Portable AC unit - only beginning of cooling coils get cold

[mikebVirginia]

I have a LG portable AC unit (10,000 BTUs). I noticed it started cooling very poorly recently. Took it apart, used an IR thermometer, and found that the inputs to the evaporator coils got VERY cold (under 30 deg) and frosted over. But just a few inches past that, the coils were almost room temp. And the input to the condenser coil was almost room temp. So it appears that the coolant is being cooled well, but not flowing. Does this mean there is low coolant? Or a blockage impeding flow? I suspect low coolant since both inputs to the evaporator get very cold, and both evaporator coils warm up a few inches in. Thanks for any input!!

 

[Dana]

That's usually a symptom of lower than spec refrigerant volume, probably a slow leak.

 

[Sponsor]

 

[WorthFlorida]

As Dana stated, you're definitely low on refrigerant and only last night did my own AC freeze up. A tech is coming to day. The only solution is a tech with gauges, refrigerant and the sniffer to detect any leaks.

The pressure must be high enough that the boiling point of the refrigerant is not lower than around 36-38 degrees. Right now your boiling point is below freezing for water, therefore your inside coil condensate will immediately turn to ice. On very hot days the compressor is constantly running to meet the cooling load (poor cooling as you have) and the ice slowly builds up to a point that little or no air can flow through the coils. At this time you'll notice that the compressor is running very loud since it is trying to compress liquid refrigerant instead of gas.

 

[mikebVirginia]

That's usually a symptom of lower than spec refrigerant volume, probably a slow leak.

Thanks for the reply! Very helpful.

 

[Jorgebaloy]

I have a LG portable AC unit (10,000 BTUs). I noticed it started cooling very poorly recently. Took it apart, used an IR thermometer, and found that the inputs to the evaporator coils got VERY cold (under 30 deg) and frosted over. But just a few inches past that, the coils were almost room temp. And the input to the condenser coil was almost room temp. So it appears that the coolant is being cooled well, but not flowing. Does this mean there is low coolant? Or a blockage impeding flow? I suspect low coolant since both inputs to the evaporator get very cold, and both evaporator coils warm up a few inches in. Thanks for any input!!

Signs Your Air Conditioner is Low on Refrigerant

Unexplained High Energy Bills
Often, the first thing that will alert you to a serious problem is an increase in your energy bill. Chances are good that you might not even notice that your air conditioner is working harder to keep you comfortable until your energy company makes it apparent.

Trouble Maintaining Comfort Level
If the air that is coming from your vents doesn’t seem as cold as it once did, if it seems like it’s taking ages for your home to cool off, or even if you can’t get the temperature down to a comfortable level, then low coolant may be the problem. The coils in your air conditioner won’t get as cold as they should when there isn’t enough coolant in them, and this means that the air passing over them can’t get as cold as it did before. As such, your air conditioner is working much harder, but without fixing the leak and recharging the coolant, it won’t be able to get the job done.

Ice on the Outdoor Part of the Unit
Finally, the last big giveaway that your air conditioner is low on coolant is the formation of ice on the outside component known as the compressor. Whenever there isn’t enough refrigerant in the system, the pressure drops in the evaporator coil. This allows the temperature to drop at the same time, causing the coil to drop below freezing and develop what could be a thick sheet of ice – even if it’s 100 degrees outside. The humid air hits the below-freezing coil and condenses there, and the beads of water forming as a result freeze rather quickly. This continues over and over again until the unit is iced over.

Regards!

 

[Jorgebaloy]

When the cooling coil has a nice thick ice build-up on its surface there will be no cool air produced by the air conditioning system at all. The fan runs, outside compressor/condenser run, but little or no air moves through the duct system. The page top photograph shows icing on the cooling coil and refrigerant lines exiting the coil inside air handler close to the evaporator coil even.

You might see ice formation on the suction line just outside of your air handler even though you cannot see the evaporator coil itself - on most residential air conditioning systems, the surfaces of the cooling coil are not readily accessible by the homeowner. But if you don't see ice on the suction line, ice could still be present on and blocking air flow through the cooling coil.

The cooling coil, or evaporator coil is visible if the air handler is opened on some air conditioner units. At other installations the cooling coil is completely covered and can't be seen at its location (say on a retrofit installation atop an existing hot air furnace) unless an inspection opening has been made (by cutting the steel and installing an access panel cover), or unless there is an opening that was made previously to install a humidifier in the same plenum chamber.

When an air conditioning system with a frost-blocked coil is turned off and allowed to warm up the ice on the coil melts and spills into the internal condensate collector tray in the air handler. Then when the air conditioner is re-started it may for a while produce cool air before becoming ice blocked again. If an air conditioning system behaves in this way coil icing is a possible explanation.

Frost build-up indicates an air flow or refrigerant problem. A blocked coil (by dirt) or a blower fan which has lost its ability to move air (such as a dirty squirrel cage fan) will reduce air movement across the coil and lead to frost build up there. We suspect this is the more common cause of this defect. We discuss the problem of dirt on the cooling coil slowing air flow and leading to ice-build-up at DIRTY COOLING COIL / EVAPORATOR COIL.