Ductwork and cold air return questions

Ductwork and cold air return questions

PostBy: wnyjim On: Wed Dec 10, 2008 12:45 pm

I connected my Hot Blast add on furnace as the manual shows however.

I have no cold air return on either furnace. I plan on correcting this soon.

My Hot blast now pushes heat into my plenium above my main furnace.

I noticed warm air coming out the cold air return opening on the main furnace.

How do I correct this?

Also the blowers on the hot blast arent near as strong as the blower on my fuel oil furnace. Any help for that? I have alot of work to do on my heating system I have learned but I would lie to do it right the first time.

I understand cold air returns need to be kept seperate but what about the heat ducts? THis backfeed situation just robs airflow from my hot blast blowers.

Than you in advance for any help or advise.
wnyjim
 
Stove/Furnace Make: Hot Blast Model 1500

Re: Ductwork and cold air return questions

PostBy: WNY On: Wed Dec 10, 2008 12:59 pm

You need a one way Duct Damper in your cold air return or where the heat is coming back thru into your furnance, it's basically like a check valve used in plumbing, it will open on air flow one way and close when it is reversed....

You might be able to update your blowers, what are they now? LIke 400-500 CFM? Furnances are usually in the 1500CFM range, so they might be lower volume.

Also, one you correct the back flow, it might help the air flow.
WNY
 
Hot Air Coal Stoker Stove: Keystoker 90K, Leisure Line Hyfire I
Coal Size/Type: Rice
Stove/Furnace Make: Keystoker, LL & CoalTrol
Stove/Furnace Model: 90K, Hyfire I, VF3000 Soon

Re: Ductwork and cold air return questions

PostBy: wnyjim On: Wed Dec 10, 2008 2:20 pm

Hey WNY your in Cuba? Im in Canaseraga. Small world and nice name choice. :lol:

The one way duct damper sounds like what I have above my Hot Blast Furnace to keep my oil furnace from back feeding. These are 8" in diameter.
My cold air return is not connected.
Do they make a damper large enough to fit over where the filter slides into my oil furnace? Or will I have to wait to run a cold air return duct and install it then?
I suspect they dont and i'm stuck till I run a cold air return.

I will have to check the CFM rating on my Hot Blast 1500. I suspect they are about half the output of my Oil Furnace.
wnyjim
 
Stove/Furnace Make: Hot Blast Model 1500


Re: Ductwork and cold air return questions

PostBy: CoaLen On: Wed Dec 10, 2008 6:07 pm

Something I am considering doing is removing my filter from my propane furnace and replacing it with something solid to act as a damper in the cold air side of the system. Of course, this will only work as long as I don't fire up the propane furnace.
But I am still trying to find a damper that will fit into the furnace plenum to direct the air from my coal furnace into the heat ducts and not allow it to go down into the furnace in the first place. I suspect I'll have to make my own because I haven't found anything yet.
-Len
CoaLen
 
Hot Air Coal Stoker Furnace: Keystoker Koker
Coal Size/Type: rice

Re: Ductwork and cold air return questions

PostBy: BIG BEAM On: Wed Dec 10, 2008 8:28 pm

The hotblast fans are 550 each but they will run 24/7.The way I hooked up my hotblast was to connect the feed from the hotblast on a 45* angle to the plenum of my main furnace so the fans blow the air in the direction of the main furnace.This way you need no flapper because the air from the hotblast is already going in the right direction and won't feed into the returns.
If you still have your hotblast manual it is like installation A but the hotblast in my set up has it's own return and is not hooked up to the main furnace returns at all.
BIG BEAM
 
Stove/Furnace Make: USS Hot blast
Stove/Furnace Model: 1557M

Re: Ductwork and cold air return questions

PostBy: WNY On: Wed Dec 10, 2008 8:42 pm

Yes, Cool, that's not too far away. probably 50 miles?

My buddy i work with is using a Hotblast 1400? also but only wood. Dont' you have a limit switch to turn the blowers on/off?

Whereever you are connecting the hot air pipes to your oil furnance, you would have to put some type of damper there so the hot air doens't go down into your other furnance.

Can you hook the vents up to the cold air return on your oil furnance and use that blower to suck the heat from your hotblast?

They should be able to make them any size. You could probalby get a piece of sheet metal or thin aluminum and maybe with a light spring to keep it closed, then if it starts to suck, it would open automatically. somehow hang it on the inside with the spring pulling it closed.??
WNY
 
Hot Air Coal Stoker Stove: Keystoker 90K, Leisure Line Hyfire I
Coal Size/Type: Rice
Stove/Furnace Make: Keystoker, LL & CoalTrol
Stove/Furnace Model: 90K, Hyfire I, VF3000 Soon

Re: Ductwork and cold air return questions

PostBy: wnyjim On: Wed Dec 10, 2008 10:24 pm

Yes I'am about 50 mi from Cuba.

I have the limit switch and my blowers run about half the time.

Right now outside temp is 25 deg and it is 70 deg inside. So not bad even with my issues.

I have dampers in place on the hot blast before it goes to the plenum.

The only issue here is with the return. I did try blocking it off with a piece of sheet metal. Should have tried it during the day. Wife had the main furnace turned up and I heard it kick on about 2am. :shock:
I shagged but down to uncover the cold air intake. Havn't tried it since. Also requested the wife not fiddle with the knobs till I straightn all this out. 8-)

Here is one interisting thing to read about add on furnaces and cold air returns.
http://www.warmair.com/html/add_on_wood_furnace.shtml

Beam: you really lost me there in your explination. I will keep reading it and maybe It will sink in.You guys have alot to offer in the knowledge department.
Right now I have researched myself into a headache lol. Headin to bed.
wnyjim
 
Stove/Furnace Make: Hot Blast Model 1500

Re: Ductwork and cold air return questions

PostBy: gambler On: Wed Dec 10, 2008 11:14 pm

CoaLen wrote:Something I am considering doing is removing my filter from my propane furnace and replacing it with something solid to act as a damper in the cold air side of the system. Of course, this will only work as long as I don't fire up the propane furnace.


Len, I had a corn stove hooked to my ducting at one time and I used a piece of that blue 1" thick styrofoam to block off the cold air return to my furnace. It was easy to cut to size and cheap because I had some laying around.
gambler
 
Stove/Furnace Make: Leisure Line
Stove/Furnace Model: Pioneer

Re: Ductwork and cold air return questions

PostBy: WNY On: Thu Dec 11, 2008 9:17 am

Put a set of mechanically controlled louvers on the inlet, hooked to your oil furnace controls, when the oil furnace comes on, it would open the louvers automatically.....just another wild idea

Like this

http://www.hearth.com/talk/threads/23900/
WNY
 
Hot Air Coal Stoker Stove: Keystoker 90K, Leisure Line Hyfire I
Coal Size/Type: Rice
Stove/Furnace Make: Keystoker, LL & CoalTrol
Stove/Furnace Model: 90K, Hyfire I, VF3000 Soon