Our house was built in 1952. We had a Fredrick oil furnace. It was replaced with a Lennox Low Boy oil furnace and an air conditioning system. With the Fredrick we had airflow to the attic bedroom of our small (900 sq foot) cape cod style house. The AC contractor has cranked up the fan to high speed, installed an air scoop in the duct which goes to the attic, and put in a 12 inch by 6 inch air return in the hallway on the first floor. All with no success. The duct going to the attic is round stove pipe. There is no return air duct from the attic back to the basement air box. The stairs leading to the attic are not closed off with door so it is the air return. All ducts were professionally vacuumed out and no duct closures (ie.e. crushed ducts) were found.

The heating and cooling contractor says we need all new ducts (supply and return) or $600 to install a booster fan on the stove pipe leading to the attic.

Why can't we get airflow to the attic?

You need to install a return air near the top of the attic bedroom space. You have to pull the hot ceiling air out so it can be replaced by cooler air.

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Originally Posted by hvac1000

You need to install a return air near the top of the attic bedroom space. You have to pull the hot ceiling air out so it can be replaced by cooler air.

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This makes sense for summer but in winter wouldn't the open stairway to the attic with the return in the hallway act as a return to pull air from the attic space? In winter would it not pull the colder air out of the attice to make room for the hotter air coming up? The problem is that there is zero airflow coming out of the registers with the "new and improved" Lennox (piece of junk) heating system. If the Fredrick could move the air there is absolutely no excuse why the Lennox unit cannot do the same. Was the Fredirick just plain a better unit than the "new" Lennox model?

An air mover is an air mover, if they both are rated the same then it boils down to the installation, something has been changed in the process of replacement, I would look at the duct going to the attic room , something is wrong here.

Cold air falls,hot air rises. Naturally. This is why I said you need a direct return upstairs for A/C

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Originally Posted by hvac1000

Cold air falls,hot air rises. Naturally. This is why I said you need a direct return upstairs for A/C

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I understand the physics of airflow but in winter wouldn't the open stairway to the attic with the return in the hallway act as a return to pull air from the attic space? The colder air would fall in the attic as hot air moves in and the return in the hallway downstairs would suck the cold, falling air down the stairs.

I still think the blower on the "newer" Lennox is not as strong as the old Fredrich blower but I cannot get anyone to agree with me. Any old timers old there who used to service the Fredrich units?

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Originally Posted by afcinc

Our house was built in 1952. We had a Fredrick oil furnace. It was replaced with a Lennox Low Boy oil furnace and an air conditioning system. With the Fredrick we had airflow to the attic bedroom of our small (900 sq foot) cape cod style house. The AC contractor has cranked up the fan to high speed, installed an air scoop in the duct which goes to the attic, and put in a 12 inch by 6 inch air return in the hallway on the first floor. All with no success. The duct going to the attic is round stove pipe. There is no return air duct from the attic back to the basement air box. The stairs leading to the attic are not closed off with door so it is the air return. All ducts were professionally vacuumed out and no duct closures (ie.e. crushed ducts) were found.

The heating and cooling contractor says we need all new ducts (supply and return) or $600 to install a booster fan on the stove pipe leading to the attic.

Why can't we get airflow to the attic?

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Ask for separate zones and isolate the attic with a closed door.