Electronically controlled HVAC damper?

The heating system in my 1970-era home was designed and installed by trained monkeys; as a result, we are constantly trying to adjust the open-ness of the various registers in a futile attempt to get the heat evenly distributed.

I can certainly imagine a system with thermostats distributed around the house and a central control system deciding where the heat needs to go, the problem I'm having is finding the right parts to actually control the airflow.

I see a lot of electronically controlled dampers around, some of them for as little as $70, which isn't bad, but it requires tearing up ceilings in order to have access to the ductwork.

Is there such a thing as an electronically controlled register? So I could just pull out the manually operated ones, drop in a couple electronic ones, and then start the fun of getting them to work right?

Thanks, Chris

There's an article on this very subject in HomeToys (one of the better HA info websites). Here's the URL:

Here's a fellow who made his own system: SmartHome (one of my online competitors) sells this unit: HomeTech (another competitor) has a more informative page on the subject: Here's another reasonably priced solution:

Servos are pretty handy things and are easily computer controlled if desired. Below is a simple setup I made to test t-stat control with a servo. If a damper is well lubed and moves very easily, then a servo could probably be used to move it to its desired position. Definately a DIY type of thing.

Bear in mind you can damage your HVAC system by not properly dealing with air pressure. If you shut things off and there's no release for the blower you risk burning out it's motor, if not right away, much sooner than it's designed lifespan. So before you go shutting off registers consider having a qualified HVAC person give the system a once-over and discuss what should or shouldn't be done to it.

-Bill Kearney

Good point ... my plan had been to do this to only a few key registers, so it shouldn't be any different from those times when we manually close those registers. Plus, there's enough leakage from the poorly sealed ducts that I'm not too worried about back pressure :-)

Regarding qualified HVAC people, I've had a few out to look at the system, and nearly all of them have had little to no imagination. Example. Here in Colorado in the summer, it's 90-100 during the day but drops to 60 at night, there comes a point every evening when I would like the system to automatically turn off the AC, open up the damper, and just have the furnace fan pump cold evening outside (filtered) air through the house. Talking to most HVAC people about a wild idea like that and you get blank stares. I can't imagine what kinds of looks I would get if I told them I was hooking up servos from remote control aircraft so my PC could open and close my registers.

Long-term, if this works, and I do it to more than just a couple registers, I've seen some pressure-controlled dampers that are designed to prevent exactly the kind of over-pressure you're talking about.

C

Not removing the heat/cooling from the heat transfer coils and the subsiquent issues would probably be the big thing to avoid..

Is it enough to make sure that at least one zone is open? or is it more complicated?

It depends on the setup. If you short-cycle a furnace, you run the risk of cracking the heat exchanger and allowing CO into the house. It all depends on the unit's safety features and configurability. You need to know, at a minimum, how much the air heats up from furnace air inlet to outlet. If it leaves the furnace at say X degrees unmodified but X+30 degrees after your zoning, you need to do something because you've lowered the over-all airflow through the system too much.

If you are going to DIY zone, factor in the cost of several good CO detectors and place them strategically throughout the house.

-- Bobby G.

While automating your HAVC system two other suggestions:

1) install a flow switch to shut down the heat or a/c if there is low flow. Problems such as broken fan belts can result in a burned out a/c compressor if your not home and it keeps running with no air flow trying to answer a cooling call. This would also address the problem of too many regisers being closed. You'd need to find a flow switch from an HVAC distributor.

2) a smoke detector in the return air duct (commonly used industrially and in commercial buidings, but not in residences) could save your life by shutting down the system if smoke is detected, otherwise a modern forced air system can efficiently fill the whole house with smoke or CO from a fire in one room. Also, connect your central fire alarm (if you have one) to shut off the system in the event of fire for the same reason. Smoke detectors for use in air ducts are available commercially. In our highrise building, the system switches to full fresh air at max fan if the fire alarm goes off, but shuts down if smoke is detected in the ducts.

Just a thought

Thanks. Sounds like some really good thoughts

I don't think I'm quite ready to DIY for zoning, but I am going to be rather specific in some wants with whatever contractors I might use. For example, I want fully communicating thermostats, regardless of what type/brand/label they would prefer to sell me. I don't think most of the guys around here understand when you say "the thermostat has to connect to my Automation system", but, we'll see.