A few registers not putting out air

Old 01-12-16, 05:05 PM
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A few registers not putting out air

Hi all! I'm sorry if this is in the archives somewhere... I'm not sure I know the right terms to search under.

I'm trying to diagnose a cold bedroom. We've got a 1998 home that was retrofitted to a Carrier Infinifty 2 zone hybrid heat pump about 5 years ago. They used existing ducting, and installed electric dampers to control the zones.

I have 2 problems I'm trying to figure out:

1. The master bedroom on the main floor has 2 registers (the same problem applies to the master bath with 1 register). One of the registers puts out a ton of air when it is running, but the other is barely noticable. It is a huge difference in air volume. What I found when I inspected for the one that didn't have volume was a manual damper on the branch that was completely open, but the branch itself was at a pretty serious angle (45degrees) going against the flow of air. (as in, any air coming down the trunk would have to turn 135 degrees in order to run down the branch. The master bath had the same backwards angle. The one register that was working great in the bedroom had a 90 degree angle coming off of the trunk. All that said, I'm not sure if the angle coming off the trunk matters at all...

So, the best I can figure, either the angle is faulty, and the system will never work unless I install some kind of air redirector in the trunk to "help" that branch get some air, or that there is something in the branch that is blocking it. (never know if my 3 year old threw a doll in there!)

The challenge is that with the cold weather we had the last few days in TN, the main floor was 71 degrees as normal, but the master bedroom stayed a nice 64.

Problem #2 is upstairs. The Zone 2 thermostat is in the hallway upstairs and is regulating the temperature great (it is right at the top of the open stairs to downstairs). However, the bedrooms have their doors closed fairly often, and they tend to run around 77 degrees. It seems like the bedrooms are well insulated and holding onto the warm air they have, which only gets worse when the system kicks on. The hallway is the right temperature, but the bedrooms suffer.

The best solution I've been able to come up with is to move the thermostat into one of the bedrooms so that it has an accurate temperature read. The other option is to mess with the dampers (maybe install them!) to the bedrooms to regulate the air. I did that at the register last night, but went too far, and the room went from 77 degrees to 67 between 10pm and 2am.

Does anyone have any advice? I really appreciate it!
Old 01-13-16, 06:06 AM
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In a hot air heating system, most rooms have a heat source register near the floor and a air return register near the ceiling. The return register is connected to ducting that returns the room air to the heat source for reheating. I think this is what you are seeing. The return duct is the lower duct at the heat source.
As far as the problem upstairs, why not leave the bedroom doors open to see if that equalizes the temperature. It is easier than moving the t'stat to a bedroom.
Old 01-13-16, 06:13 AM
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You could take a little off the bottom of the bedroom doors upstairs to encourage air movement.

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