My upstairs bedroom has very low flow out of the one ceiling vent. To make matters worse, it's on the south side and gets very warm in the summer despite a low t-stat setting. I wondered about the addition of an inline booster fan in that ceiling duct that would kick on when the air handler starts? Anyone hear about this being done?

Have you ever played with adjusting the airflow with the vents.

I at times have had systems that needed some rooms that stay cooler chocked back to force more air to the hotter room/s. Have found that the reverse needs to be done when running the heat.

Knowing nothing about your system is your A-Coil restricted from dirt and or hair causing air flow loss. Most blower motors are multi-speed. Is yours set at the right speed or could it be adjusted for better air flow? Of course a service tech would be needed to evaluate your system.

Thanks for your thoughts, Mustang. I have messed with the other room vents a bit, despite most pros saying not to do that. Maybe I'll mess with those a bit more.

As for restrictions, I'm pretty anal about changing my filter. My system is a one speed type. But speaking of restrictions, there is a very good chance the ducts need cleaning. How much difference that would make I don't know.

As the OP is indicating that there's inadequate flow from just one ceiling vent, it's almost certainly not an issue withe the Evaporator Coil being restricted, unless he's got decreased flow everywhere. It's much more likely that the duct feeding that particular vent is restricted in some way. Often times, ceiling vents (presumably in an attic space) are fed using flex (flexible duct...think dryer vent but bigger and insulated). Depending on how it's run it can easily be kinked/restricted and result in low flow. The OP should check that first. It's also possible that the design (and installation!) of the ductwork simply results in marginal flow to that particular vent, which 'could' require throttling other vents to increase the flow. An important question here is whether this particular vent has always had low flow, or has something changed to cause the issue, which would be valuable info to determine the likely cause and/or solution.

Also, 'most' blowers are single speed, NOT multi-speed. Unless it's a newer system and a multi-speed blower/air handler was purchased, much more likely to be a single speed blower.

nh, good points. This particular vent has had low flow since I've owned the place. I like your suspicion of a possible kinked flexible ducting. Something I'll have to check on.

I'll second the recommendation to check the ducts. You likely can get a combination duct inspection and cleaning.

In my last house, the farthest room has low airflow as well. Come to find out that there was a tear in the flexible ducting in the attic leading to that room, so a good portion of the airflow to that room was venting into the attic space instead.

In my current house, the furthest room has slightly lower airflow than the others. This is just due to its distance from the main unit. I've found that on the hottest days, using a fan to blow from the main room down the hallway into that farthest room helps even out its temperature with the rest of the house. You might try that to help treat the symptom in the meantime, while tracking down the root cause.

Rogue, yes, I'll plan on getting a cleaning/inspection done.

I do use a fan in the problem room to circulate the air and in fact, place it under the vent hoping to catch as much cool air as I can. Not much help. But I do like your idea of placing the fan in cooler hallway which would blow cooler air into the room.

Thanks all for the feedback.

Does the affected room have return air vent?

quote:

Originally posted by gjgalligan:
Does the affected room have return air vent?

A good question. No, however the door always stays open and there is a return vent just outside the door in the hallway.

Allow me to read between the lines...one room is not at the temperature and/or humidity desired.

That room does not have a return vent.

My situation exactly...until the HVAC was replaced. In that room, I had a small return vent installed.

Now the room maintains the temperature setpoint.

A booster fan seems complicated. How about installing a bigger supply duct and vent plus a return?

Flexible duct is notorious for improper installation when using 1-2" strapping cloth as hangers.

Even when done correctly, overtime the duct sags and can be nearly cutoff of airflow.

Check to see if they used saddles to support the duct or other means to prevent collapse.

Don't forget to check the return air temperature and the supply air temperature. Easy to do with a handheld beam of light temperature gage. If the delta T is not sufficient, you have a different problem.

^^^The OP's problem is w/ one vent, in One Room Only!