Pellet furnace ducting question

[lsirois]

I recently purchased a used St Croix SCF-050. I want to install it my basement and was planning on running a few separate ducts to the 1st floor. I am trying to get a few quotes for venting this thing and one of the guys suggested that I just run a duct into the return air of the existing furnace and use the existing furnace in "fan only" mode to to circulate the warm air. Any reasons why this would not work?

 

[hossthehermit]

Your manual will show the recommended setup, with backflow damper ..........

 

[Ejectr]

These furnaces can be installed in parallel to your existing furnace, but you are going to have to put a back flow damper in the current furnace supply air feed duct and another one in the air duct coming out of the pellet furnace. The hot air from whatever furnace is running can't be blowing into the one that isn't., so you need one at both feeds. You are also going to have to connect the pellet furnace to the return air source of the existing duct work.

It's not as simple as cutting a few extra supply vents in the floor and connecting the pellet furnace to it.

 

[ivanhoe]

I recently purchased a used St Croix SCF-050. I want to install it my basement and was planning on running a few separate ducts to the 1st floor. I am trying to get a few quotes for venting this thing and one of the guys suggested that I just run a duct into the return air of the existing furnace and use the existing furnace in "fan only" mode to to circulate the warm air. Any reasons why this would not work?

Sounds to me he is saying to run the existing furnace fan to circulate the air via the cold air tap in with the St-Croix. Doesn't sound right to me to do so and the fan would be blowing to hard to move the warm air around. It would have to be installed with the backdraft dampers like others have mentioned and go according to the stove manual suggest. The installer is probably trying to cut corners on the installation so beware!

 

[Ejectr]

It's not right and shouldn't be kluged together like that. If you're going to spend money to do it, then spend it to do it right.

 

[Markus38]

Could you put the furnaces in series and use one blower to circulate the air through both furnaces? And then could you use the old furnace as a backup?

 

[smwilliamson]

I have a customer with that kind of set up and it works well for him. The way his basement was set up he didn't have room to install next to the existing furnace so he tied in to the cold air return and installed a cut off damper at the far end of the run so the old furnace isn't getting hit with the heated air from the pellet furnace. He's actually got the same unit as you. Your pellet furnace has a blower so you don't have to use the blower from your old unit. The down side is you won't get het upstairs via ducts but if you can heat the first floor... The heat will rise. There is nothing leagally wrong with what you are proposing and no one in NH is going to shut you down for it, you couldn't sell the house with that set up and you have going to have to reroute the ducting twice a year as the season change if the old system handles your AC. good luck!

 

[smwilliamson]

I had another customer with this too...but he did it all wrong...he assumed the cold air return meant outside air and actually ducted the unit to the outside on the return side....no no my man, that is not very efficient at all. The upside....after I showed him his error he went through far less pellets!

 

[lsirois]

Thanks for the input so far! Quick question though....why can't warm air from the pellet furnace run through the existing furnace? I ran the pellet furnace outside and the heated air is really not that hot....just wondering why running that air through the LP furnace (and yes, it does handle the AC in the Summer) would cause a problem. Also, for educational purposes, assuming that I did hook up the pellet's furnace warm air discharge to the cold air return of the LP furnace, why would I need a damper on the pellet furnace duct? Even in the Summer when AC is on, cold air should never flow back into the furnace correct? I realize that air could get pulled through it into the LP furnace's cold air return, but why is that a problem? That air would never combine with the pellet furnace's burn chamber and I already have cold air return vents in the basement...so basement air does get pulled into the system regardless.

The existing LP furnace is large...house is large (>3000sqft)...the pellet furnace will not heat the entire house. The LP furnace is in the center of the house and I cannot get the pellet furnace anywhere near it because I would be unable to vent it properly (25' + horizontal run to the nearest possible wall).

My hope is to heat the mostly finished basement with the pellet furnace and have some of that heat make its way upstairs. I have a wood stove upstairs that does most of the heating for the 1st and 2nd floor. The LP furnace usually only comes on during very cold days and early morning. I'd like for it to never turn on...except when we're away. I thought about just keeping the pellet furnace separate. The installer happened to notice a cold air return duct near the furnace and his idea of blowing into the cold air return seemed like a more effective way of accomplishing what I want. The installer won't hook this up to any ductwork by the way...he was just commenting on . I will have to either do this myself or find someone to do it.