Mini-Split Freezing

Reply

  #1  
Old 01-25-21, 02:51 PM
Z
Forum Topic Moderator
Thread Starter
Join Date: Sep 2005
Location: USA
Posts: 5,654
Received 172 Votes on 153 Posts
Mini-Split Freezing

Have a 2-year old mini-split system which is having some problems. Having a technician come out to address, but I like to make sure I'm informed enough to talk to them.

The system works fine for a while (heat), but after a while starts blowing cold air. Shutting off all the units, then restarting each One of the indoor units seems to be icing up, as there was an icicle hanging from it. The outdoor unit looks normal, it's not covered by snow/ice or anything unexpected.

I know with AC, freezing coils often indicates low refrigerant. But I've never considered a heat pump freezing up in the winter.

FYI, it's not all that cold here. 32 degrees, and the units are Mitsubishi "Hyper Heat", so outdoor temp shouldn't be an issue.
 
  #2  
Old 01-25-21, 04:40 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,373
Received 1,397 Votes on 1,294 Posts
The system works fine for a while (heat), but after a while starts blowing cold air.
That sounds like the system is going into defrost mode. In defrost the system goes back into A/C mode. It tries to withdraw room heat and deliver it outside to unthaw the condenser. If there is no electric reheat.... you may feel cold air.

It's not only the outside air temperature.... it's also the humidity level. The higher the humidity the faster the unit will frost/ice up requiring more defrost cycles.

You could very well be low on refrigerant.
 
  #3  
Old 01-25-21, 06:47 PM
Z
Forum Topic Moderator
Thread Starter
Join Date: Sep 2005
Location: USA
Posts: 5,654
Received 172 Votes on 153 Posts
Interesting concept with the defrost mode. I'd imagine it's not supposed to go through that cycle too often.

I'll post back with more details - but I appreciate knowing more now than I did when I started!

 
  #4  
Old 01-25-21, 06:51 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,373
Received 1,397 Votes on 1,294 Posts
I was looking further into Mitsubishi units with VFR (variable fluid) and it appears their system work more efficiently to defrost unit. From what I was reading there isn't supposed to be cold air flowing inside. I'm guessing to a certain extent that makes sense.

Interesting reading
 
  #5  
Old 01-26-21, 01:56 PM
Join Date: Jan 2009
Location: United States
Posts: 783
Received 35 Votes on 33 Posts
The Mitsubishi "Hyper Heat" and cool are actually some of the better Mini-splits out there. As long as it was installed properly it will be fine not like the One I have in a rented apartment the install crew were lousy people both people and work ethic skills.

They will have to fix it now as I *fixed* it so it will not work in either heat or cool mode.

But I have seen a few of them completely covered in ice and frozen solid.

They are all them same model but not all have the Hyper Heat H2i badge Why don't know maybe older ones.

The place still has the 240V electric baseboards and I use that I would only use this for heat as a backup not the primary heat source.
 
  #6  
Old 01-26-21, 02:30 PM
Z
Forum Topic Moderator
Thread Starter
Join Date: Sep 2005
Location: USA
Posts: 5,654
Received 172 Votes on 153 Posts
Thanks Pete and CB. Had a tech out today and he troubleshot it to the reversing valve. Apparently there's a known issue with certain Mitsubishi models with the valve getting stuck in defrost mode (or something highly technical like that). The part is covered under manufacturer warranty, but I'm foreseeing a fight with who's going to pay for the labor. We'll see - it's a big local company who I definitely paid 'extra' for their support, so we'll see how it goes. They haven't said one way or another yet, so maybe I'll be pleasantly surprised.

But thanks Pete, you got me reading about the defrost cycles so when they said it was the reversing valve, I knew exactly what he was talking about!

CB - I do like the Mitsubishi units. I'm also a fan of the Fujitsu mini splits. Have 2 systems of each installed in rental properties. This is the first real issue I've had. Well, other than a poor install which caused a refrigerant leak. Can't really blame that on the units though - just the fly-by-night contractor I had install it.

Anyway - will keep you updated... really appreciate the help!
 
  #7  
Old 01-26-21, 04:11 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 61,373
Received 1,397 Votes on 1,294 Posts
Not keeping the insides of the refrigerant lines clean during installation can allow crap into the reversing valve too.
 
  #8  
Old 01-26-21, 04:42 PM
Join Date: Jan 2009
Location: United States
Posts: 783
Received 35 Votes on 33 Posts
Thanks Pete and CB. Had a tech out today and he troubleshot it to the reversing valve. Apparently there's a known issue with certain Mitsubishi models with the valve getting stuck in defrost mode (or something highly technical like that). The part is covered under manufacturer warranty, but I'm foreseeing a fight with who's going to pay for the labor. We'll see - it's a big local company who I definitely paid 'extra' for their support, so we'll see how it goes. They haven't said one way or another yet, so maybe I'll be pleasantly surprised.

But thanks Pete, you got me reading about the defrost cycles so when they said it was the reversing valve, I knew exactly what he was talking about!

CB - I do like the Mitsubishi units. I'm also a fan of the Fujitsu mini splits. Have 2 systems of each installed in rental properties. This is the first real issue I've had. Well, other than a poor install which caused a refrigerant leak. Can't really blame that on the units though - just the fly-by-night contractor I had install it.

Anyway - will keep you updated... really appreciate the help!
Yep fly by night I hate them the company was out of NY and is no longer in business anymore!

Yes Mitsubishi & Fujitsu are the only decent units made.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: