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My furnace has two 550 CFM blowers. Off the top are two 8 inch round outlets for warm air back to the house. My cold air return is a 8 x 24 square duct. I'm realizing my cold air return is twice the volume of my warm air back into the living area.

I want to run more ducts to the living area. My plan is to cut two more 8 inch rounds into the top of the air jacket next to the existing ones. My question is, are two 550 CFM blowers adequate for only two 8 inch runs back to the house? Or could they handle 4 of them??

lightning...
I'm somewhat curious on how the two blowers are hooked up... but regardless... you should have no problem adding 2 more 8 inch warm air ducts.
... a good rule of thumb .... figure on about 160 cfm of air per 8" round duct
... the throat size of your cold air return in essence means very little to the capabilities of the blower(s).... 8 inch by 24 inch rectangular ductwork can accommodate roughly 1300 cfm or so...
... this is just a general guideline...
... but assuming the 8 inch duct work isn't excessively long or full of turns... then you should be fine.

Oh wow, thats good information!! Thank you!!

The blowers sit side by side at the bottom on the backside of the furnace

no problem glad to help... that is an interesting setup for blowers... being side by side... I can't help but wonder if they the negate each other a little bit... maybe they have separate individual inlets?

The blowers are individual units but pull air from the same cold air return. My furnace is the Clayton 1537. You could probably find a diagram online somewhere Thanks again for the help partner!

anytime my friend
.... I will be looking that up soon

I added another 8 inch heat run to the top of my furnace yesterday (its the one in the center of the pic). It helps feed my new living room that was formerly a two and a half car garage. Until then I only had one run with one diffuser. The new room would be warm on one side and a bit cooler on the other. The new heat run feeds two ceiling diffusers, for a total of three now. The only way for me to get heat there is down thru the ceiling. Hopefully with three diffusers the room will heat more evenly, feels better already....

Do you plan to wrap the heat ducts with foil backed insulation? That should increase the air temp coming out of the vents in your room.

CoaLen wrote:Do you plan to wrap the heat ducts with foil backed insulation? That should increase the air temp coming out of the vents in your room.

....excellent point!
...if your attic space is cold...def insulate the ducts... for 2 reasons
1...the obvious-...retains more heat to put into your room..
2 heat source (heat loss)in the attic space might contribute to an ice condition on the roof

...glad to know your efforts have made an improvement !!

Btw....regarding your picture...

....nice work...and does that thing have a Hemi in it !!??

...impressive

CoaLen wrote:Do you plan to wrap the heat ducts with foil backed insulation? That should increase the air temp coming out of the vents in your room.

Actually, I only started off the furnace a few feet with metal. The rest is all insulated flexible duct work. These two runs come up out of the basement and across the attic to the ceiling diffusers. The one on the left there is feeding the bathroom too

Rigar wrote:....nice work...and does that thing have a Hemi in it !!??

Thanks for the kind words ... Heres a better pic from the front side, the new 8 inch off shoot is on the right side. I plan to put another on the right (to feed the upstairs bedrooms directly) for a total of 4 off the top of the furnace
Also is a picture of the new room facing the TV.. Right above the TV is one of the diffusers thats being used. Then another is directly above me and the other is far to my right. The other two off to the left and right in the picture aren't being used.
And here is a picture of the diffuser over the bar on the opposite side of the room from the TV

WOW.... where do I start???
.... first of all... excellent job!
Secondly... I'm glad to see a ceiling fan... that's gotta help with diffusers in the ceiling..?... and have you been able to increase the cold air supply to the stove?

...thirdly...and most important....
WHEN IS THE PARTY...????!!"!

Rigar wrote:WOW.... where do I start???
.... first of all... excellent job!
Secondly... I'm glad to see a ceiling fan... that's gotta help with diffusers in the ceiling..?... and have you been able to increase the cold air supply to the stove?

Thanks again for the kind words The ceiling fan helps keep the air from layering.. meaning warm at head level and cooler at foot level. Based on what you said about my return duct (24x8 inch square), I'm hoping its enough to handle the 4 - 8 inch round heat runs.

Someone say party?? My 40th birthday party. Thats me in the back with the RUSH shirt on

... glad to hear that was your birthday party... I thought I missed the NEPA meet and greet!!

... yes I forgot about your cold air return trunk size...
... that is more than adequate!
... again nice job... stay warm