A GBA reader by the name of Green Heron has recommendations in hand from an HVAC contractor for heating and cooling a Climate Zone 2 house currently undergoing renovations. But he’s not sure whether the recommendations make sense.
The contractor has proposed a four-zone system using a mix of ductless and ducted minisplits, Green Heron explains in a post in GBA’s Q&A Forum. A single 3-ton compressor would run the four indoor heads — two ducted units installed in the attic, and ductless units in both the kitchen and the living room.
“I don’t like the idea of putting units in the attic,” Green Heron writes. “I’m also concerned about sizing. Seems like there’s less room for error with minisplits.”
Green Heron has some questions about the specifics of the proposal, such as how difficult it would be to mount a ducted minisplit on a ceiling and run ducts through interior walls, and whether he could use a single ductless unit for both the living room and kitchen.
Overall, the heating and cooling loads as calculated by a third party are giving Green Heron pause for thought. In some rooms, heating loads are twice as high as cooling loads. Taking the house as a whole, the heating load has been calculated at 27,230 Btu/h with a cooling load of 22,197 Btu/h.
“As you see from the load calcs, some rooms have a big difference between cooling and heating loads,” Green Heron says. “If I size for the cooling load (due to my climate zone), some rooms won’t keep up with heating demand in the winter. If I size to the heating load, some rooms will be significantly oversized in the cooling season.”
Are Green Heron’s concerns well placed? That’s the topic for this…
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