My house (3,000 sq. ft.) has an HVAC system with two zones, each controlled by its own thermostat. The furnace and ductwork are located in the attic. There is a damper in the main supply duct that controls the flow of air to the zones. Is there a simple way to convert the system from two zones to one? During the day, I want to heat or A/C the whole house to the same temperature, and it would be more convenient if I only had to adjust one thermostat instead of two. How can I do this? I assume it involves disconnecting the damper control and one of the thermostats.
Your zone valves may have a lever on them for either MANUAL or AUTO operation. If your boiler is wired to maintain a constant temperature, dependant of either zone, you may introduce unwanted heat into the zone you have set to MANUAL.
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Those are the type of zone valves I'm used to seeing.
I would say it is more efficient to keep the zones in the system and control them with programmable thermostats.
-Canadian Heat
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whats wrong with the two existing t-stats? set them both for the exact same temp and leave things alone. either they'll reach set point or they wont.
the first priority is determining if the system is capable of auto-changeover, if not, installing the required components to make it so. (usually t-stats alone will do it)
for the life of me I couldnt find in the original post where he describes a 2 story house. maybe its a rancher on one floor. at any rate, we have no input on duct sizing, system capacity or zone duct sizing or capacity.
If its 2 story, I'd set the first floor stat a few degrees COOLER in ac mode and a few degrees WARMER in heat mode. Cooler because that zone will satisfy first, allowing for a much longer run time for the upstairs zone (if any).
House is one story, 3 years old, located in California, well insulated.
Furnace is a York, natural gas fired, horizontal configuration in attic,
100,000 Btu. Furnace is "builders" quality; i.e. low efficiency (80 AFUE), but more than adequate to heat the house.
AC is a York, split system, coil attached to furnace, rated at 4 tons. AC is "builders" quality; i.e., low efficiency (10 SEER). System is adequate to cool house, but when outdoor temperatures exceed 100 deg F, indoor temperature won't go below 78 deg F, even though system is constantly running. In my opinion, a 5-ton unit should have been installed.
Thermostats are Hunter programmable type. Both thermostats are set to the same programs. I normally allow the program settings to control the HVAC system, but there are many occasions where I use the manual override.
Duct system consists of flexible ducts located in the attic, with 5 main branches off of furnace (7", 8", 8", 14", and 18" diameter), other ducts range from 4" to 9" (most are 8"), with a total of 17 registers, ceiling mounted. I don't know the total cfm for the HVAC system, but it is adequate to heat and cool all rooms to approximately the same temperature.
Another possible option, get a thermostat with a seperate contoller, then wire the controller over to the other stat that you commonly use. This way, you get all the benefits of having two zones plus the convienience of all the contols being in one place.
Your "opinion" is probably wrong.... It sounds to me like the system is correctly sized, but without knowing the actual design temps for your area, I am only guessing. Bigger is *NOT* better, and grossly oversized can actually be detrimental to your home and your health.
Why are you having to mess with the thermostats?? If they are auto-changeover, and they are correctly programmed, you should never have to touch them.
Other than the cheapest builder grade equipment, thermostats, and flex duct, if the system is maintaining your comfort level, and all the rooms are the same temperature (plus or minus a degree or 2), then whats your problem??
Nothing is wrong with your system other than ignorance on your part.
Fact: single stage ac units operate at maximum capacity every time they turn on, regardless of indoor or outdoor temps.
Fact: design conditions for Ca are usually 75 degree indoor temp & 95 degree out door temp. that means when its 95 outside your ac will run
24/7 to maintain 75 indoors.
Fact: AC units operating above outdoor design temps lose capacity. At 100 degrees, your 4 ton is actually producing closer to 3 tons of cooling. Post the model number of the condensing unit and somebody might post back the engineering data that shows the capacity at temps above 95.
Fact: An ac unit operates precisly as designed for one specific set of parameters, those of design conditions. If the outdoor temp is below design, the ac unit is oversized. If od temp is above design, its undersized.
Fact: ac units remove heat from the air as well as humidity. On high humidity days, the ac unit may spend all its time just removing humidity and not lowering temps.
Someday soon manufacturers may introduce variable speed, variable capacity ac units. Until then, deal with the facts of ac as we know it today.
by your own words, the system is sized and installed correctly............as long as outdoor temp remains at or below design.
Personally I'd ditch the Hunter t-stats, as they are absolute junk.
LOL guess I misread that post. Although I still say keeping both zones is the best option. You need someone like b hate me to get up in the attic and clean the airhandler for you ;)
-Canadian Heat
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