Buffer tank sizing

[Mikeswoodpile]

Anyone can help me figure out what size buffer tank would be best? My wood boiler is a closed system with a 23 gal capacity, will be about 75ft from house. Initially to run a heat exchanger in plenum 16 x 18. Like to add some other circuits like to water heater and garage. The info i found on boiler 120,000 working to 140,000 max btu capacity and the exchanger is rated 115,000. My house furnace is a hi efficiency 80,000 and barely keeps up when its good n cold outside. Looking for ideas without breakn the bank, thinking of using an elec water heater for the tank. Im capable of doing the work but my math skills not where they should be for calculations.

 

[maple1]

Make/model of boiler? 23 gallons is tiny.

 

[Mikeswoodpile]

It is old, woodchuck 3200, built somewhere late 70s early 80s , attached is the spec page i found. Its a indoor boiler but going in insulated shed so i saw no difference, it was in a detached garage previous.

 

[maple1]

I'm not sure how much you will gain from adding storage. The really small capacity kind of implies more would help. But those old boilers are so inefficient that it might not make any more heat than your house is demanding, so it might not have any extra to send to storage. That plus plenum exchangers usually needing the hottest water you can send them, and also the distance the boiler is from the house - I am doubtful. How are your underground lines?

My former boiler had its hands full just keeping the house at temp in winter months, and i had to let the oil contribute at times. Storage would have been a wasted exercise with it. And that was with it in the basement so no line or standby losses - most of the heat was going up the stack.