Cooling coil ice & frost formation diagnosis & cure questions and answers.

These FAQs help diagnose & fix ice or frost blockage of the cooling coil or evaporator coil in an air conditioning / heat pump system. ower fan.

This article series explains the causes & cures for evaporator coil icing: the problems of ice and frost formation in air conditioning system air handler units, blower units, or AHU's, duct work, or other air conditioning system components.

FAQs on Causes of Ice or Frost Build-up on the Evaporator Coil or Refrigerant Suction Line

These questions and answers about diagnosing and curing frost or ice build-up on the indoor coil of heat pump or air conditioner coils were posted originally

at FROST BUILD-UP on AIR CONDITIONER COILS - be sure to review that article.

If your concern is ice build-up and defrost cycle for the outdoor unit coil on a heat pump system in heating mode,

see HEAT PUMP OUTDOOR UNIT DEFROST CYCLE.

Page top photo of an iced-up air conditioning evaporator coil are courtesy Guy Benfante.

Watch out: always check the obvious cooling coil icing problems first: blocked air flow for any reason, such as a dirty air filter, or an improper refrigerant charge, or a refrigerant leak leading to low refrigerant charge are common causes of coil frosting and ice at the indoor air handler.

 

A/C Cooling coil in my air handler is icing up and the blower won't work

I have a ac/heater combo in our home, the heat or furnace part works fine but I've switched over to the AC cooling part for the summer and the cooling coil on my furnace is iceing up and the blower does not cut on! What is causing this can anyone help please?

You can hear coolant running thru the coils but the blower does not come on like when in the heating mode! Central electric furnace model#E812B serial#990695614 On 2017-04-22 by Stacy

Reply by (mod) -

Stacy

The article FROST BUILD-UP on AIR CONDITIONER COILS suggests the most-common reasons for cooling coil icing, such as low refrigerant caused by a leak.

But when at the same time the blower isn't turning on the coil icing is more-likely caused by lack of air flow across it. So the root problem is probably the blower fan control.

First check the thermostat settings to be sure the unit is set to COOL and fan to AUTO.

If the blower doesn't come on then try putting the fan switch to ON or MAN - if the blower runs then the problem is probably a bad control relay or board.

See AIR CONDITIONER WON'T START - topic home

 

My A/C is freezing and not cooling and won't turn off?

What does it mean if the AC is freezing and not cooling and its turned off but still running and I had work on it two years ago on 10/28/2010 - 2012-05-23 by Stacy Evans

Reply by (mod) - frost on AC coils

Stacy,

First see if your system's air filter is dirty or blocked and if so, put in a fresh clean air filter. If that's not the trouble then

see the diagnosis and repair advice at the recommended articles at the top of this page.

 

After cooling for a while A/C airflow slows and air temps rise

My air conditioner works great for awhile and then the cold air stops coming out and the air temp starts to rise.

The outside fan is still running. Can anyone help? - On 2011-06-27 by sherry -

Reply by (mod) - check for iced coil

Check for a cooling (evaporator) coil in your indoor air handler: is it blocked by frost or ice? If so that's the trouble.

Check for a dirty air filter or blower fan or other cause of restricted airflow.

Your service tech can check the refrigerant charge level (and fix any leaks).

See the diagnosis and repair details at FROST BUILD-UP on AIR CONDITIONER COILS

 

Do you think that the evaporator is dirty / in need of cleaning; or was it just iced up due to the continuous running of the unit?

I just moved into a new 3-level townhome with Central air for the whole home PLUS a 2nd cooling unit (Space-Pak type) for the 3rd level only.

Approximately 2 weeks in, noticed a drop in cooling (hot day); checked the air filter, was completely clogged, replaced it. A few weeks later, very hot day, noticed drop in cooling again.

Thermostat temperature never reached. Manually shut down unit, restarted, worked better.

After reading this site, I understand now that the evaporator was likely iced/frosted. 3 days ago, very hot days, water backed up in the unit. Service call, drain backed up.

Cleaned the drain. My question is: Do you think that the evaporator is dirty / in need of cleaning; or was it just iced up due to the continuous running of the unit? I measured the air temperature at one of the outlet/vents and it is at 57 degrees.

I would think that a dirty evaporator would mean poor performance of the Space-Pak even before ice could build, whereas since I am still getting poor performance on very hot days only once the system is running for a very long time continuously (12-24 hours or so), I am assuming that the evaporator problem is/was ice and not dirt.

I am thinking of changing the thermostat to a more advanced model that I can program with a cycle time for both on and off (i.e. never on continuously more than 6 hours, never off continuously less than 30 minutes) as well as changing the fan (air handler) from "auto" to "on" (which I have already done.)

Since I have changed from Auto to On, I have noticed an improvement (assuming that the ice buildup is draining more quickly / evaporator coils are warming more in between cycles).

Also, the large pipe (copper, approx. 1" dia.) wrapped with insulation feeding the unit has had some small amount of ice very close to the unit where there is a small tear in the insulation.

Not sure if this is left over water from the drain backup (the serviceman said that all the insulation was likely soaked as a result and could take 7-10 days to clear up). Thoughts? - BB 9/3/11

Reply: cooling coil (evaporator coil) frost troubleshooting

BB

I'd have the system evaporator coil inspected for dirty conditions and cleaned if needed.

The thermostat program you suggest is an interesting idea, but in my opinion a properly working AC system operating in hot weather should be able to run continuously without icing the evaporator coil.

A dirty evaporator coil should also show up as reducer airflow. Also the blower fan itself may be dirty, reducing airflow and so leading to coil icing.

Reader Follow-up:

Thanks. I had a chance to read the notes left behind from the technician that performed the service call: he noted that the evaporator coils were rusted. I am assuming that this is causing the icing.

Should I look to replace just the evaporator, or upgrade the entire Unico cooling unit at this point?

What would you recommend as the cost/benefit considerations for the decision? I am assuming that the condenser and air handler are in good shape since the cooling and air flow are quite good just after the unit starts. I am assuming that it would be more cost effective to replace only the evaporator. Any thoughts based on your experience?

Reply:

Interesting. I've never seen rusted evaporator coils since they are usually made of aluminum or copper, though there may be steel parts around the coil itself that can indeed rust

. Perhaps the tech meant corroded. Gross corrosion, enough to clog the coil fins, would block air flow and could contribute to coil icing, though I don't usually find that the root cause.

I'd ask for a price estimate on coil replacement; it's a big job in that the system has to be evacuated and recharged as well as cutting out and soldering in the new coil. Let us know what you're told and I'll comment further

Reader follow-up:

I asked a different company to come quote on "repairing" the problem, where the problem was simply stated as a lack of cooling after some length of time when the unit is running, with evidence of icing (and subsequent leaking resulting from the thaw).

They suspected a low refrigerant charge, and will come back and look for a leak (for which they are charging me, no pun intended.) They did indeed say that the evaporator coils are copper, not rusted, and that no evidence of poor airflow was seen. I will keep you posted to see if a leak was found. - BB

 

Question: ice on the refrigerant line, no cooling in the house

My line set going to outdoor unit has ice on it. Lost cooling in house. What is the problem and is there anything I can do to fix the issue - Pat

Reply: check the indoor air handler for an ice-blocked coil

A problem with a refrigerant metering device (thermostatic expansion valve, capillary tube, etc), or even a dirty air filter can lead to improper metering of refrigerant into the indoor cooling coil, leading to icing; but other causes of ice formation include an improper refrigerant charge or even something as simple as missing refrigerant line insulation.

But when you also lose cooling inside, I suspect an ice blocked coil.

See these diagnosis and repair guides

REFRIGERANT LINE FROST 

FROST BUILD-UP on AIR CONDITIONER COILS - indoor cooling coil

Then see LOST COOLING CAPACITY - why is my A/C unit or heat pump not cooling ?

 

How does a low refrigerant charge cause the indoor evaporator coil to ice-up

How does a low amount of refrigerant entering the evaporator coil cause it to ice up? Bob

Reply:

Bob, low refrigerant means too little in the cooling coil, lower evaporation temperatures, ice formation. Details of the explanation begin at

FROST BUILD-UP on AIR CONDITIONER COILS

And at REPAIRS for FROST / ICE on COIL we include a more technical explanation titled

Reader Question: why does a low refrigerant charge cause frost to show up on the coil ?

 

Replaced air conditioner compressor, new system is icing up

Question: My air conditioner outdoor compressor motor blew; now the new system is icing up, what's going on? Added another return to it .

I may have to change duct size maynot if indoor unit is close to returns . I hope that helps a bit - Chris 3/15/12

Reply:

Rooster said:

Sounds like you may have put a 1500HP Blown Hemi in a Volkswagen. One thing to try: did the installer select the proper fan speed for the air handler?

If the fan is running in a slower speed (usually for heating, not A/C), air flow will be inadequate. But I'm betting on inadequate duct capacity.

Probably should have stuck with the 4 ton evaporator coil.

Sounds like an oversight or ignorance on the installers part to me.

Also see COOLING COIL or EVAPORATOR COIL for our article on causes of cooling coil ice problems. Something as simple as a dirty filter or blower fan can cause the trouble.

 

Haier AC unit is forming frost or ice on the indoor cooling coil

my question is I have turned off my 1 ton Haier ac its inner unit is shut off but not outer unit due to which it it creates ice in inner unit can you let me know what is the issue. Thanks !! - Asim Niaz 9/15/11

Reply:

Asim, if the indoor blower unit is not running and the outdoor compressor is running the lack of air movement across the evaporator coil will lead to frost and ice formation on the coil.

A TEV can jam from dirt and debris or other contaminants including moisture that can actually freeze in a TEV. It's not a part you can change out yourself.

Under COOLING COIL or EVAPORATOR COIL you'll find diagnosis of ice or frost blocked cooling coils.

 

Will the evaporator coil freeze up if the outdoor compressor is off?

If the outside unit of the heat pump does not run, and the interior unit continuously runs (even when thermostat is set to "off" position). Will this cause the evaporator coil to freeze? On 2018-08-01 by Keith

by (mod) -

Not likely, Keith.

When the outdoor compressor/condenser is not running refrigerant is not going to move through the system so the coil is likely to stay at the temperature of the building air.

Evaporator coil ices over at water sourced heat pump system

Have a water sourced heat pump and evaporator coil is iced over, what could be the cause? Also there are no strainer in the system. On 2017-06-06 by Stocky07

by (mod) -

Probably one of the causes listed in the article FROST BUILD-UP on AIR CONDITIONER COILS, Stocky. The most-common causes of coil icing are probably a dirty air filter or a refrigerant leak, followed up by a sticking TEV as a more-distant third.

Panasonic indoor A/C unit freezes up

Hi, I am finding difficulty with a Panasonic indoor unit. It freezes up right up to the piping and to the suction and discharge.

When I first attended to it, I noticed the discharge pipe icing up and the evaporator coil covered with ice. So I melted the ice, and removed the unit.

Serviced it really well and fitted it back. Everything is functioning well, but after a while, ice builds up again on the evaporator coil right up to the piping.

Gas pressure is OK. Can the problem be the PC board? and if so, which component? Thank u On 2017-02-13 by Joseph

Answer by (mod) -

Joseph:

I'd be looking for either low refrigerant (a leak to be found and fixed) or an expansion valve or cap tube that's not working properly.

What would cause oil in the compressor to boil up into cap tubes?

I am working on a Rheem 4 ton roof top unit all in one . I found the Cond fan blocked and I think the oil over heated and boiled up into the cap tubes . There are 8 cap tubes feeding the evap . I flushed out and blow nit. thru the tubes . It help a little bit but it still not blowing very cold air.

I think there is still oil in the evap coil as the coil in some spots not cold . Do you think I should blow them out again ? Or could the compersor be bad ? Thanks On 2016-08-23 Alan Gingold

Reply by (mod) -

What would cause oil in the compressor to boil up into cap tubes?

Once oil gets into the cooling coil we'd expect it to find its way back into the suction line and back to the compressor's low side, right?

Does this system have a receiver ? Probably. Have you any idea if the refrigerant charge is correct?

Ultimately you may have to replace the cap tubes and to add filter/driers

Why is there Ice on the refrigerant lines for our swamp cooler system?

Starting today the lines running from the swamp cooler on the ground to the house started icing up today it is roughly 100 degrees. What would cause these lines to get ice on them? On 2016-06-20 by Tammymontgomery46@gmail.com

Reply by (mod) -

Low refrigerant or defective expansion valve are the most common causes, Tammy

 

Heating service tech comments on why there's ice on the cooling coil

Check the TEV or Capillary tube: it may bein the wrong posistion; check the amount freon - if it's low there is a leak to be found before adding refrigerant; On 2015-11-11 by Anonymous

by (mod) -

Thanks Anon, indeed a bad cap valve or TEV valve sensor can cause improper metering of refrigerant and can cause coil frosting; But let's point out that

1. frost is normal on refrigerant lines in some conditions - Richard you may just be missing insulation.

2. Frost if there is also coil icing, suggests, in addition to a referigerant metering problem, other causes such as low refrigerant;

3. If the tech opines that nothing was wrong but a circuit board, then I infer she never opened the refrigerant circuit, so there should not be a new issue with lost refrigerant blamed on the service call;

However replacing a compressor does require cutting refrigerant lines, pulling a vacuum, and re-charging when the new compressor is in place.

4. I do worry about multiple compressor failure; some things that might cause that include:

- improper wiring

- improper refrigerant charge

- failure to install a burnout filter-drier set at the new compressor installation

- low service voltage

Searching InspectApedia for "causes of compressor failure" returns several helpful articles including

BURNED-OUT HVACR COMPRESSOR 

Fixed iced up coil by turning off the A/C system for 3 hours - now the outdoor condenser fan stopped working

AC is on AUTO. When the fan stops, the inside unit was noisier than usual so upon inspection.

I saw the coil is icy and the unit and the air around the unit was very cold similar to the temperature of a freezer. I turned the system off and flipped the main breaker off but the inside unit continued to go through the cycles without the fan.

After about 3 hours, I turned back on the breaker and the cycling stopped. Since, I changed the filter and the AC is working now but I sense that this is a temporary fix and the problem will persist. What do you think is the problem?

By the way, all my problems started after a simple service call in May - $150.00 for maintenance. In June, the tech was back because the AC was not working at all. He replaced the contactor and fuze for about $350.

Then suddenly, the outside fan was not working resulting in the system blowing warm air. The tech then replace the capacitor for another $135.00 In 3 months, I am out $635.00 and do not want to deal with that company again. Please help, what could be the problem? On 2015-07-24 by Gina

by (mod) -

Gina

Take a look at the causes for cooling coil icing in FROST BUILD-UP on AIR CONDITIONER COILS.

One of those is likely to explain the situation you describe. Some of these fixes, such as changing out a dirt-clogged air filter are easily within homeowner scope while a low refrigerant charge requires an expert service tech.

Question: Will a bad compressor cause ice to form on the cooling coil in an air conditioner or heat pump?

The unit get frozen, cleaned, freon ok, could it be the compressor?

How often is the compressor the problem with icing at the cooling coil? - Anon 6/6/11 -

Reply by mod:

The compressor itself won't cause icing at the cooling coil; if the compressor isn't working you'd have no cooling and no ice.

But if a control fails at the compressor so that it never turns off or if a refrigerant metering device (like a TEV) is not working those problems can cause icing at the cooling coil indoors.

 

Question: What causes ice to form on the cooling coil in an air conditioner or heat pump?

My friends condensor coil is iced up and his house is warm. The outside temp is 89. What can be the cause and if we run a hose on the coil will it help the problem by melting the ice ? - Jack Christian 7/8/11

I have a small haier air conditioner window until, you can open it right up in the front and see all the exposed ice. What would most likely be the problem and how could I find it to fix it? - Brianna Shollenberger 7/8/11

The article has cleared some doubts which I had since a long time. As I understand now, likely causes of ice formation are unclean filter/coil, incorrect amount of refrigerant, or thermostat not working properly.

Hope this helps to solve problem I have been having with our bedroom AC. Ice starts forming if I set the temperature to 24 degrees centigrade, or less. Without cooling, the room temperature is around 30 degrees. - Ramesh Chopra 7/17/2011

Air conditioning will not work. Frozen coils. Have defrossted unit inside and outside, replace the air filter and cleaned the outside unit.

Outside unit fan is working fine. No air being blowing into the house, except when I turn on the heater. Then the air continues to blow. Need advice as what to do to get it to continue blowing when the ac is on. (May 23, 2012) tina 

Reply: the most common causes of ice formation in the air conditioner are:

Watch out: always check the obvious cooling coil icing problems first: blocked air flow for any reason, such as a dirty air filter, or a refrigerant leak leading to low refrigerant cha

I suggest going through the text at FROST BUILD-UP on AIR CONDITIONER COILS, then ask us a specific question and well be glad to do our best to help.

Ice formation inside the equipment on the coils or refrigerant metering devices is not a normal operating condition, but it's a common defect often traced to

• Any problem that has stopped or reduced air flow through the system, such as a dirty air filter or crimped or disconnected air ducts.
  
  Collapsed or crimped air ducts, collapsed duct interior insulation, a closed duct damper, closed supply registers, or a dirty blower fan in the air handler unit, even a mis-wired thermostat or bad system control board can also cause reduced or halted air flow.
  
  Find and fix the air blockage.
• Low or lost refrigerant - can cause evaporator coil icing because of abnormally low pressures on the low side of the cooling system.
  
  Often this condition deteriorates to no more coil icing and no cooling whatsoever as the refrigerant leak continues and eventually there is just little or no refrigerant gas left in the system.
  
  Find and fix the leak and recharge the system.
• A refrigerant metering device problem such as a dirty or mi s-adjusted thermal expansion valve or a partly-blocked capillary tube.
  
  Dirt in the system, compressor oil circulating into a capillary tube, and ice on the TEV can cause these problems as well.
• Please review the more extensive description of causes & cures for ice formation in FROST BUILD-UP on AIR CONDITIONER COILS

If a cooling coil or other components inside the air handler or air conditioner is freezing up the cause needs to be found and fixed; Iced coil means less or no air flow across the coil - it stops working. That's why the indoor temperature creeps up and why air flow is further reduced in the system.

A small amount of frost found on the refrigerant lines right at the uninsulated line at the entry to the cooling coil and sometimes at the compressor is common and may not be serious.

Brianna in your small A/C unit icing is most likely one of two things:
a dirty air filter is slowing airflow across the evaporator coil OR the level of refrigerant in the unit has dropped a bit too low.

Ramseh: yes; I'd add that a bad thermostatic expansion valve could also cause coil icing. The first cause I suspect is a dirty air filter, the second cause I suspect is low refrigerant.

 

Question: Cause of ice on an ammonia based chiller

why ice on ammonia chiller or evaporator in an arena? - Ali Khan 1/30/12

Reply:

Ali ice can form on any HVACR equipment when conditions produce temperatures below freezing. The root causes are the same as those listed in the

article FROST BUILD-UP on AIR CONDITIONER COILS, regardless of the refrigerant gas or chemical used.

 

Question: Water Chilled air conditioner for a marine vessel

I have repaired a water chilled air cond for a marine vessel, our men renew the entire piping for HP and LP circulation, after install all, the refrigerant only able to inserted up to 30psi, when running the system, it wont let any refrigerant to be inserted, and the piping and cooling coil start frozen and ice build up.

I don't know what is the cause of defects, anyone can give some advises? thank you. - Dave 5/18/12

Reply:

Dave it's possible that a capillary tube or thermal expansion valve (TEV) is clogged or frozen.

Keep in mind that the procedures for charging on the high side of the system expect liquid refrigerant while charging on the low side of the system can only be safely done with refrigerant in a gas form.

Details are at REFRIGERANT CHARGING PROCEDURE.

(Sept 17, 2012) Nate said:

The run capacitor on my air handler disconnected, and the fan stopped blowing sometime in the night. When I woke there was ice and frost on the coils.

I plugged the capacitor back in and the blower ran fine. I then ran the blower for a couple hours to melt the ice. But when I turned the system back on it frosted up again even with the blower now running! Could the original freeze have caused another problem? Thanks.

 

Question: can the dog cause cooling coil icing problems?

We have a dog that goes in and out of the house continously, leaving the door ajar, causing the a/c to labor.

Will constant hot air being drawn into the house cause freezing of the coils/ (Oct 7, 2012) Bob said:

Reply:

Bob

No, not unless there is also another operating problem with the system.

But leaving the door ajar may melt your wallet. It's time to look into installing a pet door for fido.

Watch out for more subtle A/C or heating system problems traced to pets: pet hair can clog an air filter (leading to coil icing and weak air flow) as well as clogging other equipment air movement pathways.

 

Diagnose and fix AC not cooling: blocked air flow over the coils - don't forget to replace the cover or close the air handler door

Sharing to assist others.

AC wasn't cooling, automatically changed the filter. The old one was no more than 4, likely less but was the dirtiest filter I ever changed. No big deal but no cooling either. The system had frozen. OK, defrost, AC off, fan on. Defrost done, restart, ice immediately reformed.

Find out that if condensation is still on the pipes, that easily happen. Repeat defrost, try again. Frost reforms.

Learn that if any vents are closed, the air won't circulate so I checked all vents. Repeat, frost reforms again. Learn that sometimes to flow the coolant, you need to equalize the indoor and outdoor temp.

At 9:30 PM came the DUH moment. With the cover off of the evaporator system, that I left open to help defrost and to inspect, there was not enough air flow over the coils for it to operate. For my hours of reading yesterday not a single site said the key words "replace cover".

There is also no need to open it to inspect. Simply looking at the fitting going from your outside AC unit will tell you if the system is freezing over or not. On 2022-08-02 by Penny -

by InspectApedia-911 (mod) - cooling coil icing or a dirty filter

@Penny,

Thank you so much for taking the time to write those notes.

It's quite correct that one needs to inspect the system more than superficially to find a problem with cooling coil icing or a dirty filter.

We will be sure to keep your comment with the article.

 

Lost 5 pounds of refrigerant and coil iced over - is that normal?

AC iced up for the first time and required 5 lbs of refrigerant. Is that normal for a 2.5 ton unit? On 2020-11-14 by Peter Lindemann -

by (mod) - No; refrigerant leaks are common but not "normal"

Peter


Forgive me as I know this sounds a little glib, but it is never normal to have to add refrigerant to an air conditioning or heat pump system.

If you do that means there's a refrigerant leak that needs to be found and fixed.

 

How much refrigerant loss before coil starts icing up?

I agree that loss of refrigerant is not normal. But my question is: does the unit really have to lose 5 lbs (@ $50/lb) before it starts to ice up? I live in Florida and we have 85° F. On 2020-11-15 by Peter -

by (mod): 0°C or 32°F at sea level - but a quantitative refrigerant charge number can't be given

Peter

That's a great question: how much refrigerant loss can occur before we see a malfunction in an air conditioner or heat pump.

Bottom line: there is no single "right answer" because the size of HVACR equipment varies widely (tonnage for example) as does the refrigerant charge. But every refrigeration system has a low charge point below which we'll begin to see abnormal frost formation on the evaporator coil.

As soon as enough refrigerant has been lost that the coil or refrigerant line surfaces fall below freezing (0°C or 32°F at sea level) we expect to see frost or ice begin to form.

A 2.5 ton unit holds maybe 6 or 7 pounds of refrigerant.

A cooling system will continue to operate as it loses refrigerant and counter-intuitively, runs colder (because of lower pressures on the suction side of the cooling coil);

I suspect that an examination of the cooling coil in your unit would have seen heavy frost and icing well before a total of 5 pounds was lost, but the system might continue to run, though at reduced efficiency or reduced cooling output.

Many occupants or owners don't notice that trouble until so much refrigerant has been lost that either the coil is totally blocked with ice or even more refrigerant is lost and there is no cooling effect whatsoever.

Watch out: it's easy to confuse other causes of coil frosting with refrigerant loss than simply lost refrigerant (the case you report)

For example (not your case), a dirty coil or dirty air filter reduces air flow across the coil; that in turn reduces the heat load on the coil; that in turn can cause frost formation and even some icing. The danger of this condition is that a newbie HVACR tech might simply try adding refrigerant without checking out the system.

That risks liquid slugging the compressor with refrigerant, causing very costly damage.

Other causes of coil frosting that might be missed

- fan in the evaporator is not running

- burnt-out or inoperative defrost heater or defrost timer not working or improperly-set (I've seen perfectly-good refrigerators tossed out for this reason)

- over-sized unit (this condition will have been present since installation)

Expert sources I've read such as over at achrnews note that a very small amount of frost on the evaporator coil actually increases its efficiency but as more frost collects the evaporator function decreases until it may become totally blocked with thick heavy frost or "ice".

For an in-depth article on coil frosting causes and diagnoses I refer you to ACHR at https://www.achrnews.com/articles/142963-dont-confuse-a-frosted-evaporator-coil-with-refrigerant-overcharge

Coil keeps icing up - caused by bad airflow?

I recently had my blower motor replaced but my coil keeps icing up.

He thinks it is because the airflow in the ductwork is low possibly due to kinks. All I can say is the system was working fine with good airflow prior to the blower motor dying. The new one is an exact replacement but I do not seem to think I get the same airflow as before. Can you provide any suggestions? thanks On 2020-07-12 by jim -

by (mod) - yes weak air flow can cause coil icing

Jim

If we are quite sure that the ductwork was not damaged during work on your system and that it was in perfect shape before and is in perfect shape now, something worth verifying by inspection, then the next place to look would be the blower speed setting.

Why 1 of 3 units sharing a common compressor/condenser unit frosts over at shut-down?

I have a three zone mini split system. Two of the indoor units run just fine but the third runs very cold and then frosts over when shut down. Any thoughts? Thanks On 2019-09-07 by frank coughlin -

by (mod) -

Frank

Clarify if you can: do you really mean the unit frosts over when it is shut down (that to me means completely turned off?) - that would be pretty strange.

If you mean that the coil ices over when the compressor continues to run while the fan is off, that sounds like a control board issue;

Otherwise take a look through the causes of cooling coil frost-over given at FROST BUILD-UP on AIR CONDITIONER COILS as one of those is likely to be the trouble.

If the outside compressor won't run does that cause indoor coil frost?

If the outside unit of the heat pump does not run, and the interior unit continuously runs (even when thermostat is set to "off" position). Will this cause the evaporator coil to freeze? On 2018-08-01 by Keith - I

by (mod) - No

Not likely, Keith. When the outdoor compressor/condenser is not running, liquid refrigerant is not going to move through the system so the coil is likely to stay at the temperature of the building air.

 

...

...

Continue reading at FROST BUILD-UP on AIR CONDITIONER COILS - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• COOLING COIL or EVAPORATOR COIL
• FROST BUILD-UP on AIR CONDITIONER COILS
• REFRIGERANT GASES & PIPING
• REFRIGERANT LEAK REPAIR
• WATER & ICE IN DUCT WORK
• WET CORRODED DUCT WORK

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FROST BUILD-UP on AIR CONDITIONER COILS FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to AIR CONDITIONING & HEAT PUMPS

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