AC suddenly freezing up.


  #1  
Old 05-14-12, 12:33 PM
M
Member
Thread Starter
Join Date: May 2012
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
AC suddenly freezing up.

hi
I have a 2 ton carier split system that is freezing up. We had both units upstairs and down serviced 3 weeks ago, the tech, who is reputable (installed my brother's infinity system last year) had added 1lb of puron to each unit. The original install was extremely poor. The ac always worked poor up untill we had it serviced. For the last 3 weeks it has seemed fine always keeping up with being set on 69. I came home from work yesterday to 75 degrees set on 69, little air coming out of the vents. I am knowledgeable in ac so I checked the condensor, the cool line was of course completely frosted. I shut it off and let the blower run to defrost the evaporator. My first thought was the new filter i installed was too restrictive so I took it out and turned it back on. Within 2 hours it was frosted again. shut it off again, it only takes about 30 minutes to defrost. turned it back on before bed last night with the fan set to on instead of auto and it still frooze. The tech was here this am said he changed the fan speed, he feels the ductwork is undersized, and now that it is properly charged, it's freezing. he is the one that lowered the fan speed last week sayig it was set for a 3 ton when we hae 2 ton. After he left it still is freezing up just not as bad. Does it sound like it's loosing it's charge? He did not hook his gauges up this time as he remebered doing it a few weeks ago when he checked. he states that the return duct should have a box before it goes into the evaporator, right now the circular flex duct just goes straight into the evaporator leaving no room for the air to spread out and reach all parts of the coil. Does this seem logical?
condensor iis clean
evaporator is clean
filter is clean
supposedly proper charged (as of 3 weeks ago)

My question is, does the poor duct design combined with a proper charge and normal fan speed seem like it would cause this condition.
My theory is that it has worked fine up until yesterday because it has been cool and the cycles in the pm have not been long enough to cause a freeze up. Sunday was 83 which allowed it to run and freeze.

Does this sound like the metering decvice is failing?
The tech is coming back tomorrow to install the metal box, I am going to ask him to change the fan speed one notch. I will also tell him that as soon as he left this morning it begain icing up again.
Hopefully this is not confusing, but thank you in advance for any help you can give. let me know if confused.
 
  #2  
Old 05-14-12, 02:58 PM
C
Member
Join Date: Aug 2008
Location: Texas, California
Posts: 1,410
Upvotes: 0
Received 7 Upvotes on 7 Posts
First thing to check is to make sure it is properly charged. Three weeks ago is not Today, may be that AC tech did not close the valve 100% after he charged the system 3 weeks ago. Do not blame on the existing equipment, they have been there for a long time already.
 
  #3  
Old 05-14-12, 03:51 PM
M
Member
Thread Starter
Join Date: May 2012
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
ok, hope it is not low again.
one last thought while he was checking the charge during the tune-up some of the supply ducts were closed off because we have 2 units and try not to condition the hall and bathroom which would allow the air to simply go downstairs (where we hae not turned ac on yet). now that they are open, i would assume it would help the situation but, is it possible that on the hot day when it acted up, was it because those registers were closed when the tech hooked up the gauges. could the extra heat load that was not present that day be throwing the system off balance now that it is under a higher load?
 
  #4  
Old 05-14-12, 09:56 PM
user 10's Avatar
Member
Join Date: Mar 2004
Location: NA
Posts: 1,830
Received 57 Upvotes on 50 Posts
Freezing is caused by insufficient airflow or refrigerant leak.

Open every vent and change the filter.

If it still freezes, you have a leak.
 
  #5  
Old 05-15-12, 04:32 PM
M
Member
Thread Starter
Join Date: May 2012
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
tech came out this am, installed a return plenum. The return used to be flex duct and would just go right on the air handler. Tech said it was not allowing the entire coil to recieve even air flow. Apparently the freezing never happened in the first 5 years because the charge was not good and the coil never got down to 32. working fine now, will know for sure tomorrow when it's warmer.
thanks for the advice everyone!
 
  #6  
Old 05-15-12, 04:55 PM
hvactechfw's Avatar
Member
Join Date: Jan 2011
Posts: 5,491
Upvotes: 0
Received 4 Upvotes on 4 Posts
Adding refrigerant will keep the evap temp above 32F. If it were low on charge it would go below 32F. The change of blower speed is going to also affect the evap temp, especially if the duct work was undersized. FYI, systems don't get low on refrigerant unless there is a leak. You should not have to add refrigerant as it is a CLOSED system.
 
  #7  
Old 05-15-12, 08:39 PM
C
Member
Join Date: Aug 2008
Location: Texas, California
Posts: 1,410
Upvotes: 0
Received 7 Upvotes on 7 Posts
Sounds a little odd, watch the system for a few days and let us know.
 
  #8  
Old 05-16-12, 11:20 AM
M
Member
Thread Starter
Join Date: May 2012
Posts: 4
Upvotes: 0
Received 0 Upvotes on 0 Posts
Your right that is odd. it's still fine today and it's 83 and humid. The reasson refrigerant was needed was because during the initial installation none was added to compensate for the lineset. Also, initially they set the fan much higher then needed which, I would think would keep the evaporator above 32 even tho the charge was slightly low. With the fan blasting like that, it removed no humidity. Before all these changes it seemed to run excessively, fall behind, and it was still un comfortable. EVerything feels and looks much better now. Also, the air coming out is much colder then it ever was.
 
 

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