Found a tank, is storage worth the work?

I have a quick question regarding heat storage. Right now I have a central boiler soon to be replaced, the water from the boiler is fed 150 ft to the house through the water to air heat exchanger in the furnace then through the side arm on the water heat for dhw then back to the boiler always circulating 24/7. So the question is when I install a new boiler can I just add say a 500 gallon propane tank in line with the supply line of the boiler? It shouldn't be any different than the storage tank on the unit I buy. I would of course have to insulate it, and put in a building.

Graham said:

I have a quick question regarding heat storage. Right now I have a central boiler soon to be replaced, the water from the boiler is fed 150 ft to the house through the water to air heat exchanger in the furnace then through the side arm on the water heat for dhw then back to the boiler always circulating 24/7. So the question is when I install a new boiler can I just add say a 500 gallon propane tank in line with the supply line of the boiler? It shouldn't be any different than the storage tank on the unit I buy. I would of course have to insulate it, and put in a building.

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why do you circulate thru the water to air exchanger 24/7? seems like that would be a huge heat loss when there is no call for heat. there is a thread on how to plumb storage or just search out on here its been beat around a number of times.

Dune said:

2.beans said:

get the tank, more for the generator. pipe size will depend on where its placed or how far its away from the wood boiler or heat load. if you dont have a lot of heat load you may want to try and get two tanks. i think your generator will heat 500 gallons fairly easy. where do get all your oil?

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Yeah, being that is is a 25KW gensett, and a diesel, I figure it wastes about 55Kw of heat. I know I can't capture all of that, but I could certainly use at least one more tank.

The oil? Clam shacks. Getting very competitive these days though, with the high oil prices.

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i was curious on the oil because its getting to the point of almost having to pay for it around here.

In my opinion, the "Simplest sticky" is the only way to plumb a storage tank. I had a designed storage system that didnt work. Changed it to the simpest and it works great now. I have a 500 tank in a closed system and I definatly think the storage is worth it now that i have it working right. I fire my boiler when I get home from work and load it before I go to bed. Its out in the morning but storage keeps my 4000 sqft home in northwest PA warm till I get home from work again. Temps must be above 20deg outside for this to work right though. Less than that, I might have to have my wife fire the boiler around noon or house temps may start falling a few deg. One thing to keep in mind, storage temps can fall from 180 to 120 over a period of time but 120 water is still heating the house. The circs just run more at lower storage temps.

The reason I let the water circulate all the time is beacause I dont have antifreeze and fiqured it would be the eisiest way to almaost garintee that the lines wont freeze as long as the water is flowing. There are probabley better ways but its simple and works well. When I redid the lines in the basement switched from pvc (previouse owner) to 1" pex I made a header and valved it so that if one circulator failed I could just plug in the second circulator open the valves and I had heat back in the house. The pumps are the only mechanical point in my system aside from the boiler that can fail and stop the hot water.

you could install a t and a couple of zone valves to bypass the exchanger when theres no call for heat.

stee6043 said:

Note that I was careful to use the term "properly sized system" in my original post. .

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" Properly Sized System" Tell me how you would properly size a boiler to operate without storage with an the operating load range of 1'500 to 55,000 Btu,s per hour ?

The wood boiler that seen the 40% improvement when storage was added had a Gross output of 70,000 Btu,s per hour in 1980 they did not come any smaller!

Heat storage eliminates the problem of controlling combustion to match the varying heating load of a home.

Does storage even help with an oil boiler that might be (semi) short cycling because only one zone is caling for heat? Although it can follow the temp demands much better than wood, there still must be some inefficiencies with starting and stopping all the time. Then too, it'd be ready to go once the wood/pellet boiler gets "approved".

velvetfoot said:

Does storage even help with an oil boiler that might be (semi) short cycling because only one zone is caling for heat? Although it can follow the temp demands much better than wood, there still must be some inefficiencies with starting and stopping all the time. Then too, it'd be ready to go once the wood/pellet boiler gets "approved".

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The oil boiler that was connected to storage also had a coil for domestic hot water and had to maintain a standby temperature of 170 F to 185 F. To decide whether or not to do the work and spend the money, an hour meter was connected to the oil burner wire circuit on the boiler so whenever the boiler fired, the time could be recorded. The boiler was isolated from all load for three days and it was found that the burner ran 3 to 3 1/2 hours a day to maintain standby temperatures which would work out to 21-24.5 hours a week. When the boiler was connected to storage, it would on average run for 3 hours, 3 times a week or 9 hours a week. If the oil boiler did not have the tankless coil for DHW, it would have been much more efficient as it was a demand type boiler containing only 3 gallons of water.

Another important factor on whether or not to connect your oil boiler to storage would be the heat loss factor from storage tank. Will the heat loss from storage be greater than the loss from the short cycle? The storage tank that I have will lose 400,000 BTUs with no load over 14 days or just over 1,000 BTUs per hour.
In the last month or so there was a thread on this subject. The majority felt connecting oil to storage was not a good option.

Thanks!
I have an indirect 40 gallon water heater on its own zone. In a way a mini storage tank. When it comes time to recharge that, the boiler gets a nice run, which has got to be healthier for it than shorter run times. Perhaps a buffer tank (would that be what it's called) could be used.

2.beans said:

i was curious on the oil because its getting to the point of almost having to pay for it around here.

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I get mine from ONE burger joint. I do pay him though. Seems to always be someone willing to pay more for it. I've been getting mine from the same restaurant for 6 years. I'm reliable.. so I still get it.

I make about 1k gallons a year. Probably will sell some grease in the future, as I'm not running it in the home boiler now that I have wood. Two diesel benz cars love it though.

JP