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Discussion Starter · #1 ·
For reference, I live in Eastern Canada and it has been 30C with slightly below 50% humidity for a few days now and will continue to be similar for the whole of next week.
Right now the unit is set to 18C with everything else left at auto, but the house never gets below 23C, even the hallway the unit is located in.

For the past two years it has cooled exceptionally well (even when set to 22C, it got the house to that level and lower), but for some reason the air coming out of it now barely feels adequate for the set temperature. So, while it is definitely cooling, it is not cooling at a level that feels appropriate for what it is set to.

It's been running 24/7 in heat mode during the cooler months if that helps. I've also checked the exterior unit and the fan is running with no visible debris. Running the unit with maxed fan speed instead of auto does nothing.

The unit in question is one of these two:
https://www.lennox.com/products/heating-cooling/mini-split-systems/mla
https://www.lennox.com/products/heating-cooling/mini-split-systems/mpb
 

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18c is not a normal setting - it's too cold and can cause coil freeze-ups.

Check the filter and make sure the coil in the outdoor unit is clean.

If you continue to see reduced performance, you'll need to call a tech to assess - most likely have a refrigerant leak.
 

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Discussion Starter · #3 ·
18c is not a normal setting - it's too cold and can cause coil freeze-ups.

Check the filter and make sure the coil in the outdoor unit is clean.

If you continue to see reduced performance, you'll need to call a tech to assess - most likely have a refrigerant leak.
What would be a normal temperature to set it to? Doesn't feel like it makes much of a difference anyway.

How would one go about checking the filter? The coil looks clean, as in, no obstructions.
 

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What would be a normal temperature to set it to? Doesn't feel like it makes much of a difference anyway.

How would one go about checking the filter? The coil looks clean, as in, no obstructions.
Your mini-split indoor head should have a filter you pull out and wash - you may have to lift a panel to get to it.

Too low return air temperatures absolutely can create problems - but your low setpoint is not causing the problem you have now.

Do not set below 20c - beyond that, normal setting varies depending on preference, with humidity well controlled up to 25c can feel okay.
 

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Discussion Starter · #5 ·
Your mini-split indoor head should have a filter you pull out and wash - you may have to lift a panel to get to it.

Too low return air temperatures absolutely can create problems - but your low setpoint is not causing the problem you have now.

Do not set below 20c - beyond that, normal setting varies depending on preference, with humidity well controlled up to 25c can feel okay.
Nothing to clean on the outdoor part? Like I mentioned before the coil is unobstructed but are there filters or other things in that I should try and clean?

Also just pulled out two filters from the indoor unit and yeah, they're caked with dust and other stuff. Gonna shop-vac them now.
 

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There is no filter on the outdoor part - you can check both sides of the outdoor coil for dust/dirt buildup.
Clean off loose dust/dirt with a soft bristled small broom, then flush out with low pressure water from a hose, being sure the water is going through the coil straight - go at an angle and you may bend fins.
Do not use a high pressure jet nozzel ever.

Your problem may go away with clean filters.
 

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Discussion Starter · #7 ·
There is no filter on the outdoor part - you can check both sides of the outdoor coil for dust/dirt buildup.

Your problem may go away with clean filters.
Yep, shop-vac'ing the filters did the trick. Will wash them tomorrow morning as it's too hot right now to let them dry before putting them back in. Thanks!
 

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18c is not a normal setting - it's too cold and can cause coil freeze-ups.
Well you are correct....but it's a moot point since he can't get it there anyway.
Many people think the thermostat is a "gas pedal"....the lower you set it the faster it cools.
It just doesn't work that way...with the exception of multiple stage equipment.
The first thing is to check the operation of the equipment and the charge.
I would guess that the line set has a leak since that is by far the most common problem with split systems.
 

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I wash the outside units of my mini-splits. I make sure that no electricity is going to them by removing that tab thing in the cut-off box on the wall near the mini-split. I remove the lid. Be very cautious because there are lots of computer and circuits in the outside unit that should not get wet. Then I spray water gently from the inside toward the outside. I figure the dirt got there from the outside so the dirt should exit toward the ourside. I have washed them many times.
And you are right. The mesh screens on the inside units get covered with lint and dirt very quickly and must be washed, shaken, dried and returned to the unit. The little cloth type filters get dirty and are very expensive to replace so I wash them also.
 
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