Evaporator Coils frozen


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Old 05-31-09, 02:59 PM
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Question Evaporator Coils frozen

I have a Trane Heat Pump. Woke up yesterday morning to frozen evaporator coils in the indoor unit. Turned off the A/C and let the fan run to defrost. Thought that might take care of the issue, but no dice. We have ice again.

Coils look pretty clean, as far as I can tell. I replace the filter monthly and I replaced it after the first ice-over, although the filter I replaced had only been in it about 2 weeks. The house cooled okay between the first and second ice-over and the amount of air coming from the vents seemed normal until the ice reformed.

Outside blower is working fine, outside coils were cleaned about 2 weeks ago and are currently looking good. Refrigerant?

Haven't had any real trouble to speak of, despite the system being 17 years old.
 
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Old 05-31-09, 04:29 PM
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Could be a refrigerant problem which means you've got a leak to deal with. Could be the indoor coil has dirt embedded deep in the coil. How does the indoor fan blower wheel look? Any dirt buildup there? The only way I know of to really clean an indoor coil is to remove it from the unit and wash it out in the yard with a coil cleaning product.
 
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Old 06-01-09, 11:19 AM
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You more then likely have a refrigerant leak
 
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Old 06-01-09, 11:32 AM
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My money is on a refrigerant leak too.

Perhaps they will post back with their tech's diagnosis.
 
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Old 06-01-09, 02:33 PM
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It sure could be a leak, but let's play devil's advocate for a bit:

(1) What temperature do you like keeping inside the house? In other words, what set-point do you have your thermostat at?
(2) how humid has it been recently in the area where you live?
(3) Do you know if there's enough airflow through the coil? Are you perhaps using a filter more efficient now than in the past?

Some people like it cold inside their homes, ice-cold; and have their thermostat set-points way way low, say 65F or so. That is sure to cause icing on the evaporator coil if you have hot and very humid days. Start with a set-point of 75F, lower it incrementally over a period of a couple of hours down to 70F and so on and so forth. That would allow the unit to cycle and to progressively lower the humidity in the house, without so much as seeing the coil freeze-up.
 
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Old 06-03-09, 05:10 PM
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The fact that the coil is freezing up tells me that the saturation temp (low side) is below 32F. (<55 psi if R-22)

Either there isn't sufficient airflow, the indoor temp is too low, or there's a refrigerant leak. The presence of moisture is normal; high humidity alone will not cause a coil freeze up. (On the contrary humidity increases total enthalpy -> higher enthalpy = greater load on the coil, leading to higher refrigerant pressure/saturation point)
 
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Old 06-03-09, 05:37 PM
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Originally Posted by Muggle
The fact that the coil is freezing up tells me that the saturation temp (low side) is below 32F. (<55 psi if R-22)

Either there isn't sufficient airflow, the indoor temp is too low, or there's a refrigerant leak. The presence of moisture is normal; high humidity alone will not cause a coil freeze up. (On the contrary humidity increases total enthalpy -> higher enthalpy = greater load on the coil, leading to higher refrigerant pressure/saturation point)
Out on a limb here, but I'm pretty sure Muggle doesn't have many service calls under his belt.

Refrigerant leak is the most obvious cause given original post info.

Pflor's out of the box thinking is not only plausable, and possible, but it's probably happening right now in a million homes. This is reason #2 for temp limiting programing in todays programable stats.

In fact one of our guys put in a programable stat today for just the reason Pflor discribes.
 
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Old 06-04-09, 06:48 AM
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We've been waiting for a couple days for our A/C guy, but he seems to be jammed with work. Got a few recommendations from friends and have called in another tech that should be here today!

I'll preface the following by saying that I really know nothing about A/C repair other than what I have learned online over the past week! lol I can generally handle replacing the filter, cleaning outdoor coil, clearing condensate line and I know where the inside breaker is. That about sums it up.

DaddyJohn - The fan blower wheel does look a little dirty. As were the evap coils inside [that were frozen]. After watching an online video of a guy cleaning coils, I realized what CLEAN coils actually look like! I researched this forum and found a topic about cleaning indoor coils myself. Followed those directions and cleaned with a mild detergent, spray bottle of water to rinse and shop vac. It is now cleaner than it was, but I'm sure a tech could do a better job. That did result in better airflow at the vents, but system still freezes and is unable to cool the house at this point. Air is cool at the vent, but doesn't seem cold enough.

Answer to Pflor's questions:

We typically keep the thermostat at 74 and generally do not move it. We live in southeast Texas just North of Houston, so our humidity is typically pretty high. Temps over the past week have been in the upper 80's to low 90's. I'm guessing humidity has been 50% or greater, which is pretty typical this time of year. This is the first time this unit has ever frozen like this.

I did have the thermostat set around 68 for a day and took your recommendation. The temp in the house was about 83, so I set the thermostat at 75, but it was difficult to get the house to cool much at all until the temp went down at night. I have no way of checking the temp at the vents, but it just doesn't seem cool enough. Its not warm air, just not cool enough. In any case, the coils froze again, so I defrosted and shut it back down.

It seems like the airflow is good at the coil. We're using the same filters we always use. The one in place now is the last of a 5 pack [or however many were in there - 4 or 5]. Its just a basic blue filter with cardboard edging.

So, now we wait for the new tech to show up. Any thoughts or suggestions are welcome. I'll be checking back while we wait.
 
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Old 06-04-09, 09:31 AM
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The system has worked well for 17 years so something has changed. If it's a leak they should be able to find it with an electronic sniffer type leak detector. It sounds like you're in Humble or thereabouts. At one time in my life I was going to move to the Houston area and set up shop doing a/c, heat, and appliances. Plenty of work available there.
 
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Old 06-04-09, 09:12 PM
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Out on a limb here, but I'm pretty sure Muggle doesn't have many service calls under his belt.
I'm not a techician but have a good understanding of HVAC. (Mostly from reading service/install manuals and a little bit of formal education)

Refrigerant leak is the most obvious cause given original post info.
Agreed if the evap coil is clean.

Pflor's out of the box thinking is not only plausable, and possible, but it's probably happening right now in a million homes. This is reason #2 for temp limiting programing in todays programable stats.

In fact one of our guys put in a programable stat today for just the reason Pflor discribes.
Re-read the post - I did suggest that the indoor temp could be too low.

My point was that if the saturation point is below 32 (whether it's caused by low charge, insufficient airflow, low temp, or something else) freezing can occur starting at the metering device - lowering the setpoint gradually won't prevent that.
 
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Old 06-07-09, 04:04 PM
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Problem resolved: Refrigerant leak at the valve core.

The first tech I called [one we've used several times] showed up before the second and found the leak straight away. His assistant had been out several weeks ago when our A/C wasn't working and it turned out that a storm had tripped the breaker. He checked the refrigerant at that time and it was fine. The owner thought that was a curious turn of events and didn't charge us a thing this time around. He replaced the valve core, added 2.5 lbs of refrigerant and its been good ever since.

Gonna stop by tomorrow and drop off a couple restaurant gift cards for him. Its damn hard to find good service and someone so conscientious. No wonder the guy is so busy.

Thanks so much for your help and input!
 
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Old 06-07-09, 04:12 PM
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I'm glad it worked out. It sounds like the assistant didn't reinstall the valve core cap when he was there. You're right, its near impossible to find people and service like that anymore.
 
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Old 06-08-09, 06:23 AM
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Hard to find sometimes, but good people are still out there doing honest work for honest pay.
 
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Old 06-08-09, 08:35 AM
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I have to add that this forum has been very helpful as well. Its cool to have a place to come to for input/advice and I have learned a great deal from you guys and from all the researching I did on this forum. This is an awesome resource for folks like me who want to learn more and become a little more handy with things like this.

You've got a good thing going here. Keep up the good work!
 
 

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