help with water heat using a wood stove

[Mike]

Hey Dennis

that sounds very interesting. Is your garage attached to the house and if
not how far from it. What size of hoses, do you have any problems with
water expansion, etc.

On more of a reply to the group I have some more info to provide as
requested:
I finally got the pump to circulate using a drum of water in he basement.
Here are some measurements I took:
54 seconds to fill 4 litre jug with about 250 feet of 1/2 garden hose
(hose to garage is 3/4 inch)

temp of water in 50 litre drum started out at 58 degrees F

after about 1 hour it rose to a temp of 90 after about 2 hors it is 102 F

about 50 feet of the hose was submerged in tub with the rest of it just
laying on the concrete floor.

Return temp of water just before entering the stove is 99 degrees F

temp in basement is about 58 F

Hopefully I will get some feedback from the people who have responded before
as any help is appreciated.

Thanks

Mike

 

[Steve Young]

Hey Dennis
that sounds very interesting. Is your garage attached to the house and if
not how far from it. What size of hoses, do you have any problems with
water expansion, etc.

On more of a reply to the group I have some more info to provide as
requested:
I finally got the pump to circulate using a drum of water in he basement.
Here are some measurements I took:
54 seconds to fill 4 litre jug with about 250 feet of 1/2 garden hose
(hose to garage is 3/4 inch)

temp of water in 50 litre drum started out at 58 degrees F

A Texan would call that a bucket (50 litre

after about 1 hour it rose to a temp of 90 after about 2 hors it is 102 F

about 50 feet of the hose was submerged in tub with the rest of it just
laying on the concrete floor.

Return temp of water just before entering the stove is 99 degrees F

temp in basement is about 58 F

Hopefully I will get some feedback from the people who have responded before
as any help is appreciated.

From what you're saying, you're not making much heat. It's not easy to get the
heat out of a wood fire. How many feet of copper tubing do you have rolled up
inside the stove? I have 20 square feet of surface enveloping an air injected
coal bed to get good production, and still, I rarely bump against a 4 gal per
minute flow,.to cause boiling.

Now you know what it takes to get the pump to circulate. Even with the approx.
1 gallon per minute flow, you're not close to a boiling problem now. Almost as
much heat is being radiated at 102F as is being produced. You'll make heat,
you'll just have to work at it step at a time. You need to work on improving the
collection exchanger by changing its position in the stove, and/or increasing
its surface area.

Steve Young

 

[Harry Chickpea]

On more of a reply to the group I have some more info to provide as
requested:
I finally got the pump to circulate using a drum of water in he basement.
Here are some measurements I took:
54 seconds to fill 4 litre jug with about 250 feet of 1/2 garden hose
(hose to garage is 3/4 inch)

temp of water in 50 litre drum started out at 58 degrees F

after about 1 hour it rose to a temp of 90 after about 2 hors it is 102 F

about 50 feet of the hose was submerged in tub with the rest of it just
laying on the concrete floor.

Return temp of water just before entering the stove is 99 degrees F

temp in basement is about 58 F

Hopefully I will get some feedback from the people who have responded before
as any help is appreciated.

Thanks

Mike

1 litre = 1.76 pint
50 litres = 88 pints
90 - 58 degrees = 32 degree rise over 1 hour. The smaller rise the second hour
is to be expected.

Definition of one btu =a unit of heat equal to the amount of heat required to
raise one pound of water (a pint is a pound of water) one degree Fahrenheit at
one atmosphere pressure.

So, if the water starts at 58 degrees and you get it to 90 degrees, each pound
of water gets 32 btus. You have 88 pints, so 88 x 32 means you have
transferred 2816 btus into the barrel over the first hour. Round it up a little
for losses, and maybe 3100 btus were transferred. In comparison, a small
electric space heater is generally rated at about 5,000 btu.

There are aprox 6200 btu in a pound of good dry wood. You didn't mention how
much wood you used, but I would bet it was a lot more than 8 oz per hour. Your
heat exchanger would seem to be very inefficient, which is what I suspected
your first problem would be.

I estimate that you need to get about 4 times the amount of heat per hour in
order for this to be useful at all.

 

[Jim Kovar]

Hopefully I will get some feedback from the people who have responded before
as any help is appreciated.

Thanks

Mike

Hi, Mike
I told you I would describe my system, maybe you could get some ideas.
The boiler is an Energy King wood boiler installed in a un-attached
garage. It is 70 feet from the house. I already had propane fired hot
water heat in the house. I ran 2 1" type L copper lines to the house,
buried 18" deep. I boxed the lines in underground with Dow blueboard,
filling the box with zonalite insulation.I installed another Taco 007
circulation pump and another pressure tank in the garage, as I wanted to
be able to separate the two systems. The systems work well with each
other, I have the aquastat on the wood boiler set to fire at 140 deg and
off at 180. I set the limits on the propane fired boiler to fire at 120
deg in case the fire went out in the wood boiler. To heat the garage I
piped in a Dayton 40K Btu air handler and fan, with a line voltage
thermostat controlling it. The pressure relief valve on the boiler is
set at 30 lbs. The system normally runs at 15 lbs. When I piped this
system into the house, I put in a bypass so I could separate the
systems. I am using "No-Burst" inhibited propylene glycol for
antifreeze.

The payback time on this system I judge to be about 4 years.
There are things to consider though, there is a LOT of firewood up here,
and I installed everything myself. If I would have to buy the wood, and
pay someone to install this, I may have had second thoughts.

Good luck on your project!

Jim Kovar
Vulcan, Mi (In da U.P.)

 

[Dennis Davis]

Hey Dennis

that sounds very interesting. Is your garage attached to the house and if
not how far from it. What size of hoses, do you have any problems with
water expansion, etc.

I'm using 1" copper pipe, its run inside 8" drain pipe buried 3' under. I
used foam pipe insolation to keep the pipes from conducting heat to each
other. The stove has about 40 turns of 3/4" soft copper(20 turns in
parallel with 20 turns). I bought a barrel stove kit and modified it to
work using the 30 gal barrel as the burn chamber,the 55 gal simply holds
the sand in. The pump is a pool pump leftover from one of our old pools.
Its feed from a tank (30 gal drum) that sits under the barrel stove. This
way the pump can push the water through the system and prevent the steam if
produced from interfering with the pump. Yeah I probably should get a new
pump, but for now this one works, and pumps made for hot water heat cost
alot more. 1" is the smallest you should go with the distance you're going.
My "garage" (barn style shed) is about 100ft away from the house, and 1" is
the least I can use to get decent flow from the system. Also I have zoned
or separated the house areas so that there are 4 parallel circuits to
increase the flow instead of one big loop. 2 circuits for the baseboard
heaters and 2 for the tubing (7/8" pex tubing) that I installed under the
floors(i hate cold floors). The baseboard heaters use 3/4" pipe so I had to
valve the floor heat to get good flow to the baseboard heaters.
I'm working on a new stove, welding it up from 1/4" plate and gunna try
using this refractory mortor stuff a neighbor has(silica mortor) to put
between the burn chamber and the sheet metal jacket. He says that it will
tranfer more heat to the tubing. Will find out soon enough,should finish it
in the next week or two if my work hours slow a bit.
Oh yeah,um for flow rate, I used a 30 gal drum at the return in the shed to
measure it, it fills up in about 2min 25 seconds, so I'm probably pumping
too much water. the pump has 1-1/4" tubing conn and is rated at 3/4
horse,way overkill but it was cheap as I already had it(was too small for
my pool)
Dennis