Turn Tarm boiler into hot air furnace?

[rcurtis]

I appreciate the great info on wood furnaces and boilers! I just now joined to see if I could get some thoughts on turning a 1978 tarm wood/oil combination boiler.....into a hot air furnace.

Why?

Because the Tarm has seen better days, and I do not trust it with the water and pressure for another season. Also, I just moved into a doublewide, and am going crazy listening to the furnace sucking up fuel oil.

I was thinking that the tarm converted to a hot air furnace would allow me to put it outside (insulated of course) and pipe it into existing duct work.

What do you think?

Curtis

 

[Adios Pantalones]

The Tarm relies on dumping heat into a water tank or jacket, then pumping that around to deliver heat. People use exchangers to get the heat out of the water into an air system, but bypassing the water entirely in a unit designed as a boiler is going to be more effort than building one from scratch... I think.

 

[rcurtis]

I used the tarm as intended for about five years. I am thinking the water jacket could be used as an air jacket. I would use the domestic coil opening on top for hot air out, and cut a ten inch hole in the back near the bottom to return cold air, with a fan inline.

nothing to lose, if I am not able to convert it, it will be off to the junkyard anyway.


Curtis

 

[btuser]

I used the tarm as intended for about five years. I am thinking the water jacket could be used as an air jacket. I would use the domestic coil opening on top for hot air out, and cut a ten inch hole in the back near the bottom to return cold air, with a fan inline.

nothing to lose, if I am not able to convert it, it will be off to the junkyard anyway.


Curtis

Use a hydro-air coil. You keep your boiler as intended, then run hot water out to a fan coil that will warm the air. I'd have to say dry-firing a wood boiler like you're suggesting is a very bad idea. This is the exact moment when boilers become a fire hazzard.

 

[rcurtis]

Thanks for the response!

I often have ideas that are a little out in left field. Most of them are motivated by lack of $, which can sometimes make things even more costly

Anyhow, I thought that without the water, I would basically have a firebox inside of a bigger box (formerly the water jacket). I do not think the boiler will make it another year under 18 pounds of pressurized hot water (and what you suggested with hydro/air heat exchanger was what I was doing before I moved and brought the tarm with me) but maybe it would work fine with just hot air blowing through the water jacket. The boiler will be outside, so there is no chance of a fire hazard, however, if the firebox burned through, that could be a problem, the same as any other forced air furnace would be.

I would really like to try a Russian fireplace or cob jet stove. That way I could burn off some of the lesser quality wood in my woodlot.



Curtis

Huskies, stihl, mauls, pickeroon.........yada, yada, yada

 

[webbie]

If you use it to drive a furnace heat exchanger, you don't need 18 Lbs of pressure. In fact, you don't need any pressure at all.....it could be done with an open loop.........open at the top.....like many do in Europe and elsewhere. Or you can just keep it under 4 lbs or so...enough to lift the water up to the heat ex.

Yes, if you were on a desert island it could probably be made to function quite well as a hot air unit in the fashion you describe - but as long as you can use stop leak on it, it will do a better job with water.

You will notice a new advertiser here - we always like to support those who help us publish - who sells this stuff and PEX, etc. - the banner should be running in this forum - Outdoor Furnace Supply.

 

[rcurtis]

Craig,

What worried me about the Tarm was that I could hear some hissing when it was really cranking up pretty good, I do not know if I was loosing water, due to the pressure reducing auto fill valve, but there was definately some sort of a leak.

I did run it as an open system while I had a domestic hot water coil gasket on order. It seems that while I was out of town, the spring in the draft control malfunctioned and left the draft wide open. My wife was very dutiful to keep putting wood in the boiler, even though the pressure relief valve popped off and we were making steam at this point, a long story short, the heat melted the rubber gasket on the domestic hot water coil.

I suppose I could run it open again, just need to keep an eye on the water level.


Thanks for your input and a fantastic site!

Curtis

 

[Nofossil]

The heat transfer ability of water is vastly more than for air, so you'd never be able to extract heat from the boiler fast enough. That would lead to extremely high temperatures in the inner water jacket.

Hot air furnaces have a lot more surface area per BTU and much larger air passages to deal with this issue.

 

[leaddog]

Using it as a air furnace would be a good way to KILL someone. If it will leak water it will leak co2 and you will blow that into your living area. On any furnace that starts to leak they are scrapped. A boiler isn't as dangerous as you aren't leaking co2. I'd use it as a boiler at very low pressure or as an open system. If it started to leak to bad then scrap it. You might just get by this year. Just DON"T use it as a furnace as we don't want to hear about your family being hurt.
leaddog

 

[rcurtis]

Thanks for the "heads up." It had crossed my mind that it could possibly let some smoke through. I guess I should quit being so lazy and do an air pressure test on the boiler and see what is up.

I only paid $200 bucks for this thing five years ago so maybe it is time to give it a decent burial.

Everyone's input is much appreciated, it is nice to talk with folks that are as interested in wood burning appliances as I am....the wife gets awful tired of hearing about my latest "idea."

Curtis