A-coil Freezing Up

kg321March 26, 2008

I have an A-coil that is freezing up at the orifice area first then going thru rest of a-coil.

Freon level is fine, A-coil very clean, I checked orifice and is fine, filter is fine, nothing blocking return vents, ducts fine, fan motor/blower motor fine, and

I even blew air with air compressor thru a-coil at orifice to break any restriction but no luck, ran a vacuum afterwards and fine so no leaks. Carrier unit 2.5 ton condensor and a-coil. Outside temp about 70 so doesn't seem cool enough to cause freeze up.

My question is does where the freezing begin give any indication of problem (in this instance on liquid line at orifice vs outside first)? Any other ideas on what it could be, or would you condemn A-coil as having a restriction inside?

any help would be appreciated.....thx....kg

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Most likely cause is incorrect refrigerant charge,or a restriction in the metering device.Do you have a set of service gauges?What is your suction and discharge readings?You will need to gather these readings before coil freezes up,because it will change as it gets blocked by ice.If the outside temperature being at 70 degrees is the reason,there is a way to simulate a summertime condition -by blocking the airflow to the condenser coil,but I wouldn't resort to that yet....I will have to talk you through it.

    Bookmark   March 26, 2008 at 10:38AM
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how do you know the indoor coil is freezing up at the cap tubes. if you have the door off of it looking at the indoor coil that is your problem. the system is desighned to pull air through the coils., not around it. if the system is charged properly filters are clean and you are moving the proper amount of air across it, then put the door on it and let it run. you will not have any problems with it. but if you take the door off of it it will freeze up a solid block of ice.

    Bookmark   March 26, 2008 at 6:07PM
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I can see the small line freezing up behind the orifice with the door on, and then can see the others frozen when taking door off.

The guages read 40 / 300 (low on low side/ high on high side). When adding freon, the high side continues to go up so would not be due to low on gas. The outside temp reading was 74 degrees today when checking.

Would you say it is a restriction in a-coil at this point?

For some reason, I could not get orifice out when checking it. I would stick tooth pick in, and pull on it but would not come out but appeared not to be clogged up, as I stuck tooth pick in hole to clear anything out.


    Bookmark   March 26, 2008 at 7:47PM
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Obstruction according to pressures

Pull the orifice clean and backflush coil with nitrogen and install new suction and high side filter dryer along with proper purging, evacuation and charging procedures.

    Bookmark   March 26, 2008 at 8:31PM
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there is deffinately a problem. restriction, wrong orfice something is deffinatley wrong with the indoor coil with those pressures. how old is the unit. has any body opened the system is it a mobile home. what brand system is inside.

    Bookmark   March 26, 2008 at 10:44PM
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You have a restiction that is easy to ascertain the hard part is finding where it is it seems you hav already done everything that anyone would do so you have to be creative if you blow pressur back through system again you need to obstruct the airflow in certain areas I know that is not very specific but I can't see what you see just know that air pressure like water will take the path of least resistance so you need to plug up some stuf to blow out the obstruction

Here is a link that might be useful: Air Conditioning and Heating Repair Made Easy

    Bookmark   March 26, 2008 at 10:58PM
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How old is your system ? Your pressures are also indicative
of a bad compressor. Does it pump down ? Do the pressures
equalize immediately ? The pressures will equalize more
slowly in a restriction but will equalize. You just need the experience to tell the difference. Blowing air into the
system, VERY BAD thing.

    Bookmark   March 27, 2008 at 2:51PM
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"How old is your system ? Your pressures are also indicative
of a bad compressor."

The suction pressure would be much higher than normal if the compressor was bad.....What do you think - krantzcool or z1700?

    Bookmark   March 27, 2008 at 5:48PM
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the compressor is operating perfectly if the compressor was bad then the pressures would be close together for example 120 and 130 its kinda like your blood pressure you want them to be different for example 65 and 225.and if the compressor was bad it would not be freezing up. restrictions are tricky. you need to call a hvac company for that. if you try and fix it yourself you will do more damage than good. they have the tools to fix this problem. they have to find the restriction, remove the restriction, install dryers and vacuum the system down. this problem is not something you want to take on yourself. if you dont do those things your system will not ever function properly. you could have moisture in the system that is freezing and that could be your restriction.you need to call an expert for this problem

    Bookmark   March 27, 2008 at 8:13PM
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Let me run this by you. I have a semi hermetic compressor
valve plate in my hand right now. The suction pressure is 0 high side 600. What's wrong ? As i said before. Does the compressor pump down ? That has to be done or you will be playing guessing games all summer. If it doesn't the comp. is bagged. Put the compressor in a closed loop and if it equalizes in 5 seconds it's bagged. If it doesn't equalize it's bagged. That will eliminate one problem. Then work on the other problem. How fast does the suction pressure drop ? That will tell you how bad the restriction is if the compressor is good. It's just experience.
Sorry about the trick question on the valve plate. I know
what is wrong with it. Oh Yah. The suction pressure would
be much higher if the compressor was bad. YES. If the valves were carboned shut and suction pressure was 0 is the compressor good or is there a restriction ?

    Bookmark   March 27, 2008 at 9:01PM
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Correct gardening engineer & the ones that follow

If the compressor was failing, either the rings or valves the pressures would be more equal and you would never see that high of a head pressure.

This system has been opened; with out proper purging and triple evacuations, possible itÂs alot of non condensables in the circuit?

    Bookmark   March 27, 2008 at 9:43PM
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when valves in the compressor goes bad it causes refrigerat to leak by the valves which causes the pressures to get closer together. but yes if the valve was stuck shut it would be 0. but i have never seen that happen. but with these pressures that they tol you and twith the coil freezing up like it is where does a bad compressor even come into question.

    Bookmark   March 27, 2008 at 10:49PM
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The system is 13 yrs old. I've got another a-coil same size, 2.5 ton carrier. Think I'll replace A-coil and hope this takes care of restriction. Krantzcool, you mentioned could have moisture in system. How does moisture get into system and how do you get out? If the restriction is in the a-coil and I replace the a-coil, should I still replace the drier filter outside?

    Bookmark   March 28, 2008 at 12:25AM
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there is moisture in the air. any time you open the system always replace the dryer and vacuum the system atleast 3 times. if you install a suction line dryer you should replace it after 24 hours of running. suction line dryer is probably not needed but i would only know for sure if i saw the system. if you replace the coil install liquid line dryer and vacuum the system you should be fine. the problem is if nobody has opened the system something else in the system has broken down and that is where your restriction came from. so something else may be going out

    Bookmark   March 28, 2008 at 11:10PM
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If this was a moisture problem it would not be constant there is a resriction. either the orifice is improperly sized or some other obstruction is causing this problem most times taking the orifice apart and blowing backwards through the system will get rid of whatever is causing the problem but don't use air use dry nitrogen then do all the previously stated things to clean up the system or as many times as you have had it open you will have more trash come through

Here is a link that might be useful: Air Conditioning and Heating Repair Made Easy

    Bookmark   March 29, 2008 at 9:03AM
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1. what's the best method to charge freon for hermetic or semi-hermetic compressors?

2. is it recommended to charge using freon 12. 22 or 502 by letting the cylinder upside down..meaning can we charge it with liquid freon? will it damage the compressor?

3. our filter dryer is cold what's the possible problem of the packaged type unit?..10 ton capacity

4. our package type unit has 25 to 35 suction and 275 psi disch pressures..what is the possible problem?..

* would like to ask your expertice regarding these questions and some problems encountered and for the benefit of other readers to know the best and more profesional way of dealing with refrig and air-conditioning practice.

thank you in advance and best regards..

note: would like to share also my exp next time..

    Bookmark   June 7, 2008 at 4:56PM
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