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Duct Opening Under Cabinet???

Posted by edlakin (My Page) on
Thu, May 1, 08 at 8:15


I have a question for all you HVAC folks. We're having our kitchen re-done and part of the new cabinetry is covering the spot on the floor where there was a heat/ac register opening.

The way the contractor dealt with this was to open up the side of the cabinet that's covering the vent, and then the side of another cabinet next to it which has a front valence-type opening rather than a solid toe kick.

I hope I'm explaining myself good enough. Sorry if this is hard to visualize.

So the air can certainly move from the duct opening out into the room, but to do so, it first has to occupy the space under two base cabinets, which seems wasteful to me. I'm concerned that the air flow is going to be weak, causing the heat/ac to kind of slowly waft up into the room rather than entering the room as it would through a small duct opening.

Also, the valence is just wide open as is the space under the cabinet, so all sorts of dust, dog hair and other debris could easily get into the duct. I'm concerned that the area will attract tons of crap and that accessing the duct to clean it will be very difficult.

Any thoughts?

Follow-Up Postings:

RE: Duct Opening Under Cabinet???


Typically, the toe kick is sealed off with a 1"x3", a rectangular hole cut in the toe kick and a toe kick grille is placed over the hole (Not necessarily in that order), a good contractor will provide an extension duct between the register opening located near the wall and the new toe kick grille. Some contractors leave out the extension duct, not a good idea, but works ok if the space is sealed. In your case if the cabinets are in already, you would have to remove a cabinet or cut an access panel just above the existing floor register, to install the extension duct. This would be a good idea, you can mount a grille directly onto the extension duct if there is not a toe kick to mount it to. This will direct the air directly into the room. If your toe kick is not sealed, yes it will be a cleaning nightmare. Also, did your contractor install manual balancing dampers for each branch?

Take Care,

Dan Martyn

RE: Duct Opening Under Cabinet???

hi dan, and thanks for your response.

upon further investigation, i believe my contractor isn't finished yet. the duct hole is still accessible even though the cabinets are in place, due to the valence. so i think his plan is to snake a duct extender like the one you describe into place and, hopefully, seal off the open area by putting a toe kick grille slightly behind the valence.

what are "manual balancing dampers"? are those the louver-type things that you move with that little wheel on the grille?

RE: Duct Opening Under Cabinet???

Manual balancing dampers are placed in the branch ductwork (Typically round) along the main supply duct. Each branch duct run should have a way to balance the airflow coming out of the register. A register, by defination, has a damper, but if you use this damper as a primary way to balance the system, the registers will be noisey. You really need to have a primary damper in the ductwork located away from the register to eliminate noise transfer. Dampers can be bought at the big box stores and easily installed after the fact, but your contractor should provide these when installing a new ductwork system. If you want to do this yourself, get the dampers. One side of the damper will have a spring loaded pin which you retract to install the damper into the duct. First you need to locate the damper on the branch near the main. disassemble the duct section so you have access. The damper holes need to be directly opposite each other for the damper to work, I took a sheet of paper that would wrap around the duct, taped it together, slide it off and folded the cylinder flat, then fold again the opposite way. Where the folds intersect is where you make holes in the paper tube, this is a template that wil give you holes which are directly opposite each other. slide the template on the duct, mark through the holes where you will drill the holes for the damper. Remove the wing nut from the damper, remove the handle, retract the pin, slide damper into the ductwork, place the handle back on the damper pin with the handle parallel with the damper, place the wing nut back on the damper. The handle has a pointed end as an indicator, when the handle is parallel to the duct, the duct is open, when the handle is perpendicular to the duct, the duct is closed. You can mark the ductwork "open" and "closed" with the indicator pointing correctly. Kind of long winded, hope you get the idea.

Hope That helps,

Dan Martyn

RE: Duct Opening Under Cabinet???

oh, gotcha. thanks, but this is not a new installation. the duct run already existed (and it wasn't ever noticeably noisy), we're just relocating the vent opening in the room a foot or two to accommodate new cabinetry where the vent used to be.

but thanks for the info, nonetheless!

RE: Duct Opening Under Cabinet???

Every HVAC Contractor ought to have a Designer Dan, Dan Martyn on their team, he knows his trade.

Airflow problems rob efficiency of operation & can be very costly!
- udarrell

Here is a link that might be useful: The Air Side of Air Conditioning

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