We are just finishing an addition on our home (or rather, our contractor is).
We had already decided (based on our contractor's advice) to have a mini split (cooling and heating) installed for the addition (single room open to the rest of the house - about 17' x 20' with ceiling heights of 8' and 11' and 3 exterior walls facing west, east and sheltered south - pretty well insulated with energy efficient windows).
However, the install cost seems a bit high (our contractor was going to sub this out to an HVAC guy), so I want to do some independent research before I proceed with this guy - quote is $4,000 installed.
I have a few questions. We are thinking of the 12,000 btu Mitsubishi mini split - heat and cooling single unit.
1. How does it handle the really cold temperatures? Although Ohio tends to stay above 20 degrees F in winter, we do usually get a cold snap for about a week or two in winter - below zero. The sub mentioned something about making sure we have emergency back up heat for those times. Is this the auxilliary heat that kicks in on these units or is this an additional heat pump? In other words, if you buy any of the mitsubishi units, do they all have this emergency back up heat? Is it really expensive to operate when this kicks in?
2. Not sure what kind of circuit this needs. We have limited capacity on our 100 amp service. Does it need a 20 amp circuit or more?
3. We are getting additional quotes from "regular" HVAC contractors, but so far, they seem a bit unfamiliar with this. One person said we would have to upgrade our electrical service because the unit would require close to 50 amps. All the specs I am reading show 20 amp. What should we look for when picking a contractor to install this system. Are they that unusual?
4. What are the operating costs for something like this compared to hooking it into our gas forced air/heat pump system? I am kicking myself for not investigating that option before starting the remodel. Our air conditioning unit (heat pump?) is pretty old and probably is very inefficient, so we may have killed 2 birds with one stone. I am unsure if our furnace could have handled the additional load. So we may have faced upgrading our air and furnace and running ducts, but would the total system have been more efficient to operate in the long run? Or is it better to zone the addition with a mini split.
Any feedback would be appreciated.