During this past Summer I noticed that the master bedroom, and the master closet and bathroom that make up the ‘suite’ seemed to dminate the AC in terms of cooling. Well, the weather has gotten cooler and the furnace has been on more than once so far and I’ve noticed the same thing regarding the apparent dominance of the master suite compared to the rest of the floor.
The master suite occupies about 350-SqFt of the upstairs 1100-SqFt total. Yet, the HVAC return for the suite is minimal–same size as found in the other three bedrooms. There is no centralized HVAC return for this floor, meaning all return airflow comes from four bedroom returns.
What I am curious about this morning is if the master suite has three HVAC feeds and one return while the other bedrooms have a single feed and return (all measuring the same sized ducts (removed grills to measure), wouldn’t this create a necessary airflow at the to push air out of the master bedroom toward the other returns? The master bedroom walk-in closet and bathroom branch off of the master bedroom itself.
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Are the supply ducts flex ducts or sheet metal?
Flex. No sane cookie-cutter builder in my area is going to waste time fabricating sheet-metal ducts. lol
Right - we only use flex ducts here too.
First try cutting back the supply air by adjusting the supply outlet registers if they are adjustable.
Normally with flex ducts, they come off a plenum (metal box) of some sort. There may well be manually adjustable dampers in each duct, right where they connect to the plenum. They will be a bit hard to find because they are probably covered up by the outer cover of the flex duct, however you can feel them as a bump under the plastic flex outer cover. There will be a small handle maybe 1.5" long that is used to turn the damper. The handle is parelel to the damper. The damper itself is simply a metal disk used to restrict airflow into the duct. Try cutting back the supply air going to the closet and bathroom.
The source registers are adjustable in the sense of being able to open/close them. The flex ducts feed from a fiberglass-board formed plenum at the AC/furnace. While the angry octopus in the attic intimidates all (in walking around that attic), I do not see any signs of dampers, unless they are inside the plenum as you suggest.
I do remember removing the grill from the return register sometime late Spring or early Summer. The grill had started to vibrate, audibly, due to the amount of airflow into that return. At the time, I had not thought about adjusting the source registers to see if it would quiet things down.
BTW, one concern I have is that a source register exists in the closet and the bathroom, but they themselves do not have returns. For the bathroom this isn't a major concern since that door is usually open, but the closet door is usually closed (wife's clothes and our cats don't mix). I never noticed an inability to keep cool the closet, but I have noticed a complete inability to keep the closet warm.
I thought you were saying that there was too much heating/cooling going to the master suite.
Re the closet door being shut, what is the size of undercut (space below the door)? It should be about 3/4" is the door is going to remain shut. Be aware that while doors are easy enough to cut off, most hollow core doors can only be cut off a max of about 1/2" since the solid piece in the bottom is probably 3/4" thick.
As far as the dampers, like I said, they are not the easiest things to find. here http://www.nailor.com/Submittals/Air_Control/1800/1800-3_B.pdf is a pic of roughly what they look like. In the illustration the right side of the cylinder would be inserted into the plenum. the left side receives the flex duct. The damper control is not inside the plenum.
In my area these dampers are always installed in new construction and their purpose is to balance air flow into the different rooms, although the install techs always just leave them fully open.
Edited 12/11/2005 9:08 am ET by Matt
I was concerned that the relative number of instances of installed returns for the given number of installed source registered is creating multiple problems. It wasn't until it got cold outside I realized that the airflow in the master bedroom closet was affording it to keep from getting cold in there unless we left the door open--allowing airflow out of the closet and toward some return elsewhere on the floor.
I then also wondered if the number of returns was much less than the number of source registers would be causing another problem. So, its actually two different things I suspected is going on.