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Posted: 4/19/2017 4:38:45 PM EDT
Last year my AC froze up, I read it could be as a result of an airflow issue and sure enough, I had forgotten to change the filter. Swapped it out and no more issues.

Anyway, it froze up again yesterday, even though my filter is almost brand new, what could be causing this?
Link Posted: 4/19/2017 4:39:57 PM EDT
Low on coolant which means you have a leak.
Link Posted: 4/19/2017 4:40:52 PM EDT
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Quoted:
Low on coolant which means you have a leak.
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Link Posted: 4/19/2017 4:42:09 PM EDT
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Quoted:
Low on coolant which means you have a leak.
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I only froze up once and then was fine all year, does that sound right?
Link Posted: 4/19/2017 4:42:57 PM EDT
+1 to the low on coolant responses.  to thaw it out, just run it on fan for a few hours.  that'll buy you some time before the a/c guy comes over.  he can't troubleshoot/fix it if your coil is frozen over so might as well start thawing it.
Link Posted: 4/19/2017 4:43:04 PM EDT
When this happened last summer, they checked my coolant levels and they said they were ok, but it could be a blockage in the line somewhere.  Cause once I thawed it out, it never came back all summer (struggled to keep up though, old system).  I changed the attic and outside unit out back in Feb.
Link Posted: 4/19/2017 4:44:19 PM EDT
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I only froze up once and then was fine all year, does that sound right?
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The first time was lack of air flow which you learned can cause this.  This time you think you don't have a flow problem so the next thing would be low coolant.  Eitherway somebody needs to check it out.  If it's low coolant they'll try to sell you a new one.  You can get buy with just topping it off and see how it goes.

And ditto on thawing the coils before he gets there.
Link Posted: 4/19/2017 4:45:22 PM EDT
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Quoted:
Low on coolant which means you have a leak.
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QFT
Link Posted: 4/19/2017 4:45:31 PM EDT
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Quoted:


I only froze up once and then was fine all year, does that sound right?
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Lower the coolant gets the more often it will freeze up.  I'm not an HVAC tech but I'm the guy who has to get the HVAC fixed at work when it goes TU.  I've been down this road many times...

We have 10 HVAC units in our office.
Link Posted: 4/19/2017 4:57:18 PM EDT
If I had a leak, where would it be likely to be?

Anywhere?
Link Posted: 4/19/2017 4:59:16 PM EDT
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Quoted:
If I had a leak, where would it be likely to be?

Anywhere?
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Could be anywhere.  But usually it's the outside coils.  The constant vibration from the compressor eventually causes a tear.  If your installer didn't put your unit on vibration dampers it's practically a guarantee.
Link Posted: 4/19/2017 5:01:06 PM EDT
Could be a lot of things. Cheapest easiest is air flow (filter).
Next thing I would check is the Evap coil itself being dirty, not allowing air to pass.
Then superheat/subcool to check Refrigerant levels, txv (if applicable) operation, and for an over/under charge. Systems don't usually just start leaking out of the blue... Unless it's a shrader valve. Then look for non condensables in the system. Generally speaking, evap coil freezing up means the system is to cold, so it's not pulling enough air through it to evaporate the refrigerant. Or possibly incorrectly charged, (pressure/temperature relationship).  It's hard to diagnose without the proper tools.

Eta: YMMV, everyone has their own opinion/experience.
Link Posted: 4/19/2017 5:09:26 PM EDT
Evaporator coil is dirty.
Link Posted: 4/19/2017 5:10:59 PM EDT
Low coolant can cause it.

But it could still be an airflow issue. The coils may be heavily caked with dust/dirt causing condensation to build up around it and freeze into a dirt/ice block.

Happens to several units a year on the apartment complex I manage. I would clean the coils first and see if this fixes it before calling the HVAC guys out. If your airflow seems low through the vents when it's not frozen this is likely the case.

While it is frozen just switch the thermostat to fan, it will go from blowing no air to cool air to warm air once it is thawed.
Link Posted: 4/19/2017 5:14:05 PM EDT
Coils are dirty constricting flow
Link Posted: 4/19/2017 5:14:52 PM EDT
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Next thing I would check is the Evap coil itself being dirty, not allowing air to pass.
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I'm going with this.  I've had to clean mine a few times.

Tony
Link Posted: 4/19/2017 5:16:17 PM EDT
If the coolant levels are OK you could also have a restriction or piece of debris in the thermal expansion valve...meaning it acts like its low and freezes up when you get hot enough weather.  I've had that happen to me...unit would run fine until about 3pm then freeze up.  They had to drain the unit, replace the TEV and restart.
Link Posted: 4/19/2017 5:17:25 PM EDT
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Quoted:
+1 to the low on coolant responses.  to thaw it out, just run it on fan for a few hours.  that'll buy you some time before the a/c guy comes over.  he can't troubleshoot/fix it if your coil is frozen over so might as well start thawing it.
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Link Posted: 4/19/2017 5:18:49 PM EDT
Commercial Industrial HVAC Tech.

Like stated before. Lack of air flow (dirty filter or bad blower motor).

Non-condensables in the system. Ice pellits will form (water vapor in the system) and cause a restriction causing a pressure drop and the system can freeze up.
This would explain why you could thaw out the AC and it will be fine for a little or a long while. It depends.

Low refrigerant. Again causing a pressure drop and the system will freeze.

Freon is now like liquid gold in a bottle. Wholesale houses are charging anywhere between $750 and $950 for a 30lb jug of R-22.

Depending how low the system is and where the leak is at, your going to have to make a decision.

Hope this helps OP.

Sean
Link Posted: 4/19/2017 5:19:06 PM EDT
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Quoted:
If I had a leak, where would it be likely to be?

Anywhere?
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My leak was in my capillary tubes on my A-coil in my inside air handler.
Luck my neighbor was able to spot weld and save me some coin.
Link Posted: 4/19/2017 5:30:32 PM EDT
I would check the air flow over the coils first, low coolant levels will cause short cycling and cause the compressor to overheat and then shutting off on high pressure. I'm not a HVAC guy but I do have a jounrneymans license for commercial refrigeration, both freon and ammonia, the principals are the same, low coolant level won't cause freezing of the coils, low coolant will be first noticed by warmer air from the registers, followed by high pressure shut offs. Generally your coils freeze up from inadequate air flow over the coils during defrost, you may also have a malfunctioning timer. First thing to try is shut it down, wait until the ice has melted, than restart it and when it starts to freeze up put a fan on the coils and see if that helps. Your defrost fan may be malfunctioning causing insuffiect air flow. Your freon levels may be low, but when ever a "tech" shows up the standard reply is freon leak, and they do loose some, but generally a leak means you loose it all, the reason your low after a freeze up is the compressor gets hot and as the pressures increase they will release some to lower the pressure through a high pressure regulator or else something's going to blow apart. Check your temps at the register that is the surest way and easiest way to check if your output.
Link Posted: 4/19/2017 5:33:13 PM EDT
The air is always cold, I checked the evaporator coils, they were dirty. I've cleaned them and turned her on again. Keeping a close eye on it, hopefully that will do the trick and I won't be out a bunch of money.
Link Posted: 4/19/2017 5:36:30 PM EDT
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Quoted:
Low on coolant which means you have a leak.
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This. I had the same issue last summer. Turned out my evaporator coil had the tiniest leak which I had patched by a friend in the business.
Link Posted: 4/19/2017 5:47:40 PM EDT
What are the symptoms when the A/C freezes up? I have an updraft unit, I am pretty sure that sucks to check the coils on.
Link Posted: 4/19/2017 5:57:18 PM EDT
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Quoted:
The air is always cold, I checked the evaporator coils, they were dirty. I've cleaned them and turned her on again. Keeping a close eye on it, hopefully that will do the trick and I won't be out a bunch of money.
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The coils need to be removed and cleaned with the special coil cleaner, it takes at least 3 hours, and it's messy.
Link Posted: 4/19/2017 5:57:47 PM EDT
What's the weather been like? A low ambient/ load condition can case it to freeze up. Do you have a humidifier that's still on and should be shut down for the season?
Generally residential AC. Is designed to run when it's 65*F or higher ,unless it is set up control wise when the temps outside are lower.
What do you have the indoor temp set to? Sometimes during the spring time it can get warm enough and, humid enough and people will turn on the AC.
Temp at night may the drop below design running temp. Could freeze up. Just some things to consider.
Link Posted: 4/19/2017 6:07:23 PM EDT
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Quoted:
+1 to the low on coolant responses.  to thaw it out, just run it on fan for a few hours.  that'll buy you some time before the a/c guy comes over.  he can't troubleshoot/fix it if your coil is frozen over so might as well start thawing it.
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Use a hair dryer to melt the ice, DON'T use anything sharp such as ice pick.
Link Posted: 4/19/2017 6:16:03 PM EDT
Same thing happened to mine this year on a 5 year old house and the leak ended up being a bad coil in the air handler. They replaced the entire air handler under warranty.
Link Posted: 4/19/2017 6:20:22 PM EDT
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Quoted:
Low on coolant which means you have a leak.
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Link Posted: 4/19/2017 6:24:03 PM EDT
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Quoted:
Evaporator coil is dirty.
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I would suspect this, especially if you had not been changing filters. Air flow is a thing dude in HVAC Land
Link Posted: 4/19/2017 6:39:22 PM EDT
I just recently had a bad relay causing the bower fan to not come on every time it was called. It would eventually come on, but sometimes only after no airflow caused the evaporator coil to freeze.
Link Posted: 4/19/2017 6:43:28 PM EDT
If it froze up you're leaking.

I went through it twice last summer and am about to pay 6500 for new shit.
Link Posted: 4/19/2017 6:51:57 PM EDT
Either evaporator coils are dirty or low freon.

The first place I'd check for leaks are the Schrader valves on the CU.
Link Posted: 4/19/2017 7:08:01 PM EDT
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Quoted:
If it froze up you're leaking.

I went through it twice last summer and am about to pay 6500 for new shit.
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Here in FL you need a new unit every 10 years, I have a Rheem that bought down my energy bill from about $250 to about $60 during the summer. I keep it at 80 during the day and 77 at night
Link Posted: 4/19/2017 8:00:27 PM EDT
My old coils after putting many pounds in every year.



Local place offers a 80 per year check up subscription. I now sign up for it. 2 times a year they do a tune up and check things out and routine maintenance.
Link Posted: 4/19/2017 8:17:56 PM EDT
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Quoted:
Low on coolant which means you have a leak.
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Or your blower isn't running. 
Link Posted: 4/19/2017 9:05:52 PM EDT
It was an airflow issue, and has been resolved.

Thanks everyone.
Link Posted: 4/19/2017 11:07:08 PM EDT
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Quoted:
It was an airflow issue, and has been resolved.

Thanks everyone.
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Filter again?

I gotta know!
Link Posted: 4/20/2017 10:16:47 AM EDT
We had a power outage last month during a storm in which it flickered on/off before staying off.

This caused the contactor on the compressor to get stuck so it couldn't shut off. This caused the coil to freeze up.

So OP, is you compressor running all the time? If yes, it may be the contactor.
Link Posted: 4/20/2017 10:25:38 AM EDT
Dirty blower dirty coil fan running wrong direction fan running slow low charge
Link Posted: 4/20/2017 10:34:19 AM EDT
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Quoted:
If it froze up you're leaking.

I went through it twice last summer and am about to pay 6500 for new shit.
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Thirty years experience says this is only true about 10% of the time. It is most likely airflow, dirty filters, dirty evap, dirty blower, something blocking return air grill, could be restriction in cap tube or orifice type metering device, could be txv, then maybe charge... But airflow is most likely.
Link Posted: 4/20/2017 12:23:28 PM EDT
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Quoted:


Filter again?

I gotta know!
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@Riley1980

There is a kind of filter over the coils as well, it was dirty, so I cleaned it and wiped the coils down.

No more issues.
Link Posted: 4/20/2017 3:17:39 PM EDT
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Quoted:
@Riley1980

There is a kind of filter over the coils as well, it was dirty, so I cleaned it and wiped the coils down.

No more issues.
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Quoted:
Quoted:


Filter again?

I gotta know!
@Riley1980

There is a kind of filter over the coils as well, it was dirty, so I cleaned it and wiped the coils down.

No more issues.
Nice. Cheap fixes are always great.
Link Posted: 4/20/2017 4:00:46 PM EDT
I had this issue as well and it ended up being some sort of regualtor/valve that allows a certain amount of coolant to flow through the coils. (sorry forgot the name) Anyway, it was malfunctioning and stuck wide open causing the coils to freeze over. Replaced and no issues since.
Link Posted: 4/20/2017 4:31:01 PM EDT
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Quoted:
I had this issue as well and it ended up being some sort of regualtor/valve that allows a certain amount of coolant to flow through the coils. (sorry forgot the name) Anyway, it was malfunctioning and stuck wide open causing the coils to freeze over. Replaced and no issues since.
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TXV
(Thermal expansion valve)
Pretty common issue, depending on the quality of install.
Link Posted: 4/20/2017 4:44:13 PM EDT
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Quoted:
Commercial Industrial HVAC Tech.

Like stated before. Lack of air flow (dirty filter or bad blower motor).

Non-condensables in the system. Ice pellits will form (water vapor in the system) and cause a restriction causing a pressure drop and the system can freeze up.
This would explain why you could thaw out the AC and it will be fine for a little or a long while. It depends.

Low refrigerant. Again causing a pressure drop and the system will freeze.

Freon is now like liquid gold in a bottle. Wholesale houses are charging anywhere between $750 and $950 for a 30lb jug of R-22.

Depending how low the system is and where the leak is at, your going to have to make a decision.

Hope this helps OP.

Sean
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There are cheaper replacements for R22.
Link Posted: 4/20/2017 5:08:52 PM EDT
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Quoted:


Could be anywhere.  But usually it's the outside coils.  The constant vibration from the compressor eventually causes a tear.  If your installer didn't put your unit on vibration dampers it's practically a guarantee.
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we replace a 100 or more evaporator coils for every condensor coils we replace 
Link Posted: 4/20/2017 5:56:24 PM EDT
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Quoted:
we replace a 100 or more evaporator coils for every condensor coils we replace 
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Quoted:
Quoted:


Could be anywhere.  But usually it's the outside coils.  The constant vibration from the compressor eventually causes a tear.  If your installer didn't put your unit on vibration dampers it's practically a guarantee.
we replace a 100 or more evaporator coils for every condensor coils we replace 
This, its extraordinarily rare to have leaks at the condenser (not counting some dipshit not paying attention to the schraders when removing his gauges.)
Link Posted: 4/21/2017 8:58:03 AM EDT
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Quoted:
we replace a 100 or more evaporator coils for every condensor coils we replace 
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Quoted:
Quoted:


Could be anywhere.  But usually it's the outside coils.  The constant vibration from the compressor eventually causes a tear.  If your installer didn't put your unit on vibration dampers it's practically a guarantee.
we replace a 100 or more evaporator coils for every condensor coils we replace 
Well, I'm going by my small sampling size.  We've never had an evaporator go bad but at least half the outside units have been replaced.  A couple years ago we ripped everything out and converted the whole building over to Geo Thermal.  I will see how that works out in a few years.
Link Posted: 4/21/2017 9:14:04 AM EDT
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Quoted:
Could be a lot of things. Cheapest easiest is air flow (filter).
Next thing I would check is the Evap coil itself being dirty, not allowing air to pass.
Then superheat/subcool to check Refrigerant levels, txv (if applicable) operation, and for an over/under charge. Systems don't usually just start leaking out of the blue... Unless it's a shrader valve. Then look for non condensables in the system. Generally speaking, evap coil freezing up means the system is to cold, so it's not pulling enough air through it to evaporate the refrigerant. Or possibly incorrectly charged, (pressure/temperature relationship).  It's hard to diagnose without the proper tools.

Eta: YMMV, everyone has their own opinion/experience.
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This
Link Posted: 4/21/2017 9:32:48 PM EDT
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Quoted:
Could be a lot of things. Cheapest easiest is air flow (filter).
Next thing I would check is the Evap coil itself being dirty, not allowing air to pass.
Then superheat/subcool to check Refrigerant levels, txv (if applicable) operation, and for an over/under charge. Systems don't usually just start leaking out of the blue... Unless it's a shrader valve. Then look for non condensables in the system. Generally speaking, evap coil freezing up means the system is to cold, so it's not pulling enough air through it to evaporate the refrigerant. Or possibly incorrectly charged, (pressure/temperature relationship).  It's hard to diagnose without the proper tools.

Eta: YMMV, everyone has their own opinion/experience.
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He is correct. 
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