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Posted (edited)

Look what the cat dragged in!


I have a mini split that serves my sunroom on the back of the house.  Its rating is more than enough for the area it serves.  Obviously, in really cold weather it’s going to be less efficient.  I also have a free standing gas stove (vented) in the same area that is more than capable of heating the area without struggling even in the coldest weather I get here in Maryland.  
 

I’ve been trying to decide if I should shut the mini split down and run the gas stove during lower temps such as below 30.   I’m guessing the gas stove will be more expensive to run and that’s ok but only if there’s some other benefit.  The benefit would be reducing excessive wear on the mini split.   I’m ok with the mini split being less efficient and I’m even ok if it falls behind a few degrees as it tries to keep up.  I’m not ok if it suffers excessive wear while it struggles to keep up.  The mini split has a built in automatic defrost cycle and I see it performing that task now and then.  I never let snow or ice from inclement weather obstruct the coil 
 

So, my question is this.  Does a mini split suffer excessive wear while it’s struggling to keep up in cold weather, or, is the only issue that it can’t meet the heating demand?

 

Thanks gents.  

Edited by John Dirks Jr
Posted
11 hours ago, John Dirks Jr said:

So, my question is this.  Does a mini split suffer excessive wear while it’s struggling to keep up in cold weather, or, is the only issue that it can’t meet the heating demand?

Hey John,

The answers depends solely on whether or not it has the inverter driven compressor.  Hope you don't have an economy DIY system.

A properly-sized cold climate system shouldn't ever "struggle to keep up".  Even down to 5°F.  Again, hope you don't have an economy DIY system.

Posted (edited)

Thanks for the reply Bill.  I’ll look closer at the system to see exactly what it is.  The first system I had was a DIY that failed due to a bad line set.  The second one was not sold as DIY, although I installed it myself. 
 

When I say it struggles to keep up, I mean the room temperature may drop 2 or 3 degrees below the 70 degree set point  when it gets below 25 degrees outside.    Now, if I crank the demand way up, say 80, it will ramp up and start pumping more heat to catch up.   But if I just leave it at 70, it may fall behind a couple degrees 

Edited by John Dirks Jr
Posted

I've never heard of that brand - maybe exclusive to home improvement stores? 

The inverter controlled compressor is variable speed - usually resulting in longer run times.  Less on/off cycles should result in less wear.  So, I wouldn't be concerned about it running for very long periods.

I would be curious however, about why it drops 2-3° below the thermostat setting.  I haven't experienced that with correctly sized systems intended for cold climates until they get close to 0-5° ambient.  I know Mitsubishi has one that doesn't skip a beat until below -13°.

Posted

It was either Home Depot or Lowes where I got this one.  I can’t remember off hand.   
 

The data sheet says its low end operating range is -13.   
 

This morning it was 15 degrees outside.  The thermostat had been set last night at 70 degrees.  The temperature in the room when I woke up was 65 degrees.  I grabbed the controller and bumped the demand to 80 degrees and went to take a shower and make my lunch for work.  I went back out to the sunroom after that and the room temperature was up to 71 degrees in that short (30 mins) time frame.  
 

Clearly the system can produce adequate heat as long as you increase the demand.  However, it’s obviously not matching the set temperature when it comes to the “maintaining” 

Im not going to do anything about it.  I just wanted to make sure that it’s reasonable to leave it as the primary heat source instead of the more expensive to operate gas stove.  

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