Pressurized Storage Tank and Harman SF 360 Boiler

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dosat1
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Post by dosat1 » Sat. Nov. 27, 2010 9:41 am

Anyone have experience with the use of pressurized storage tanks while burning anthracite. I have a Harman SF 360 trident boiler with oil boiler back up. I burn wood and coal in the boiler for fall/spring and winter heat supply as well as solar in the summer for domestic supply. I have a 500 gals. propane tank ready for plumbing as the storage system. I have and plan on using a laddomat 21 for the mixing valve. My goal is to minimize or eliminate any oil use as well as increase the efficiency of the Harman especially during the "shoulder seasons" of spring and fall in Maine. I have reviewed plumbing diagrams from this web site as well as John Siegenthaler's (sp?) (mechanical engineer) work. I will insulate the tank after installation. Looking for any advice or experience. Thanks.

 
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steamup
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Post by steamup » Mon. Nov. 29, 2010 1:04 pm

I am in the process of commissioning a 500 gallon tank on a system with both wood and coal boilers. I hope to use it for the wood boiler or for light loads during the shoulder seasons. I have my coal boilers remote with a lot of piping that will have heat loss. It takes about 12 to 15 lbs a day of coal to keep my K-6 fire going with no load. For hand fired systems, it makes some sense to have a thermal mass as hand fired boilers do not perform well a part loads. the thermal mass also helps you swing though the night with hand fired systems.

Note that 500 gallons may not be alot of thermal storage. Depending on what your load is, the best you can hope for is charging the tank to about 200 to 210 deg. F and have usable heat down to about 140 deg. f. If you have radiant floor heat or preheat domestic water, you can probably drop the storage temperature lower to about 110 to 120 deg. f. before you don't have enough themperature difference for good heat transfer.

500 gallons x 8.33 lb/gal x 1 btu/lb. x (210-120) = 374,850 btu's.

Caution - make sure you upsize your expansion tanks. I needed (3) B&G HFT-60V expansion tanks piped in parallel to accomodate the water expansion. Three smaller tanks were cheaper than one large tank.

With the cost of the tank, piping, insulation and controls, the paypack is fairly long but may be worth it if you don't plan to move for many years.

 
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BigBarney
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Post by BigBarney » Mon. Nov. 29, 2010 6:44 pm

Was the tank used to store propane? If so you will have a hard time getting

the mercaptan smell out so you will probably need a water to water heat

exchanger to use the stored heat.

BigBarney


 
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gizmo
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Post by gizmo » Mon. Nov. 29, 2010 10:16 pm

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I used a 80 gallon insulated electric water heater to make my storage tank.It has
3" foam insulation and was WAY cheaper than any other tank I looked at,plus it has
plenty of ports.My boiler runs between 150-170 degrees,but the aquastat in the tank
only lets the tank get to 140.I call it a storage tank on the outlet side and a buffer
tank on the return.I didn't want a huge tank because I don't want the boiler running a
long time everytime the tank calls for heat,that way it doesn't get all hot and bothered.I
run 100 degree water in my floors, so in my system I have plenty of time for the boiler
to wake back up and get going without the outlet water temp changing much.I have
plenty of time to make heat and don't have overshoots on my boiler because it never
seems to work real hard to keep the tank aquastat satisfied.The domestic coil can make
plenty of hot water because the controls on the boiler keep it warm without circulating into
the tank if there is no heat load.This works GREAT for my system and don't know what I would
do to make it better for me,I would cut the pipes in a second if I thought it would make it better.

 
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steamup
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Posts: 1209
Joined: Fri. Oct. 03, 2008 12:13 pm
Location: Napoli, NY
Stoker Coal Boiler: Axeman-Anderson AA-130, Keystoker K-6
Hand Fed Coal Boiler: HS Tarm 502 Wood/Coal/Oil
Coal Size/Type: pea, buck, rice

Post by steamup » Tue. Nov. 30, 2010 6:02 pm

BigBarney wrote:Was the tank used to store propane? If so you will have a hard time getting

the mercaptan smell out so you will probably need a water to water heat

exchanger to use the stored heat.

BigBarney
Mine was a used propane tank. Not only a hard time with the smell (flushed it several times, including two complete fillings with soap and water) but much care was taken to pruge the tank outdoors of any leftover propane gas fumes before moving indoors.

I won't use a water to water hx because the sealed system won't give off smell until you have to drain it for service.

 
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gizmo
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Stoker Coal Boiler: AA-130
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Post by gizmo » Wed. Dec. 01, 2010 12:09 am

I have a question.Why do you need such a large tank?Boilers don't make excess
heat all the time do they?When you take hot water out of the tank you probably
replace it with cooler water.Won''t that lower the temp. of the remaining water.If
the tank is horizontal you don't get as much stratisfication shuving the hot water upwards
do you?Now you have a big load of tempid water to reheat which will take a long time.I
am sure a lot of this doesn't matter but someone out there can tell us the relavence.

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