Low charge causing frozen evap coil?

[georgelass]

I'm at odds with another tech and he's a stubborn relative. :)

One of says a low-charge can cause a frozen
evap coil. The other one of us says the only way
a low-charge can "cause" a frozen evap coil is if the homeowner
is so frustrated with the poor cooling that he/she leaves the
a/c on all night when outdoor ambient (and ultimately indoor ambient)
temperatures drop beyond what a normal person would use a/c
with. This person also believes that between a low-charged unit
and a proper charged unit, the proper charged unit would
ice over sooner in such conditions because it would be
better at dropping the temp of the return air to very cold.

This person believes that under normal ambient conditions and with proper airflow,
a low-charged system canNOT ice over. Who is wrong?

(Uh, this is residential A/C, not a heat pump, not refrigeration.)

Thank you.

[Redwood650]

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...

[Tony3696]

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.

[catmanacman]

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

[Pete954]

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.

[newoldtech]

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.

[martyinlincoln]

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.

[VanIsleRefrig]

Low refrigerant equals low pressure equals low temperature equals ice.

Bazinga

[drife678]

31 degrees will freeze lol

[pecker head]

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.

I second that... I have been on many many calls for a iced up evap coil due to low pressures...

[kamersoutdoor]

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

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

[kamersoutdoor]

I second that... I have been on many many calls for a iced up evap coil due to low pressures...

You add refrigerant on low pressure alone?
How about checking airflow?

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

[KnewYork]

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.

[pecker head]

You add refrigerant on low pressure alone?
How about checking airflow?

Sent from my SAMSUNG-SGH-I717 using Tapatalk 2

No I would not add gas on low pressure without checking airflow first.. Dude I am past my first day of working service..

However I will repeat my first post " I second that... I have been on many many calls for a iced up evap coil due to low pressures..."

True Story...

[georgelass]

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.

Is the saturation temp and the line temp/temps of the coil (as opposed to the
line temp of the suction line) the same or pretty close? I've encountered
very undercharged units, those with saturation temps below 20 F, and icing
wasn't a problem. That is, I could charge the unit immediately, not have
to wait for a thaw before supply/return temps indicated normal airflow. Of
course, I can't say I was aware of the run times for those units.

I would be interested in how the temp along the coil does vary, whether it
is in fact near the saturation temp or whether it rises somewhat linearly
towards the suction line (past the coil) temp. Maybe taking temps
along the path of the coil in the condenser would give some insight into
how saturation temp and coil line temps differ. Obviously it is
easier to get temps at the condenser. Anybody ever try that?

[mark beiser]

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.

[jkv]

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.

[kamersoutdoor]

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


sent from my Samsung Galaxy Note

[bigtime]

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.

[kamersoutdoor]

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

[kamersoutdoor]

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

sent from my Samsung Galaxy Note

[garyed]

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


sent from my Samsung Galaxy Note

I don't want to offend you but i don't see any way around it unless I just let your off the wall post slide. You obviously don't have much field experience to make such a statement & you're misunderstanding what you've been taught. Low charge is one of the major causes for a system to ice up & probably the most common of all. Mark Beiser posted an excellent explanation of why it happens. Low air flow of course can be a cause but its usually pretty obvious such as a blower motor out. A dirty coil can also freeze up but a lot of times shows signs of poor cooling before it gets that bad. Also an overcharge is not going to cause an AC unit to freeze up except in a very rare instance with a slight restriction.

[kamersoutdoor]

I don't want to offend you but i don't see any way around it unless I just let your off the wall post slide. You obviously don't have much field experience to make such a statement & you're misunderstanding what you've been taught. Low charge is one of the major causes for a system to ice up & probably the most common of all. Mark Beiser posted an excellent explanation of why it happens. Low air flow of course can be a cause but its usually pretty obvious such as a blower motor out. A dirty coil can also freeze up but a lot of times shows signs of poor cooling before it gets that bad. Also an overcharge is not going to cause an AC unit to freeze up except in a very rare instance with a slight restriction.

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've thawed many of iced coils due to low charge (primarely in refrigeration), but many more due to low airflow (residential).
What I degress is tunnel vision on the low charge.

Maybe I'm being a little biased. Last outfit I worked for condemned "EVERY" ice-up as a low charge. To the point they would'nt consider air flow.
Now, seeing the general consensus, no wonder 90% of systems are overcharged.
Can someone "in the field" honestly state that they run into more ice-ups due to low charge than low air flow?
Someone can't sit behind a desk and tell me this!
Next thing I'll hear is that the high limit needs changed evertime it locks out. Or better yet, just up the range (seen this done too many times to count)

sent from my Samsung Galaxy Note

[mark beiser]

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

Maybe things are different in your area, but down here leaky coils icing up, purely due to a low refrigerant charge, is a very common occurrence.

There are often other contributing factors, but it isn't in the least bit uncommon for a coil to ice up in a system that is low of refrigerant, but otherwise has appropriate airflow through the coil, and normal load and ambient conditions.

[KnewYork]

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.

[mark beiser]

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!

If you read back over the thread, you will find that nobody has posted here that a low charge is "the" most common cause of coils icing over.
It is merely one of a number of very common potential causes, or contributing factors, that any competent technician will check whenever a coil is found to be iced-up.

The OP presented a scenario where one technician was claiming that a coil "cannot" ice up due to a low refrigerant charge. That position is clearly incorrect.

As for how common the problem is, I'd think that there will be regional differences too.
Those of us in the south have much longer cooling seasons than you have in Indiana, and likely encounter a much higher percentage of systems that run low of refrigerant due to leaks in the system.

[kamersoutdoor]

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!!!


sent from my Samsung Galaxy Note

[kamersoutdoor]

I don't want to offend you but i don't see any way around it unless I just let your off the wall post slide. You obviously don't have much field experience to make such a statement & you're misunderstanding what you've been taught. Mark Beiser posted an excellent explanation of why it happens. Low air flow of course can be a cause but its usually pretty obvious such as a blower motor out. A dirty coil can also freeze up but a lot of times shows signs of poor cooling before it gets that bad. Also an overcharge is not going to cause an AC unit to freeze up except in a very rare instance with a slight restriction.

"Low charge is one of the major causes for a system to ice up & probably the most common of all".

sent from my Samsung Galaxy Note

[bigtime]

Low charge is one of the major causes for a system to ice up & probably the most common of all.

sent from my Samsung Galaxy Note

Glad to see your coming around. :grin2::couchhide:

Most common or not, who knows. But fairly common from my experience. I think most people will check the filter before they call for service. I think we can all agree low charge can freeze the coil. Also agree to make sure you got correct airflow before adding refrigerent.

[kamersoutdoor]

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

sent from my Samsung Galaxy Note

[beenthere]

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.

[jtrammel]

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.

[lsu4life]

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.

[kamersoutdoor]

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

sent from my Samsung Galaxy Note

[pecker head]

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!

[toyo066]

Bazinga

101

[Freezeking2000]

I agree most common by far is low gas.



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've thawed many of iced coils due to low charge (primarely in refrigeration), but many more due to low airflow (residential).
What I degress is tunnel vision on the low charge.

Maybe I'm being a little biased. Last outfit I worked for condemned "EVERY" ice-up as a low charge. To the point they would'nt consider air flow.
Now, seeing the general consensus, no wonder 90% of systems are overcharged.
Can someone "in the field" honestly state that they run into more ice-ups due to low charge than low air flow?
Someone can't sit behind a desk and tell me this!
Next thing I'll hear is that the high limit needs changed evertime it locks out. Or better yet, just up the range (seen this done too many times to count)

sent from my Samsung Galaxy Note

[Freezeking2000]

Yeeeeeeeeeeeep!


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!

[AYservicetech]

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

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

[jkv]

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.

[kamersoutdoor]

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.




sent from my Samsung Galaxy Note

[Pete954]

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?

[hurtinhvac]

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.

[Redwood650]

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 :)

[Freezeking2000]

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.





sent from my Samsung Galaxy Note

We find many units overcharged trying to compensate for undersized ductwork or poor zoning.

Most units thet are way overcharged loose so much capacity they do not freeze up.

[newoldtech]

Originally Posted by Redwood650
The only time I have seen a frozen coil is from low/no airflow...



Originally Posted by Pete954
I don't recall anybody here saying that low airflow wasn't a common cause.


Redwood650
um, second post in the thread :)

I'm confused Red. He did say that we all agree that improper air flow can also cause a freeze-up. What are you saying that I"m missing?

[woody19]

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. :whistle::.02:

[jkv]

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.

[hurtinhvac]

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. :whistle::.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.

[zxcb]

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

[timebuilder]

One pertinent point mentioned above is the idea that a system that is TOO low on charge will not do anything. This is because you must have liquid at the metering device ready to experience the pressure drop. If there is no liquid to change state, no heat absorption besides sensible heat can occur. That's nowhere near enough absorption of heat to cause any real cooling.

A moderately charged system can freeze the evap, unless the heat available to the evap can overcome it. Similarly, if a normally charged system is not getting enough heat at the evap (due to low airflow) that system can freeze up as well.

If, however, a system is overcharged, and the airflow/heat available is normal, a freezeup cannot occur because too much liquid is in the evaporator, and not enough liquid that is changing to a vapor because there is not enough heat to be absorbed. That change to a vapor is where latent heat is absorbed to "power" the process of change of state. So, the overcharge of liquid tends to remain as a liquid, and a Little liquid takes the available heat and changes state to provide some cool air.

I'm trying to keep this simple, but yes. The OP is correct that a low charge CAN cause evap freezing.

[beenthere]

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.



Unfortunately many techs aren't taught to check charge by measuring SC and SH.

But its not the over charge that causes the frozen coil. Its the low air flow, its just that the over charge can't keep the suction temp above freezing anymore. And now you or some other knowledgeable tech comes out and thaws it, and checks SH and SC, and discovers the low air flow and over charge.

[hurtinhvac]

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.

[hurtinhvac]

I went on an install follow up the other week - no cooling, freezing. Gauged it and found low pressure on the low side (even with a txv) and high subcooling but was troubled as the thing was not yet a month old. Stuck my hand in the blower and felt the blades filled with crap. Pulled the blower, vacuumed, brushed and beat out all the junk and returned to the gauges. Respectable SH but way too much subcooling. Recovered until subcooling was at data plate.

Should have never tried to add puron with a blower wheel in that condition. Laziness that ended up being an on-call for me.

[PM Heat n Cool]

3 biggest causes of freezing I see, low charge, bad txv, airflow problem. How can this debate go on for six pages lol

[Pete954]

um, second post in the thread :)

Too shay :oops:

[SoFlaDave]

While I think this thread has run its course, I have to point out that there is NO scenario where an overcharge can cause a freeze up. I'll also point out that while during a low charge condition, while it will eventually get to low to form ice any more, don't forget that the ice is simultaneously lowering airflow and heat transfer across the evap and compounding the problem drastically.

Therefore, if the refrigerant charge drops below say 60% (purely as an example) and there is no ice present than it may not have enough liquid to flash off and start the formation of ice. However if ice is present on the evap with the same percentage of charge it WILL continue to build ice even as it leaks out to a much lower % of charge.

[Danae12]

um sometimes rookie tech's mix GAS, which also freezes systems up at times... Or frosts up LOL...


Non condensables also screw things up and can also freeze up e coils.. Allot of things can freeze up e coils not just a clogged up abused e coil or filter, return duct etc. Low of refrigerant etc. etc. Also lets not forget 410a is a blend..

:cheers:

something to think about.

[Pete954]

This thread has definitely run it's course but I just had to laugh tonight. Storm conditions (damn you Isaac), no power at home, pissed off family and I'm on call. Have enough time to eat dinner before going out to a call that the previous tech went to in the morning. They tell me all I have to do is go add some 22 to get them by until change out bc guy was there and the evap was frozen. Since this thread was fresh in my mind I dig further an find a filter so dirty that it fought me when I went to pull it out. Suction pressure jumped by 8 psi just from that.
Glad I did't trust someone else's diagnosis ad checked for myself.

[hurtinhvac]

This thread has definitely run it's course but I just had to laugh tonight. Storm conditions (damn you Isaac), no power at home, pissed off family and I'm on call. Have enough time to eat dinner before going out to a call that the previous tech went to in the morning. They tell me all I have to do is go add some 22 to get them by until change out bc guy was there and the evap was frozen. Since this thread was fresh in my mind I dig further an find a filter so dirty that it fought me when I went to pull it out. Suction pressure jumped by 8 psi just from that.
Glad I did't trust someone else's diagnosis ad checked for myself.

Vacationing over on the island (Estero) and listening to the blower struggling upon each start up and heard the compressor sputter mid cycle.

And me without so much as a 5/16 nut driver.

Maddening.

[jkv]

Sounds like you are about to heat up :whistle:

[Kerplacknia]

I have seen many coils frozen from low charge, more so with 410a but some with 22 also. It is deffinatly possible.

[jkv]

low charge will always freeze up come on no matter what refrigerant you use. :.02:

[Tommy knocker]

Interesting debate. Alot of very good points on both sides. In reality both airflow and low charge can and will ice a coil up. A low charge can freeze system all the way to and on comp as can airflow. In my experience if coil is partially iced over its a charge issue. If its completely froze including suction line and perhaps comp it's almost always airflow, almost always not always. It would take awhile for a low charge to build ice all the way across coil and typically a low or no cool call will come first. I would also add that airflow should be the first thing that is checked since you cannot establish whether the charge is low with out knowing the airflow is good. You should be checking both regardless but airflow must come first. Good topic.

[mofotech]

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

LOLLLLLLLLLLLLLLLLLLLLLLLLLL

[mark beiser]

This thread isn't dead yet?


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

Lies, I've seen a many lakes that were low on water, but I haven't seen one freeze up yet! :p

[drife678]

Im currently looking at my lake, low on water. It is.not frozen and its 95 degrees. Lol. I love this website.

[zxcb]

Wait till January and see what happens. The intardnet never lies! ;)

[B1978]

Things i see in commercial are

Dirty coils
Restrictions
airflow
txv issues
cold return air, supply mixing with the return.
poor ducting design

Rarely is it ever a leak, unless its a ductless split system.

[Pete954]

Rarely is it ever a leak, unless its a ductless split system.[/QUOTE]


False! It is not rare! Maybe in your experience but not overall. If a unit is frozen let it thaw THEN check airflow AND charge. It could be either one or a combination. All the guys who kow what they are talking about agree on this. Can this thread be done now? Please? Pretty please with sugar on top......and a cherry. :gah

[mark beiser]

Wait till January and see what happens. The intardnet never lies! ;)

I've yet to see a lake of any water level freeze in January, or December, or February, or any month of the year!

Teh intardwebz liez!

Or maybe its just that I've lived most of my life in Texas.:whistle:

[cumminundun13]

either low on charge or loss of airflow in my 39 years in the business its 9 out of 10 times always dirty filters. lazy homeowners.













I'm at odds with another tech and he's a stubborn relative. :)

One of says a low-charge can cause a frozen
evap coil. The other one of us says the only way
a low-charge can "cause" a frozen evap coil is if the homeowner
is so frustrated with the poor cooling that he/she leaves the
a/c on all night when outdoor ambient (and ultimately indoor ambient)
temperatures drop beyond what a normal person would use a/c
with. This person also believes that between a low-charged unit
and a proper charged unit, the proper charged unit would
ice over sooner in such conditions because it would be
better at dropping the temp of the return air to very cold.

This person believes that under normal ambient conditions and with proper airflow,
a low-charged system canNOT ice over. Who is wrong?

(Uh, this is residential A/C, not a heat pump, not refrigeration.)

Thank you.

[zxcb]

Texas must have low subcooling... :)


I've yet to see a lake of any water level freeze in January, or December, or February, or any month of the year!

Teh intardwebz liez!

Or maybe its just that I've lived most of my life in Texas.:whistle:

[jackintheboxtec]

This is why I dont do residential.

We dont have this problem in commercial! :D

[truck12]

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.

[david912]

Low airflow, Low refrigerant charge, And metering problems(starving evap coil) can cause unit to freeze! If your sat temp is below 32 deg you can freeze no matter the situation, with low charge theres a small window where it will freeze, but yes it most certianly can and will, seen it time and time again.. SATURATION TEMPERATURE

[timebuilder]

This is why I dont do residential.

We dont have this problem in commercial! :D

Yeah, that never happens...

305151

[hvacgr]

My company did a lot of installs in the mild winter MI had. Been on more calls than I can count this summer on frozen coil. Air flow was fine,low charge on every one.

[BigBacardi]

omg


but what if i dont have abrown or purple wire?




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.

[shaka]

This the exact thing a classmate and I argued and debated about 22 years ago
He claimed it will not freeze on low on charge.
I told him it will.
We even got other instructor arguing about it,

His instructor that sided with him
Even embarrassed me in front of his entire class
Telling me it will definitely not freeze
He made me feel so dumb and almost yelling at me.

Today I can tell you

We were both correct

It really depends on how low you are.
If unit is low but still have liquid condensing in condenser
That means evap still have liquid evaporating = freeze up

If you are soo low that you have no subcooling going on then
No FREEZING

Now I can say to my instructor
Your an A$$ Hole

Sorry guys brought back some bad memories
I feel better now...

[shaka]

Oh I think the lake will freeze faster if it's dirty

[timebuilder]

Oh I think the lake will freeze faster if it's dirty

Let's use an ice maker as the standard for freezing water, shall we?

In the Manitowoc service literature, it says "the purest water will freeze first." This leads to the concept of the water purge and flush before a new freezing cycle is started: the impurities have not frozen into the ice sheet, and they are left suspended in water in the trough. The dump valve opens, the pump runs, and the fill valve admits some fresh water to help start with a "clean" slate of water for the next ice sheet.

So, a lake of cleaner water should freeze more quickly and have more thickness of the ice.

[garyed]

The reason an instructor may tell you that a low charge alone can not cause the system to freeze up is because of a lack of field experience. The laws of physics do not change but how we relate them to the real world do. It takes a sharp mind to be able to see all the different scenarios that relate to a particular law. There are not really exceptions to the laws but there are certain circumstances that can cause different results than expected. Instead of just thinking that a low charge will cause a starved evaporator & high SH, think about if frost can begin to form anywhere at all on a starved coil & extrapolate from there.

[shaka]

Let's use an ice maker as the standard for freezing water, shall we?

In the Manitowoc service literature, it says "the purest water will freeze first." This leads to the concept of the water purge and flush before a new freezing cycle is started: the impurities have not frozen into the ice sheet, and they are left suspended in water in the trough. The dump valve opens, the pump runs, and the fill valve admits some fresh water to help start with a "clean" slate of water for the next ice sheet.

So, a lake of cleaner water should freeze more quickly and have more thickness of the ice.

LOL..

Ok
Let's say then the lake is verry verry dirty.

Let use the ice machine as example.
Your distributors get so plug and water just trickling down the plate.
The pressures drop down very low, flooded plate, SMOKING COLD
DUMB AND DUMBER sticking his tounge on pole cold

The water that tricke down the distributer will freeze so fast
That it will not make it down the trough.
Very cloudy ice, cause it froze so fast..

So
Dirty lake that has no flow
Will freeze faster.
LOL

[mark beiser]

So
Dirty lake that has no flow
Will freeze faster.


But we have lots of dirty lakes, with low water level due to low/no flow into them, yet none of them are frozen! :confused:

:D

[calubeda]

This thread isn't dead yet?



Lies, I've seen a many lakes that were low on water, but I haven't seen one freeze up yet! :p

Where in FL?

[shaka]

But we have lots of dirty lakes, with low water level due to low/no flow into them, yet none of them are frozen! :confused:

:D
You must
Have wrong refrigerant
Or mix refrigerant in your lakes
:grin2:

[kamersoutdoor]

But we have lots of dirty lakes, with low water level due to low/no flow into them, yet none of them are frozen! :confused:

:D

I think your stuck with tunnel vision on the low water issue.
Try troubleshooting a little harder. You may find that you have a restriction in your distributor inlet channel. Adding water will just make things worse!
You may start slugging your docks making your harbor uselesss.
Just a thought
;)

sent from my Samsung Galaxy Note

[ICanHas]

Is the saturation temp and the line temp/temps of the coil (as opposed to the
line temp of the suction line) the same or pretty close? I've encountered
very undercharged units, those with saturation temps below 20 F, and icing
wasn't a problem?

Saturation temperature is only valid in the presence of adequate liquid refrigerant If there is no liquid left in the evaporator, its like expecting your empty glass to be at -315F because, that's the saturation temperature of liquid air at 1 atm.

[ICanHas]

You must
Have wrong refrigerant
Or mix refrigerant in your lakes
:grin2:

He didn't vacuum the air out good enough and the low side is too high to get SST of <32F
Keep the pressure below 5,000 microns and when the water gets low enough the latent heat to get there would freeze the lake. I think a giant 3 stage 10million CFM willl do

[ReferYankee]

I enjoy the lake debate much more than the evap talk. jesum crow.... 7 pages? I feel like posting HVAC fundamental book links on amazon!!!!

[bja105]

Stupid thread, I can't believe I read it.
Can we debate if a dirty filter will make a limit trip, now? It is heating season in some of the country.

[ReferYankee]

Im with the last post

[ICanHas]

Stupid thread, I can't believe I read it.
Can we debate if a dirty filter will make a limit trip, now? It is heating season in some of the country.
Not if the ECM can compensate for resistance :)