Fireplace heater (heat exchanger) - fan question

[tcusta00]

Hello,

First post here and was hoping to get some help. I've been looking at heat exchangers for my wood burning fireplace and decided that I would be better off cost-wise building one myself. I've gotten as far as putting together my galvanized piping system that would blow room air into the system, through the pipes sitting in the hot coals, and out the front of the fireplace. I'm in need of a fan that would work in this type of situation. I've tried a 6" in-line duct fan (http://www.hvacquick.com/suncourt/Duct_Fans.htm the DB206) with reducers to get the output down to the 1.25" pipe that goes into the system, but that doesn't produce any noticeable airflow out - I'm thinking because it needs some kind of backflow, but I'm new to the physics of ventilation. The pipes coming out are reduced to 1". I'm thinking I need a different kind of fan but I'm unsure what. I was looking at this type of furnace fan that I thought may work:

http://www.grainger.com/Grainger/items/1TDN1

Anyone have any idea what I'm talking about and what I may need?? Thanks in advance for your help.

 

[webbie]

We've never had a user ask about this in all these years - I guess most folks bought them.....

But, yes, it takes a squirrel cage type to produce the static pressure needed to blow air through smaller pipes.
Check the CFM of some existing models:
http://www.raytechstore.com/fireplace/heatgrates.htm (180cfm)
http://www.hearthfan.com/closer_look.html (100 CFM)
http://www.fireplaceradiator.com (50-180)

Personally, I think you will end up better off on all counts if you purchase a pre-made unit, but I know how tempting it can be to reinvent the mousetrap (I am an inventor myself)

 

[tcusta00]

Thanks for the reply.

I'm just of the (admittedly stubborn) volition that if I can make it and make it more customized for my own fireplace, I may as well. I'm going to give a squirrel cage fan a shot. In my stumblings around the internet today I've concluded that I probably need a high pressure fan to force the air over a longer run of ductwork (or pipe, in this case). Correct me if I'm wrong, but I don't think I need a high CFM blower to just get the air out of the pipes and warm just my family room of about 20x15. I guess I'll have to play with it to find out. Total cost of the piping was under $100, and the fan is $40. I figure I'm saving myself at least $250-300... Even if I have to spring for a fan that delivers a higher CFM to match that of these pre-fab units the total cost will still be under $200.

Oh well, if it works I'll let you know. If it doesn't I have more junk for my shed and will have given my wife more ammo next time I try something harebrained like this!

 

[tcusta00]

Got a fan hooked up with the system from electricmotorwarehouse.com. Those guys are great - tech support, shipping, selection, everything! The squirrel cage motor I got hooked up to the system puts out 65 CFM which is just right for our room. The total cost for the system is around $200 and cranks out some good heat. Will post some pics later when I get a chance. Thanks for your help, webmaster. The headaches were well worth the troubles (IMHO).

 

[JRP3]

Sounds good. I'd like to see some pictures of what you came up with. The pre-made ones are nice, but no way would I pay that kind of money for what is basically a fan and some piping.