mini split buying and help with measurements

Old 11-21-21, 01:28 PM
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mini split buying and help with measurements

I know what everyone will tell me its not that easy figuring this out but I am giving it a go anyway. I am going to install 2 dual zone mini ductless systems in my home. I need to know how to calculate how big of a unit I will need for my second floor rooms though. since the house is a cape style with an addition on the rear it is a very odd setup.
The rear room has 3 ft knee walls and is 30x13. how do you take into account that the ceiling is sloped in your calculations for BTUS for heat and cooling?
according to the standard chart this would need a 12K air handler inside but in reality with the sloped ceiling it gets hotter and cooler faster up there then I thought. there is only one electric heater currently in that room 1750 watt and it seems to get warm right away when I kick the heat up and have to turn it down to around 66 to keep it from getting too hot up there. any help would be greatly appreciated. I know this is something that a professional would be able to work out with numbers but I do not have the time or money to hire a lot of people to figure these numbers out. I am installing the units myself since I have done them in the past for others but they never really had a sloped ceiling to deal with. My biggest concern is oversizing the units since we really need to get the humidity out of the room also.
Old 11-21-21, 03:32 PM
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Most mini splits always run the indoor fan. This can cause very high humidity. I recommend researching the brand of minisplit that you are considering to verify that this will not happen.

If it only comes with a remote control then the fan will probably never turn off.

I have only found that Mitsubishi enables you to cycle the indoor fan with cooling demand.
(If you purchase the optional MHK1 thermostat and cut the JRRE jumper in the air handler)
Old 11-21-21, 04:02 PM
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Old 11-22-21, 07:14 AM
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If it only comes with a remote control then the fan will probably never turn off.
Cielo makes smart controllers that replace remote controls and has a setting for humidity control in its Comfy mode.

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