compresors runs, after t-stat is satisfied

[bdr]

What would cause my CAC to run long past the t-stat being satisfied? Its not just the fan either, the compressor is running 30 minutes or longer past the pre-set temp. being reached.

[amd]

Does your t-stat have a dehumidify feature by any chance?

It it digital or mercury switch based? Mechanical stats can be a few degrees off.

[bdr]

no dehumidify feature and its digital. the current displayed temp. reaches the set temp., but the unit keeps running. often the curret temp. drops below the set temp. and the unit is still running. its a LUX Pro programmable t-stat

[amd]

Lux = consumer junk. Rip it off the wall and get something decent. (like honeywell)

If however the temp reading does not go below the setting, there is probably no problem.

[star882]

That's hysteresis at work. By running your unit for longer (and stopping it for longer), startup wear is reduced.

[smngmu]

Have you thought about calling a service tech out? I have seen this happen before with contactors that are old and crusty.They are trying to weld themselves closed.

[RoBoTeq]

Originally posted by amd
Lux = consumer junk. Rip it off the wall and get something decent. (like honeywell)

If however the temp reading does not go below the setting, there is probably no problem.

I have had very good operations from Lux in the past couple of years. Had some problems with the power stealing stats a few years ago, but in the past couple of years I have been selling thousands of Lux stats with very little issues.

Besides; this sounds more like an equipment or condition issue.

Poster; What are the equipment model numbers? Depending on the controls, there could be a back feed from a sticking control in the system somewhere.

[kevinmac]

Sound like the thermo has a setpoint window, which will not allow the AC to shutdown until it reaches the lower limit, even though the setpoint on the thermo is met. You may want to check with LUX on what the window actually is! It may be adjustable by dip switches, jumpers or by how you set it up etc.
Looks like some of the LUX thermos have a clabration mode!

http://www.luxproducts.com/support/support_9000calibration.htm

[Edited by kevinmac on 06-30-2006 at 11:15 AM]

[bdr]

If you mean the equipment number from the t-stat its a TX 1500 PB.

I don't know if this will help figure out where the problem is but...should the t-stat "click" when it reaches the desired temp.? Sometimes when I get tired of it running past my desired temp I will manually raise the temp. setting 1 degree. The t-stat then clicks and the AC turns off very shortly thereafter.

thanks for all your help

[bdr]

The system seems to respond immediately to manual t-stat adjustments, in either direction (warmer or colder). It appears that it never recieves a signal to shut off when the t-stat is satisfied. Can that be right?

[t527ed]

is it getting colder than set point??

[RoBoTeq]

Originally posted by bdr
If you mean the equipment number from the t-stat its a TX 1500 PB.


No. I was referring to the model numbers of the outdoor unit and the indoor unit.

It does sound like the thermostat itself is at fault though. Have you had it calibrated as the instructions call for?

[mjk_na]

Originally posted by bdr
The system seems to respond immediately to manual t-stat adjustments, in either direction (warmer or colder). It appears that it never recieves a signal to shut off when the t-stat is satisfied. Can that be right?

Wiring problem? Compatibility issue? Try using another thermostat of the same make and model # to find out the reason behind this.

[jdb52]

I have a Lux. Newly installed. It does the same thing. It's probably the temp swing adjustment. It can be adjusted from 1-9. On my stat, on the 1 adjustment it takes the temp about .7 degrees above setpoint and then down to the setpoint. On any other setting, it takes the temp below setpoint. You can learn how to adjust it from the website if you don't have instructions or they have a help line you can call. Adjustment is very easy, but it takes a few cycles to normalize for the new setting.

good luck
jdb

[bdr]

exact model I'm not sure.

Air Handler: ADP BC- Series
Compressor: Comfort maker 12SEER

[bdr]

t527ed
Professional Member

Registered: Mar 2005
Posts: 2528
is it getting colder than set point??

YES, it is

[t527ed]

Originally posted by bdr
t527ed
Professional Member

Registered: Mar 2005
Posts: 2528
is it getting colder than set point??

YES, it is


then its out of calibration or a bad stat. as others have said i never had any luck with lux or hunter stats. i always stick with honeywell or the high end robertshaw. like every thing else in life you get what you pay for.