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Mini Split Low Temp Setting

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13K views 4 replies 2 participants last post by  xk49  
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#1 ·
I have just recently had a Mitsubishi Mr. Slim mini-split installed. I wanted to have the system as a backup system to the oil boiler in case the oil burner ever quit(it's in a vacation home) while I wasn't there. I usually set the thermostat on the oil system to 45-50 degrees as I'm not there most of the winter(house is in Maine). I was completely surprised the remote for the mini-split only allowed me to set the temperature of the mini-split unit to 59 degrees, no lower. Well, that is going to work as the mini-split will be running all the time.

I've contacted the installer and he said to use the "Smart Set" feature on the remote, but what I've read in the instructions that Smart Set only adjust the temp +/- 4 degrees from the heat setting, which is still not what I want.

Is there any reason why this unit can't be set to lower than 59 degrees? Does anyone know how to do it? I don't have the mini-split unit model/serial # as I'm not currently living at that house right now, but I just had it installed so it would be a newer model.
 
#2 ·
Heat pumps are not designed for large swings in set point temperatures and not as a back up to the primary heat source. As far as the oil I would keep the heat set at 55 (45 - 50 is to low) when not there and get a stat that you can remote monitor and notifies you when something is wrong.
When you arrive and the house is warm then the heat pump can maintain the set point.
 
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#3 ·
I can remotely monitor the house and if an issue does come up, I can be there in about 2.5hrs. I understand the heat pump should not be used as a primary, but if the oil furnace is set to lets say 50 and the heat pump to 45, then the heat pump would just be used as the "oh ****" factor. It's not trying to compensate for a large heat swing, just maintaining an above freezing point until I can get there. Does that make sense?
 
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#5 ·
pecmsg said:
Mitisubishi Minis are one of the most efficient units on the market. 59* is the low end on the control then leave it there. Its still cheaper then burning oil. Call there tech support # they can tell you why the 59* Minimum.
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Heat pumps systems perform poorly in low temperatures, which is why I only wanted it as a backup. I would find it hard to believe a system running at 59 degrees would be more cost effective then a system running at 45degrees, especially with oil as cheap as it is. I'll try tech support if I can find a number.
 
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