Dual-Zone vs. Single-Unit Minisplit Heat Pump
Hello folks.
I’m considering buying a mini split heat pump system for my house in Portland, OR which I recently purchased. This was due to the overwhelming heat we recently experienced, and the increasing wild fires which may not allow us to take in cool air during night.
The house was built in 1951. The area is 889 SF, only at ground level. See the attached layout. Each room is small, but we keep almost all the doors open all the time. We don’t care the temperature in “LDRY/STORAGE”, but would like to control the temperature in the rest of the rooms holistically. So, 739SF, the total area of the rooms except “LRDY” is our scope. Overall, the house doesn’t have large opening.
However, I cannot determine whether I should install dual zoned system or single unit because of the complexity of the house layout. Below is the two scenario I can think of:
1) Single unit on kitchen wall – 18k BTU
2) Dual zone, 12K + 12k BTU – one in kitchen (Same location as option #1), the other in BED(13×9)
3) Single unit on kitchen wall – 12K BTU
I’m thinking of Mr Cool DIY units regardless of those two options. Those units come with 25ft long pre-filled lines. This length limits the location of the units, especially in case of option #2. Anyways, we think the locations are suitable for our current work from home situation. My wife works in “OFFICE/BONUS” while I work in “BED(13X9). Our main purpose is condition our offices, kitchen and living rooms. my office has high ceiling (13ft max at the ridge, and sloping down to 7.5ft).
I wonder option #2 could be overkilling. However, option #1 may not be able to condition the air thoroughly due to the complexity of the layout.
We don’t care “BED(10×8)” much. This is the reason of the layout of option #2. Another reason of option #2 is the existing powerful gas heater in “LIVING” which unable to provide enough heat to “BED(13×9)”, my office. I believe my office could be pretty cold in mid-winter also due to poor insulation. This is part of the reason I still don’t eliminate the option #2.
One reason I hesitate the option #2 a bit is our daughter. She is still 5 years old, but will soon be old enough to demand her privacy. In case she claims my current office as her room in future, and keep closing the door, 12K unit must be overkilling for 13×9=117SF room even though this has high ceiling.
The option #3 may be short to our demand. However, this unit is 115V, 20amp while the other need 230V (Dual zone requires 35amp). So, thinking of energy saving, the option #3 may not be bad idea as long as we close the doors for a couple of rooms.
Can anyone please advise?
Thank you.
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Replies
First let me say I am a fan of the Mr Cool DIY units.
I am not a fan of the multi head systems because
1 They can’t operate at as low a speeds as the single head systems
2 Finding a leak is so much more difficult
3 When you have a fault all the unit stop working.
Yes the materials cost 33% less but it cost more to operate and you lose flexibility, serviceability and redundancy.
Walta
Hi Walta,
Hearing that, I'm leaning towards single unit. Actually, 18K unit doesn't fit in the kitchen because of the cabinets in the adjacent area. Is 12K too small for the area? I guess I can keep the door for a couple of rooms, but will it keep running too hard? And will it end up consuming energy a lot? Regardless, I assume it uses less energy than 18K single unit or the dual zone.
Masa
Is your house on a slab?
Hi Kyle,
My office and the Laundry are on slab (no insulation underneath, I bellieve), but the others have crawling space underneath.
Masa
The best way to size the units is to do a manual J calculation for you home anything else is a wild guess.
Is that a wood stove in the living room? If you are comfortable when heating with the wood stove you may well be OK with a single head but I see nothing wrong with two heads plan in your drawing.
Walta
I would go with multiple units. Like said....if one fails you have another.....also the single units usually have better efficency rating.
Walta & DirkGently,
J calculation was 14K - 16K BTU.
Yes, I think dual zone makes sense for better air circulation. However, we won't use the mini split that often since we are in NW region. It's just for emergency like when the recent heatwave and fire attack at the same time!! So, I'm thinking of 12K single unit because it only spare one slot in the electrical panel, and don't consume as much energy as dual-zone, as you motioned. We will close a couple of the doors to limit the cooling area less than 500SF. That may not cool down my office, but I'm okay just for a few days working in such situations (I'm the guy who is okay even in the mid-summer in India). Single 12K BTU unit saves almost $1,000 compared to dual zone. So, I would go with it.
Thank you very much for your advices!