How to connect a wood burning furnace
Due to last winter's 2000-2001 fuel cost
in the midwest, I set out to hook up a viable alternative, a wood burning
furnace. The reason for creating this page was two fold.1) I had called
numerous (9) HVAC contractors in my area, and as soon as I mentioned a
wood furnace they either told me that they could not do it, or never returned
my calls. 2) After asking Scott Meenen (owner of this site) some questions
he suggested that I write the page for others to read. So I created this
page for others Do-It-Yourselfers (DIY) like myself.
Wood burning furnaces are not
a new idea. They have been around for quite a while. One of the oldest
Companies in the US is United States
Stove CompanyUSSC.However they are not the only manufacturer of
wood furnaces (see links below) All wood furnaces
are based upon the same principal. See figure 1
(Shown below).
Figure 1:
(Diagram of most wood burning furnaces)
I chose to use a furnace by USSC called
the Hot blast 1500. While its slatted to be a coal only furnace, you can
also use it as a wood furnace. The only difference's between the model
1400 and the 1500 is 1) the grate in the 1500 is a shaker style grate.
2) the 1500 also has a "spin draft" on the ash pan door, allowing you to
control the amount of air reaching your fire.
Regardless of the furnace you use, most
companies recommend that you install your wood furnace in Parallel installation
with your existing forced Air-Gas or Oil fired furnace. The main reason
this is, is due to the blowers of the wood furnace, are not adequately
matched to push the air through the ductwork throughout your house. However
the wood furnace can also be used as a standalone. See diagrams
taken from USSC owners manual. Pleas note that while all the diagrams show
up-draft furnaces, you can use this on a down-forced-draft:
Diagram 1:
(Diagram of stand alone wood furnace)
Diagram 2:
(Diagram of Add-On Installation)
Diagram 3:
(Diagram of Installation A)
Diagram 4:
(Diagram of Installation E)
Diagram 5:
(Diagram of Installation F)
Diagram 6:
(Diagram of Installation H)
Now for the setup. Figure
2 Shows my HotBlast 1500 wood furnace. Figure 3
shows the wood furnace and my Bryant Gas-Air furnace together.
Figure 2:
(Hot Blast 1500)
Figure 3:
(Both wood furnace and gas furnace)
Right now I am running both Heat Outlets
to a single 8 inch round duct pipe to my furnace plenum (which houses the
"A" coil) directly underneath the gas furnace See Figure
4 (directly to the right is a 6 inch round duct pipe for my whole house
humidifier)
Figure 4:
(Heat Outlet connection)
Next is a Diagram
7 from the owners manual on how the electrical connection between the
wood furnace and the gas furnace should be.
Diagram 7:
(Diagram of the electrical connections)
Now I show what they mean in real
life ;-) Figure 5 and Figure
6
Figure 5:
(Heat Outlet connection)
Figure 6:
(Heat Outlet connection). Note: the white control wire
is a mistake. You should never mix control voltage with line voltage. It
has since been corrected.
All in all that's it. Right now I'm
running into a problem when the wood furnace is running, and it kicks in
the gas-furnace blowers, the temp coming out of the furthest air duct is
only 75 F. This means all in all the house does not warm up past about
60 - 62 F. I think it is a problem with the wood furnace blowers and the
gas furnace blowers sort of canceling each other out. I am going to try
to either put in a "Baffle" as show in Diagram 4
or place my Hot Air duct further "down line" of my gas duct as shown in
Diagram 5. I will update this page upon my findings.
Sept 2004, Response from: jeff<HghsMrlbrMn@aol.com>:
I believe if you re-route your duct
work so that the heat side of your wood burner enters the COLD AIR return
duct, the furnace blower will DRAW the heat from the wood burner instead
of causing the 2 pressure blowers from having difficulty. The blower in
the gas furnace is much more powerful than the blower in the wood burner.
The cold air return is a negative pressure & will suck the heat out
of the wood burners plenum. The gas furnace will then circulate the heated
air throughout the house without any back pressure through the woodburner.
Installing a baffle will only serve to restrict the amount of heat that
can be used. Try that & see if will help your system work more efficiently.
jeff
Links:
Related Pages:
Wiring
colors.
Fan
Motor Replacement.
Problem
solving.
FAQ.
MoreF.A.Q.
More
definitions.
Gas
burner system page.
Oil
heat page.
Heat
pump repair page.
Heat
pump defrost cycle.
What
is a combustion blower motor system?
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Written By: Matt Fearnow:
Who does computer security work
as an Incident Handler for The SANS Institute
Page hosted by Scott Meenen
N3SJH of:
G&S MECHANICAL SERVICES.
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This text written by: Matt Fearnow, edited by Scott Meenen
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