Sizing a Multisplit Air Handler
What are the practical effects of undersizing a multi-split air handler for its’ zone load? We are looking at a Mitsubishi multi-split system for our HVAC replacement–Outdoor unit MVZ-4C36NAHZ-U1 with an SVZ air handler in zone 1, and either one (12k) or two (9k) units in other zone(s) depending on whether we go with 2 or three zones total. If we go with a two-ton air handler (SVZKP24NA) it has a heating capacity of 27000 BTUs, but the heating load of the zone is 28817 BTUs, leaving a 1817 BTU deficit. Moving up to the SVZKP30NA leaves us about that much more oversized. The house (in Zone 4) is 110 years old with some opportunities for improved air sealing and insulation, so I find myself wondering whether it would be better to deliberately undersize and look for ways to reduce heating load down the line, but I don’t want my family shivering through winter before I can make those improvements.
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