DIY Install of Ducted Minisplit System
I am building my own house in Washington State on the Olympic Peninsula and doing most everything myself with minimal sub contracting. I am to the point of needing to finalize some HVAC decisions. In short, I need to decide if I will tackle the install of a ducted mini split / heat pump myself. I have received quotes from local HVAC companies and have been shocked by the cost of professional install and while I would prefer a a licensed specialist to perform the install for warranties sake and perhaps sanity sake, I am feeling like it is to the point of being cost prohibitive. I am building a small (850 sqft) 2 bedroom home with a cathedral ceiling (i.e. no attic). I have a portion of one loft within the building envelope designated for a ducted minisplit and the install seems very simple in my minds-eye. There will need to be a plenum with three supply registers, but the runs from plenum to each register will be very short (<3 ft), which is to say that I am >95% confident that I am within the static pressure limits of the machine. My plan is to have return registers from each room back into the enclosed area of the loft containing the handler (i.e. there would be no return ductwork… The negative pressure generated by the handler would bring air into the enclosed area from each return register, or that’s my thought at least. I have been looking at the Mitsubishi 15k M series Condenser + Mitsubishi 141000 BTU handler (SEZ-KD15NA4k1). I can purchase the necessary items, including lineset, disconnect, whip, wired programmable thermostat, etc. on eComfort for well under 50% of the installed bids I have been receiving. I have been given quotes of 11,000 and 12,000 dollars for 12k BTU slim duct units- this feels outrageous for single head systems, that are going to be installed in an easily accessible loft space with very minimal duct work. Am I crazy to try to install a unit myself? I understand that I would need to find someone to pressure test the system, purge the lineset and add any necessary refrigerant, but as far as roughing in the system, pouring a condenser pad, mounting the handler and installing the ductwork, am I crazy to try it myself? Knock some sense into me please!
Also, there are some prefab plenums that I found for the aforementioned Mitsubishi unit that make the duct work all that much easier. And while I do have some outstanding duct design questions, like sizing each run, etc. I believe I would be able to figure it out with more research.
I should mention that I very much appreciate the expertise and skill that HVAC professionals bring to the table, I am just a young man trying to build his own home in a pretty challenging economy already and these bids are throwing me.
Perhaps I should also mention that I have already installed a woodstove in the main living area and plan to use that regularly as well, and this adds to my feelings about the cost of the minisplit/heatpump.
Thanks in advance for any thoughts,
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