve was setup on the exterior then an appropriate length of cord would not raise my eyebrow.

'Cord' (400.7/400.8) useage is one item that raises questions, whenever it appears on a plan/sketch, or is buried within the 'Electrical Notes' of a design professionals plans/specs.

BTW, with 5k gal of propane, & the solar storage, that sounds like someone preparing to be a survivor!

Thanks for your input Hotline!

Survivor or Doomsdayer...

From my experience, and research with comparing generators from the same manufacter and line of gensets have told me that a 10 kw load on a 10kw generator uses less fuel per kilowatt than a 20 kw generator carrying a 10kw load. Totall opposite for a gas motor. Diesel is expensive to setup but can be cheaper than gas to operate. Too many variable to determine that. Scope scope and scope will give you the answers

Shortcircuit...

If this project is to be in the Northeast, then Heating Fuel can substitute for Diesel fuel.

Both are middle distillate #2. The only difference being that the home heating fuel has a dye in it and carries no road taxation.

In every other sense, they are the same.

In which case, any stationary Diesel is going to use 'home heating oil.'

Out here 'home heating oil' does not exist.

The only significant deterioration for middle distillate is water vapor absorbtion. So, middle distillate stores extremely well.

In contrast, gasoline loses its volitile components. No end of lawn mower difficulties are due to this one factor.

If I were in New England, I'd probably favor middle distillate over propane -- no pressure vessel -- and the tank can be buried.

They bury propane tanks here. I have one in the ground as we speak. I got the propane kit for my 5.5KW briggs. It is still in the box.

We bury propane tanks here in NJ also. 'Home heating oil' tanks are not very popular, major concern is leaking, and the nasty liability issue for polution.

Most of the diesel gens I know of have 'belly tanks', surface/above ground that the gen sits on. Gens that are inside tractor trailer boxes have a tank in the trailer, these are mostly rental gens, or former rentals.

Depending on the tank size, and GRHr, a contract diesel dealer is a prudent move.