Heat/AC zoning system
Can a two zone system and ductwork configuration be used as a one zone by propping the dampers open and just using one zone on the thermostat.? We just purchased a new variable speed 4-ton furnace, kept the existing plenum and coil and now the board (that operates the zones) needs to be replaced for over $3000 more. It was offered, as an option, to just make it a one zone and put in a new thermostat more centrally located. ( I don’t know if we have a bypass damper – was just reading about those and it sounds like its not too good. ) I’ve never liked the two zone system and I don’t mind making it all one zone- supposedly our duct work can handle it. Just curious if thats a good plan. We have not checked with another company – just dealing with the same company that put the new furnace in and they said we could do either. Very disappointed that we replaced our furnace because our heat quit working and the wrong part came in so we decided rather than spend $650 for a part, to replace the whole furnace because its 20 yrs. old, and now something else broke.
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Replies
Zoned systems make since in 2 story homes and when some rooms have very different heat loads, like a sunroom or an addition with different insulation and windows.
You may want to get a second opinion about the zoning repair preferably from someone with experience servicing that brand. It seems like the most expensive parts fail all the time with this guy.
Walta
Not sure how you're set up there, or what brands you have, or the fact that I'm not an HVAC tech but usually furnaces these days can handle zoning within themselves, or have a zoning module which usually isn't 3k. I just looked on supply house and found a zone module for $150. I remember looking at Lennox systems and their zone module was $100.
But to answer your question, being in your position, it's not ideal but reverting it back to 1 zone should be a viable option. I assume it would be a matter of disabling the motorized dampers (in the open position!) and replacing one of the zone tstats with a regular t-stat and wiring it directly to the furnace.
I assume that you are referring to a 2-stage furnace and not a modulating furnace. Modulating furnaces require a different type of thermostat.
Converting to an un-zoned system should be feasible with some simple wiring changes in the mechanical room. Whether the system will work well un-zoned and whether one of the existing thermostat locations will work well would require much more information about the layout of the house and how tolerant you are of temperature variation. Also, do you have access to manual dampers on individual duct runs. Sometimes with a single zone system, you need to manually change those based on the time of year.
The thermostats themselves are not different between zoned systems and un-zoned systems. In an un-zoned system, the logic for staging a two-stage furnace can be in the thermostat or can be in the furnace. If it is in the furnace, the logic is pretty primitive but works. It uses first stage for a fixed amount of time (10-12 miinutes) and then bumps to second stage if the heating call is still not satisfied. The thermostat has access to a little more information, so it could have more sophisticated logic.