Central A/C - Coil Freeze-Up Normal?

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?

Reply to
Dick
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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

Reply to
m Ransley

Low on Freon.

Reply to
Michael Baugh

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

Reply to
stretch

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.

Reply to
m Ransley

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

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

Reply to
HvacTech2

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> From: "Michael Baugh"

MB> Low on Freon.

not necessarily. see my reply to the original poster.

"Dick" news: snipped-for-privacy@4ax.com... >> 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

Reply to
HvacTech2

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

Reply to
Dick

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.

Reply to
Joseph Meehan

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.

Reply to
Travis Jordan

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?

Reply to
larry moe 'n curly

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

D> 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

Reply to
HvacTech2

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> From: "larry moe 'n curly"

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.

-=> HvacTech2

Reply to
HvacTech2

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

Reply to
Dick

Could be other things too, Monkey boy....

Reply to
HeatMan

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.

Reply to
m Ransley

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.

Reply to
Edwin Pawlowski

Reply to
Dick

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?

EP> From: "Edwin Pawlowski"

"Dick" > 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?

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.

-=> HvacTech2

Reply to
HvacTech2

Hi Dick, hope you are having a nice day

On 27-Mar-05 At About 19:08:28, Dick wrote to All Subject: Re: Central A/C - Coil Freeze-Up Normal?

D> From: Dick

D> If the return air to the evaporator coil is above 68F, The evaporator D> should not freeze unless the filter is very dirty, the ducting D> is undersized, or the unit is low on freon. There could be other D> problems with the unit, but these are the most probable.

D> If you set the thermostat below 68F, and the return air gets that D> low, then the evaporator could freeze because the coil is at 32F or D> lower.

D> It doesn't matter what temperature the thermostat is set at so long D> as the return air does not get below 68F.

D> Does that sound about right?

No, you should never set the thermostat below 68 degrees or it will eventually get there and freeze. not only will it freeze but it is very hard on the compressor.

-=> HvacTech2

Reply to
HvacTech2

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