Propane backup generator

[reb]

A nearby forest fire knocked out our power for nearly a day last week. That got the wife concerned, primarily about running the pump to ensure we had water for the goats. We are considering getting a 7kW propane powered backup generator to connect to our garage/workshop to run the pump and freezer. When it is needed, we don't expect to run it full time. Therefore, to simplify the installation, we figure to get a couple of portable propane tanks instead of plumbing it to the household tank. While researching generators, I noticed that some people have had concerns that their natural gas supplier might not guarantee adequate pressure for their natural gas powered generators. Are portable propane tanks likely to restrict the flow too much for a generator?
Thanks ahead of time for any help.

 

[GRUMPA]

REB,
Your generator I would assume will be for emergency purposes only. Living in Az myself and having remote property in the north eastern part of Az we have 2 stand by generators. 1 being gas and one being propane, the propane type are a little touchy when it comes to the volume of propane they require for operation. Just one bottle of propane wont work when the generator is working under a load, I have to hook two of them when under a load of any type.


I know it may be a pain in the neck but consider hooking it up to your big tank (if you have one) it will provide it with what it needs to work properly. Mine is rather old (circa 1966) so these new ones (if you have a new type) my work a bit differently I'm not sure but I wouldn't expect it to be much different than the old ones per-se. Thats what I ended up doing.


If you are using it as back up you'll need to install a special switch on your main so that when its working you want zap the line guys trying to fix the power line. And one more thing, we use 5K generators with everything on (no A/C) we use only 1 third of what they're rated at.

Now we use only one generator at a time not both at once, dont mis-interpet that we use both at once and we have nothing thats 220V just 110V even our well pump.

 

[reb]

Grumpa:

Thanx for the reply. I assume you are using the small (20 gal?) tanks. Is it likely that larger portable tanks would provide a better flow?

As you assumed, the generator would be for emergencies only. The one we are looking at comes with the necessary transfer switch to ensure it is disconnected from the main lines. It is ideal for my setup. The garage/workshop has its own service panel, so the electrical hookup will not be difficult. Routing the household propane tank to the generator would be a major pain. The water, power and phone lines between the house and garage are all in the way.

The load won't require the full 7kW. I used a portable 4kW generator to run the pump while building the garage. It requires a big chunk of that capability to start the pump, but not much to run it. It just happens that the best deal I have found is 7kW. The price includes a weatherproof setup and automatic starting and weekly exercising. A quality (Honda or equiv) portable generator with the transfer switches and some kind of shelter would cost more.

 

[5030]

Ah yes, the backup gen set scenario....

During the summer last year, we lost our power as did most of the east coast and lower Michigan. I think it had something to do with free enterprise or whatever. Anyway, being a farming operation we have stock to water and toilets to flush not to mention freezers to keep cold and the air conditioning and furnace to run.........After 3 days, we were collecting rainwater (it did rain, thank heavens), sweating our selves to a major stink and getting really frustrated. As soon as the power came back on, I jumped on the computer and via the "information highway", bought a Generac 15KW propane fired standby gen set. www.generac.com I didn't get it direct from Generac but from an outfit in Arizona: For some reason, I can't get the URL right. Do a Goggle search for Norwal Power Systems. Nice folks.

It was delivered in about a week. I did the physical install, had my propane supplier hook up the propane (we have 2 500 gallon tanks). The propane installer had to put a regulator on the gen set as well as a shutoff valve. Cost me about $60.00. I had a Generac certified installer do the electrical hookup, hooking the transfer switch to the main panel. You need a certified generac installer to do this as the warranty on the gen set has to be validated by the installer. That cost me $450.00.

I run everything at the farm, furnace, well pump, tank heaters, air conditioning, shop, lights, barn....everything.

The unit cycles once a week at the time you pre-determine. Scheduled maintenance is every 6 months. An oil change (I use Amsoil 5-15 and an oil filter is all that is needed. The unit trickle charges it's starting battery so it's always ready to go.

Transfer time is about a minute after the internal sensors detect a power level less than 190 volts. That allows you to run through a brown out. The unit will continue to run until the power stabilizes at 225 volts for 3 minutes or more. The same scenario applies for a total loss. Transfer back to utility is instantaneous. The transfer switch is a double pole single throw, magnetically actuated unit and completely disables the utility from the standby power.

My 15 KW unit (30 horsepower) uses about 1 gallon of propane per hour at full load. It cost me $2500.00 not including the electrical and propane hookups.

I'd suggest hooking the unit directly to your bulk tank. Portable cylinders won't provide the delivery required of a gen set.

Finally, get the 15KW unit. The 7KW unit is only about $300.00 cheaper. With the 15KW you get a twin cylinder engine versus a single cylinder and almost twice the reserve capacity.

 

[Junkman]

Here is a link to Nowall Power..... web page . I presently have a 8 KW Propane generator running a Tecumseh single lung noisy engine. It spins at 3600 RPM and it is so loud that it revived one of the dogs that died 5 year before!!! /forums/images/graemlins/grin.gif If you get a generator, make sure that it runs at 1800 RPM. Much quieter. I would upgrade ours, but since we installed it, there hasn't been any power outages lasting more than an hour. /forums/images/graemlins/smile.gif

 

[Slamfire]

A gas powered generator will put out more power than the same one powered by propane. By the time you deduct for the difference in "peak" power and continuous power, then deduct for the loss of power to propane, you won't have a 7kW generator, but it'll probably be adequate to run the pump, freezer and a couple of flourescent lights. Have you figured out how you are going to cook? /forums/images/graemlins/confused.gif

 

[reb]

</font><font color="blue" class="small">( Have you figured out how you are going to cook?
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You might note from my previous posts that this is emergency power for the garage. We don't plan to do anything for the house, beyond possibly finding a way to run the furnace in the winter. My wife is happy to cook on our camp stove in emergencies. Sometimes I think she wouldn't mind living in a tent as long as she has my company/forums/images/graemlins/grin.gif.

 

[Ches]

We have an 8Kw generator with a B&S 18 Hp VTwin engine. It was converted to run on propane. I have found that using the 20 lb propane tanks do not work well. The generator does work (and that is what I use for the monthly start-ups). After a while, the 20lb tank begins to freeze and the generator stops. The local propane gas supplier told me you need at least the 100 lb tank to prevent the freezing...something with the amount of flow being provided. Can buy a 100 lb tank (empty) at Lowes or Home Depot for about $90-$100, and about $55 to have it filled.

 

[5030]

That is not quite right....The 7kw unit is rated at 7KW on propane as is the 15KW unit. They derate on NG.

Propane gensets are designed to run on propane for convenience and less danger. Gasoline powered units are usually portable units while propane units are stationary.

Junkman:

The 3600 rpm units are 2 pole generators while the 1800 units are 4 pole. Ours runs at 3600 rpm but is in a soundproof attenuating enclosure. It's real quiet. I wnat a turnkey unit. One I don't have to fool around with. The Generac unit fill that bill really well. The added benefit is that my wife can run it.......It runs itself.

 

[GaryM]

I have the Generac 15KW unit running on Propane. Yes, at 3600 RPM it's not too quiet, but I can hear the TV fine and the air conditioning works fine too.

Didn't want to spend the extra cash for something I hope not to use too much.

I bought mine from the Electric Generator Store.

 

[PineRidge]

I agree with 5030 (Daryl) I think a Generac self contained unit is the way to go. I had originally planned a spring installation of one of their 15KW units to be fired on natural gas but I have had my hands full here with other projects already in the works. I'm still going to get one installed and I'm still also still wanting a Generac.

 

[mahlers]

You might want to consider having a dedicated permanent propane tank installed for the generator. I thought it was overkill, but then a guy explained to me what the usual scenario is if you *really* need long term power - you lose power for a couple of days, and your generator runs your main propane tank dry - which leaves you with nothing. If there's a widespread outage and/or disaster, the propane company probably won't be able to get your tank refilled as quick as you might want. If you have a dedicated 350 gallon tank for the generator, you're good to go for at least a couple of weeks with round-the-clock electricity.

I'd also suggest looking at the Onan units. They're more pricey than the Generac generators, but they really are very nice, run forever, and they're *real* quiet.

 

[reb]

5030:

The Norwall site has the best prices I have seen on the Generac units, with free delivery.
You said it cost you $450 for professional hookup, just to validate the warranty. For those of us capable of doing it ourselves that amounts to about an extra 20% for the warranty. For that price I would forego the warranty--that will buy a lot of parts.

 

[40Kchicks]

Reb

Here is one more thing you could consider since the backup is just for your shop. I bought a used Miller Bobcat welder for $800. It is an onan powered 8.5K generator that runs on gas. I think I got a pretty good deal on it because it’s in good condition and starts easily. A new one will run about $2500 but you can use it to weld out in the back forty. Mine is kind of noisy but I needed a short term emergency generator, a portable welder for the farm, and the price was right so I went for it.

That is another option but if I was in your situation I would backup the whole house with the setup like 5030 bought.

We also have an 85KW onan that we use to power our chicken farm. It starts and transfers power automatically. Auto transfer switches are really nice but are a luxury item for a house. On the other hand they are needed for situations that are life and death like on my farm or hospitals.

Eric

 

[reb]

40Kchicks:

I like that idea about the welder. I have thought a lot about getting one. The downside to using it as a backup on my garage is that the wife might have problems setting it up if I am not around when the power goes out.

The way my place is laid out it would require a separate generator to back up the house. Setting it up for one to operate both would be too expensive--poor planning on my part when we built.

The automatic features of the Guardian units I have looked at are almost gravy. When I considered the cost of a quality portable generator, transfer switch, some kind of weather protection for the generator, and the extra maintenance (keeping fresh gasoline, manually testing it periodically) I figured $2100 for a 7kW Guardian was a good deal.

 

[5030]

Gary:

I have mine in the back of the house. It certainly is not any more noisy than a lawnmower and I can't run my electric appliances with a lawnmower.

I have 0 trouble with the generac. I tend to forget about it, that is, except for the 6 month maintenance.

I bought a Yamaha unit for the camper. It's only 2500 watts but it's one of those new ones that provide true sine wave 60hz power even at an idle. It was $1300.00, half the cost of the Generac. I think it has a 9 pole generator head.

 

[5030]

Reb:

Maybe I stated that wrong. Generac recommends that a "qualified generac Installer do the hookup". Any qualified, certified journeyman electrician can do it. I just wanted to be doubly sure that in case of any trouble with the unit, that I was covered as far as warranty issues. On the warranty card for the unit, there is a spot where the installer has to sign and state his license number.

I did the physical install myself, setting the unit, ground rod, breakout box, installed the transfer switch and conduit. The installer load tested the unit, check it for proper frequency, wired the breakers into the transfer and did the 4 hour load run-in.

There is a lot of stuff in that enclosure. Stuff that I make no pretense of knowing about. I wanted to make sure that when the power went out, and it will in the future, that the unit operates as it should without a hitch. that is why I covered my butt with the installer.

I certainly don't want to have a backup unit that won't backup when it has too and when I need it the most.

 

[AndyR]

I bought one of the little Honda 2KW gensets (EU2000i, ran about $975) last year for our camper. It is super quiet and actually pretty usefull - I use it alot now for power tools instead of dragging out the big extensions.

Glad to hear your Generac is working well. I figure the large propane source is needed just to keep the gas presure up. I seem to recall a thread a while back about storage leakage over time - though with the simple gauge on most tanks it would have to be pretty extreme to notice it.

 

[5030]

Andy:

All the inverter generators, Yamaha and Honda make the box store units look like rocks. The ticket price is higher but the power is true sine wave and pound for pound the inverter units are much lighter and I believe they will last longer too.

 

[v8dave]

Mentioned here is the reason you need bigger propane tanks is because they freeze--true. Propane is a liquid in the tank. It evaporates to make the gas vapors (actually, it boils). Evaporating/boiling liquids uses energy, heat in this case, and will reduce the overall temperature of the remaining liquid--which slows the evaporation rate and eventually the flow rate of the gaseous vapors. The bigger tanks have a larger surface to absorb heat from the surrounding area and keep the evaporation/boiling going. As the tanks get colder the outside gets frosty. If it continues long enough, and the outside air is cold enough, the propane will no longer boil and the gas stops flowing.

You can get a Propane system that has a tank bottom feed and supplies liquid propane to the power plant carburetor. It will evaporate in the carburetor. Gaseous and liquid propane carburetors are different. You need a specific one for either type of propane fueling--one size does not fit all. In addition, if you live in an area where you have extended periods of sub zero temperatures, propane my not work for you as a reliable fuel source either way. Not enough ambient heat to boil the liquid.

In temperate climates propane is an ideal fuel, providing you don't run out, because it doesn't go bad in the tank. It is always there ready to go. Gasoline and Diesel fuel go bad over time and will require draining and replacement if not consumed (time varies, but they are not likely to last a year).