Better Supply Registers

[wraujr]

In another post about zoning returns, BeenThere mentioned that better supply registers can provide better mixing and throw... I have the typical 2-story, one-system with weak airflow upstairs.

1st floor internal duct dampers closed half-way. 2nd floor duct have no internal dampers.

For cooling, have closed (almost all the way) 1st floor supply registers and 2and floor supply registers wide open. Still have 4-6* diff.

What brand/model are these "better" supply registers, I'm talking 6x10 in-floor (could be 4x10, I'll have to check)????

[beenthere]

Might try a hart&Cooley 210 floor register. They have a good throw.

[wraujr]

I was think for the upstairs to replaced with un-dampered as I always leave them wide open, heating or cooling season.... Is there a downside to no dampers on second floor??
Don't imagine I'll ever close off a room when kids finally leave, etc.

[beenthere]

Generally, any floor supply register will have a damper in it.

[Shophound]

Bottom line: if you don't have enough airflow to offset the heat gain to the warmest areas of the house, upstairs in your case, you won't eliminate the temperature gradient between floors. You can mitigate it with less restrictive supply registers with better throw patterns, but not eliminate it.

Two choices: reduce heat gain into the house or increase air flow. Zoning is in essence an increase in air flow, but does nothing to reduce heat gain. Reducing heat gain may get you to where your existing airflow is sufficient when before it was not.

[Texas-Tech]

I'm afraid your problem is one not easily fixed, usually requires some changes in your system, of some kind or another. Did you new to this house or has this been a continous thing?

[wraujr]

I "feel" that the temp diff has gotten worse since 2 seasons ago when the Trane XV95 was installed. Runs AC mostly in 1st stage, rarely reaching 2nd stage. New system is quieter, so old system was running fixed 1200 CFM with a PSC blower and maybe with longer run-times as it was 16 years old.

Might have to try setting Trane T-stat to "Circ" to have fan come on more often to circ air, but hopefully not raise humidity...

[Shophound]

I "feel" that the temp diff has gotten worse since 2 seasons ago when the Trane XV95 was installed. Runs AC mostly in 1st stage, rarely reaching 2nd stage. New system is quieter, so old system was running fixed 1200 CFM with a PSC blower and maybe with longer run-times as it was 16 years old.

Might have to try setting Trane T-stat to "Circ" to have fan come on more often to circ air, but hopefully not raise humidity...

I'm taking it the thermostat is downstairs?

If this is so, it's no wonder your two stage system runs on the first stage most of the time. When your blower is at reduced speed, it isn't delivering enough air to the upstairs portions of the house in order to offset the heat gain to that area.

If you were to move the thermostat upstairs, the system might run on high speed more often, but possibly freeze the downstairs areas. If your tech could force the system where the thermostat is now (downstairs) to run longer in the second stage, you might get the same result...cold downstairs, barely adequate upstairs.

[REP]

I agree with Shophound but I have a feeling that you might need more return on the second floor.
If thats not the problem I might suggest cieling fans upstairs.If you go that route then make sure you get energy star fans.Most of the big box stores sell them but they are sometimes covered by the non energy star fans in piles.They will run at half the electric standard fans use.

[wraujr]

Open foyer/stairway to second floor.
1st floor return in this foyer, 6' up on wall.
T-stat has remote temp sensor mounted next to 1st floor return.
Ceiling fans upstairs in each room and they definitely help.
2nd floor return on ceiling, in hallway, just off the foyer.
All doors are under-cut and are left open to help air flow.
1st floor return definitely pulls more air as it has about 20' run to filter/air handler.

2nd floor return shares last 15' of return but is probably another 25' of run.
So when furnace pulls return, 1st floor is 20', 2nd floor is 40-45'. Guess which one pulls the most air???

Some local contractors suggested to neighbors to put magnetic sheet over half of 1st floor return to force more 2nd floor returns. Starving blower makes me nervous. If I did this, would ECM motor compensate (albeit at an energy cost) and keep constant CFM across coil???

R-38 blown-in in attic, but obviously more heat load upstairs. About only choice in attic is to remove fiberglass, foam attic ceiling for air infiltr. and then reinstall fiberglass. That would help infil.

I appreciate all comments, just thought a discussion might be nice. All problems could be solved by starting from brute-force, start-from-scratch (i.e. zoning, two-systems), but there is more fun in "trying" to solve/optimize a problem thru finesse..If possible.

[udarrell]

Bottom line: if you don't have enough airflow to offset the heat gain to the warmest areas of the house, upstairs in your case, you won't eliminate the temperature gradient between floors. You can mitigate it with less restrictive supply registers with better throw patterns, but not eliminate it.

Two choices: reduce heat gain into the house or increase air flow. Zoning is in essence an increase in air flow, but does nothing to reduce heat gain. Reducing heat gain may get you to where your existing airflow is sufficient when before it was not.

Best solution - by shophound
On the second floor, - Reduce all Sources of heat-gain as much as possible.

Yes, also try moving the room stat to the 2nd floor.

[Shophound]

Some local contractors suggested to neighbors to put magnetic sheet over half of 1st floor return to force more 2nd floor returns. Starving blower makes me nervous. If I did this, would ECM motor compensate (albeit at an energy cost) and keep constant CFM across coil???

Not a good idea. Any contractor saying such things is revealing a lack of understanding in HVAC air distribution principles. If they went to school they slept through systems design class, or just sat there with that deer in the headlights look.

R-38 blown-in in attic, but obviously more heat load upstairs. About only choice in attic is to remove fiberglass, foam attic ceiling for air infiltr. and then reinstall fiberglass. That would help infil.

No need to go to that extreme. Find every location in your house where something, be it a can light, a supply air box, etc. and seal any gaps between it and the drywall. For can lights, best thing there is to replace them with ICATS (insulation contact air tight) models, and use LED bulbs. I don't know of a satisfactory way to seal and insulate a non ICAT can light without running a risk of overheating the fixture and/or a fire.

I appreciate all comments, just thought a discussion might be nice. All problems could be solved by starting from brute-force, start-from-scratch (i.e. zoning, two-systems), but there is more fun in "trying" to solve/optimize a problem thru finesse..If possible.

Focusing mostly on the return side of the equation won't get you there. It's more comprehensive than that. From strictly an HVAC system design perspective, excluding any building science talk, you MUST have enough air entering and leaving a room to offset the heat gain to that room on the hottest day you anticipate your house to endure for that room to be comfortable. You can play around with supply registers and return locations all you want, but if the overall required volume of air is not there (air in/air out) you won't have the turnover of air required to keep space temperature comfortable.

[wraujr]

From strictly an HVAC system design perspective, excluding any building science talk, you MUST have enough air entering and leaving a room to offset the heat gain to that room on the hottest day you anticipate your house to endure for that room to be comfortable. You can play around with supply registers and return locations all you want, but if the overall required volume of air is not there (air in/air out) you won't have the turnover of air required to keep space temperature comfortable.

Focusing on the above I have a couple choices:
(1) Set ECM to "Comfort" (Low) 350CFM and have longer run times, thinking that yes less air gets pushed upstairs but with longer run-times and increased humidity removal, overalll 2nd floor comfort increased,,,
(could even set fan to CIRC to run blower more often)
OR
(2) Set ECM to "High" 450CFM to push more air upstairs, but may have higher humidity, noise, etc.
OR
(3) Leave it at "Normal" 400 CFM and live with it as there is no hope-in-heck of making it better.

[Texas-Tech]

#2 along with a dehumidifier upstairs, maybe it would help out with the moisture