What do I need in a wood furnace?

[jdew1920]

New member - first post. Hope some of you could shed some light on this for me.

Here's what I'm dealing with. 1800SF ranch in SE michgan, our main furnace is a high efficiency 70K BTU nat gas furnace with variable speed blower. Gas bills are not too outrageous but wouldn't mind reducing them greatly, plus nat gas has been steadily increasing in cost. My wifes dad recently passed away and he heated with wood (wood/oil combo) for about 30 years and was still stacking his own up untill last year - kind feel like I have no excuse not to, plus I could use the excercise.

I have probably a couple years worth of free wood on my lot - dead and dying elm, ash, some box elder (probably not great to burn). After that I think I could still get access to mostly free wood if I want to put in a little labor to get it.

Based on the lower cost of natural gas I don't think I can justify a real expensive furnace and was thinking something in the $1500 ball park could be justifiable for me. Now that I am looking at them I am not sure what I should really be looking for. I know that will not get me a top of the line furnace but there seems to be some decent ones in that ball park.

These are my questions:
Is a draft blower recomended, or is a manual good enough? Seems like it'd be nice to more thermostat control with the blower.
How much of a difference do you see with secondardy air combustion?
Secondary heat exchanger?
Size of firebox? Is bigger necessarily better?
Do any of the above make a big impact on effeciency?
Worth getting one with its own blower or just use the current furnace blower? Can they be hooked up to utilize variable speed capability of current furnace fan? If getting one with a blower is a multi-speed blower much prefered?

Anything else I may be over looking let me know. In the $1500 range it seems like the Yukon Eagle Big Jack is nice furnace but fan is extra. There are others less than this but they seem somewhat cheaper. Englander does not seem bad but if I recall they do not come wiht a draft blower. The Caddy's (US Stove 1950) look nice but in the $2K range.

Any help is appreciated.

 

[Eric Johnson]

Welcome to the Boiler Room, jdew. I've owned a wood-fired furnace, but that was a few decades ago, so I'm the wrong guy to ask. But we have some very sharp hot air people around here, and I'm sure they'll give you the information you need. You've asked some very good questions & it sounds me like your wood situation is good for what you want to do.

 

[reaperman]

It seems your on the right track with the questions you ask. I can only say that my unit has worked well for me. I have a firechief model 500. This is my second year using it. I have a forced draft motor, on my unit that is suppost to be thermostatically controlled. Dont fall for this one. In my opinion there is no such thing as a thermostatically controlled wood furnace. When the furnace gets up to temp, the plenium fan kicks in, and runs until the furnace is cooling down. Once the desired temp in the home is reached, the plenium fan will keep running regardless of what the theromstat says. And when the thermostat calls for heat and does kick in the forced draft blower, you better hope the house heats up fast. Because with a good load of wood in the furnace, and the draft blower running, you better have a fire truck handy, because after only a few minutes your going to have one serious fire in your furnace. I know there is a upper limit on the draft blower, but mine has never even got close to shutting down, before I step in and shut it down myself. I since have wired it to only run manually, which I use very little. But you will find once the furnace is up to cooking temps, it will heat the home just fine without the draft blower.

As far as secondary burns, I'm not sure how likely this is on a regurlar basis. I know there is a secondary burn chamber, but wood furnaces are not the most efficient wood burners. The designs are all pretty much similar to one another. As far as firebox size goes, you may get longer burns with a larger box. My unit has a 5 cubic ft, box and I get plenty of heat. I dont always fill it to the brim, or it just seems to burn faster with more wood. My unit has a 3 speed plenum blower, I use low or medium when its real cold out. Believe me, if the plenum fan is
running for 6 or more continus hours, and the heat coming out of your registers is 100-115 degrees, the highest speed isnt necessary. Id check with a local heating contractor and see which set-up would be the most beneficial in tying into your current furnace/ductwork. As far as which wood furance, I'd maybe hold off until spring or summer when they may be going on sale, and pick one up then and have it all ready for next season.

 

[jdew1920]

I'm definately waiting till later to purchase. Just researching now.

Anybody else have an opinion? Recommendation on a brand?

Here's another question. I've seen where the manufacturers say to add only to existing furnace that is similar in BTU rating. Is that becuase presumably the duct work would be sized right? In my case my 94% effiecient 70K BTU furnace replaced an 80% 125K BTU furnace, furnace output is about 35% less than the original furnace - sized correctly now. Should I be looking at furnaces that are rated no higher than 100K BTU?

Thanks

 

[eekster]

jdew1920, where about in SE. MI. are you? I"m also in that area and I have a EKO 40 gasifier, You are more than welcome to come and see it in operation.
Keith

 

[jdew1920]

I'm in Novi. Looks like you are using a boiler.

Thanks

 

[ISeeDeadBTUs]

All the Hot air you should need . . .

 

[jdew1920]

All the Hot air you should need . . .

There's no way I'd put that thing in my basement!