# Propane Tank Size



## Expediter (Mar 12, 2014)

Well that sounds large, but perhaps the gas company is responding to complaints of existing customers that have the smaller tanks and have starved for fuel in the cold climate of winter? While plenty of liquid is still in the tank?


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## backstay (Feb 3, 2011)

Expediter said:


> Well that sounds large, but perhaps the gas company is responding to complaints of existing customers that have the smaller tanks and have starved for fuel in the cold climate of winter? While plenty of liquid is still in the tank?


Maybe, I haven't seen that myself. Most tanks I see are either 250 or 500 gal, and I haven't had call yet. I'm wondering if the gas man wants to just set a bigger tank.


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## Expediter (Mar 12, 2014)

My dad had a trailer in New Hampshire (while his house was being built) and the heater would draw enough out of the tank and it froze up the regulator. I can easily imagine that happening on full load with a tank that is too small.


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## hardworkingstiff (Jan 22, 2007)

Have you had 20KW generators hooked up and working with smaller tanks w/out incident?


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## hardworkingstiff (Jan 22, 2007)

> I had a Seimens 20 kw generator installed at my home. My propane company is saying I need a 1,000 gallon propane tank to run it correctly (something to do with the cold weather and vaporization). Does this make sense at all???????


http://www.dslreports.com/forum/r24893575-20-kw-generator


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## Jlarson (Jun 28, 2009)

I can see a 20 needing a 1,000 gal tank in cold climates.


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## backstay (Feb 3, 2011)

hardworkingstiff said:


> Have you had 20KW generators hooked up and working with smaller tanks w/out incident?


I can think of four. My own system has a 1000 gal tank, so I can't compare it.


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## wildleg (Apr 12, 2009)

I'd just go with the 1000. It's a better solution than the 500. why screw around with it.


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## backstay (Feb 3, 2011)

Talked with a second gas company, 20kW in northern MN needs a 1000 gal tank. Now I have a customer with a 38kW generator. What do you think that baby will need.


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## wildleg (Apr 12, 2009)

backstay said:


> Talked with a second gas company, 20kW in northern MN needs a 1000 gal tank. Now I have a customer with a 38kW generator. What do you think that baby will need.


diesel ?


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## backstay (Feb 3, 2011)

wildleg said:


> diesel ?


I don't know, I'm just wiring it. But I saw the box it came in and it is big.


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## hardworkingstiff (Jan 22, 2007)

backstay said:


> Talked with a second gas company, 20kW in northern MN needs a 1000 gal tank.


 It sounded like you were dubious about the need for the 1k tank, have you changed your mind?


> Now I have a customer with a 38kW generator. What do you think that baby will need.



1.5k? IDFK. :laughing:


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## backstay (Feb 3, 2011)

hardworkingstiff said:


> It sounded like you were dubious about the need for the 1k tank, have you changed your mind? 1.5k? IDFK. :laughing:


His propane company told him he needed a bigger tank. He wanted me to find out if that was true. I did some research and gave him what I found. I don't trust his propane supplier. But it turns out a 1000 gal is a smart play. I would say you could get by with a 500, but at -40 you may not. I own a 1000 gal tank because I get to chose based on price when to fill it.


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## Nigmas (Aug 29, 2014)

There are several factors in tank size, how many other propane appliances run and what they are, and also how long you typically are without power, a 20kw generator runs about 2 gal/hr on 50% load, if they dont have a buried tank they might just consider a 100 gal tank just for the generator if they dont want to bump up to the 1000. But again piping size is usually a bigger screw up for most depending on what other things will be drawing gas and how much, you dont want to starve your generator and have it fail because of gas volume issues.


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## don_resqcapt19 (Jul 18, 2010)

Nigmas said:


> There are several factors in tank size, how many other propane appliances run and what they are, and also how long you typically are without power, a 20kw generator runs about 2 gal/hr on 50% load, if they dont have a buried tank they might just consider a 100 gal tank just for the generator if they dont want to bump up to the 1000. But again piping size is usually a bigger screw up for most depending on what other things will be drawing gas and how much, you dont want to starve your generator and have it fail because of gas volume issues.


I think that gas volume issues at lower temperatures is the reason for the larger capacity tank. The smaller tanks cannot produce enough vapor at low ambients to support the generator.


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## RFguy (Sep 11, 2013)

I looked at some reference material and it indicated a 500 gal. tank would not be adequate under certain circumstances (Florida OK, Northern states/Canada, not good).

A 20 KW generator will need around 250,000 to 275,000 BTU at full load.

A 500 gallon horizontal tank will only provide about 200,000 BTU under certain conditions (even less at lower temperatures).

The calculation is based on 0 degree F temperature, and the tank 10% full.

Hers's the calculation:
Tank diameter (inches) x length (inches) x K

K at 60% full = 100 
K at 50% full = 90
K at 40% full = 80 
K at 30% full = 70
K at 20% full = 60
K at 10% full = 45

500 gallon tank = 37" x 119" x 45 = 198,000 total BTU available
1000 gallon tank = 41" x 192" x 45= 354,000 total BTU available

Adjustment for other temperatures:
Apply the following correction factor to the above calculation:
-15ºF 0.25 
-10ºF 0.50 
-5ºF 0.75 
0ºF 1.00 
+5ºF 1.25
+10ºF 1.50
+15ºF 1.75
+20ºF 2.00

If you had to design for -10 F temperature, you will lose 50% of the BTU's calculated above.

If you only had to design for a minimum temperature of 20ºF, then you would have double the BTU than the above calculation.

There are other losses to take into account. Pipe sizes and lengths, regulator types etc, so you need some margins.

Things really drop off when the tank gets below 30% full, but as with many systems, you don't design for best case.

Sources:
Tank sizes: http://www.missiongas.com/lpgastankdimensions.htm
Calculations and propane info: www.regoproducts.com/pdfs/L-545_Servicemans_Manual.pdf


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## backstay (Feb 3, 2011)

RFguy said:


> I looked at some reference material and it indicated a 500 gal. tank would not be adequate under certain circumstances (Florida OK, Northern states/Canada, not good). A 20 KW generator will need around 250,000 to 275,000 BTU at full load. A 500 gallon horizontal tank will only provide about 200,000 BTU under certain conditions (even less at lower temperatures). The calculation is based on 0 degree F temperature, and the tank 10% full. Hers's the calculation: Tank diameter (inches) x length (inches) x K K at 60% full = 100 K at 50% full = 90 K at 40% full = 80 K at 30% full = 70 K at 20% full = 60 K at 10% full = 45 500 gallon tank = 37" x 119" x 45 = 198,000 total BTU available 1000 gallon tank = 41" x 192" x 45= 354,000 total BTU available Adjustment for other temperatures: Apply the following correction factor to the above calculation: -15ºF 0.25 -10ºF 0.50 -5ºF 0.75 0ºF 1.00 +5ºF 1.25 +10ºF 1.50 +15ºF 1.75 +20ºF 2.00 If you had to design for -10 F temperature, you will lose 50% of the BTU's calculated above. If you only had to design for a minimum temperature of 20ºF, then you would have double the BTU than the above calculation. There are other losses to take into account. Pipe sizes and lengths, regulator types etc, so you need some margins. Things really drop off when the tank gets below 30% full, but as with many systems, you don't design for best case. Sources: Tank sizes: http://www.missiongas.com/lpgastankdimensions.htm Calculations and propane info: www.regoproducts.com/pdfs/L-545_Servicemans_Manual.pdf


Nice work, thank you!


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## hardworkingstiff (Jan 22, 2007)

I answered my own question.


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