Is the duct work located in the attic? If it is, go into the attic and locate the duct feeding the problem register. It most likely has a lot of leakage. The fix is to replace and/or seal the duct work and not add dampers. You may still need to add a damper, but address the duct problem first.

I don't think it's leakage otherwise adjusting the register in the living room wouldn't help increase the flow to that bedroom.

Also, I have had the ducting looked at when I first noticed this issue years ago and no leak was found.

you write :I read that sometimes there are dampers inside the duct work that can be
adjusted to redirect and balance airflow to the registers and solve
this problem without adding the noise you get when adjusting at the
registers.

fee around each duct at the supply plenum.

if they have dampers you will feel the adjustment.

often the damper adjustments are under the outer

liner & insulation of the duct.

you have to know what you are feeling for unless

the dampers are exposed.

some installers will always install dampers,

others don't. the standard is that there is no

standard.

each duct system is different.

take a look, post some pics.

best I can suggest at this point.

best of luck

I'm having annual a/c tuneup service done next week and I'll ask the guy to go up in the attic to look at it while he's here. Normally, they only go in the attic when the furnace is being serviced.

I know all the ducts are wrapped in thick insulation, so it will be hard to tell and maybe there are no dampers since it is a tract home and no mention of dampers where ever made when I got the maintenance booklet from the builder back when it was new.

Just in case there are no dampers, what would a reasonable price range to have a damper or two installed to help redirect air from the other rooms into the problem room?

I need to know a ballpark price range so I know whether I should just have them do it for their quoted price or pass and get more quotes.

jaxo,you are going about his all wrong. Forget about dampers and telling incompitent techs how to solve your problem. It's better to increase duct size to subject room than restricting flow to other rooms. It's unbelievable you have been putting up with this eventhough you have spent hundereds on annual check ups. You should have hired a reliable hvac company years ago to fix this problem,it's not too late. If there are no reliable contractors in your area pay rater's air fare and hire him to check out the system. The most common reason for the problem you are having is crushed duct feeding subject room. Cable tv installers are famous for mashing ducts flat while crawling over them.

I believe energy_rater is a her, not a him.

I don't know how a bigger duct is going to help since the register will still be the same size. I don't want to make bigger repair job out of the fix than it takes to improve the issue.

The room is the farthest from from the a/c and after air goes out of the other 6 registers, there isn't as much air pressure left for the 7th register.

The two rooms closest to the side of the house next to the outdoor a/c unit have way more air velocity than the room that's on the opposite side of the house.

I'm sure there is no crushed duct. It was looked at and nothing wrong was found, but I'm still not satisfied with how weak the air volume is in the last room. Also, if the duct was crushed, disconnected or leaking, partially closing the living room register wouldn't have made much difference with the air volume in that room, but it did.

"but the house is so small that "furthest away" is still only maybe 15 feet away from the rooms that are getting too much air flow."

This statement leads me to believe you have a duct problem. The air will flow through the path of least resistance. An additional 15 feet should not be causing poor air flow to the last register. By closing the other registers, the increased volume and velocity of the air is compensating for the poor duct work. Adding a damper may be addressing the symptom and not the problem. It may turn out you still need to add a damper to balance the air flow. But it should not be the first thing done in my opinion.

The duct connected to the last register needs to be inspected carefully for kinks and leakage. It is unlikely the last register in a run would have a damper in front of it, but then again any mistake is possible when it comes to HVAC installation. If the duct is too small then it should be increased. You should not need to change the register size unless it is undersized.

No one here is going to be able to estimate how much labor and materials your HVAC company will charge for addressing a duct issue. Prices vary greatly across the country. Go into the attic with him and have him show you what needs to be done. Get an estimate and post it here if you think it does not seem reasonable.

It's better to increase duct size to subject room than restricting flow to other rooms.

I agree

It's unbelievable you have been putting up with this eventhough you have spent hundereds on annual check ups. You should have hired a reliable hvac company years ago to fix this problem,it's not too late. If there are no reliable contractors in your area pay rater's air fare and hire him to check out the system.

Or DIY, ductwork isn't that hard to learn. Otherwise you could hire a handyman in the area to do it.

I don't know how a bigger duct is going to help since the register will still be the same size. I don't want to make bigger repair job out of the fix than it takes to improve the issue.

New boot and register. Not hard.

The room is the farthest from from the a/c and after air goes out of the other 6 registers, there isn't as much air pressure left for the 7th register.

If the larger duct does not address the issue, you may need a duct booster fan in that line. I would not recommend hindering the airflow to the other registers with any possible dampers, as this can ice up your evap coil due to not enough airflow. Duct booster fans in general should be a last option as they can be noisy, you need to run power to it and possibly a ductstat there also, and at some point the fan will need to be replaced as any motor dies or the bearings go bad eventually.

I still don't understand why that room would need a larger duct than any other room. It is the smaller of 2 bedrooms and much smaller than the living/dining area and master bedroom that both have plenty of air. However, those two rooms are along the same exterior wall where the a/c unit is located and the problem room is on the opposite side of the house.

The register in the problem room is no smaller than the registers in the other rooms that have no problems.

So, it looks like most of the air flow just goes out of the registers that are closest to the a/c unit.

Couldn't the issue be caused by too much air going out of the closest to a/c unit registers leaving very little left over for the last room? If so, wouldn't either smaller ducts to the other rooms or a damper to redirect some of the air to the problem bedroom solve this?

So, it looks like most of the air flow just goes out of the registers that are closest to the a/c unit.

For starters you need to know how long the duct runs are. If those two registers with good airflow are closer to the air handler it makes sense why they get more airflow, the air travels in the path of least resistance. It also makes sense why that duct run farther away is weak, it is a long run and less air is going through that. The larger duct will allow more airflow due to less resistance. More air will enter the larger duct and it will have more push to it allowing it to travel a greater distance.

Couldn't the issue be caused by too much air going out of the closest to a/c unit registers leaving very little left over for the last room? If so, wouldn't either smaller ducts to the other rooms or a damper to
redirect some of the air to the problem bedroom solve this?

Yes and no. If you damper the high airflow registers then the overall airflow available is reduced which may or may not affect your AC operation. Your AC needs a minimum amount of airflow to operate properly.

In any case you need to inspect your ductwork as originally advised. Any further hypotheticals are a waste of your and our time. You need to know if the duct is messed up anywhere or if it is disconnected. Then you can go from there.

placement of the duct on the supply plenum also affects

air flow. plenums with end cap tap offs reduce air flow.

there are dozens of things that can be causing the problem.

if you increase the supply box, (supply grill) and duct to

this room you may solve the problem. but the problem could

be many things. post some pics of the duct, attic & supply plenum.

what size house, what size system and location of said house.

btw, techs aren't interested in ductwork. not their focus.

if you don't want to find duct loss, you won't.

if you want to know how much leakage & where...

you get ductwork tested.

we need more info.

best of luck

The hvac guy came and found no leaking or squashed ducts and there are no dampers.

The duct to the problem room is a 5 inch and he said increasing to a 6 inch duct should help. He said the same register can be used.

The duct run is only 7 feet and thinks it would be about $150 installed, but would have to schedule the work for another day,

He also bent the panes on the register to point downward into the room instead of blowing air close to the ceiling, but that is only a minor help since that doesn't increase the volume of air,

I'll see how much it improves after the duct is swapped out next week,

"The duct to the problem room is a 5 inch and he said increasing to a 6 inch duct should help"

Had anyone told you that previously? Did you tell him you don't understand,therefore he must be wrong?

rubbing salt is best for preparing meat

Good because nothing else seem's to work for meatheads.

The new, larger duct was installed, but it didn't cure the problem, It "helped" because the air flow was increased, but the room is still the slowest room in the house cool down (despite being the smallest room) meaning we have to be too cold in the other rooms in order for the a/c to run long enough to get that room cooled to a comfortable temperature.

It may still need a damper to redirect more air that way or else a larger register to increase the airflow enough for that room to cool as quickly as the living room and the bedroom on the other side of the house cools down..

Yes, as long as you have enough CFM for your coil to not freeze up, you can adjust a damper to the other registers to help in balancing.

An anemometer is what pros use to measure airflow and attempt to balance the system. It may help your cause. You can just turn off heat and cool then set the fan to on at the thermostat while you are attempting to balance.

http://www.lightinthebox.com/professional-digital-anemometer-split-type-air-flow-meter-elecall-em8901_p2239209.html?pos=ultimately_buy_3&prm=1.3.5.0