Tying coal/wood furnace cold air return into NG cold air return

crzybowhntr · Feb 12, 2016

I am looking to see if the overall difference of tying the cold air return from my coal/wood furnace into my NG furnace ducting is worth it. I know every install is different but what has the consensus been overall with everyone else’s install that started with the cold air return box on the back of the unit and then tied into the main return? Mine is in the corner of my basement and there are no doors that block the return air from coming into the basement. If I hold the door to the bedroom furthest away from the furnace almost closed, I can feel the air being sucked out of it. Would tying it into the ductwork allow the air to be warmer as it circulates the house? Also, since my delivery and return air ducts run side by side, my cold air return duct is warm to the touch (might help with warm air circulating?).

Thanks

blades · Feb 12, 2016

it stops those nasty ankle freezing drafts getting back to the furnace and is the preferred way to install your furnace. Now you didn't mention if the heat output is tied into the ducting as well or not. and if so did you install back draft dampers ( on the hot side) for when the ng unit runs.

crzybowhntr · Feb 12, 2016

blades said:
it stops those nasty ankle freezing drafts getting back to the furnace and is the preferred way to install your furnace. Now you didn't mention if the heat output is tied into the ducting as well or not. and if so did you install back draft dampers ( on the hot side) for when the ng unit runs.

Yes, my furnace is tied into the supply line of my NG furnace via a run of 8x16 duct and there is a damper at the plenum of both furnaces to prevent back feeding.

crzybowhntr · Feb 13, 2016

blades said:
it stops those nasty ankle freezing drafts getting back to the furnace and is the preferred way to install your furnace. Now you didn't mention if the heat output is tied into the ducting as well or not. and if so did you install back draft dampers ( on the hot side) for when the ng unit runs.

Yes, my furnace is tied into the supply line of my NG furnace via a run of 8x16 duct and there is a damper at the plenum of both furnaces to prevent back feeding.

crzybowhntr · Feb 14, 2016

STIHLY DAN · Feb 14, 2016

Absolutely worth it. Everything will improve from creature comfort to the unit. It has never been a (good ) idea to take from the basement, just cheaper and easier without catastrophic problems.

3fordasho · Feb 15, 2016

I'm finally connecting the return air duct work to my Tundra. Should have it finished later this week. If nothing else I will be able to close the furnace room door with out worry of creating negative pressure in the furnace room and the chance of that negative pressure reversing chimney draft.

I am hoping to report a less drafty house and better heat distribution once it is connected.

crzybowhntr · Feb 15, 2016

STIHLY DAN said:
Absolutely worth it. Everything will improve from creature comfort to the unit. It has never been a (good ) idea to take from the basement, just cheaper and easier without catastrophic problems.

3fordasho said:
I'm finally connecting the return air duct work to my Tundra. Should have it finished later this week. If nothing else I will be able to close the furnace room door with out worry of creating negative pressure in the furnace room and the chance of that negative pressure reversing chimney draft.

I am hoping to report a less drafty house and better heat distribution once it is connected.

@3fordasho please let me know. I'm changing filters every 4 or 5 days and it is starting to add up cost wise and dust.

STIHLY DAN · Feb 15, 2016

Do you have a dirt basement?

crzybowhntr · Feb 16, 2016

STIHLY DAN said:
Do you have a dirt basement?

@STIHLY DAN - My basement is concrete. I have 4 kids who ride bikes, skateboards, skates, etc. on it and since my contractor didn't know how to finish a floor, my floor gets dusty.

blades · Feb 16, 2016

the old cut corners and run deal

crzybowhntr · Feb 17, 2016

Off of the plenum of my wood/coal furnace If I have a service duct feeding into my NG duct work that is 14*8 for the first 8 feet and then transitioned up to 16*8 for the next 8 feet, what size return should I use? Can I use a 12*8 coming off of my main cold air return that is 16 or 18*8 and not have issues such as whistling or reduced air flow?

3fordasho · Feb 18, 2016

crzybowhntr said:
Off of the plenum of my wood/coal furnace If I have a service duct feeding into my NG duct work that is 14*8 for the first 8 feet and then transitioned up to 16*8 for the next 8 feet, what size return should I use? Can I use a 12*8 coming off of my main cold air return that is 16 or 18*8 and not have issues such as whistling or reduced air flow?

Not sure on the duct sizing but I can tell you what my set up has- The Tundra uses 2 - 8" round on the hot air side so ~100 sq in of area. For the cold air return my existing had a convenient 8x12" to connect to so I used that and a transition to 12" round to drop down to the filter box on the Tundra. Both those sizes are close to 100 sq in area.

I finished connections last night and my observations so far: blower / fan noise is less noticeable. Even though I dropped a fan speed - output at the registers is the same or better. I need to install a backdraft damper to prevent the hot air from short circuiting through the propane furnace, before the filter there was enough to prevent hot air from back feeding through the propane furnace into the cold air returns. Now that the tundra is pulling from the cold air returns this damper is more necessary. For now I partially blocked off the filter in the propane furnace. Less or no drafts in the stairways leading down to the furnace room. Overall I'm pleased with the results.

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Tying coal/wood furnace cold air return into NG cold air return

crzybowhntr

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blades

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