Uneven heating & Cooling

[vette-kid]

I'm putting this here because Its in reference to the house and not the garage.

We recently moved to a ~2600sf house with a large, open concept living/dining/kitchen/family area and bedroom off in the wings. THe open area has higher ceilings (10 and 12ft I believe) while the two bedroom and hall in one side are standard height, master off on its own is also higher. The open area tends to be warmer than the wings of the house. Enough so that it can be uncomfortable in my daughters room now that its cooler outside. Our HVAC is recently serviced and running well and is appropriately sized for the house. In fact, in the summer it tends to be colder in the rooms than we have the thermostat set for. Raising it makes it warm in the living areas.

Is this an insulation issue? All the vents seem to have adequate airflow from them. House is built in 2004, single story, slab in north Florida. Any thoughts? I could use space heaters, but those make me nervous, especially since the worst parts are young kids rooms.

 

[Zeke]

AFAIC, HVAC systems can't be at their most efficient in both modes, heating and cooling. If you have access to any of the ductwork, you can install power actuated dampers to control flow. Sounds like you need to cut down on flow to the open area.

Also, and this is very important, if closed, the doors to the rooms must have at least 1" of clearance at the bottom for circulation to the return air vent. Example: if you have a register in a room that is 12 x 6, you have 72 sq in of flow. If the door is a 30" door with 1" clearance you have 30 sq in to return that air. Or less than half.

 

[LS6 Tommy]

One of the biggest issues with high ceilings is it causes uneven temperatures if the thermostat is located in the area with the high ceiling. Do you have ceiling fans?

Tommy

 

[kwschumm]

Air balancing and adequate returns are the key to even temperatures. I've found that residential HVAC contractors often don't bother, they generally walk through the house and say "put one here, one there, and another there", etc.. They should do a Manual J calculation, properly sizing the equipment for the size of the house AND properly sizing the air flow requirements of each room.

The supply air should be balanced to supply enough air to each room, accounting for construction type, insulation type, and windows. There should also be enough properly located return air registers to prevent pressure build up in the room (which would reduce supply air effectiveness). Home contractors often skimp on return air design by putting one big return somewhere in the center of the house. It is much more expensive to put return air registers in each room (and, maybe build a plenum to connect them all together).

An easy way to test for pressure buildup is to measure the temperature in the affected rooms with the door closed and then again with the door open (obviously allowing time for the temperature to settle at the door closed and open position). If the room is warmer with the door open then, as Zeke said, cutting an inch off the bottom of the door would likely help some (or putting louvers in the door).

 

[danski0224]

Air balancing and adequate returns are the key to even temperatures. I've found that residential HVAC contractors often don't bother, they generally walk through the house and say "put one here, one there, and another there", etc.. They should do a Manual J calculation, properly sizing the equipment for the size of the house AND properly sizing the air flow requirements of each room.

Residential contractors will only do the job as well as the builder is willing to pay for.

Local codes are addressing issues such as Manual J, D and S to establish a minimum requirement because the builders wouldn't pay for it. If a contractor bid the job with everything included, it would be higher than those that did it by rule of thumb.

Obviously, the hacks and cheats are out there too.

 

[Voi]

We did a major remodel on a 2500 square foot raised ranch. I greatly improved temperature consistency throughout the house by re-doing the air returns and switching to a higher efficiency furnace with a variable speed motor.

Most of the air returns were added or moved before the new furnace was installed and it was clear it was making a significant difference.

I did all of the air return work myself but ran it by the HVAC guys who came it at the end to do the furnace swap. They said everything was fine and made one final suggestion for the air return at one end of the house that I hadn't thought of. Wish I had hired them from the start.

 

[Firebrick43]

Mom house was laid out much as you describe. Some rooms especially one bath was chilly.

So was on NG so heat bills were not bad per say. Ducting was in the attic as its a slab house.

I looked in the attic and the celleous was there but uneven and average out some what less than the r38 code when built in 2001. Mom didn't want to spring for the 700 dollars for me to blow it(just materials). If I recall I blew in an even r50 and burried the flexible ducting one chilly November day two years ago with my wife and mom loading the hopper.

That night my mom called and wished she would have listened because the comfort of the house was so much greater, even if she didn't save any money. Her heating and cooling bills were lowered an average of 25 dollars a month(cold/hot months more and shoulder seasons less) so not huge but ROI was just over two years. She doesn't where turtle necks and slippers around the house any more even though the thermostat set point stayed the same.

 

[vette-kid]

So I wander what it would cost to add a return or two. We have one large one in the open area in the ceiling.

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[vette-kid]

I should add that all doors do have a good inch at the bottom. I may have a pro come out and check the duct work and insulation.

 

[bazar01]

Have you tried leaving the indoor unit fan ON all the time to balance out all the room temps?

 

[vette-kid]

Have you tried leaving the indoor unit fan ON all the time to balance out all the room temps?

No, I'm not really sure how to do that. As far as I know switching to fan only mode will run the fan constant but not the furnace or compressor. So it will get really cold at night (but evenly?) and hot in the day; north Florida, low last night was 36 and high today is low 70's and sunny. Enough to kick on the air.

 

[cmanningjr]

When we had our heat pump installed 3 years ago the fancy thermostat it came with has a fan setting you can turn on to circulate the air every so often.. I can tell a big difference in summer and winter. No more hot or cool spots..See if that's an option on what you have..


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[bazar01]

No, I'm not really sure how to do that. As far as I know switching to fan only mode will run the fan constant but not the furnace or compressor.

What brand and model thermostat do you have?
Most thermostat have a fan switch you can set in Auto or ON and will run the furnace or compressor when actual temp is below or above set point.

 

[gregtwojeeps]

Whenever a person chooses to run their A/C air handler fan on "Manual/On" during the cooling season, just a note. The air handler evaporator's condensate water drains the most, when the unit fan cycles off. While the fan is off, is when most all of the water in the evaporator's condensate drain pan is allowed to drain...

If the unit's fan runs continuously, then a certain amount of water that is not getting drained, lays in the catch pan under the coil. The fan pushes a water mist airborne back on to the coil, while adding humidity to the duct system and sometimes the water will even be dripping through the cracks on the evaporator /fan housing compartment.

Been there done that, but my air handler was in my crawlspace, not above a finished ceiling, so no harm was done as the water not draining in to my Little Giant condensate sump pump, just dripped out of the air handler cabinet on the vapor barrier. With my fan running full time during the cooling cycles though, it did raise my home humidity level above its average....from the constant water mist the fan was picking up out of the drain pan. JMO

 

[LS6 Tommy]

Whenever a person chooses to run their A/C air handler fan on "Manual/On" during the cooling season, just a note. The air handler evaporator's condensate water drains the most, when the unit fan cycles off. While the fan is off, is when most all of the water in the evaporator's condensate drain pan is allowed to drain...

If the unit's fan runs continuously, then a certain amount of water that is not getting drained, lays in the catch pan under the coil. The fan pushes a water mist airborne back on to the coil, while adding humidity to the duct system and sometimes the water will even be dripping through the cracks on the evaporator /fan housing compartment.

Been there done that, but my air handler was in my crawlspace, not above a finished ceiling, so no harm was done as the water not draining in to my Little Giant condensate sump pump, just dripped out of the air handler cabinet on the vapor barrier. With my fan running full time during the cooling cycles though, it did raise my home humidity level above its average....from the constant water mist the fan was picking up out of the drain pan. JMO

If that happens your trap is improperly deigned.

Tommy

 

[bazar01]

Whenever a person chooses to run their A/C air handler fan on "Manual/On" during the cooling season, just a note. The air handler evaporator's condensate water drains the most, when the unit fan cycles off. While the fan is off, is when most all of the water in the evaporator's condensate drain pan is allowed to drain...

If the unit's fan runs continuously, then a certain amount of water that is not getting drained, lays in the catch pan under the coil. The fan pushes a water mist airborne back on to the coil, while adding humidity to the duct system and sometimes the water will even be dripping through the cracks on the evaporator /fan housing compartment.

Been there done that, but my air handler was in my crawlspace, not above a finished ceiling, so no harm was done as the water not draining in to my Little Giant condensate sump pump, just dripped out of the air handler cabinet on the vapor barrier. With my fan running full time during the cooling cycles though, it did raise my home humidity level above its average....from the constant water mist the fan was picking up out of the drain pan. JMO

That does not explain why units are designed to keep draining condensate even when the unit is running. There is a trap that is calculated based on the negative static pressure (inches of WC) the unit is pulling against the designed column of water on the trap.

 

[gregtwojeeps]

This happened on the home we sold two years ago. Horizontal Amana gas furnace/ AC unit in the crawl space.

The unit had this trap on it

installed by the original HVAC installer guy I guess. It dumped right in to a Lil' Giant condensate pump.