Computer controlled HVAC vents.....

[Rfsmith48]

Hey,

I saw a show on "This Old House" (I think) several years ago that demonstrated HVAC vents that were individually controlled via several room controllers working thru the home Wifi. (I couldn't find a web reference to the show.)

We have a '70s Bilevel house, and the lower level is COLD this time of year.

I did a search on the web and came up with two vent suppliers: "Flair" and "Keen". Neither of these suppliers provide detail info for a system design. (That I could find). I corresponded with one guy at Keen, he could not provide any useful info.

My questions to you guys:
1. Does anyone have some experience with these sorts of products?
2. Can you recommend a product line?
3. Any pitfalls to avoid?

All help/guidance is appreciated!

Rog Smith
720 326 7296

 

[Jadnashua]

When Keen came out, I asked my brother-in-law, who is a mechanical engineer with experience in this type of stuff, and he suggested I not install them because there is a fairly fine line on how the heat exchanger's air flow works along with the fan loading, noise, and longevity. I know they talk about some of those things in their website. I guess it would depend on how far out of whack your system is.

What you're seeing could be caused by various reasons:
- poor insulation
- air leaks (both in the duct work and the dwelling)
- improperly sized and routed ducts
- improperly balanced airflow
- improper return
- oversized furnace
- poorly placed thermostat
- uninsulated ducts, or ducts running through unconditioned space, especially without insulation
- leaking ducts that let a lot of air out before it gets where it is supposed to go
- too many changes of direction which add to the effective length and slow down the volume available
- and probably more...

A room without a proper return duct won't get the proper air flow into it since the pressure is too great...you need a proper return. Opening the door may resolve a lot of it, but that may not be an option. If the ducts are not sized for the room's heat load, even if they have a return, it's losing more heat than can be supplied. That could be caused by air leaks, poor insulation, improper sizing. Intermittently, it could be because of solar loading, or winds.

If your furnace has the ability to run the fan continuously, try that for a bit to see if things get better. This works much better if you have a variable speed fan, because, when the furnace is not calling for circulation, it can turn way down to a whisper...saving both power, wear, and noise. When I put mine in, I opted for this option, and it does make a difference. It's slow enough to not be drafty or be heard until the a/c or heat comes on. If the ducts do not have dampers, adding some, or adjusting the ones there, may help to balance the temperatures. Any changes need to be done incrementally, with time in between for things to stabilize. For a room that is too hot, try slightly cutting back. This is better done closer to the source than at the outlet which can get noisy when partially closed. It also prevents losing more heat out of the duct. IF the rooms that are too cold have dampers, make sure they are fully opened.

 

[Sponsor]

 

[Dana]

Running the furnace blower continuously induces wind-chill when the burners aren't firing, and if the ducts aren't tight &/or well balanced the amount of parasitic air-handler induced infiltration can overventilate the place, and make the wintertime indoor air extremely dry.

Blower door directed air sealing followed by IR imaging & blower door directed spot insulation is more likely to improve comfort than screwing around with the active ventilation air setup.

 

[Rfsmith48]

Folks,

Is there another Web Forum with a larger number of HVAC folks?

BTW: Not sure what a "Blower door" is. There are no movable parts near the fan on this furnace.

Thanks again,

Rog

 

[SteveW]

Folks,

Is there another Web Forum with a larger number of HVAC folks?

BTW: Not sure what a "Blower door" is. There are no movable parts near the fan on this furnace.

Thanks again,

Rog

doityourself dot com has a good HVAC section. I've gotten some good advice from HVAC pros there.

 

[Dana]

Folks,

Is there another Web Forum with a larger number of HVAC folks?

BTW: Not sure what a "Blower door" is. There are no movable parts near the fan on this furnace.

Thanks again,

Rog

A blower door is a temporary door with a variable speed fan/blower and calibrated pressure sensors and speed sensors designed to test the air tightness of buildings. It is NOT a piece of HVAC equipment. Since at least the 2009 version of the IRC building codes have required testing and meeting air tightness standards specified as a number of total air exchanges per hour for the whole house at 50 pascals pressure, both postive & negative pressurization, often refered to as ACH/50. Current code-maximum air leakage in in Colorado for new construction would be 3ACH/50.

At 50 pascals pressure difference it's pretty easy to find and fix bigger air leaks just following the flow of a smoke pencil (or a wet finger.) Smaller leaks are more subtle- sometimes they can be heard, but with an infra-red camera the temperature differences show up near the air leaks fairly easily when there is at least a 15F difference between indoor & outdoor temperatures.

 

[Jadnashua]

The Trane multispeed (16) blower barely is turning over on the lowest setting, and at least in my situation, does not seem to produce any 'wind chill' effects, but does help keep the place more consistent in temperature. You would not probably want to do this with a typical single, or maybe even dual-speed fan in a furnace or air handler. It is also designed to ramp up and down during heating/cooling cycles, so it can extract all of the energy you've paid for and is almost imperceptible in operation. It rarely gets to max speed unless you've set a steep setback and it's REALLY cold or hot outside.

 

[Dana]

The problem with focusing on ever more sophisticated HVAC equipment to treat the symptoms of what is more likely to be fixable defects in the thermal envelope of the house is that it doesn't fully deliver the comfort sought, and it usually isn't the best place to spend the money first.

A cold lower level on a split level house COULD be an HVAC problem, but far more often than not it's the building, even if the HVAC isn't perfect either.

 

[Jadnashua]

Insulation and sealing air leaks should be the first line of defense. Those will both save money in the long run, and improve comfort.

A surprising number of HVAC systems are really very poorly designed, installed, and maintained. Oversizing is a big component. Ideally (we don't live in an ideal world), when heating, the system would adjust its output so it can just offset the heat lost to the outside, and run constantly. The more oversized the system is, the shorter its cycles, and the less comfortable it is. Some thermostats are smarter than others and can help, but they cannot overcome major design errors.