Indirect heater sizing

[Burn-1]

Although I have done pretty well heating with two wood stoves I can see the handwriting on the wall for my oil boiler and future costs so I hope to be able to get a wood boiler this next season. But in the meantime I also want to get away from the tankless coil which eats up a fair amount of oil running my hot water in the summer and go more to a cold start setup.

The house is an 1,800 SF ranch with three full bathrooms and an extra kitchen in the bar. It's just me my wife and two daughters and we don't expect to have more children but we have a lot of overnight company when the grandparents visit. Would a 60 gallon Superstor/Vaughan. etc be too big? Or would something more like a 40 gallon be fine. Any input is appreciated.

 

[Bob Rohr]

How much boiler do you have to power it? I used a 32 gallon Triangle Tube Phase 3 for 10 years. With an 80,000 boiler it would run a 2 gpm shower continously. If you use a bath tub with a fast fill valve you will need "dump load' or storage capacity.

If you have 100,000 BTU or more and properly pipe the indirect with a separate pump and large 1-1/4 piping, you will be fine with 40 or 50 gallons. Be sure the tank has enough coil to handle the flow. The tank in tank designs work well, Weil or Triangle Tube. Bock and Bradford White (enamaled steel) use large 1-1/2" coils. Heat Flo has a nice stainless tank with 30 feet of 1" coil.

Consider a dual coil tank with solar connected to the lower coil. Dual coil tanks are getting more popular for that reason, or real high output with both coils piped to the boiler.

Sizing DHW has a lot to do with the individuals use. I've never had a customer complain about too much DHW. I have under shot a few Most reasonable familys get used to the amount of DHW that a 50 gallon tank provides. Body sprays and large tubs are the exception.

Pretty easy to calculate the amount of DHW you use.

hr

 

[Gooserider]

I would look seriously at seeing what your potential is for solar, especially in the summer. The stuff I've seen claims that a reasonable solar array plus a decent storage setup can supply the household DHW needs pretty completely in the summer time, and possibly even in the winter with the right setup (either a glycol anti-freeze setup, or a "drain-back" system - I tend to prefer the latter)

Gooserider

 

[Jersey Bill]

I recomend the Triangle tube Smart 80. its a tank-in-tank design. the inner tank is the domestic water, the shell is the boiler water. that unit has so much heat exchange surface area that i would call it a hybrid between a storage heater and an instantious water heater. as long as you feed it enough boiler water, you will never run out of domestic hot water in the house.
the superstor is a 1.25" spiral tube heat exchanger inside the tank. i think that the length is about 12 ft or so. i have used them on jobs and ahey work alright.