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Old 12-11-2010, 12:28 PM   #1
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outside unit freezing.


Hey I have a split system that runs all the time. I have a t-stat that tell you haw many hour it ran - today, yesterday, last month and last year. This thing is running 22 hours a day. Im in NC so it is not that cold, but cold for us. It is about 38 degrees in the day and high 20s at night. Should this thing run that much? I checked the freon about 4 months ago and every thing was fine. I took off the t-stat last week and jumpered the white, red and green and got heat so I know the aux heat is working once I added the yellow wire I got 110 degree heat comming from vent. So everything looks good. When I put back the t-stat and set for normal opperation I only get 86 degree from vent, even if I crank it up to 90 on the t-stat(The second stage should come on more than 3 degree difference). I replaceed the t-stat and the outcome was the same. should I get 110 ( or at least better then 86) degree on normal opperation?

Thanks for the input!

oh yeah today i noticed a little ice on the outside unit, very little!
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Old 12-11-2010, 06:58 PM   #2
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outside unit freezing.


When a heat pump gets near, or at, it's thermal balance point for the house it will run like that. At those temps it's still 3 times cheaper then the electric back up heat. Your back up should have come on when the thermostat was turned up to 90 though. Double check the wiring on the new thermostat since it works with the wires jumpered .

Last edited by Marty S.; 12-11-2010 at 07:25 PM.
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Old 12-17-2010, 01:44 PM   #3
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outside unit freezing.


OK I am checking to outside unit just to make sure everything is working.

It is in heat mode and it is 40 degrees outside, the suction line (in ac mode) (big line) is reading 290 psi, the temp is 121.

The high side (in ac mode) or (the small line) is reading 78 psi and at 100 degrees.
How does that sound to yall?

Thanks for the help

Last edited by wetbar; 12-17-2010 at 02:30 PM.
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Old 12-17-2010, 04:12 PM   #4
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outside unit freezing.


Data will be different for every size,brands and coil match up. Just looked at my Lennox and it's calling for 330/90 at 40 degrees(410A system)
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Old 12-17-2010, 05:06 PM   #5
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outside unit freezing.


Will it say on it what it should be?
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Old 12-17-2010, 05:15 PM   #6
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outside unit freezing.


Most made in the last 15 years say what it's supposed to be. Might be on the back side of the access panel or in the installation instructions but usually there's a chart somewhere.

Edit
Should have said most that I have worked on in the last 15 years instead of the broad "most" above.

Last edited by Marty S.; 12-17-2010 at 05:41 PM.
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Old 12-18-2010, 10:25 AM   #7
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outside unit freezing.


Quote:
Originally Posted by wetbar View Post
ok i am checking to outside unit just to make sure everything is working.

It is in heat mode and it is 40 degrees outside, the suction line (in ac mode) (big line) is reading 290 psi, the temp is 121.

The high side (in ac mode) or (the small line) is reading 78 psi and at 100 degrees.
How does that sound to yall?

Thanks for the help
are you refering to suction line and winter port for your low side pressure the suction line and liquid line should be bout the same in heat mode
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Old 12-18-2010, 02:32 PM   #8
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outside unit freezing.


when the reversing valve reverses the low side(big pipe) becomes the high side right? I know it pegs my guage in heat mode. . . but what I did do was go ahead a recover the freon. I recoved 7 pounds and the factory charge is 6.4, so the rest was the lines - make since to me right ? I have about 60 feet of line.

So the freezing up is not due to low freon. I checked all filters today and cleaning the coil less than 4 monthes ago. What is strange is when I put my fieldpiece meter on it, and measure the temp and LL presure and so forth it says it is low on froen.

any clues what to do next?
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Old 12-18-2010, 03:05 PM   #9
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outside unit freezing.


One last piece of info. After I recovered the freon, I pull a vacuum and cant get it below 11 or so. It has been running for 30 minutes. Normally I can hit 25 or 30 in that time frame. A vacuum has nothing to do with the outside temp right?
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Old 12-18-2010, 04:26 PM   #10
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outside unit freezing.


What the heck is going on here! OK I get the vacuum down to -15 that is as low as I could get it to go after 45 min. I decide just to shut it off, close all valves and see what happens. Stayed at -15 for 10 min or so then went to +40PSI. WTF? How that that happen?
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Old 12-18-2010, 04:43 PM   #11
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outside unit freezing.


Still had refrigerant in the compressor that didn't boil off when you reclaimed.
Buy a micron gauge and use it every time you put the vacuum pump on. A manifold set isn't nearly sensitive enough to show nonconsenables are still in the system or if there's a micro leak.
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Old 12-18-2010, 05:45 PM   #12
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outside unit freezing.


45 minutes is a short vacuum time in the winter. At 20F outdoor temp. It takes 24 hours to boil off 1 drop of moisture.

The compressor, liquid line filter drier(if its outside), and accumulator will all have refrigerant in them after you recover..
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Old 12-18-2010, 06:15 PM   #13
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outside unit freezing.


Quote:
Originally Posted by beenthere View Post
At 20F outdoor temp. It takes 24 hours to boil off 1 drop of moisture.
WOW! Nobody ever told me that. Sure drives home the importance of keeping things clean and dry when the system is open.
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Old 12-18-2010, 06:41 PM   #14
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outside unit freezing.


AT 20 degrees. the moisture freezes to ice. And has to vaporize by sublimation. Which is a very slow process.

So yep. Clean and dry is best. Saves time in vacuuming.
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Old 12-20-2010, 03:54 PM   #15
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outside unit freezing.


"The compressor, liquid line filter drier(if its outside), and accumulator will all have refrigerant in them after you recover.. "


Even if the guages show 20 or 30 vacuum?
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