HVAC Automation Help

[pete]

What, if any, are the opinions here of having a centrally located return vent instead of having individual returns in each room?

individual returns are better, but more expensive . .

single return is acceptable, just make sure the doors are undercut to allow for return air flow . .

I've done design/installs where there are two central return grills, one in the ceiling (for A/C) and one low on a wall(for heat) . . I used filter grills and used a peice of foamboard to block one, with a filter in the other . . homeowner just changes the foam and filter depending on the seasons . .

 

[pete]

It seems to me that the problem is that the damper is close to the door and thus the warm air follows a path straight to the door leaving the room with less heating (e.g. thermal short circuit). It seems like I could redo the ducting to go to the far side of the room (away from the door) and have the warm air 'flow' through the room on the way to the hall way. Alternatively, or in addition to, I could increase the diameter of the ducting (I have good access).

Any thoughts?

your dead on w/ the short circuit . . you should modify the duct as you suggest by moving the register to the far side of the room . . maybe even add an additional register in the corner room (one on each exterior wall) . .

usually I like to place the registers in a heating system under a window, as this is were the heat loss is greatest, and there's less of a chance they will get covered with furniture . .

 

[politics123]

What, if any, are the opinions here of having a centrally located return vent instead of having individual returns in each room?

individual returns are better, but more expensive . .

single return is acceptable, just make sure the doors are undercut to allow for return air flow . .

I've done design/installs where there are two central return grills, one in the ceiling (for A/C) and one low on a wall(for heat) . . I used filter grills and used a peice of foamboard to block one, with a filter in the other . . homeowner just changes the foam and filter depending on the seasons . .

Well, there are several options:

(1) undercut doors (most people don't like those, because to be truely effective, you need to undercut them by 2". This causes issues with light and sound.
(2) transfer grills (most people don't like these, because you often have issues here because of light and sound
(3) offset transfer grills (eg: a transfer grill on one side of the wall that is low on the wall, connected to a transfer grill that is offset (higher) on the same wall, connected with a duct. This solves light issues, but only marginally helps with sound issues.
(4) isntall return ducts. This is the correct solutiom, but not practical as a retrofit.

I'm doing #2 and #3.

The best way to size ducts is to get the HVAC duct-sizing software. These tell you the correct size duct and air-flow to each room. Then, use a airflow meter to determine the air-flow, and adjust the flow restrictors to get the correct flow.

If its a new house, you might be able to complain about the imbalances, and get the builder to hire a contractor to solve it. Else, if your utility might provide you a free home enegy audit (and they might bring the tools for you to orrow/use)

Balancing supply without balancing return is not going to get you very far.
PS - Some of these things can be rented, too

 

[Ranger Digital]

Its very uncommon to have a return in EACH room. At least in my experience. A good designed system CAN be layed out whereby there is NOT one in each room, thus keeping cost down yet having a well designed system. Of course, if money is not an issue,,,,,,,