Generator and propane tank sizing feedback needed

[rbstern]

i recently picked up a generator 7500-Watt Dual Fuel Generator from costco that runs on both propane and gas.

I'd love an inexpensive solution like that. Lord knows I'm spending enough on a lot of other home-building issues. Unfortunately, I don't think it's the right long term solution.

 

[check]

RB... Another aspect of propane tanks sometimes forgotten is that they need access to energy to evaporate the propane for you to use. In large installations, a boiler for a school for example, there will actually be a burner where the liquid propane is vaporized before entering the boiler. In residential and farm installations, snow can be a problem. If the tank is buried in snow, the ambient air, which can be very cold itself but still contains enough energy to boil the propane, cannot get to the tank shell as the snow is like an insulator. Also, if the propane level is low in the tank, there may not be enough surface area of the tank where the liquid propane level is to vaporize it fast enough to meet the generator demand. The area of the tank above the liquid is of little help in the vaporization. On a very cold day with a low propane level in the tank, say 20%, you may be out of luck running your generator. This is why in cold climates additional tanks are installed just to have the surface area of the liquid propane be sufficient to meet the demands of the generator. Dave M7040

Very interesting. I think I want a bigger tank. A green one. (I have a white one now.)

 

[coldsteelva]

Cold shouldn't be much issue if the tank is buried below frost line; the earth is 50-60 degrees. The amount in the tank is definitely a concern re: vapor pressure. I'm in northern VA and have a buried 500 gallon LP tank and never have an issue running furnace, fireplace, hot water and range simultaneously. A whole house generator, with only a 300 gallon usable capacity wouldn't last a week at full load. If you were present to load manage, it could likely last a month.

 

[TheMan419]

Regarding the sizing of the generator....

I have a 6800 watt (8k peak) that runs on gasoline. When I bought dual/tri fuel sets were expensive. They have come down quite a bit lately. Since you appear not to have natural gas where you are a tri would be a waste of $ of course.

Only you can decide if having a permanently installed whole house type is worth the expense.

To me you would ideally know how (un)reliable your grid power is. Knock on wood the house we are in for the last 2 years has never lost power for more than an hour, and only once or twice there.

We have horses so we need water no matter what. When we upgraded the house to 200 amp I had them put in the 30 amp sub panel, lock out switches etc. So I can just plug the generator into the house. I have to do some load management, but no biggie.

For me, with limited fuel on hand I would not want it to kick on automatically when the power went out. If you are out of town it could suck down all the propane and you not even know it. I like the prior idea of having it set to kick on only if the temp is below 40 or run for so much time per day to keep the contents of the fridge/freezer cold.

Another thing to think of is if you get water in the basement. Do you need some kind of way to make sure the sump pump cycles periodically to take care of that. There are water sensors that will trigger an alarm if they get wet. So I would imagine there are sensors that could be used to fire up the generator and power the sump pump if needed.

Good luck!

 

[Deere Dude]

Cold shouldn't be much issue if the tank is buried below frost line; the earth is 50-60 degrees. The amount in the tank is definitely a concern re: vapor pressure. I'm in northern VA and have a buried 500 gallon LP tank and never have an issue running furnace, fireplace, hot water and range simultaneously. A whole house generator, with only a 300 gallon usable capacity wouldn't last a week at full load. If you were present to load manage, it could likely last a month.

I agree plus as in your example, the furnace, fireplace, range, water heater etc. will not all run simultaneously or even for long periods of time. I wouldn't go nutso with the size of tank. I would not get more than a 500 but a 250 would be more than enough unless your gas electricity goes of for months.

 

[rbstern]

Regarding the sizing of the generator....

I have a 6800 watt (8k peak) that runs on gasoline. When I bought dual/tri fuel sets were expensive. They have come down quite a bit lately. Since you appear not to have natural gas where you are a tri would be a waste of $ of course.

Only you can decide if having a permanently installed whole house type is worth the expense.

To me you would ideally know how (un)reliable your grid power is. Knock on wood the house we are in for the last 2 years has never lost power for more than an hour, and only once or twice there.

We have horses so we need water no matter what. When we upgraded the house to 200 amp I had them put in the 30 amp sub panel, lock out switches etc. So I can just plug the generator into the house. I have to do some load management, but no biggie.

For me, with limited fuel on hand I would not want it to kick on automatically when the power went out. If you are out of town it could suck down all the propane and you not even know it. I like the prior idea of having it set to kick on only if the temp is below 40 or run for so much time per day to keep the contents of the fridge/freezer cold.

Another thing to think of is if you get water in the basement. Do you need some kind of way to make sure the sump pump cycles periodically to take care of that. There are water sensors that will trigger an alarm if they get wet. So I would imagine there are sensors that could be used to fire up the generator and power the sump pump if needed.

Good luck!

Generally, the power is fairly reliable, but Irma just knocked out power for two days.

The house plan calls for a daylight (walkout) basement, and I'm having a drain plumbed in the basement floor, so there won't be a sump pump. However, the grading demands a pump tank for the septic system, so that has to be powered in an extended outage, too.

 

[check]

We have a propane powered Kohler 17kw automatic standby generator, which we got for up at our cottage because we had a hot tub. And Hot Tubs use a heck of a lot of power when they run! We have a 10 foot torpedo propane tank, which holds over 1000 L. But, I think we had better upgrade to a 16 footer, given what I am reading here. And the company that wants our business for the new tank provides remote monitoring, which is great!

Only problem is, it uses a lot of propane, so if we are out of power for several days it costs me hundreds of dollars!

 

[rbstern]

We have a propane powered Kohler 17kw automatic standby generator, which we got for up at our cottage because we had a hot tub. And Hot Tubs use a heck of a lot of power when they run! We have a 10 foot torpedo propane tank, which holds over 1000 L. But, I think we had better upgrade to a 16 footer, given what I am reading here. And the company that wants our business for the new tank provides remote monitoring, which is great!

Only problem is, it uses a lot of propane, so if we are out of power for several days it costs me hundreds of dollars!

Is it a year round cottage? Assuming you are protecting the tub and plumbing from freezing with the generator?

 

[TheMan419]

We have a propane powered Kohler 17kw automatic standby generator, which we got for up at our cottage because we had a hot tub. And Hot Tubs use a heck of a lot of power when they run! We have a 10 foot torpedo propane tank, which holds over 1000 L. But, I think we had better upgrade to a 16 footer, given what I am reading here. And the company that wants our business for the new tank provides remote monitoring, which is great!

Only problem is, it uses a lot of propane, so if we are out of power for several days it costs me hundreds of dollars!

I was looking at a whole house set up like that only running of natural gas which is cheaper. They told me it would cost $50 a day to run. So several days would be hundreds of dollars there too.

I figure even my gasoline powered generator is going to take min of 12 gallons of gas per day. So at current prices like $30.

I look at it as still cheaper than a hotel. Plus with animals we couldn't just decamp to a hotel.

 

[zmountaineer]

Size the propane tank to the generator. My 22kw generac requires a MINIMUM of 500 gallon tank. The only things I have running off of propane is the generator and the furnace when it dips below 35 degrees outside. I have a 500, I wish I went with the 1000. Last year I think I used 200 but no generator runs in that.

I had an "evaluation" and was told for a whole house unit I would need 40kw. I told the guy i was not going to be roasting 2 turkeys and cooking the rest of thanksgiving dinner when the power is out while running the ac to cool the house to 59. He told me he would have to have me sign that the unit is undersized and warranty will be voided. I told him to get lost.