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  • From: "Paul A. Bock" <bockpa AT plesh.com>
  • To: "'Market Farming'" <market-farming AT lists.ibiblio.org>
  • Subject: RE: [Market-farming] Heaters
  • Date: Mon, 22 Dec 2003 15:55:36 -0500

I personally hate all water-jacket type wood burning furnaces. They don't
let the wood burn hot enough. You need to burn at 1100F to burn up creosote
and to get smoke free operation. The water jacket sits about 150-200F and
cools the combustion down so much that the wood never gets burning hot
enough. Everywhere I see them they are always putting out smoke. I am
talking about the circulated hot water types. Also most of them don't
operate under any pressure, all vented to the outside air. This lets the
water evaporate as well as let oxygen into the system, The oxygen in the
water is what lets all the metal components get rusted out. (The circulating
pump housings, the pump impellers, the water jacket to the furnace, the
control valves, etc.) To get the hot water to different areas (zones) you
will be using something called PEX tubing, which is a special cross-linked
polyethylene tube, able to handle pressure at the high water temperatures.
This tubing is made with a special layer that prevents oxygen from getting
into your system.


I never purchased from this place, but this is the best wood stove made,
IMHO.
http://www.radiantdirect.com/page15.html

A nice refractory combustion box lets the wood burn hot. You will end up
getting more heat out of the wood. The wood will last longer, you won't
have creosote problems.

Let me tell you one more thing, don't oversize the system. I delivered
firewood to a guy who had a hot-air indoor wood furnace. He got the next
larger size because he was going to put on an addition someday. Well that
larger furnace was always idling in the smaller house. It would kick on for
a few minutes every few hours, but never had good consistent burns to burn
up the creosote. His chimney looked like it had been coated in tar. And if
there was a good cold night where the furnace might actually burn for a bit,
all that creosote could go up in flames like a jet engine.

Also think about your current furnace. It might be rated at 200,000 btus.
That means while it is on, it is putting out 200,000 BTU's per hour. Maybe
your house only needs 20,000 btus per hour to stay at a certain temperature.
Well your furnace will kick on in cycles. So if you only need 20 and it
puts out 200, it might only be on 1/10th the time or 6 minutes per hour. A
hot air furnace doesn't idle, it is completely off during the off cycles. A
wood burner idles during the off cycle. The firebox is still hot, but
usually the combustion air is cut off, or the combustion fan isn't blowing.
So the fire starts cooling down and if it cools enough, especially in a
water jacket furnace, it gets down enough to not burn up the creosote. It
is best to have these things burning at full bore most of the time.

The nice thing about the refractory wall style wood burner that I provided a
link to, is that the refractory (masonry) stores up the heat and insulates
the fire so that it keeps its temperature up and doesn't start making
creosote during the idle phase.

A couple good books I have come across:
http://www.amazon.com/exec/obidos/tg/detail/-/0882667882/qid=1072126254/sr=1
-1/ref=sr_1_1/103-2336155-0361454?v=glance&s=books

The New Woodburner's Handbook.

http://www.amazon.com/exec/obidos/ASIN/0766816370/qid=1072126349/sr=2-1/ref=
sr_2_1/103-2336155-0361454

Modern Hydronic Heating

-Paul Bock
Stone Gully



-----Original Message-----
From: market-farming-bounces AT lists.ibiblio.org
[mailto:market-farming-bounces AT lists.ibiblio.org]On Behalf Of Leigh
Hauter
Sent: Monday, December 22, 2003 2:24 PM
To: Market Farming
Subject: Re: [Market-farming] Heaters


I have a 30X96 ft greenhouse (it just grew 24 feet this year) and I'm
in the market to purchase an outside wood furnace to heat it a the
addition on our house we are building plus maybe the shop. Anyone
have experience with outdoor wood furnaces and can you recommend or
condemn a manufacturer?
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