We are in the process of constructing our new home (after 15 years, WOO-HOO!), and I asked the builder if we could zone the downstairs (approx 1900 sq ft) into thre areas. We are using a slab configuration (no basement) so all the downstairs ductwork will be buried under the slab. The upstairs will have it’s own units.
The builder talked to the HVAC guy, and was told that “he didn’t think it could be done because we are installing a downdraft system.” Now, I thought zoning could be accomplished by installing control valves in the ductwork to control airflow to each zone, and then tying control of those valves to each zone’s thermostat. It seems doable regardless of updraft or downdraft. Am I missing something? Also, any references to websites that could provide me more information would be greatly appreciated.
The plumber just finished his stuff so the HVAC is ready to move in, and we hope to have the slab ready to pour within the week, so any help would be GREATLY appreciated!
Illini boy turned Okie
Replies
I don't know the answer to your question, but I would guess that they need access to the zone control dampers and there isn't room to do it in the mechanical room.
Thanks gents, after thinking more and reading more, I figured out that with the dampers in ducts buried under the slab any kind of damper drive motor failure would be a bear to fix. And I thought about maybe raising the unit in the mechanical room too, but I just don't have the room. I sure do appreciate your responses, though!
It really wouldn't take that much more room to place the dampers in the mechanical room with the furnace. Modern condensing furnaces are generally fairly short, and you shouldn't need more than about a foot of additional height. Or you could use an updraft unit, and trade about 18" of width or depth for ductwork.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
The difficulty would be with installing the zone control dampers in the ducts. Probably there would have to be a sump of sorts for a plenum, with the dampers controlling the air as it leaves the sump through various ducts. The sump would have to be kept reasonably dry.
The other alternative would be to elevate the furnace on top of an above-slab plenum (or simply have an up-draft unit do a U-turn), and have the dampers there, feeding ducts that would quickly dive into the slab. This would be preferable if moisture was a worry.
Doable, but more work.