Another Wood furnace problem!
Hey everyone,
a few years ago I asked about how to solve a problem with my wood burning furnace, and last year I got a heating guy to do what was suggested but it didn’t seem to help very much so I’m going to try again.
Here’s the situation:
First of all, I have an 1870 farmhouse which has been added on to a few times, and the weakest links in the thing are heating and plumbing. The natural gas furnace is a Heil from about ’88 or so and it is so-so. When I bought the house, the wood furnace was attached by an 8″ pipe that came out of the top of the woodburner, and elbowed its way down and around the back of the furnace, entering on the return side. The former owner said he did that so he could filter the heated air.
I thought it was almost worthless, because when I had the wood fire roaring hot, I could still hold my hand on the pipe entering the furnace for a few seconds, but the exhaust pipe going to the chimney was practically red hot! Anyway, it certainly did not heat our house.
He had formerly had the pipe go straight up into the main heat run going from the furnace to the main addition but this had been patched off.
Someone recommended I take rectangular sheet metal and run it from the top of the woodstove into the plenum of the gas furnace. This I had done by a heating contractor, who had scratched his head about what to do also. It worked marginally better, but he didn’t install a damper so now when the wood fire dies down and the gas comes on, it blows a large amount of air back into the woodstove, and I feel like any benefit I get from burning wood is lost later in the night when gas takes over and blows all kinds of hot air into the woodstove and consequently up the chimney.
I can try to get some pictures posted but I’m new to the digital thing and haven’t done it enough to just remember how. But maybe in the mean time someone may have some ideas.
At this point I’d settle for re-connecting to the original place in the heat run to the addition and just heat that part of the house with wood if anyone thinks that is my best option.
Thanks,
Dog
Replies
Dog,
See what happens when you stay away for long periods of time?? Your questions get ignored.
Me? I have no idea what you should do!
Merry Christmas!
...and make the Fest a PRIORITY!!!
Rich Beckman
Another day, another tool.
MD
Isn't possible to have a separate chimney for the gas furnace and the wood stove or is there something I'm not picking up on with your description?
Are the two units not separate?
Or are you talking about a gas/wood furnace?
Gabe
Gabe,Good to see you too. To answer your question, the wood burning furnace is completely separate from the gas furnace. It has its own electrical circuit, a fan to introduce air, and a blower to circulate the heat into ductwork, which it shares with the gas furnace. The wood furnace requires its own chimney, which runs from the basement floor through two stories, an attic and out through the roof. The gas furnace is direct vented through the main floor sill.Merry Christmas,Dog
MD,
Looks like you need to have a motorized damper installed to prevent the heat loss that you're experiencing.
Talk to an HVAC contractor specifically. He's better equiped to understand and solve your problem. The savings alone will easily pay for the service.
Nice to see you back
Gabe
BTW Nice to see you posting again.
Merry Christmas and a safe holiday.
Gabe
Mad Dog - "I thought it was almost worthless, because when I had the wood fire roaring hot, I could still hold my hand on the pipe entering the furnace for a few seconds, but the exhaust pipe going to the chimney was practically red hot! Anyway, it certainly did not heat our house."
Not sure I can help with any ideas regarding the routing of you wood heater pipes but I have an observation I gleaned from a job were were working on the other week that you may or may not want to hear.
We were working on a house with sections of the house built between 1790 to 1860. It was the first day of temperatures in the teens for use around here and while it wasn't windy there was a breeze blowing. We had occasion to shut down the power to the house for a while and I noticed that in under an hour the house was cold. And I don't mean "not warm" or even "cool", I mean cold. I even asked "what the hell is going on here, did someone open the doors and windows somewhere".
The problem was the old house was drafty. At one point I was standing on a ladder in the corner of one room up near the ceiling at least 14' away from any windows (which were brand new Marvins and closed tightly) and yet I could feel a breeze. Blowing out a match so the I could get some smoke, I could see that cold air was coming in from behind the 100 year old crown molding in that spot.
We found many other places in the house where the same thing was going on. There was even a wall that had just been insulated that you could stand in front of and feel a breeze moving through it. It turns out that breeze was primarily coming through the electrical box that an outdoor light was stationed in. I sprayed some Good Stuff foam around the box sealing it up and put the fiberglass bat back in place and that took care of the big breeze but that wall was still cold.
It may very well be that the wood furnace and other heating systems you have even if they're working to peak performance are fighting a losing battle against a house that just doesn't want to hold in the heat. Maybe you need to work on a strategy to tighten up the house so to speak.
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Edited 12/24/2004 9:22 pm ET by Jerrald Hayes
Hey Jerrald,Thanks for the thoughts. My house is old, and there are some facets of it that may never be really "tight" but it's not a real leaky house. I am about half done residing it and as I go around, I am sealing it as tight as I can to keep the air and bugs out. There is one big situation that contributes to heat ineffeciency--an unheated, uninsulated crawlspace under the kitchen and two additions. The crawlspace is not a real air leaker either, but it certainly makes for some very cold floors in those areas.But the main issue I'm having with the woodburning system is that the air coming from registers is usually not hot, or even what I'd callvery warm. For some reason it seems like 80% of the wood btu's are going out the chimney, and not getting into the house at all.Good to see you around. Merry Christmas.
I would suggest you find a local business or heating contractor that can understand the problem and help you. It isn't always easy to find such a good resource but it is well worth it.
I had a lot of trouble with my gas furnace when I lived down south, Rotar Rooter ran up a $1000.00 bill before I found a gas furnace technician who fixed it for $280.00 and phoned the better business bureau on Rotar Rooter because he said, "they were endangering costumers." I paid 1/2 of the Roter Rooter bill which was $500.00 I didn't need to spend in the first place. My point is that your furnace needs an experts opinion, they can solve so many problems. don't tell them what you want ask them what they suggest.
There are some very knowledgeable people on this forum but unless a furnace technician or mechanic sees the furnace and checks it out you might not be getting complete advice.
Hope this helps.
I thought Rotor Rooter had to do with drains rather than heating problems.
Why in the world did you call them for a furnace problem.?
In British Columbia Roto Rooter also services furnaces, unfortunately the guy who is snaking plugged drains is not trained to fix heating systems. Gas fired furnaces need trained technicians, Rotor Rooter was happy to just change parts, hence the $1000.00 bill, and not diagnose the real problem.
David,You're quite right. I would probably never have had to try to solicite advice here if I could findan expert to look at this first hand. Unfortunately, I have not found anyone, and the heating contractors who've looked at it agree that it's not set up correctly, but they also don't know where to turn. There is a local wood heat store in the nearest town (about 7 miles) but they won't service anything they didn't sell, and have been reluctant to give out advice. That makes me not want to buy a stove for upstairs from them though I'm considering doing that and getting rid of the wood heat furnace altogether.I've talked to the fire department and they only offered up this dealer as someone they knew. But someone around here must know this stuff. I've got my ears on.Happy Christmas,Dog
Happy Holidays Dog,
If you are considering a new woodstove for upstairs that may be your best option for getting btu's from the wood pile to the interior of the house. Old woodstoves and furnaces tend to be less efficient than the new models.
As far a the temperature of the air at the registers, try to check it with a thermometer. Moving air feels cooler than it is, my 90+ furnace often feels like it is blowing cold air but it does a good job of keeping the house warm.
Blower output, duct size and location(inside heated space or not) are also major factors in delivery of conditioned air.
I think the other post are right on about a damper between the two units to keep them from backdrafting, and sending your heat up the chimney. Does the wood furnace itself have a damper that shuts when the unit is cold?
Best of luck,
G-Rott
I understand what you are going through, it frustrating when you cannot find the expertise you need but keep looking and ask around someone or something always comes up.
Merry and blessed Christmas
It sounds like your old wood furnance is like the old coal furnaces, all gravity hot air circulation.
Sounds like what you need is a fan or blower in the return air to the wood furnace to get a faster air velocity across the wood fire to air heat excahnger. If you have it hooked into the gas ducting, you need a manual or automatic duct closing mechanism. My own house has a wood 'furnace' coupled to the ducting of the heat pump: when the heat pump is on a door in the ducting closes on the wood furnance blower and the wood blower is locked off by a relay. When the wood furnance is on, the HP is locked off by a relay and the wood furnace blower motor also actuates a duct closer to the HP output. If you are really interested in doing something like this, e-mail me and I can sent you a diagram. DIY with surplus extra blower would cost you under $100 (me, $10<G>), probably $500 or so by a HVAC contractor.
To get a good idea of how much more thermal transfer you get with a fan on the wood furnace, take a look at some engineering sites for heat sinks http://www.aavidthermalloy.com/bin/exdisp.pl?Pnum=63730&LengthUnits=in&ExLength=3&airflow=1000
On the graophs on the likn, look at the ten to one difference in heat transfer with air flow on the graphs on the link.
JH,Nope, there is a blower on the bottom rear of the unit. I'm not sure at all what the internal configuration of this box is like, but the ductwork does not appear to directly connect the blower, as on a regular furnace. Maybe that's a problem? On your diagram, is the exhaust regulated by a gravity damper?As far as relays go, I gotta tell you this: I understand house wiring thoroughly. I've wired quite a few from service entrances right on through. But I don't know anything about appliance wiring, don't know anything about relays, capacitors, resistors, transistors, etc. Always wanted to, but never got into that. I bet it's pretty handy knowledge.Nonetheless, you've got me interested. I definitely think you're on the right track to solving my problem with the furnace competing with the woodburner when the fire dies down.Thanks, and happy holidays to you.
diagram and pix of HP damper solenoid control (typical DIY hack job -solenoid activated by wood blower, pulls counterweight for internal flapper over center, hits disconnect microswitch so solenoid turns off, etc. )
relay box is bunch of custom circuits, 6 various relays and simple transistor circuits for time delays, enhanced HP defrost, wood furnace controls (e.g hood fan, water circ pump, water heater preheat circuit, etc. - too lazy to take cover off for pix with one arm)