Replace compressor/evap with mini-split/cassette in 3 storey townhouse?
Paul_OOS
| Posted in GBA Pro Help on
I have a 3 storey townhouse, 1700sqft. I’m replacing a 20yrold 1.8T Bryant by front door, evaporator coil in the plenum. Problems with leaks (40ft line!), noise, energy $ to push cold air up 30ft of duct + (in winter) evaporator obstruction to hot air. I’m thinking a mini-split on the roof gable, feeding a cassette in 3rd floor ceiling (line ~12ft). How can I make this work?
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Replies
Paul,
If it were my home, I would hire an independent engineer calculate your loads and spec a replacement system. For more info, see https://www.greenbuildingadvisor.com/article/who-can-perform-my-load-calculations.
If you have an open staircase a ceiling cassette on the 3rd floor would do a decent job of cooling most of the space bellow, or at least anything that doesn't have a door. It will only heat the 3rd floor though.
The best solution would be to combine the two. Keep the exiting ducting and replace the leaky air handler. There are some modulating split systems that come with standard air handlers such as the Mitsubishi PUZ-A24NHA7 PVA-A24AA7. These are not cheap, your selection will come down to what is locally avialable, climate zone and local energy costs. You can then add in a ceiling/wall mount on the 3rd floor for better comfort there.
One thing to be careful with is the outdoor units. You generally don't want these mounted onto wood framing as it will pickup the vibration from the compressor. These should only be mounted onto masonry walls or the ground. Long lines are much better than dealing with the noise.
It is no surprise that your system is being replaced because it leaks. I suspect most are replaced because it take time and hard work to find and fix the leaks or component failed due to contaminants entering the system thru the leak. Often people get tired of having the gas and go guy come by twice a year to recharge the system.
Clearly lots of mini splits get installed high on wall and seem to work.
It seems the installed and service men must be working from some type of lift. I am not sure saving 40 feet of copper line is worth the cost of getting a lift on site.
I would be concerned that the outdoor unit will vibrate the wall and make noise inside the house.
Walta