Oversizing a multi-zone inverter heat pump – does it matter?
I’m trying to figure out a strategy to heat a large one level house with many rooms, and it seems that a multi-zone mini split could give me the overall capacity I need with the greatest comfort. But I’ve also seen many warnings about oversizing and its ultimate effect on COP, which makes me a bit nervous.
Looking at the heat pump specs, though, I’m confused as to why there would be a problem. My heating contractors aren’t necessarily heat pump engineers, so I’d like to run some thoughts by the contributors to see where I might be off base.
Looking at the lineup of Mitsubishi H2i unit submittal sheets, it seems that they all have about the same low end of the capacity range – roughly 7KBtu/h. So whether I pick a 48 or a 20, the unit can modulate down to the same level. I see no downside in sizing for max capacity, or am I missing something?
The indoor unit capacities are a bit more mysterious to me. If I have a 12K indoor unit, can it operate down to the 7K minimum from the outdoor unit? Or is the unit always at its max capacity for a given return air temp? And if two units call for heat, can the 7K be “split” between them?