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Anonymous Poster

A/C Freezing on Compressor and Suction Line

08/20/2008 6:23 AM

Hi Guys,

Please I have a split A/C system, I noticed some ice block forming on the Compressor (within the outdoor unit). I first suspected the refrigerant not been at the proper gauge but a colleague told me that it was not the cause. According to him, its due to weather condition (rainy season) which I wasnt really convinced. Plaese Help me out.

Regards to all

EB

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Associate

Join Date: Jul 2008
Posts: 45
#1

Re: A/C freezing on the Compressor and suction line

08/20/2008 7:58 AM

There are several reasons for this as follows:

  1. It may b a LG brand unit with more numbers of finns in cooling coil getting choked by dust in return air very offen causing liquid flooding back to compressor. Frequesnt cleaning of air filter and keeping the coil very clean will avoid this.
  2. Thermostat might have been set on very low temperature with low speed indoor fan operation there by cooling coil not geting enough heat to eveporate the liquid and flooding back.
  3. Indoor unit Blower motor bearings are dry and enough cfm of air is not supplied over the cooling coil thereby allowing the raw liquid to flood back into the compressor.

In all these cases, it is harmful to the compressor. The refrigerant is a dry cleaning agent and will dry up the bearing surfaces causing over loading of compressor motors and in long run will burn out the windings. Only super heated dry refrigerant should enter the compressor for best performances.

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Guru
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#2

Re: A/C freezing on the Compressor and suction line

08/20/2008 9:41 AM

In my experience, there is two main reasons the compressor will have a build up of ice: insufficient air flow, or the compressor running too long.

Insufficient airflow can be caused by;

  • a closed vent, or
  • clogged filters, or
  • slipping belt on the fan, or
  • slipping fan blades, or
  • bad brushes on the fan motor or faulty motor,or
  • anything that obstructs the air flow.

The compressor running too long is usually caused by an electrical fault;

  • It could be a faulty thermistor. Usually it, or the wires are shorted to the frame.
  • It may also be caused by a faulty relay, or
  • the control dials or switches are faulty.
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Associate

Join Date: Dec 2006
Location: Silverdale, Washington
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#3

Re: A/C freezing on the Compressor and suction line

08/20/2008 1:15 PM

All mechanical refrigeration is based on the changing state of the refrigerant.

The relationships between the liquids / gas / temperatures / sub-cooling and superheat of the refrigerant as applied in any unit will answer your problem.

Cold outdoor temperatures would cause the condenser to sub-cool the liquid more than at a higher outdoor temperature. The effect would be more cooling capacity.

The temperature difference between the indoor entering air and the temperature of the air leaving the indoor coil factored into the amount of air moving across (CFM) the coil will tell you the amount of heat being transfered.

As most small A/C units are working with a fixed refrigerant flow (Cap Tube), a lower amount of heat transfer will cause refrigerant to flood back in the suction line. The refrigerant has not transfered enough heat to rise the superheat of the refrigerant vapor.

Low air flow across the evaporator coil is the most common cause of this problem.

Learn to check the refrigerant system operations correctly and you will be on your way to solving this problem and most refrigerant cycle issues.

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Guru

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#4

Re: A/C Freezing on Compressor and Suction Line

08/20/2008 7:08 PM

the system is low on freon.

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Power-User

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#6
In reply to #4

Re: A/C Freezing on Compressor and Suction Line

08/20/2008 11:56 PM

Of all the answers in this blog, you are probably correct! Without checking temperatures and pressures we cannot really tell, but the chances are that low freon is correct. It can also be from a kinked suction line.

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Participant

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#10
In reply to #6

Re: A/C Freezing on Compressor and Suction Line

08/21/2008 7:28 AM

A low pressure on the suction gauge can be caused by a blocked Filter or a clogged A/C coil.Adding refrigerant because of a low suction pressure is a common mistake made by techs that dont investigate the real problem.

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Guru

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#5

Re: A/C Freezing on Compressor and Suction Line

08/20/2008 11:36 PM

The rainy season and high heat combimed will cause some units to freeze up.

Sheilding the outside unit from the sun and making sure it has nothing blocking the air flow is about all you can do without making changes to the system .

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Active Contributor

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#7

Re: A/C Freezing on Compressor and Suction Line

08/21/2008 3:43 AM

I AGREE WITH ALL POINTS MENTIONED

PLS CHECK THE GAS VALUE OR GAS QUANTITY , IF THE GAS VOLUME IS LESS IT WILL MAKE ICE FILM ON THE CONDENSER AND THE OUT PUT POWER WILL BE LESS TOO.

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#8

Re: A/C Freezing on Compressor and Suction Line

08/21/2008 4:48 AM

If you find ice formation or frosting on the suction-side of the compressor check suction side gauge if its less than set its one of the indication low ref regent in the system ,moisture in the ref regent also leads to frosting on the section side best option would be pump down the refergrent in to the receiver if its provided or in to the condenser flush the system with Co2 as co2 has grate affinity for moisture and will absorb the moisture present any, maintain vacuum in the system for 24hours ,replace silica gell cartridge before charging the system and run your system good luck

crm

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Commentator

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#13
In reply to #8

Re: A/C Freezing on Compressor and Suction Line

08/22/2008 7:26 AM

Never use co2 in a refrigeration system. Nitrogen as the only gas to be used for leak testing or double and triple evacs. Moisture is removed by the evacuation process. Filter drier changes are also part of the moisture removal procedure. Evacuation to at least 500 microns or better.

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Active Contributor

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#9

Re: A/C Freezing on Compressor and Suction Line

08/21/2008 7:06 AM

How old is the system? If the evaporator coil has never been cleaned, even with regular filter changes, it tends to weave a "wool" blanket on the inner face where it can't be seen. This causes a severe loss of air flow that will flood the compressor and cause freezing. In small split systems I have rarely found loss of refrigerant will cause freeze up. It usually just runs with a warm suction line and no cooling effect.

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Participant

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#11

Re: A/C Freezing on Compressor and Suction Line

08/21/2008 7:33 AM

Low refrigerant charge can cause this. Also low or no air flow on indoor evaporator coil can cause icing which can eventually cause the icing outside. Check for dirty indoor filter, low fan speed or fan not running; all of these can cause the coil to become completely iced over. Low refrigerant charge should be checked with pressure gauges designed for refrigeration; must use caution because of high pressures and chance of freezing your fingers attaching and removing hoses. If you aren't sure about which line to connect to, you had best not try the procedure.

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Anonymous Poster
#23
In reply to #11

Re: A/C Freezing on Compressor and Suction Line

09/23/2009 9:14 PM

low charge freeze up would only reach the first few bends on the evaperator, never making it to the compressor....frozen lines means liquid present with the vapor returning to the compressor which happens with low air flow or over charge...low air flow will give a frozen evaperator also and overcharge will have a normal evaperator but frozen suction line starting close to the compressor or frozen when exiting the accumulator to the compressor...other obscure reasons also but most likely if the system was working then its an air flow thing

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Guru
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#12

Re: A/C Freezing on Compressor and Suction Line

08/21/2008 11:51 AM

Running your AC at low ambient temperatures can cause icing up. Define rainy season.

All the other comments are on the right path. The one thing that was not mentioned was the outdoor condenser coil. When was it last cleaned? A dirty condenser will give you symptoms that mimic loss of charge or poor air flow over the evaporator coil.

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Commentator

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#14
In reply to #12

Re: A/C Freezing on Compressor and Suction Line

08/22/2008 7:32 AM

Dirty condenser will result in high head pressure. Hardly mimicking low refrigerant charge. Little to no subcooling on hi side, hi suction and superheat on low side.

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#17
In reply to #14

Re: A/C Freezing on Compressor and Suction Line

05/27/2009 9:26 PM

Initially you are correct. but if the problem is left un attended,I have seen refrigerant starved evaporators ice up. Please note: we do not have ambient operating temperature, compressor discharge pressure, suction pressure, sub-cooling, evaporator superheat, etc.

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Anonymous Poster
#15

Re: A/C Freezing on Compressor and Suction Line

05/27/2009 7:52 PM

You guys are fairly useless, try reading back over the replies here. Half conflict with the other half. Is this a forum for engineers or technicians?

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Guru
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#16

Re: A/C Freezing on Compressor and Suction Line

05/27/2009 9:03 PM

You asked for information and you got responses, most all them are probable causes for your problem. Do want an engineer or a technicians answer? We are both here on this forum, and yes, we may disagree. If all else fails, break down and bring in a reputable air conditioning company to correct you problem.

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Anonymous Poster
#18

Re: A/C Freezing on Compressor and Suction Line

05/30/2009 6:26 PM

Any freez up in suction line in an AC system indicates unsaturated raw liquid refrigerant flooding back. This may be due to (a) low heat load on eveporator indoor fan being runing at low speed or air dirty filter n there by less cfm of air across the eveporator. (b) Room thermostat is set at v low temperature (c) low ambiant temperature (d) at last over charged refrigerant in the system.

In either case it is harmful to the compressor as the flood back of liquid refrigerant will dray up the bearings there by over heating n burn out of winding. It is very essential that the compressor is fed with super heater vapor refrigerant only. It is not a liquid handling pump but a compressor designed to handle saturated vapor refrigerant only. It is necessary to analyse the problem with reference to the ambient temperature, operating suction and discharge pressures and indoor room temperature along with the amps that the compressor is drawing against the rated load. If the AC system is over sized to the room load, it should also be cross checked

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#19

Re: A/C Freezing on Compressor and Suction Line

06/02/2009 9:32 AM

I can't beleive how many bad answers there are. You cannot create frost/ice on a compressor that is flooded with liquid!

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#20
In reply to #19

Re: A/C Freezing on Compressor and Suction Line

06/02/2009 3:35 PM

The term flooding back to the compressor is used when liquid refrigerant is entrained in the returning refrigerant. The liquid then flashes into gas at the compressor, adsorbing heat. The other term used is low superheat

It is not truly flooded. As mentioned before, this is bad news and will kill the compressor by washing out the lubricating oil, or if enough comes into the compressor while it is running. mechanical damage may occur. Liquids do not compress well in this part of the universe.

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Anonymous Poster
#24
In reply to #19

Re: A/C Freezing on Compressor and Suction Line

12/13/2009 7:54 PM

It is true that you cannot create frost/ice on a compressor if the condensor is filled with liquid on a usual AC system. But this is a split system, it is possible that while on one evaporator it is receiving liquid and if the entire system is low refrigirant, then the second evaporator will be sucked of it's refrigirant thereby freezing the suction line from the second evaporator to the compressor. This can be confirmed by checking the working evaporator's suction line to were it joins to the second evaporator line, it should not be frozen.

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Anonymous Poster
#21

Re: A/C Freezing on Compressor and Suction Line

09/06/2009 10:40 AM

hello

If the ice forming is on the discharge pipe (the narrow pipe),the problem is that the system is short of gas.If it is on the suction pipe (the wider one),check the indoor unit filter,or the system is a little bit over loaded with freon.

Elton Spiteri

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Anonymous Poster
#22

Re: A/C Freezing on Compressor and Suction Line

09/23/2009 9:05 PM

I cant believe there are so many different answer to this problem, change the filter!

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Participant

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#25

Re: A/C Freezing on Compressor and Suction Line

07/18/2010 3:26 AM

Can someone answer me this? If a system a is so-called low on refrigerant charge, meaning that the refrigerant will quickly evaporate into vapor in thee evaporator. How is it an inkling of a possibility that a system may be low on charge when "ICE" or "FROST" forms on the suction line?

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#26
In reply to #25

Re: A/C Freezing on Compressor and Suction Line

07/20/2010 11:28 AM

Keeping it simple. Treat the system as a closed system. Fixed volume. Refrigerant pressure and temperature are relative to each other. The higher the pressure, the higher the temperature. I will not get into superheat and de-superheating.

As the pressure drops in the evaporator so goes the suction line. At a certain point the gas temperature is low enough to cause the condensation on the evaporator and the suction tine to freeze. As the leak continues there will not be enough in the system to provide any sensible cooling.

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#27
In reply to #26

Re: A/C Freezing on Compressor and Suction Line

07/20/2010 11:03 PM

ok thanks make more sense now

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Anonymous Poster
#28

Re: A/C Freezing on Compressor and Suction Line

07/29/2010 12:52 PM

10-year-old gas pack, suction line ice-covered , house 83 degrees with thermostat on 73 degrees. Cause was a clogged freon filter. This unit has had compressor replaced due to lightning damage. Don't know if filter was changed when compressor was changed.

This cost me $483.00.

Bob, Surry VA

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#29
In reply to #28

Re: A/C Freezing on Compressor and Suction Line

07/29/2010 3:11 PM

The plugged refrigerant filter will mimic a low system charge. Both will have low suction pressure. The difference will be in the head pressure (discharge). A low system charge will have low head pressure and the restricted/clogged filter will give you high head pressure.

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Participant

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#30

Re: A/C Freezing on Compressor and Suction Line

06/26/2012 1:09 PM

The only main reason why there is ice formed in the compressor and suction line is because there is lacking or freon in the unit.Charge exact refrigerant in the system and the icebuilds will removed.

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