Residential Zoning Systems

[Strategic Energy Solutions]

After doing mainly large commercial work we're now getting into some larger residential projects. I'm looking for some input on residential zoning systems. In the past I've stayed away from them thinking they were problematic. I'd now like to give them some more consideration. I'm wondering if anyone can provide input on brands and how they interface with a two stage heat pumps and ECM fan motors. I once heard someone say that a bypass is not needed with an ECM motor. I'm not sure I believe it. I also question whether the bypass should be a barometric damper or a motorized damper.

Any input would be appreciated.

[alliedairtexas]

With the cost of multiple geo units, zoning is almost always needed. With most units offering 2 speeds, a 2-3 zone system is OK without a bypass damper. the zone system has to determine the load and adjust the compressor and fan speed to match. If trying to use more than 3 zones you may need a bypass damper, if say, only 1 zone is on. While a powered bypass damper is nice, it is a little more costly and probably not necessary in a small 3-6 ton) system. Barometric dampers are OK. Water Furnace sells a damper system that integrates well with their units, but I use a conventional Honeywell residential system that is both cost effective, and easy for local guys to service.

[teetech]

The problem I've most often seen is too many zones and too many small zones. Then there's those zones that only get used when my mother in law shows up or the basement that is unfinished.

Show me the economics of running a 5 ton unit with a 1 - 2 ton load. This is only my opinion, but using a bypass damper only moves the air in circles and it costs money to move that air. It's all about the duct work.

[engineer]

I agree that a big unit serving a small zone for a short cycle will be less efficient.

However the economic analysis has to include first cost reduction from not having to buy and install 2 or 3 smaller units.

A problem we have is zones / floors whose load is so low that none of the standard offerings are anywhere near small enough.

Zoning configured in recognition of diversity (the load kind, not the politically correct kind), may allow total tonnage to be dropped a notch since capacity can be focused where needed at different times of day

[alliedairtexas]

Too much is too much. I once had a customer who had a 4000 sq ft ranch house with...no kidding...one thermostat per room. The house had 4-2 ton heat pumps with custom built air handlers that had one blower to each room. A suction temp sensor cycled the compressors. (Two condensers per air handler) This lady would turn on/off stats like light switches as she moved from room to room. Over the years,as the system finally began failing, I replaced it with 4- 2 ton systems and 4 thermostats, which she reluctanctly agreed to. Botom line is, one zone per 1000 sq ft is plenty of control, and least one zone per floor on multi story is a must.

[engineer]

We are often called upon to build three story beach houses facing east, and the bottom floor tends to be small (part of that level is unconditioned garage) as well as low in cooling load (limited glass, sits on a cool slab) Being on its own level, it needs a zone, but load is tiny, so we're stuck with a bypass.