Posted By engineer on 12/06/2009 8:18 AM
John S
I agree with the idea in paragraph 1 - heat gathered from solar is likely to be of higher 'quality' (temperature) than heat from the ground, so ideally it is retained and used as directly as possible in the home, not dissipated into the ground. I also wonder if the capital costs and additional running costs of the solar assist would ever pay off in increased efficiency / reduced operating costs.
Conventional zoning should accommodate variable loads summer and winter, upstairs and down, as long as it is properly designed (that is, ductwork for each zone sized for that zones highest CFM requirement) That is the central purpose of zoning. By recognizing the diversity of the load, i.e. peaks occurring at different times of day, zoning sometimes allows a slightly smaller total system capacity, which in turn helps the zoned system cope with part loads. Zoning must additionally be designed to accommodate minimum airflow needed by the system in low stage.
It doesn't work right and I'd like to fix it, conventional systems that is. My HVAC has three speeds for the fan and with an ECM blower I don't undertand why only 3 speeds. Why not connect the ECM blower to the pressure in the main plenum? Where am I going you ask.
My house is a wide 2,400 sq-ft ranch with a south and north side. I would like to have three zones, south, middle and north. The basement being mostly underground needs only one. You can't have three zones without having all kinds of extra stuff because if you take one zone and put 1,450 CFM into it you'll think you're taking off on the space shuttle.
If you had a constant variable system you could just shut off any branch and even any room and not have this problem.
If all the three zones were on the plenum pressure would fall and the fan would increase speed to bring the pressure up. This way if you want 400 CFM in a large bedroom you'd have it and the unit would only run at the right speed to deliver only the 400 to that room. Maybe the other room wants 400 and now the unit feels the opened zone control and now delivers 800. The best part of this is while I'm in my bedroom I can't tell that the other bedroom is on/off.
I really want to pull the CXM board out of my Climatemaster and work on that next. Want to come over and help?
John