need some ideas

[aaronmach1]

long story short... Installed my wood furnace then found out on this site i need a cold air return line and box round the blower so it isnt sucking the air out of the same room as the fire is burning in. Sunday i boxed in the blower and ran a 5 inch line from blower to the existing air return lines for my gas furnace which has return vents in 3 bedrooms and the livingroom. Turns out 5 inch wasnt big enough. Yesterday i changed it to 8 inch. Now the blower seems to push twice as much air than it ever has. Great right? Not really, now i seem to be over heating my plenum with the one heating line coming from the wood furnace. My big gas furnace blower comes on every 8-10 minutes and runs for 1 minute and the plenum gets so hot i cant really hold my hand on it more than 1 second. Also the closest heat register in the livingroom is pretty hot.
Another new issue with this is now it barely heats my upstairs, i get about half as much air coming out of the registers up on the first floor. Is this all due to the location i tapped into the cold air return lines being too close to the gas furnace?

Here you can see that i have one heat supply pipe going into the Plenum of the gas furnace just like they show in installation instructions and then i chose to have one blowing into the basement.

 

[hoosier daddy]

???

are you just looping the air from your wood furnace through your gas furnace and sucking it back in to be heated again??? Can you try to close off your gas furnace...maybe (just temporary) take out the furnace filter on the gas unit and replace with a piece of plywood or cardboard to restrict air flow...if this pushes more air upstairs you know you have a loop...

Not a HVAC guy but I had the same issue with the first corn burner and have to cut off the gas furnace when I heat with other source.

HD

 

[laynes69]

You need a backdraft damper in the central furnace, your pulling heated air back through the furnace, tripping high and activating the blower. Also your reducer on the flue is galvanized, which is a no-no. When heated it causes toxic fumes.

 

[Whitespider]

You need a backdraft damper in the central furnace…

AGREED!

What you’ve done is create a “loop”.
The blower on your wood furnace is sucking the heat backwards through the gas furnace and recycling it back into the wood furnace. The heat being pulled backwards through the gas furnace is closing the contacts of the heat sensor in the gas furnace, causing the gas furnace blower to kick on. You’re not getting heat upstairs because most of what is exiting the “loop” is being bushed out the open basement vent. A “dual blower” setup cannot use a common return and a common plenum without the mentioned back-draft damper, vent splitter, or gate with associated control motors/solenoids and safety sensors as needed. Typically, a single blower is used when two appliances share both venting systems. The low volume blower on your wood furnace is not designed to be used as a “forced air” heating system… basically it pushes the hot air into the heating duct work, but from there it is mostly relies on convection to carry it on to the exit vents. Your “loop” has reversed, or overcome the flow of convection.

Now, to address your statement…
…then found out on this site i need a cold air return line and box round the blower so it isnt sucking the air out of the same room as the fire is burning in.

Don’t believe everything you read on an internet board without doing your own research and conformation. Although that is “code” in most places… the reasoning is so you don’t create a vacuum that will pull air down the chimney and out the combustion air intake of the appliance, filling the house with carbon-monoxide. It is doubtful that would happen in a large open basement, more likely in small enclosed furnace rooms. Besides, if your home is up to code there is (probably) an outside air intake somewhere in the basement that will keep that vacuum from developing. Really, all you need is a way for cold air to return to the basement, such as leaving the basement door open an inch or two so you don’t get as much air sucked in from outside (probably enough air would return under the door if it was closed). Or if you’re really worried about it, you could cut a vent in your floor and hook the “return” pipe from your wood furnace to it.

 

[aaronmach1]

are you just looping the air from your wood furnace through your gas furnace and sucking it back in to be heated again??? Can you try to close off your gas furnace...maybe (just temporary) take out the furnace filter on the gas unit and replace with a piece of plywood or cardboard to restrict air flow...if this pushes more air upstairs you know you have a loop...

Not a HVAC guy but I had the same issue with the first corn burner and have to cut off the gas furnace when I heat with other source.

HD

Awesome idea thanks!!!! i will do this when i get home. why didnt i think of this.

 

[aaronmach1]

well done guys thanks alot! im 100% sure that i know the fix now from your help! No need for an 8 page thread this time!:hmm3grin2orange: After adding the cold air return and the outside air supply though i have to say the burning wood part now is going great!

 

[stihlrookie]

I read your 8 page thread the other night and the consensus was to seek professional help.....for your furnace. Here you are starting another? I wonder what the outcome will be? Seriously man, come on, why not call someone in to get you straightened out? You are playing with fire, literally, and dangerous fumes here. Carbon monoxide is deadly, call a professional stove person, please, and stop wasting your time.

 

[aaronmach1]

I read your 8 page thread the other night and the consensus was to seek professional help.....for your furnace. Here you are starting another? I wonder what the outcome will be? Seriously man, come on, why not call someone in to get you straightened out? You are playing with fire, literally, and dangerous fumes here. Carbon monoxide is deadly, call a professional stove person, please, and stop wasting your time.

The two guys around my area do not deal with wood burning. thanks

 

[stihlrookie]

The two guys around my area do not deal with wood burning. thanks

Didn't realize, sorry man. Did you place one of your new CO detectors down in the basement yet? Good luck.

 

[aaronmach1]

yes two new detectors no new reading on them at all so far, soon as i get this last problem fixed i should be good to go.

 

[Chris-PA]

I dunno man, you're going to have to learn and understand your system yourself. You have two heating appliances in the basement room, each with flues to the outside and blower systems intended to circulate air. Now the two systems are connected in loops. Each blower wants to push air out and draw it back, and that airflow will follow the path of least resistance. So when the wood furnace blower sends air out, what is the easiest path back to its inlet? If it's the short path backwards through the gas furnace heat exchanger, then that is where it will go.

When the gas blower runs, what is its least resistance path? If it's the short path through the wood furnace and back to its blower inlet in the return duct, then that is where it will go.

What happens when they both run?

What does that open outlet on the wood furnace do? Where does air go that comes out of there (if any), and how does it get back to the blower inlet? I don't see any path now.

You need to make sure you don't have a situation where one of the blowers is creating a low pressure in the furnace room and pulling smoke/CO back down the flues. This was what I was worried about in your other thread.

These issues all need to be understood and solved. With the addition of that return allowing multiple air flow loops, the system is quite a bit more complicated now.

 

[stihlrookie]

yes two new detectors no new reading on them at all so far, soon as i get this last problem fixed i should be good to go.

Yes, I know you bought them and installed them in your living spaces. I am asking about the basement where your furnaces are located. CO is heavier than the air we breathe and will displace said air making your basement area virtually a death trap. I was asking if you had moved one of the detectors down to your basement? If you have them upstairs and CO is gathering in your basement how are you going to know?

 

[cantoo]

stihlrookie, I can answer that question. I know co isn't gathering the the basement because he's still alive and replying to questions. When he stops replying we will know he has a problem.

 

[Whitespider]

aaronmach1,
I just went and found that 8-page thread… I’m not sure how I missed it, maybe something on the first page turned me off or something. I didn’t read all 8-pages word-for-word, sort’a skimmed over it in places.

First let me say this… A building ventilating system is a lot more complicated than just a cold air return side and a heat side. Blower size must be matched to the size of the ducting, the size of the return vents and the size of the heat vents. When the blower is running there should be positive pressure on the plenum side and negative pressure (vacuum) on the return side… if either side is over-vented or under-vented the system will not work correctly. When the venting system is installed a HVAC man will make precise measurements and calculations in order to get all this correct.

After reading the 8-page thread, and now in this thread seeing what you have done, it is obvious to me that you do not understand even the most basic principles of HVAC. It even appears that you hooked up the “return” to your wood furnace on the wrong side of the filter… a big, big, NO, NO! In a reverse flow situation the dust can be pulled off the filter and sent into your wood furnace plenum where it could ignite from heat, causing an explosion that would send flames shooting from your heat vents, and possibly damaging both appliances… even to the point of exploding the gas furnace.

I strongly suggest you remove that cold air return to your wood furnace ASAP…
You do not have the necessary basic knowledge to install dual-appliance/dual-blower into a single venting system… and it ain’t possible to walk you through it without being there to see the entire system… plain and simple, you need a HVAC man before something bad happens. And something bad will happen if you continue to screw around with guess work.

 

[kstill361]

It looks like that furnace got extremely hot since there are two hot spots on the cabinet. Have you taken the cabinet apart and checked for cracks or weld seperation. I would do that asap

 

[kstill361]

Your return air should be 10% larger than the output. Its too small

 

[psu927]

After you get all of tht straightened out I'd recommend reducing that vent you have in the basement to get more air upstairs. You could probably get away with 5" for the basement supply. (depending how large the basement is and how warm you want it)

 

[aaronmach1]

It looks like that furnace got extremely hot since there are two hot spots on the cabinet. Have you taken the cabinet apart and checked for cracks or weld seperation. I would do that asap

The 2 spots are from the previous owner. This is why ive been trying to figure out how hot i can get the firebox before it over temps. Nobody seems to be able to say. I try to keep the temp on my thermo dial under 180. whats too hot?

 

[kstill361]

The 2 spots are from the previous owner. This is why ive been trying to figure out how hot i can get the firebox before it over temps. Nobody seems to be able to say. I try to keep the temp on my thermo dial under 180. whats too hot?

Im not sure what temp is too hot for your furnace but I would take the cabinet apart and inspect all the welds for sure, maybe put a bright light inside the fire box and turn out all the lights and look for cracks

 

[aaronmach1]

Im not sure what temp is too hot for your furnace but I would take the cabinet apart and inspect all the welds for sure, maybe put a bright light inside the fire box and turn out all the lights and look for cracks

Where the two spots are i can see perfectly from inside the box through the load door. If there are cracks shouldnt i be able too see them from there?