Generator and propane tank sizing feedback needed

[rbstern]

That is true! If you use any portable devices with propane you should make sure they are not too portable! Maybe an eye bolt to he deck or wall and a bike chain to show the grill who's the boss...

Trying to teach mother nature who's boss ... I'll bolt the grill to the house and she'll throw the house across the yard just to keep the matter of who's boss clear.

 

[Dave M7040]

Whoa! I think you mistook my meaning.

RB.... sent you a PM

Dave M7040

 

[RNeumann]

Whoa! I think you mistook my meaning. The little icon I pasted is supposed to mean "confused." As in...I am confused by your answer. You described your thermostat control solution as having little to do with freezing, but you described keeping the house from freezing as one of the reasons for the solution. I figured there might be two meanings to freezing (something to do with the generator vs. the house). I was looking for clarification.

So, yes, I am guilty of ignorance, because I clearly didn't know what you meant with your freezing reference. But arrogant? For seeking clarification? Geez, I hope not.

No offense was intended. I do appreciate your comments in response to my original post.

No "confused" icon on my side. It came across as though you were less than receptive to input. Your last helped to clarify and who knows where the icons go on my end- I'm on the taptalk app on a smart phone. Half the time I can't attach photos either.

To be clear the "typical" remote start generator uses "dry contacts" to start. This is the input a "typical" remote transfer switch uses and it happens to be the same thing a "typical" low voltage thermostat uses.

So if you want your gen to run every Tuesday at 1pm simply program your thermostat to run at that time. Or if you want to maintain your auto start feature put the thermostat and transfer switch in series.

This was my biggest dilemma when sizing my propane tank with an auto start transfer switch- how can I easily control when to start and stop the generator when I'm away.....this prevents the unneeded burning of fuel. And thus, in theory, requires less storage.
I figure my needs would be to maintain some battery backups that keep some of my electronics going, my refer cold and my house at an acceptable temp. With that, I would need about an hour a day of gen run time.
If you live in a more moderate climate you may actually need more time per day to keep the refer or freezer if that's important.
If you are home you will need more time per day- as stated in my first post only you can decide that.

So in summery-
-Find the gen's specs for fuel consumption per hour
-Calculate and decide your needs per day and how many days you want the gen to run
-decide if you want a dedicated tank. If so take the stated tank volume and deduct 20% for its inherent design and another 20% because the gen will get used for weekly runs so it won't always be full.
-if you tap the existing tank the math is similar except I'd deduct 50% for usage and you will obviously want to keep the tank topped off. Murphy's Law would have an outage occur when the tank is low!

I have an ASCO automatic transfer switch with the auto start wiring in series with a thermostat and a Winco stand-by generator with Honda motor.

 

[rbstern]

Thanks for the additional details and sorry about the confusion.

 

[TractorGuy]

Just remember when you bury a propane tank it should be coated. My last below ground tank was coated with something that resembled truck bed liner.

You folks can have your gas appliances. Sure the heat is easier to regulate on a stove but the extra cost is not worth it to me. Been there, done that! I went all electric in 93 and never looked back. Before my electric bill was the same I pay now and heating cost was that much again in the winter.

As far as generators go I've gone diesel. I have a tractor and backhoe to use it and keep it rotated. I keep two 55 gallon drums on hand for everything. ran the generator 15 straight hours after the storm and consumed about 10 gallons.

 

[radioman]

i recently picked up a generator 7500-Watt Dual Fuel Generator from costco that runs on both propane and gas. it comes with a propane hose connection to a bbq tank. i took it out of the box, added oil and hooked it up to propane only and it ran right out of the box. i was quite surprised how much quieter it was compared to my old 10hp coleman gas gen. i dont plan on using gas at all unless im out of propane but its unlikely. Its battery start or recoil for under 800. i dont think it would be too hard for you to modify the hose to use your to be large propane tank. I really dont think you need to run much in the house since everything will be running off propane for heat, cooking and hot water. what do you really need for power? some lights, fridge,freezer and water pump, maybe septic tank pump if needed. what else do you really need? you "could" run the whole house lights no problem if you meticulously made sure every bulb is led.

 

[3Ts]

As has been noted, propane tanks can only be filled to 80% capacity. However, you also need to consider how empty you are willing to run the tank. Around here if the tank is fully emptied, a pressure test at $50 has to be done before the tank can be refilled. The propane companies recommend that they be refilled once the tank gets down to 20%. That would leave only 60% of the tank capacity as truly usable.

 

[rbstern]

As has been noted, propane tanks can only be filled to 80% capacity. However, you also need to consider how empty you are willing to run the tank. Around here if the tank is fully emptied, a pressure test at $50 has to be done before the tank can be refilled. The propane companies recommend that they be refilled once the tank gets down to 20%. That would leave only 60% of the tank capacity as truly usable.

A fair point. I like to think of that last 20% as "wartime/emergency use only."

Besides, the heavier-than-LP odorant they add starts becoming evident as the tank gets close to empty, and it's pretty stinky.

 

[Dave M7040]

A fair point. I like to think of that last 20% as "wartime/emergency use only."

Besides, the heavier-than-LP odorant they add starts becoming evident as the tank gets close to empty, and it's pretty stinky.

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

 

[rbstern]

Well south of the Mason-Dixon line here...

 

[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.