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Posted by Scott on December 30, 2008, 7:48 pm
On Tue, 30 Dec 2008 00:49:59 +0000, in alt.energy.homepower, Eeyore

How much does a pint of water weigh?  How many stone?  What's the speed
limit on the M1?  The US isn't the only place using anachronistic units

Posted by z on December 30, 2008, 7:48 pm

In the US all the wildland fire spread analysis is done in Chains and
Rods -- I had to do all that to qualify back in the day.

You'd get a question like:

Known rate of spread equals 10 chains per hour and flame length is 4 feet
.. what is the heat per unit area (in BTU)

I don't recall now, but the instructor gave a pretty solid reason for why
they used rods and chains.  Something about the nature of fire behavior
that made using those measurement methods easy to use in the field.  I
think they divide evenly or something.

Posted by Eeyore on December 30, 2008, 9:20 pm

Scott wrote:

Why would I care ? 568g roughly actually.

Only 2 officially in the UK. The mile and the British pint.

Liberia and Myanmar also use 'traditional' units.


Posted by ransley on December 29, 2008, 2:34 pm
 On Dec 27, 2:14pm, humphil...@yahoo.com wrote:

Sorry I should have proof read , 35f incomming, my main is on an
eroding hill, Its probably broke today as I am not there. It goes to
-15f midwest US. But the type of exhaust hood and distance from
exhaust is important, mine has a slight horizontal rise and its maybe
5-6ft. If valve is open at top and bottom all should be ok, but then
again only recently did I let the basement completely freeze. Im Ng
city supply and used 3/4 pipe. But that is a pitfall installers make
by not using a Manometer with competing apliances on and a calculation
on a high demand period of lower pressure. 20 lb Propane is maybe
325000 Btu I think, at 100% power my bosch pulls 177000 btu hr, figure
most home furnaces are 1-125000 Btu and you see it takes alot of
energy to heat cold water. But I never need mine on high with 35f
incomming, at full power its to hot for a hot water only shower, you
are 40F incomming? Tank size is not from what I think relavent to
heat, its how the regulator is set and pipe size. I bet I could shower
for 3 minutes with a 5lb tank if I figured it out. I know a 20 lb tank
will work, I use a 235,000 btu Roof torch off them, all roofers do,
open a 20lb tank and it might output 3,000,000 btu for 5 minutes, they
empty fast, they fill fast

Posted by humphill40 on December 29, 2008, 10:04 pm
It sounds like you are saying the heater is in your basement which you
only recently stopped heating and thus you now drain unit. Not
sure,What was room temp was when you did not drain an got away with
it?. But I'm starting to think will have to drain all winter
regardless to be sure, even if i moved heater to a warmer room then

 . But I never need mine on high with 35f

Specs on your Bosch show max 2gpm at 90 degree rise. so to get to 115
would be maybe 2.2 gpm.

 Tank size is not from what I think relavent to

The heat required to boil liquid propane comes from surrounding air.
As the fluid level decreases there is less surface area to absorb heat
and the gas freezes, stopping vaporization and dropping pressure to
zero. Heavier the btu draw the faster it cools, obviously. So a full
20 lb tank requires warmer temps then a full 40 pounder, and a 20lb
tank 1/2 full will not do as well as full 20lb. Lot of wiggle room
tho. You can run way undersized for a short period of time before tank
cools down too much. In  my case i'm unsure and wish someone had
experience with this and could give details. One doesn't like to go
for refills when tank only 50 or 75% down. Hope a 50 gallon, 200lb
tank will run empty, at 30F, since only on for 5 minutes. Two 100
pounders joined might do better cause more surface area to absorb heat
even tho gallon amount the same ,but such a union is harder to
transport on dolley etc. If I need two 200lb tanks (or total 100
gallons) I'll be sorry I got a tankless.


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