Back-up Generators

[AHNC]

I'm looking for a back-up generator for my house. I'm thinking, from the Generac website that a 17 kw unit would do. For those that have done this, any comments, experience or suggestions would be much appreciated. I'll be running propane. Last winter, was pretty intense from a power loss standpoint here. Approx 15-18 days.

 

[ultrarunner]

I'm looking for a back-up generator for my house. I'm thinking, from the Generac website that a 17 kw unit would do. For those that have done this, any comments, experience or suggestions would be much appreciated. I'll be running propane. Last winter, was pretty intense from a power loss standpoint here. Approx 15-18 days.

17kw should be plenty for most homes... since you have propane... do you heat and cook with propane?

The best way I know is to figure your loads and go from there.

You might have someone calculate how much it is going to cost per hour to run with the anticipated load...

I've run a whole house during the Loma Prieta Quake on a Honda 5000... power was out for days... gas was OK... so heat and hot water not a problem and the generator was able to handle the oven OR a couple cooktop coils no problem...

The nice think about propane is it shouldn't get stale... the trade-off is not much you can do to refill if the outage goes for days...

My first home, 1200 square feet 3 bedroom, only had a 3.6kw electric service from the Utility... 30amp 120 volt...

 

[schmism]

The nice think about propane is it shouldn't get stale... the trade-off is not much you can do to refill if the outage goes for days...

If the outage goes for days a normal 500 gal tank will have that covered. IF it drags on to weeks is when you may have issues. But supply of propane is likely going to be much more abundant than diesel at that point. You can always acquire 20lb tanks for short emergency rationing periods. (again easier to find than diesel when your 2+ weeks into an outage)

most houses can be run on comfortably 10Kw. If you have livestock needs then certainly more KW is better than less.

 

[ultrarunner]

Generac say a little more the 2.5 gallons of propane per hour at full load... I was looking for a number at half load and couldn't find it...

 

[doxford jim]

My current house has a 12kW diesel generator in a shed about 25 yds from the house. It was installed some years before I bought the place. It has a 250 gallon heating oil tank holding winter diesel - I live in central BC and it gets down to -40 F/C once in a while.

The diesel is sized to match the house service of 100 amps. That is enough to run the heating system (main is a heat pump, back up is propane furnace), the cook stove - in fact all the normal appliances. The diesel burns 1 gallon every two hours at 50% load or there abouts IIRC.

I have had no trouble starting the genset in the cold weather - there is a glow plug system which makes things easier.

As far as propane vs diesel - the propane was more expensive and less efficiant (i.e. uses more fuel than diesel). Propane is easier to fuel with 100 lb gas bottles readily available and filled. With my propane back up furnace uses one 100lb bottle in about five days with temps around 0F or -15C. I don't know how a propane generator would run in those temperature.

Footnote. Years ago I had a F150 with dual fuel - gas and propane. When starting on propane in cold weather, the different metals in the valves and components allowed propane to escape/leak. Once warm the propane leaks stoppped. Needless to say I used to start the truck on gas and once it warmed up, I would change over to propane with no further problems. I don't know if this could be an issue where very cold temperatures are concerned - possibly modern products perform better ?????????

Jim

 

[Swiftriver]

Make sure you get the carb heater. It's an option that Generac doesn't push. All the Kohler gensets I install here in the North come with it and the service guys say you will need it when the temps drop to sub-zero. Don't let you're propane guy undersize you're tank.

 

[tlbuser]

If the outage goes for days a normal 500 gal tank will have that covered. IF it drags on to weeks is when you may have issues. But supply of propane is likely going to be much more abundant than diesel at that point. You can always acquire 20lb tanks for short emergency rationing periods. (again easier to find than diesel when your 2+ weeks into an outage)

most houses can be run on comfortably 10Kw. If you have livestock needs then certainly more KW is better than less.

Not sure, but would probably need 40# or larger cylinders, I would get 100#ers. The liquid needs headspace to vaporize and at 2.5 gallons per hour the 20 lb. would ice over and vapor lock most likely sometime during the first hour of use. And depending on where you get propane, a 20 lb. tank only holds up to 4.5 gallons of liquid.

 

[NC tractor driver]

Not sure, but would probably need 40# or larger cylinders, I would get 100#ers. The liquid needs headspace to vaporize and at 2.5 gallons per hour the 20 lb. would ice over and vapor lock most likely sometime during the first hour of use. And depending on where you get propane, a 20 lb. tank only holds up to 4.5 gallons of liquid.

Here is an excellent article on sizing propane tanks for gensets.

Care and feeding of Propane Fueled Generators « Engineering Radio

The necessary tank size may be much larger than you first think.

 

[Malvern]

AHNC,

I pondered the same thing several years ago and decided on the gas version of Generac's 17,500 watt portable. I have propane on the property to heat the pool (my money pit) but I didn't have near enough to run maybe 2 days at the most on propane. I looked at a gen set for the tractor 10KV unit and didn't like that. I chose gas as the best for my needs since I have 3 cars and I can siphon fuel from them if I needed to. The problem I have now is since I got this thing we haven't had a power outage for greater then 4 or 5 hours at any given time so I'm second guessing my self on selling this unit. I can tell you this thing is a beast, easy to work on and runs well even on stale gas. I do start it monthly to charge the battery but I bet you she doesn't have 10 hours total run time in 3 years. Now that I said this my power going out soon.

Malvern

 

[AHNC]

Thanks for the replies and advise. I currently have a stone fireplace with an old Earth Stove insert in the place. It is incredible how much fuel an insert can consume and generate so little heat. So after 25 yrs with no wood stove I went shopping for a new stove. The old one is coming out and the stone fireplace is coming down regardless. The Vermont Castings Encore I want is in the neighborhood of $2,600. The Jotul 400 option is a bit less. Plus new metal chimney, stove pipes, accessories I've got to be approaching $4k. With that kind of money a generator is absolutely the better choice, although I'd like the stove too.

Sizing on my part is way over I'm sure as I just filled in the blanks on Generacs site and my equipment is more efficient than most. I have replaced the central furnace/AC with high efficiency Mini-split heat pumps. As well, I have two Rinnai Energysaver DV gas wall furnaces. They only draw 33-55 watts. A Rinnai tankless at 50W when running. I'm not sure of the well pump sizing but it is a dug well with water about 50-60 down, so no huge draw there. So my first glance sizing will tumble back to probably...10kw?, when I actually do the fine figuring. Maybe less!

Also, being in the gas business I have always maintained that the way to do propane is to buy a 1000 gal tank and bury it. That way you can carry through the mid season demands without having to re-fill, unless you have a big load. I'm working on a new water line, underground power service (trees fall/snow/ice took mine off the side of the house twice last winter) and a new gas tank/line location in the same trench before winter hits. Btw, low temps here in the foothills are about 20f.