Standby Generator - Diesel or NG?

Tig · Dec 20, 2007

NG for all the reasons listed above. In a major outage you won't find diesel untill the gas station gets a generator fired up. That could be days. We've had two major outages in the past ten years. It's a busy time, especially if you have to feed a generator.

MikePA · Dec 20, 2007

Skyco said:
Where do you get the NG? From a local gas utility? Are you positive they'll be in operation during an outage/disaster? Diesel you can haul yourself, NG you can't.

If there's no electricity, how are you going to pump the diesel?

MrJimi · Dec 20, 2007

Just a thought, diesel can and will go bad, natural gas will not
Jim

techman · Dec 20, 2007

I will disagree with the majority. Diesel is much cheaper to operate than NG. At 40 KW you are talking about 200 ft^3/hour. Is your suppl and regulator big enough ?

As far as diesel, it will last years in a storage tank. Keep it closed to minimize moisture, and a stabilizer to prevent algae growth. Most commercial and industrial backup generators are diesel, and fuel is not an issue. Also if it is some sort of major disaster, NG supply could be an issue.

At that size I would not consider NG. Also whatever you get, make sure it is a 1200 RPM driven generator for life and noise.

paul

rosietheriviter · Dec 20, 2007

techman said:
I will disagree with the majority. Diesel is much cheaper to operate than NG. At 40 KW you are talking about 200 ft^3/hour. Is your suppl and regulator big enough ?

As far as diesel, it will last years in a storage tank. Keep it closed to minimize moisture, and a stabilizer to prevent algae growth. Most commercial and industrial backup generators are diesel, and fuel is not an issue. Also if it is some sort of major disaster, NG supply could be an issue.

At that size I would not consider NG. Also whatever you get, make sure it is a 1200 RPM driven generator for life and noise.
paul

Pros..... NG or LPG are both clean burning, fuel can be stored nearly forever, and contribute to long engine life. Easy starting, low maintenance costs.

Diesel - Long engine life, more HP and KW per cubic inch displacement, much more readily available in low RPM models, in longer term emergencies (disasters or whatever) diesels CAN operate on nearly any oil as fuel (with certain preparation) - that is diesel, heating oil, jet fuel, biodiesel, lube oil, hydraulic oil, vegetable oil, transformer oil, transmission oil, and probably any oil you can think of. Unlimited KW capacity availability.

Cons.... NG or LPG, have certain safety issues (explosive vapors), some concerns with fuel supply (refill) in long term usage, usually of the higher RPM ranges, limited KW capacity availability.

Diesel - stinky, long term fuel storage requirements (to maintain usability of the fuel), heavier machine, usually more expensive to purchase.

I'm sure others will add to this list.

My own preference is diesel (actually diesel welder/generator) I am much more alternative fuel oriented than most. I believe most others will be more interested in the convenience of vaporous fuel though.

By all means, look for the lowest rated operating speed you can buy for the quietest longest lasting unit available!

Rosie

Tig · Dec 20, 2007

I think you would be well advised to do a load calculation to include what you need as opposed to what you have.
With the experience of two major outages keeping me dark for over two weeks, my need list would be;
Water pump.
Furnace fan only.
Limited lighting.
Freezers and fridge.
Computers and network (I work from home)

If I had the choice I would go NG but minimal size to power pump motors, freezers, fans. Turn all the other house breakers off at the panel. Computers and a few lights I would power from a very small battery bank and inverter. I would only start the generator as required. I just don't like the noise and the fuss of having to run a generator 24hrs a day.

ultrarunner · Dec 20, 2007

All good information above.

I power ALL the essential Electrical Loads for a Hospital, including a 20hp ventilation motors with a 125kw Onan Genset with a Turbo Cummins Diesel.

Due to the strict Bay Area Air Quality Regs, I'm only allowed 1 hour per month for testing and exercise... which works out to 30 minutes every other week.

I choose Diesel for ease of refueling in the event of a prolonged outage.

kennyd · Dec 20, 2007

I have a 400 amp 220 Volt single phase service. By my calculations that 88kVA or 88KW so a 40KW generator would provide less than half maximum possible load, although I doubt I ever get close to that.

I have a 400 amp service also, but my B/U gen-set is only 15kw and it runs about 1/2 the house, You do not need to switch the hole house. You can add a new sub-panel and wire the critical circuits to that panel so when the mains go out the gen-set will power the sub-panel.

I have the Generac 15kw that comes with a 16 circuit panel and transfer switch all built in one. It is very similar (older model) to THIS.

RobJ · Dec 20, 2007

ultrarunner said:
All good information above.

I power ALL the essential Electrical Loads for a Hospital, including a 20hp ventilation motors with a 125kw Onan Genset with a Turbo Cummins Diesel.

Due to the strict Bay Area Air Quality Regs, I'm only allowed 1 hour per month for testing and exercise... which works out to 30 minutes every other week.

I choose Diesel for ease of refueling in the event of a prolonged outage.

Bet that sucker sucks the fuel at full load (if it ever gets near a full load, 125kw a bunch!). I'd use NG espacially if it's piped into the house by a utility company. You'll still have gas even it the power is out.