Sizing heat exchanger and circ. pump

Just got a new outdoor wood burning appliance and I'm getting ready to purchase a heat exchanger for my forced air furnace and was looking for some advice on sizing components.

My simple thought just says coil btu's should match furnace max btu's and pump should be slightly over sized then throttled back.

Can anyone help out and explain out calculations or give a general rule of thumb on sizing?

That's a good idea. I am doing a forced air install and have a 20x20 plenum I can put the heat exchanger in. I should probably just stuff the plenum with the highest rated BTU heat exchanger I can fit in there. I was not planning using storage and my capacity is only around 100 gallons. The more I have thought it over storage would be a good idea but I don't really have a good place to put it at this time.

Checked those alpha pumps out. They look like a really good unit. Thanks for the heads up. I found tho the biggest heat exchanger I can fit is an 18x18 without doing some major mods to my existing plenum. It's only 120k btu. I will probably run a radiant loop on my kitchen/dining room floor.

I forgot to mention that I saw the inlet pressure of the alpha pumps to be around 4psi. Does the head pressure in the boiler provide this necessary inlet pressure?

maple1 said:

Yes.

Well, maybe not. You've got an unpressurized OWB? You'd have to see what your pressure is where the pump would be - and are you sending boiler water thru the HX? Or do you have another HX (plate?) between your boiler & your heating system?

BTW, the 4psi also applies to the non-Alpha 15-58 3 speed.

Click to expand...

Yes its unpressurized. I'd guess that I have 6 feet of head between the OWB and the proposed pump location. I can mount the pump a lot lower and try and get more head pressure on the inlet side. Yes the boiler water would be going directly through the HX that is in the plenum.

Also while I am on the subject of circulating water, anyone have any good recommendations as far as water treatment chemicals for an unpressurized boiler?

mark I see your local to me....how many cords you go through this past winter? I got 7 cords of 2 year seasoned ash and a cord of 2 year white oak that im hoping will get me through next year.