Propane 101 for newbies?

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jcarbon
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Propane 101 for newbies? - Fri, 08/23/13 11:43 AM
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Would like to hear some from the experts. 
 
Lets see if my math is correct.
 
Lets say I have a 100 LB tank that should contain about 25 gallons of propane(divide LB /4) . If 1 gallon = 91,500 BTU then I have 2,287,500 BTU (25 x 91,500). 
 
**Is it correct that one must take out 20% from total BTU since tanks can only be filled to 80% capacity??
 
If so then I have 1,830,000 BTU in a 100 LB tank.
 
If I have 30,000 BTU burner then in theory I have 61 hours of use at full burn, correct? 
 
If I used them at 50% then I double the use time, correct?
 
Is a 30,000 BTU burner the same as any 30,000 BTU burner or is there diferences?
 
Finally, most suggest 3/8 cooper line to burners. Is this best??
 
Thanks in advance.
 
John
 

top^dog
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Re:Propane 101 for newbies? - Fri, 08/23/13 12:46 PM
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hmmm sorry i cant help...but i just refill my tanks when they get low.... 3/8 might be good you need to double check your appliance spec's for inlet pipe sizing

edwmax
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Re:Propane 101 for newbies? - Fri, 08/23/13 2:48 PM
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jcarbon


Would like to hear some from the experts. 

Lets see if my math is correct.

Lets say I have a 100 LB tank that should contain about 25 gallons of propane(divide LB /4) . If 1 gallon = 91,500 BTU then I have 2,287,500 BTU (25 x 91,500). 

**Is it correct that one must take out 20% from total BTU since tanks can only be filled to 80% capacity??   

 
If the tank is rated correctly, then it should hold 100lbs of liquid LP @ 80% of tank volume.  This is full.   Check the tank label to clarify the capacity.  The tank should hold the rated capacity and have the correct head space.
 
20lb tank: approx 18 lb empty ... 38 lbs full
100lb tank: approx. 68 lb empty ... 170 lbs full
The empty weight should be stamped on the side of the tank.
 
  ... Now some tank fillers claim the amount they can put into the tank is 100lb less 20%=80 lbs.   This usually happens when the filler charge a set fee per tank.   ... ie: the filler is cheating the consumer by charging for the gas he didn't put into the tank.   ... where the filler charges by the weight he puts into the tank, this usually doesn't happen and if the tank still has some gas remaining the consumer doesn't pay for it again.

jcarbon
...
If so then I have 1,830,000 BTU in a 100 LB tank.  ...
   You should have 100 lb / 4.22 = 23.7 gal   ... 23.7 X 91,500 = 2168550 btu

jcarbon
...
If I have 30,000 BTU burner then in theory I have 61 hours of use at full burn, correct?  
    It is not quit this simple.   A lot depends on the outside temperature and if the tank was properly sized for the equipment being served.   ... But assuming the outside temp is 60 deg F or higher, then you might get close to 70 to 72 hrs of burn time.    ... A tank is not going to completely empty before pressure drops and the flame has problems.   ... In cold or freezing temps, the tank might still contain 25% or more of its liquid gas.

jcarbon

...If I used them at 50% then I double the use time, correct?  
correct, as long as all conditions are the same.

jcarbon
...
Is a 30,000 BTU burner the same as any 30,000 BTU burner or is there diferences?  
  As long as they are working at the proper gas pressure and flame/air mixture are correct, then they would be near the same.

jcarbon

Finally, most suggest 3/8 cooper line to burners. Is this best?? 
   This is hard to answer.   A lot depends on the length of pipe.  80ft of 3/8 copper can pass about 25,000 btu per hr.    10ft about 75,000 btu per hr.
 
So if you are talking about short connections from a supply manifold, then yes.   But 200 ft across the yard to supply several heaters and a range, no.  You need a gas pipe sizing chart.     http://www.engineeringtoolbox.com/propane-gas-pipe-sizing-d_827.html
 
In most cases for short runs, the 3/8 copper would be ok.   Most truck or trailer concessions are plumb with 3/4" dia manifold supply line and 3/8" copper pipe connection lines.
<message edited by edwmax on Fri, 08/23/13 3:35 PM>

top^dog
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Re:Propane 101 for newbies? - Fri, 08/23/13 3:43 PM
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now thats a detailed answer...good job!!

CajunKing
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Re:Propane 101 for newbies? - Fri, 08/23/13 5:00 PM
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edwmax - I want your brain! 
I can never remember all that information and always have to look it up over and over again.

top^dog
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Re:Propane 101 for newbies? - Fri, 08/23/13 6:03 PM
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CajunKing


edwmax - I want your brain! 
I can never remember all that information and always have to look it up over and over again.

  same here thats why i said i just fill it when it gets low

jcarbon
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Re:Propane 101 for newbies? - Fri, 08/23/13 8:12 PM
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This is looking more and more like a buy it rather than build it. LOL
 
Thanks,
 
John

edwmax
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Re:Propane 101 for newbies? - Fri, 08/23/13 11:50 PM
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CajunKing


edwmax - I want your brain! 
I can never remember all that information and always have to look it up over and over again.

hahaha  ... much of this is available at 'propane 101' and 'generator joe'.   Over the years here, I have bookmarked and printed pdf copies to a 'roadfood' directory  for LPGas on my  computer.     ... the same questions keep being asked on the forum and the answers can be easily found with a web search.    ... hum ... may be I shouldn't give away my secrets and links ...???...