I suppose it all depends on the Saturation temperature of the evaporator no? If its too low, the gas will absorb too much heat (SH) and wont allow the coil/lineset to freeze... The only time I have seen a frozen coil is from low/no airflow...

 

The only time I have seen a frozen coil is from low/no airflow...

I don't recall anybody here saying that low airflow wasn't a common cause.

um, second post in the thread

 

Ask them both if the "Flux Capacitor" was checked. Whoever answers incorrectly get's kicked in the squash and sent back to school. Better yet, hook up an old A/C and try it both ways. The answer is 42.

 

Low charge can a frozen coil once the saturated temp drops below 32 degrees the system can freeze sometimes it will somtimes it wont depends on the conditions

 

I thought this was basic but I guess it's different everywhere. Here in So Fla this is fairly common. So much so that my mentor taught me that all frozen evaps boil down to either low/no airflow or low refrigerent charge. Let it thaw completely, check your pressures and break out the leak detector. Unless of course it's a dirty coil or bad indoor fan, or bad cap, or restricted return, or.......you get the idea. Good luck, hope you were on the right side of the debate.

 

I've run so many calls for frozen coils and the cause was low refrigerant that I stopped counting many years ago. Low refrigerant equals low pressure equals low temperature equals ice. Could air flow issues be contributing? Sure you need to check the coil and air flow, but usually adding the proper amount of refrigerant makes the Icing magically go away.

 

Low refrigerant equals low pressure equals low temperature equals ice.

Bazinga

 

A unit can have suction saturation temp above 32 degrees and be low on charge. Once it gets below that,to a point, then it will start to freeze any condensation on the evap coil. Keep on going until the charge is low enough that the metering device is fed gas instead of liquid and it won't freeze. You both lose the bet.

 

A unit can have suction saturation temp above 32 degrees and be low on charge. Once it gets below that,to a point, then it will start to freeze any condensation on the evap coil. Keep on going until the charge is low enough that the metering device is fed gas instead of liquid and it won't freeze. You both lose the bet.

You made another assumption that wasn't part of the OP question. I've seen compressors almost completely cased in ice with the coils in the same condition...cause: low refrigerant charge. Your assumption is that the refrigerant will eventually leak to the point of no liquid feed which I agree with, but before it gets to that point you are going to have a below freezing evaporator which will freeze the condensate. Once that gets started the airflow gets compromised and the freezing accelerates.

 

31 degrees will freeze lol

 

Only if conditions are right will coil freeze (low return temps). Otherwise high superheat as result of starving evap.
If i have an iced coil in 80 deg dwelling I am not looking for low charge. I am tackling overcharge, or low airflow.
Last guy I worked for assumed every frozen coil was a low charge situation. He was wrong 100% of the time. I told him that you cannot apply that scenerio to every job cause you caught it once!!!
Maybe this is why i find so many overcharged systems

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When the system is low of refrigerant, to the point that the saturated temperature is below freezing, icing can/will occur in the portion of the coil where refrigerant is changing state.
Depending on the load, and other factors, it may not progress much beyond that, but usually the frost line will progress until the coil is entirely iced over, and can progress to the point that the compressor ends up with a thick coating of ice.

Anyone who claims otherwise doesn't have much field experience, and/or a good understanding of the refrigerant cycle.

 

Textbook
Yes, iced coil can be caused by improperly low charged system. Whats this, maybe 2% of real life scenerios? (coil icing as dwelling reaches set point)
98% of "real life time", When a tech arrives at the scene it will be due to low air flow/overcharge.
Again, we're speaking real life over textbook scenerio.
I am relating to air conditioning over refrigeration in regards to op's original question


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Those other tech. are looking at the small picture, I had this problem low ambient temps block it up get the temps and pressure good check your charge make shur your fan speed is on high, air flow good and if all is good and it still freezing up put a low ambient fan control on it problem done.

 

It freezes bit by bit. The first section of the coil has saturated liquid and gas below freezing temps. After the liquid is gone it starts warming up. After it runs a while this first section with sat liq gets iced over, has no airflow due to the ice, and very little heat transfer. The liquid in the coil makes it a little farther, and the next section starts freezing. And on and on...

If the system can still keep up and cycle, maybe the coil will defrost enough in the off cycle to keep from totally freezing.

If someone said "my coil is frozen" and I got a prize for guessing right, I would guess low charge.

 

Really!
I would guess dirty filter. And 90% of the time I would win the prize,
Next guess would be that last tech on sight seen frozen coil, added gas and left without checking filter
:banghead:
Then I simply change filter, let blower defrost coil, and pull the 2 lbs of excess refrigerant dumped in by mis-guided tech (who probably read this thread and now thinks all frozen coils are undercharged systems),
Collect check and say goodbye to my newly acquired loyal customer
sent from my Samsung Galaxy Note

 

This thread reminds me of previous employer.
Hand me work order: frozen coil
Check charge, probably low
REALLY, didnt we have to change miss Johnsons filter last winter when unit was locked out on high limit?
First thing I should due is check charge????
Lmao

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I agree to disagree that low charge as being the most common! I understand all to well on the low charge, I do not contest this. But to state that low charge is the most common is rediculous!

I find it interesting that you "Will work for knowledge", yet are trying very hard to dismiss the notion that evaporators will ice up due to a low refrigerant charge. I don't know about the others, but I've been in the business longer than you've been alive. I've even seen icing in the evaporator pan of a 800 T. absorber where there is no airflow. The cause? Low refrigerant charge. It happens more often than I think you realize.

 

Maybe you didn't read the paragraph that you quoted me on. Please be as kind to read it again.
I do not dissmiss it at all.
What I am dissmissing is low charge being anywhere near as common as low air flow!!!


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Mark, I will agree with geographical differences. Humidity being lower here up north.
Again, I've seen seasoned techs add a charge to a system because of an ice-up and be way off base (I had to come back later and pull charge).
So I'm biased, and irritated on the subject.
And I'll continue to feel comfortable at not assuming an ice-up is DIRECTLY related to low charge. Besides, it's not hard to check charge.
2% of my calls may end up being a low charge in regards to iced coil

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What I see for frozen coils in the summer.

1. Low on charge, (its a leaker, and find most of those leaks).
2. Dirty/plugged air filter, or coil.
3. TXV power head lost charge, or something blocking its port.
4. Restricting piston(foreign crap in it).
6. Blown blower run cap.
7. Burned out blower motor.
8. They closed all the low returns, but only opened the high returns in the bedrooms, to make them cooler.
9. Control board won't run blower.

 

10. stuck contactor.
11. dehumidistat wired parrallel and set wrong.
12. zone control a mess and or supply duct going into the return.
13. dirty contacts on mechanical thermostat.
14. leaking batteries on digital t-stat, ate up the G circuit.
15. tech on maintenance tested the cap and switched the purple and brown wires causing the blower to run backwards.
16. x13 motor failing but working when I'm there.
17. blower wheel exploded.
18. return flex full of water due to a clogged drain, vertical a/h.
19. White paint on copper lines and the customer thinks it's frost :Faint:
20. blower door fell off. :gah: :Faint:
21. cabinet insulation sucked into blower.

Seen it all in the last 12 months.

 

In south Carolina I would have to say low charge is the most common for an iced up evap. Airflow does get overlooked a lot of times.

 

That goes for Massachusetts too... If I got a iced up coil, the filters are usually stuck in the ice anywho, so I throw them out.. I would say 8 out of 10 times, low charge is a cause of the ice up... FACT!

 

Low pressures will cause frozen coil just as a stopped up filter or bad fan motor on inside unit or low air flow maybe from a to small of return for size of unit.

 

Stopped up filter causes low pressure, except now i have a saturated coil instead of starving coil thus bringing ice formation quicker!

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KnewYork is right.... IMO.. That is..

Kamers, u say iced coil makes u think overcharge??? What exactly is ur theory behind that???

 

Tech overcharges system trying to compensate for frozen coil.
Tech was taught iced coil=low charge, thus neglecting to verify charge and find root cause. Tech thaws coil, adds charge and runs to next job.
My fight in this goes back to heated debates with a senior tech in which he did the above on numerous occasions.




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I have heard that some feel that overcharging a system will flood the coil and not condence and cause one to freeze up I feel that there is more that has to be wrong to ice up I have seen one iced up being overcharged but the real problem was not enough air flow causing low head which caused low suction not from being overcharged will ice one up alone.

 

I gotta say I find the dismissive attitudes of two posters in particular really sad. The OP came looking for knowledge and got a bunch of petty nonsense. I don't recall anybody here saying that low airflow wasn't a common cause. Instead they answered the Op's question and confirmed that low charge CAN cause icing and in fact is in fact one of the most common causes. Asserting that too low of a charge won't allow it to cool let alone freeze is useful but was presented in (I feel) a crass manner. People come here to discuss their experiences and too learn, why be rude to guys who are in the trenches right along with you?
I'll end by asking how many of you have had a frozen coil due to over charge? Where I am I have never seen or heard of it but conditions will affect diagnosis and here it's always humid. Is this only in dryer climates?

 

I'm mildly surprised to see this even being debated. One of the irritations of this industry when you are trying to learn it is the never ending debate over even the fundamentals.

In my short time I've found that:

1.) frozen coils have always been due to low air flow, low charge or a combination of both.
2.) with one or both of the above two conditions present, a coil is more likely to freeze in low OAT conditions when the condenser is not pumping as much (regardless of the metering device - a TXV is a fixed orifice when wide open), thus making low OAT a legitimate factor. I experienced this long before even considering doing HVAC when my leaking system was turned on in mild temps by my wife when she was drying her hair in the morning.
3.) a system so low on charge that is is significantly below the 32 degree freezing point on the low side will not do anything - no cool, no freezing, nothing.
4.) a system can freeze up from the coil, along the suction line and make a freaking glacier out of the compressor if left running long enough regardless of any conditions or high temps and loads, inside or out.

I have never encountered a system freezing from excessive charge and do not see how it's possible apart from an airflow problem. That said, this is only my second cooling season, so I'll tuck it away for possible consideration in the future.

And that's all you can do sometimes when you are newer...file it away in case you come across it one day. But for now go with what you have seen first hand.

 

After reading a few replies I decided not to read all of them and just jump to the end and add my 2cents worth. One of the very first things I was taught over 40 years ago was that the only way a coil would ice up is due to either lack of airflow or lack of refrigerant. Now, that being said, there are many reasons that could cause either to occur i.e. dirty filter, blocked registers; refrigerant restrictions, low charge...etc. etc. etc. Too many "techs" jump to conclusions when they see a coil iced up and don't take the time or effort into finding the root cause as to why and just add refrigerant which, as we know, can result in additional problems.
In the not too distant future I will leave this industry and when I go ice fishing I will think: damn lake didnt have enough wind blowing over it so it froze. :.02:

 

Nonsense! Obviously the lake pumps capacitor was weak and the impeller was not turning at sufficient RPMs, resulting in lack of water flow. That's why the lake froze.

 

Love your last response thats great! In fact I wish I could be there and we could come up with all kinds of reasons why that lake frosed up lol.

 

If a lake is low on water it will definitely freeze up. It says so on the internet.

 

But it's only low on water because the pump isn't turning fast enough. You should also check the damn for leaks. Don't just h20 and go.