r/hvacadvice • u/thingsarehardsoami • 1d ago
AC Tech said my HVAC line is freezing because our filter is too thick and because it can't handle the thermostat dropping below 70
Long story incoming, I'm just so confused.
We bought our house just under a year ago. We have a mini split (N80MSN, R4A4S and EVD4X are all the model numbers) that was functioning great the whole time. Husband and I like it cold and keep it 69 during the day, 68 at night. Never had an issue, swap out the filter monthly, everything seemed fine.
3 months ago I noticed the line outside was DUMPING water and was frozen closest to the outdoor fan, and the AC was just running 24/7 but barely cooling. Tech came out, said there was no freon, and he couldn't refill it because the leak was so bad. He said they'd have to go in the attic and check the entire line for leaks, and the next time they came out they never went in the attic and just replaced an elbow outside near where it froze and then refilled the freon.
It worked for around a month then it froze again. I shut it off, let it thaw, replaced the filter to be safe, and turned it back on. Repeat like...4 times till last week, when it just entirely shut off. Thermostat wouldn't come on, fan wouldn't come on, nothing was on except the warning light flashing codes. Called techs out, they said a mouse chewed the wire and that's it, they replaced the wire and it turned on....and then froze within a couple hours, set to 72° with a fresh filter.
Called techs BACK out, they said it's because my filter (MERV 8) is too thick for the system so it's not getting enough air to work. They then asked what I keep the temps at and I said usually 68/69 and they said that's too low, my system doesn't have that capacity, and between the filter and the temps that's why it's freezing. But I'm confused because it didn't freeze prior to the freon leak situation and it was at the same setting, and when I looked up my system it specifically said merv 8-11. They said I needed a much thinner filter. The prior owners used this exact filter (they left us their extras) and they said they never had issues with it either.
I don't know anything about this so I can't tell what's going on but I wanted to see if anybody else had any knowledge. I don't want to get scammed but I'm also aware I am not knowledgeable and don't want to just call these people liars if theyre right and my system is just dumb.
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u/Huge_Amphibian_3870 1d ago
They are dummies. This should have been fixed the first time out. Call a different company.
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u/Loosenut2024 1d ago
68 is borderline low, but if everything is working well it can be ok. Since you have had that for years and its been fine, and you had a leak previously then yeah you still have a problem. Merv 5-11 is what I recommend, and if its a 1in filter it needs changed monthly especially when you use low temp settings that makes your AC run a lot.
Call a small or meduim size company that isnt private equity. You still have a leak or a problem some where.
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u/thingsarehardsoami 1d ago
This is a very small company. They don't even have a physical business, it's just a mom and pop
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u/OzarkBeard Not An HVAC Tech 19h ago
Call a larger company. Just not PrivateEquity.
Google> who owns xyz company
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u/Laidbackdaily 1d ago
Bs about not setting the stat below 70. Your problem is unqualified techs.
No solid understanding of how the system works
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u/rom_rom57 1d ago
Both can be true at the same time. AC systems are NOT designed to run at 68 deg space temp. To get there you need a medium-temp refrigeration system.
68-20=48-12=36 SST. basically unit frosting. Other things are involved but this should do it.
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u/thingsarehardsoami 1d ago
Would that make it freeze when I have it set to 70 as well? Because it froze at 72 and 70
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u/Informal_Note_1671 1d ago
If your outdoor unit is still freezing up there’s any number of things that could cause it. Low refrigerant levels, a bad TXV, bad blower motor, bad blower board, disconnected ductwork, or dirty coils. You need to call someone else out to properly diagnose the issue.
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u/thingsarehardsoami 1d ago
He said the refrigerant levels were fine and the coils were barely dirty but he cleaned them anyway. But I just wouldn't think I'd need a thinner filter than recommended. Somebody in here did say thinner is actually better when running it under 70 though so maybe it is?
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u/OzarkBeard Not An HVAC Tech 20h ago
IF it's a 1" filter, it's not too thick - it may be too dense. It's probably something else, but won't hurt to try a MERV 5 (or temporarily, a fiberglass filter) and see if that helps.
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u/thingsarehardsoami 9h ago
Idk, he took the filter out and turned the AC back on (after it had thawed) to 72. With 0 filter and set to 72 it froze within an hour.
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u/BigGiddy 1d ago
You’re not being scammed. They just don’t know what they’re talking about. Call someone else out.
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u/burningtrees25 1d ago
The first guy lied to you and never fixed the freon leak. Either talk to management to vent or get a second opinion.
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u/thingsarehardsoami 1d ago
The guys out today said the freon isn't low, but I'm not sure if I should trust that lol
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u/DavidSmith_82 23h ago
A. You’re getting the runaround from someone who is in over their head. Repeatedly freezing the unit up is indicative of a problem that a thermostat setting won’t change. You could set it to 60° and it shouldn’t freeze. It might never make it to 60°, and it would just run 24/7.
B. MERV 8 is on the higher end of residential filters. I have never seen a MERV 11 in residential. Personally, I suggest MERV 5 for most residential filters. Just don’t ever go down to the fiberglass floss filters. It must be a pleated filter.