Minisplit setup for New Jersey, 750 sq. ft. house over crawl. Bouncing my HVAC contractor’s plan off you guys.
The short. I have a 25×30 rancher over a currently vented crawl. It sets almost perfectly south facing on the 30ft long side. No tree shading on south or west. Deciduous tree shading in the east and some on the north side. It’s two bedrooms one bath, kitchen and living room. Standard stick frame 2×4 construction and vinyl siding. House was built in 1963 in a post WWII development.
Bath: 5×9 rough estimate
Living: 14×14 rough.
Short hallway off living room with bedrooms at the end: 4×7
Living and kitchen I would treat as open concept/one room as there is no physical barrier or wall between them.
Short term goals: roxul comfortbatt r15 walls, roxul comfort batt r45 ceiling (r30 between joists and r15 ran across tops of ceiling joists in a vented attic). Then address the crawl space grading the yard the weeping tile, sump and converting to a closed crawl with foundation insulation.
Long term goals. If we stay put we plan to rip the roof off and go up for a master suite and out one side for an eat in kitchen. If we to this route I will be leaning towards doing a remote wall or persist treatment to the home along with upgrading the windows and doors.
Anyways I used a free online manual j and come up with roughly 30,000-34,000 btu/hr whole house requirement. But I’m an electrician not an hvac guy by trade.
My hvac contractor is suggesting a multi split unit for the bedrooms…two 6000btu heads on the smallest mitsubishi multi compressor they make which I think is 20k btu. He is also leaning towards a 15,000btu single zone for the living roomand kitchen area.
My concern is with the bedrooms. Mostly. I feel that the 20k compressor for two 6k btu heads is excessively oversized and the minimum demand for that outdoor unit is roughly 7,800btus. Which means those heads will only be able to throttle to roughly 65% to meet minimum demand.
I can post a floor plan later if it will make this a more productive conversation.
I was hoping to use a higher seer single zone 9 or 12k btu wall or floor model in the tiny hallway which connects the bedrooms and bathroom.
The current AC compressor is a 2 ton unit that is quite vintage. I don’t see why hitting somewhere around that number with an equivalent mini split offerings wouldn’t work. The heater is like a 90,000btu gas air handler from like 1970/80 which. Even with the ductwork removed from the bedrooms now ( in the middle of renovating) the three remaining registers in the bathroom, livingroom and kitchen keep the bedrooms comfortable.
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