Does anyone know an easy way to tell if a heat/cooling duct has collapsed?

Question

It ain't THAT easy! Did I forget to mention the ductwork is in the floor of my family room which is built on a concrete slab? The REALLY odd part is outside my garage (which is in front of the family room on the same concrete slab) when the air conditioning is on, cold air blows out from the space between the front of the garage slab and the driveway -- a good 20 feet from where the duct is!!!

Anyone know a place where I can rent a duct cam? I'm too cheap to pay a HVAC co something I already know.

And if that is the case... do I fix the duct or just fill it in with concrete and run another duct run from the basement through the ceiling?

Answer 1

Well, the most certain method is to get someone with a camera in there.... I would check with your local plumbing company, or air conditioning service... both types of companies may have the little cameras they can run into a small space by remote. The plumbers use it to check drain lines, etc.

If you can feel it blowing out from the space tho... I'd say you don't have one that has collapsed... its more likely you have one that has become disconnected, or opened up. You might be able to take the vent cover off in the home, and shine a light down the vent, and use a small mirror to take a peek at the run, from that end. If it is close to there, you might even be able to repair it. I suspect tho, that if it has come loose, it probably came loose at the trunk end, since you can feel it blowing 20 ft from the duct.

If you were not feeling any air at all outside the home, I would have suggested closing all the vents, and checking for airflow at the one you think might be collapsed.

You may want to check the rest of the vents... see if they are blowing as strongly as they should be. If they are not... you may have lost a piece of sheetmetal near where your air goes into your ductwork.

I went by to visit an elderly lady one day, and she was sitting in her home, and it was miserably hot. I asked her why didnt she have her air conditioner on? Seems she had had some trouble with it, and called a local service company....They told her she needed a new condenser coil outside. And... they rigged the furnace so she couldnt even turn on the fan.... Nice huh? I told her I would look at it.... I found where they had failed to engage the safety switch on the furnace with the cover plate, rendering it inoperable and popped it back in correctly. Flipped the thermostat switch to fan, and it kicked right off... That in itself was a big help.
She commented she didnt seem to have the air flow in her living room like she used to have...and I checked the vents... and there was just a bare minimum of air flow. Her furnace was a downdraft, by the way. So, I go around the back of the home, and open up the crawl space... and I'm hit with this blast of air.... much like you are describing here....

I crawled under, and discovered that where her furnace was placed, and it blew straight down.... the duct work had corroded out right there.... literally, the bottom fell out of it...

All it took to fix it was some sheetmetal, screws, and metal tape...and about a half hour. I asked her if the service company had looked under the home, and she said yes, but they didnt see anything wrong.... Obviously, someone was about to take her to the cleaners....and they had rigged her furnace so she couldnt even run just the fan....I thought that was a pretty rotten thing to do, and I went and told them so.

If you have a downdraft furnace, you may be able to get a look at the vent underneath, by going thru the furnace itself, or moving it out of the way, while you work on the vent. If you can access the ductwork from your basement... then I would pop that open there....take a section down, open a corner, etc. I would start out looking with a mirror and flashlight first.... then, If I couldnt determine anything, I'd call some service companies to find one that used one of those remote cameras.

As far as pouring cement.. i wouldnt go that far.... Id stuff some batten insulation in there instead, and maybe use some foam sealant, to redirect the air flow... but you need to see where it has popped loose at first.

Good Luck!

Answer 2

Underground ductwork often corrodes away and allows soil and/or water to enter or the soil will cave in and block the duct. Repairs are always possible but are usually cost-prohibitive. Stuff some fiberglass in it and see if you can run another duct. There really ought to be some major changes made in the heating building codes regarding residential underground ductwork. Current installation practices really suck. Good luck.