Help - no hot air coming out of some registers

[skohl]

Hi, any advice would be appreciated. We have a gas furnace about 15 years old in a small attic above our 2nd floor. Our intake is on the second floor ceiling. Hot air is coming out very strong from the upstairs registers and also strong out of 1 of the 4 downstairs registers. The 3 registers that are not blowing any hot air are very close together (downstairs area is only about 700 square feet.)

Could it be as simple as dirty or blocked air ducts? If it was the filter I would think it would affect all registers. I would love advice on what it might be before I have a HVAC service come out.
thanks!

[energy_rater_La]

maybe ducts came lose. can you take a look in the attic @ the ductwork/plenum?

best of luck

[skohl]

It seems like a tangled mess of ducts in the attic. I'll crawl up there and try to take a look.

[skohl]

Thanks, You were right. I got up there and one of the ducts had completely come apart - totally obvious. So I've been heating the attic. I've jury rigged it for now with duct tape and will get my husband to do a more thorough job when he returns. Thanks again!

[lentz]

Be careful. Don't fall through the ceiling. You might call your service person and have him check all the duct work.

[wahoo]

And make sure your filter is clean. It will affect ALL of the outlets air flow. Sounds like you found the larger part of problem!! Good job!

[energy_rater_La]

you're welcome.

now the question is ...why did it come apart?
so...have hvac company go back to each duct and mastic
seal them. at the plenum where they take off, and to seal the
area you found. any tri boxes..where one duct enters & two
exit should also be mastic sealed.
either yourself or DH should go into attic to make sure they
are doing the work with mastic.
the added benefit over just keeping them attached...is that it
stops duct leakage at the masticed area.
this is how it should have been done originally.

unlike duct tape, mastic is a long lasting seal.
did they use lock ties? I use them sometimes, but usually
just to hold the duct in place until the mastic dries.

and keep those filters clean.
good for you that you got up there & fixed it temporarily.
most wouln't.

best of luck.