Distribute Hit in house with Motorized Register?

Let's say... Open/closed venting. (Not variable position control.) How about a bunch of thermostats in parallel to the furnace. The furnace runs until the last thermostat open cct's. Each thermostat controls a motorized vent. If every room comes up to temp, all flaps are closed, there's nothing conducting in the parallel circuit and the furnace shuts down..

No software...

D from BC

There's a company in Beaverton, Oregon that produces a system that'll do this for you.

But I've been trying to remember the name for the last ten minutes and can't.

Homer wrote in news:1192456452.265210.235580 @i13g2000prf.googlegroups.com:

Most central heating systems have "valves" for the duct work ususally located near the furnace. These allow you to control the airflow to various areas of the house. Close the upstairs a little and open the downstairs a little.

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Very smart thinking D. All I need is a motorized vent with thermostat. I can even forget about linking them together and downsize the project to replace old vents with new motorized ones. I then think of something else for shutting down furnace is all vents are shut (presure control switch or something like that).

Now here comes the big question: Is there anything like that in market? anybody?

Homer

Yep. Search for 'motorized damper'. But these are for installation in duct runs and may require chopping holes in walls and floors for a retrofit. Motorized registers would seem to make a better option for a retrofit.

I wonder how such a system would work if only a few rooms call for heat. The furnace might not work well with the back pressure and reduced flow. In fact, the heat exchanger may reach a high temperature. Most modern furnaces have safety sensors to shut down in this case, but hey will still treat this condition as a fault and may not even restart until properly reset (usually following an inspection).

High back pressures might also cause 'closed' registers to whistle.

Don't know what' available in the HVAC world. But perhaps you could use the kind of mechanism found in some greenhouses to open windows. AIUI they use a cylinder that extends a piston when the gas inside expands with heat. When the temp goes down, the gas contracts and the piston retracts.

Ed

The company you are thinking of is at

-bill

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That's the one. I know a guy who does software work for them, and they've interviewed me to do consulting but nothing came of it.

Neato idea, and the bladders are a clever way to avoid having to wire the house for control (apparently the prototype systems used beach balls).

But I never looked at the price until now -- that's steep, isn't it?

Ok, I did a little research on this a while back, and this is what I found.

First, you use either motorized dampers ($200+ each)or the 'balloon' controls ($60 each, but you also need an air compressor and controls for around $1000) for each zone you want. You have a separate thermostat for each zone that turns on the system and activates the damper for that zone.

Next, you have a little pressure regulator thingee that is basically a weighted flapper that you put right next to the furnace, between the output and the return air ducts. This keeps the pressure from being too great and burning out your fan. Also, the recirculated air requires less conditioning, possibly saving a buck or two.

Altogether, it can get pretty expensive and complicated.

Now, in my old two story house, all I did was buy a second thermostat for upstairs, and wired it to a two position switch directly above it so that I could either switch to the top thermostat at night, or the lower thermostat during the day. Funny thing was, I almost always just left it on the top one all day!

Charlie