Oversized Minisplit System and High Humidity
We are remodeling our 2300 sq ft 2-story home in Charlotte, NC (built in 1998). All new windows, 60% new plywood/wind wrap/r15 insulation. It should be complete in 4-6 weeks.
Our duct work needed to be replaced on both floors so we replaced (2) Trane 2-ton AC/gas furnace units with (2) Mitsubishi MXZ 36k Hyper Heat units from a local company with a good reputation.
First floor (MXZ 36k + 3-port branch):
1. ~800 sq ft open living area – Mitsubishi Gl 18k wall mount
2. ~400 sq ft 2-car garage (very little insulation)- Mitsubishi Gl 15k wall mount
This system was installed first. It works great, easily keeps the living area and garage heated/cooled with humidity in low 50’s (entire house was low 50’s before)
Second floor (MXZ 36k + 5-port branch)
1. (4) Mitsubishi Mlz 9k ceiling mount units in Master ( 300sq ft + 150 sqft attached bath), Bonus (192 sq ft), Spare (130 sq ft), Spare ( 144 sq ft).
The system cools well, but is barely regulating humidity. It can average in the 60’s and can easily jump to the high 70’s. We added portable dehumidifiers to the rooms until we can find a permanent solution.
I read a few posts here and it sounds the upstairs system is oversized and the mini splits are short cycling? I relayed this to the hvac company and they opened a case with Mitsubishi and changed jumper settings for coil temp and fan speed = no difference. They are already trying to say it’s normal and trying to find non-existent air leaks as the source of the humidity.
What options do I have to correct the issue?
1. Fix the current system?
2. Add a ducted dehumidifier (no ducts currently)
3. Replace the (4) mlz ceiling mount units with (2-3) mini-ducted units + ducts
4. Replaced (4) mlz ceiling mount units with (1) SVZ full sized ducted unit + ducts
For 3/4, assuming the 36k outdoor is likely oversized as well.
Thanks in Advance!
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