Central A/C - Coil Freeze-Up Normal?

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A relative's central air condenser coil froze up completely with ice and stopped working. Had to let it melt before it would work again. This was in very dry and very hot Phoenix. 115F at the time. They blamed it on the thermostat being set too low and the unit working too hard to cool the house down. Is this normal? I would think the A/C would shut itself off before the coils were allowed to ice up. Seems to me there is something wrong with the A/C, not that the thermostat was set too low. Low on freon?
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Get a tech out they can ruin the unit, likely low on freon or a totaly restrited air filter, an air filter probably wouldnt cause a complete freeze, just partial
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Low on Freon.
"Dick" <LeadWinger> wrote in message

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D> A relative's central air condenser coil froze up completely with ice D>
and stopped working. Had to let it melt before it would work again
. D>
This was in very dry and very hot Phoenix. 115F at the time. They
D>
blamed it on the thermostat being set too low and the unit working
D>
too hard to cool the house down. Is this normal? I would think
D>
the A/C would shut itself off before the coils were allowed to ice
D>
up. Seems to me there is something wrong with the A/C, not that
D> the thermostat was set too low. Low on freon?
It could be that the thermostat was set too low. it could also be a dirty filter, refrigerant charge low or a dirty coil. and there are a few other reasons. it is alway good to have a regular maintenance done on any A/C
system.
Dick
It could just be low Freon, but most likely it is low Freon, coupled with low cooling load.
Low load can be caused by restricted air flow or too low an indoor temperature in the house.
I normally would measure the air flow with a flow hood, also called a capture hood. You should normally have around 400 CFM (Cubic Feet per Minute) per ton. Half of the systems I measure have 200 CFM per ton OR LESS. This will be agarvated by a dirty air filter, Restrictive high efficiency air filter or grilles closed in rooms that you are not using.
Normally, do not turn the thermostat down below 70 degrees.
If you find a dirty air filter or the thermostat turned down too low, these are easy fixes. Replace the filter ot turn the thermostst back up. Otherwise, you need aqualified proffessional. Ask if the contractor has NATE certified trechnicians.
Good Luck.
Stretch
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No you did not cause the problem you had nothing to do with it, if they had that issue in the past then it is their ignorance and obvious they never had it regularly serviced or improperly serviced. It should be checked out completely yearly. Freezing is bad for the condensor and will shorten its life, not your problem also. Its like never changing or adding oil in your car and loaning it out and it breaks.
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Hi Dick, hope you are having a nice day
On 27-Mar-05 At About 00:41:19, Dick wrote to All Subject: Central A/C - Coil Freeze-Up Normal?
D> From: Dick <LeadWinger>
D> A relative's central air condenser coil froze up completely with ice D> and stopped working. Had to let it melt before it would work again. D> This was in very dry and very hot Phoenix. 115F at the time. They D> blamed it on the thermostat being set too low and the unit working D> too hard to cool the house down. Is this normal? I would think D> the A/C would shut itself off before the coils were allowed to ice D> up. Seems to me there is something wrong with the A/C, not that D> the thermostat was set too low. Low on freon?
It could be that the thermostat was set too low. it could also be a dirty filter, refrigerant charge low or a dirty coil. and there are a few other reasons. it is alway good to have a regular maintenance done on any A/C system.
-=> HvacTech2 <=-
... "If you were going to shoot a mime, would you use a silencer?"- s.w.
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HvacTech2 wrote:

dirty
other
A/C
How can a thermostat be set too low when it's 115F outside? At that temperature the inside of my lightly insulated house can't go below 70-72F even when the A/C runs continously (almost 20F in-out temp dif).
Also how can an A/C cool a house if it's outdoor coil freezes? Does that mean that the indoor coil is even colder?
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If the outdoor coil is frozen, it sounds like a major restriction of some kind right after the compressor. With that, the indoor coil would be seriously warmed up.
--

Christopher A. Young
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Hi Michael, hope you are having a nice day
On 27-Mar-05 At About 04:59:46, Michael Baugh wrote to All Subject: Re: Central A/C - Coil Freeze-Up Normal?
MB> Low on Freon.
not necessarily. see my reply to the original poster.
"Dick" <Le wrote in message MB> >> A relative's central air condenser coil froze up completely with ice >> and stopped working. Had to let it melt before it would work again. >> This was in very dry and very hot Phoenix. 115F at the time. They >> blamed it on the thermostat being set too low and the unit working >> too hard to cool the house down. Is this normal? I would think >> the A/C would shut itself off before the coils were allowed to ice >> up. Seems to me there is something wrong with the A/C, not that >> the thermostat was set too low. Low on freon?
-=> HvacTech2 <=-
... You can't have everything. Where would you put it?
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It is interesting that you and others have suggested that the temperature was set too low. As I understand it, the thermostat was set at 69F when the outside temperature was 115 in the daytime. Could that have actually been the cause of the freeze-up?
Dick
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Dick wrote:

Let's see. It was hot and you were running the A/C to cool off and they said it was your fault it iced up. I suppose he thinks you to run it only on cool dry days? A/C is designed to cool on hot days, that's the way it works.
There are a couple of mechanical problems it is likely to be, Any tech should be able to figure it out and fix it. Since it requires tools, skills and equipment (not to mention a license) you will not be able to do it, but the cost should not be too high.
--
Joseph Meehan

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Dick wrote: Low on freon?
Either that or a badly clogged air filter. If the system is low on refrigerant (Freon, Genetron, or any other brand) then it is leaking.
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Hi Dick, hope you are having a nice day
On 27-Mar-05 At About 09:14:57, Dick wrote to All Subject: Re: Central A/C - Coil Freeze-Up Normal?
D> From: Dick <LeadWinger>
D> wrote:
D> It is interesting that you and others have suggested that the D> temperature was set too low. As I understand it, the thermostat was D> set at 69F when the outside temperature was 115 in the daytime. D> Could that have actually been the cause of the freeze-up?
D> Dick
Set at 69 degrees probably not. anywhere above 68 is OK. on an A/C system you should never set it below 68 degrees or it could freeze.
-=> HvacTech2 <=-
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Hi larry, hope you are having a nice day
On 27-Mar-05 At About 09:18:12, larry moe 'n curly wrote to All Subject: Re: Central A/C - Coil Freeze-Up Normal?
lm'c> HvacTech2 wrote:
lm'c> How can a thermostat be set too low when it's 115F outside? At that lm'c> temperature the inside of my lightly insulated house can't go below lm'c> 70-72F even when the A/C runs continously (almost 20F in-out temp lm'c> dif).
It all depends on the sizing of the system. if it gets below 68 degrees inside, the coil is now below 32 degrees and the condensation will now freeze on the coil.
lm'c> Also how can an A/C cool a house if it's outdoor coil freezes? Does lm'c> that mean that the indoor coil is even colder?
not the outdoor coil. the indoor coil will freeze.
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OK. Thanks everyone for the inputs. When I try to put it all together, here is what I get.
If the return air to the evaporator coil is above 68F, The evaporator should not freeze unless the filter is very dirty, the ducting is undersized, or the unit is low on freon. There could be other problems with the unit, but these are the most probable.
If you set the thermostat below 68F, and the return air gets that low, then the evaporator could freeze because the coil is at 32F or lower.
It doesn't matter what temperature the thermostat is set at so long as the return air does not get below 68F.
Does that sound about right?
Dick
On Sun, 27 Mar 2005 12:41:19 -0700, Dick <LeadWinger> wrote:

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I am no pro but have put a thermometer in my coil area since im oversized and need reduced airflow. All set ups are different but I dont get near to freezing even with 70 inside. At 115 outside I dought if you were near that at all. You need a service call to point out all the issues to you. Were all registers open.
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"Dick" <LeadWinger> wrote in message

No. The AC has a given capacity to remove heat. Setting the thermostat low does not make any difference if the unit is operating properly.
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wrote:

Actually, in this case the humidity was probably down to around 10%RH. This is Phoenix, not Florida.
Dick
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Hi Edwin, hope you are having a nice day
On 28-Mar-05 At About 06:32:04, Edwin Pawlowski wrote to All Subject: Re: Central A/C - Coil Freeze-Up Normal?
"Dick" <Le wrote in message >> It is interesting that you and others have suggested that the >> temperature was set too low. As I understand it, the thermostat was >> set at 69F when the outside temperature was 115 in the daytime. >> Could that have actually been the cause of the freeze-up?
>> Dick
EP> No. The AC has a given capacity to remove heat. Setting the EP> thermostat low does not make any difference if the unit is operating EP> properly.
Actually Ed setting it below 68 degrees or so it will definitely freeze the coil if the humidity is up any.
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