New Carrier AC runs past setpoint when I shut thermostat backlight off
 

We have a new Carrier furnace/AC & Touch & Go thermostat.

1) The AC keeps running past the setpoint but only shows the setpoint as Actual temp. Set=73 Actual=73 but real temp is 71. 1st repairman said it was normal to run 3 hours for 1 degree & be 2 degrees colder than setpoint & this is how new ac works. Told him I set U2 backlight to OFF & U4 program to NP. Still told me nothing wrong. 2nd repairman replaced thermostat & it worked. That was until I set the Advanced Settings U2 backlight to OFF, that makes the AC run on. So I turned the U2 backlight back to ON & now it stops at set temp. Why is the backlight controlling the AC shutoff? Hoping someone can figure this out before I call for the 3rd time because we are stuck with the backlight on.

2) The Actual Temp drops 1 degree when you go to start the AC. Actual=74 & I Set=73, then Actual drops to 73 immediately & doesn't click on. You then have to go to 72 to hear the click on & reset to 73. So now I click down 2 degrees to 72 to hear the click & bump up 1 degree back to 73.

Anyone have this problem?

New Carrier AC runs past setpoint when I shut thermostatbacklight off
 

On 8/15/2017 11:56 AM, JR wrote:
We have a new Carrier furnace/AC & Touch & Go thermostat.

1) The AC keeps running past the setpoint but only shows the setpoint as Actual temp. Set=73 Actual=73 but real temp is 71. 1st repairman said it was normal to run 3 hours for 1 degree & be 2 degrees colder than setpoint & this is how new ac works. Told him I set U2 backlight to OFF & U4 program to NP. Still told me nothing wrong. 2nd repairman replaced thermostat & it worked. That was until I set the Advanced Settings U2 backlight to OFF, that makes the AC run on. So I turned the U2 backlight back to ON & now it stops at set temp. Why is the backlight controlling the AC shutoff? Hoping someone can figure this out before I call for the 3rd time because we are stuck with the backlight on.

2) The Actual Temp drops 1 degree when you go to start the AC. Actual=74 & I Set=73, then Actual drops to 73 immediately & doesn't click on. You then have to go to 72 to hear the click on & reset to 73. So now I click down 2 degrees to 72 to hear the click & bump up 1 degree back to 73.

Anyone have this problem?

I've seen many badly designed thermostats that over and undershoot the
set temp. I've always tried to stick to brand name units, like
Honeywell. It could be a software issue or even warmth radiating from
the LED used as a backlight.

OT, a little: I once had a Buick Park Avenue that had a thermostat for
the heat and AC. When the car was left out in the Chicago cold, it
would overshoot the set temp by something like 20 degrees. Of course
the dealer thought I was a nut case. But I did measure it with
instruments. I found that the senor was sucking in air from a trough on
the dash. And because it was a big hunk of steal and plastic, it stayed
cold for a long time. Eventually, it would warm up and then would work
properly. But this would take a about a half hour or so. I moved the
sensor to a better place ... problem solved.

New Carrier AC runs past setpoint when I shut thermostatbacklight off
 

On Tuesday, August 15, 2017 at 11:56:20 AM UTC-4, JR wrote:
We have a new Carrier furnace/AC & Touch & Go thermostat.

1) The AC keeps running past the setpoint but only shows the setpoint as Actual temp. Set=73 Actual=73 but real temp is 71. 1st repairman said it was normal to run 3 hours for 1 degree

Sure, if it's one of the hottest days ever in the area, 100 and you're
trying to maintain 70, I can see that. If it's 80 out and you're
trying to maintain 75, it should't take 3 hours to go from 76 to 75,
unless the unit is way undersized.




& be 2 degrees colder than setpoint

Time to get a new tech. I've never had any thermostat go 2 deg lower
than set, nor would many people put up with that.


& this is how new ac works. Told him I set U2 backlight to OFF & U4 program to NP. Still told me nothing wrong. 2nd repairman replaced thermostat & it worked. That was until I set the Advanced Settings U2 backlight to OFF, that makes the AC run on. So I turned the U2 backlight back to ON & now it stops at set temp. Why is the backlight controlling the AC shutoff? Hoping someone can figure this out before I call for the 3rd time because we are stuck with the backlight on.

2) The Actual Temp drops 1 degree when you go to start the AC. Actual=74 & I Set=73, then Actual drops to 73 immediately & doesn't click on. You then have to go to 72 to hear the click on & reset to 73. So now I click down 2 degrees to 72 to hear the click & bump up 1 degree back to 73.

Anyone have this problem?

IDK what's wrong, but it doesn't sound right. Higher end thermostats
have various programming options, some including how far over or under
the temp it will go. Do you have the full manual? Call Carrier help?

I hope this HVAC just has the old conventional interface for a thermostat.
It looks to me like some of the high end type sources are now forcing
you into their thermostats which may have a different interface so you
can't easily switch.

Like Art said, Honeywell makes excellent thermostats. I have experience
with several of their VisionPro and they are easy to set up, easy to
program, good features, etc. If I was buying a new one today, I'd
probably get an internet connected one so that is away on a trip
you can check to make sure it's working, or if you can't remember
if you set the temp back you can do it remotely. And you can fire
it back up on your way home, so it's at the proper temp for you when
you get there. Mine has a vacation mode that kind of does that,
you can set a vacation hold of X days.

New Carrier AC runs past setpoint when I shut thermostat backlight off
 

On Wed, 16 Aug 2017 07:29:47 -0700 (PDT), trader_4
wrote:



Time to get a new tech. I've never had any thermostat go 2 deg lower
than set, nor would many people put up with that.


Things get fancier every year. My new Lennox will go up to 3 degrees
below the set point in order to lower the humidity. (That feature is
can be disabled and the number of degrees is a user setting).

New Carrier AC runs past setpoint when I shut thermostatbacklight off
 

On 8/16/2017 12:56 PM, Pat wrote:
On Wed, 16 Aug 2017 07:29:47 -0700 (PDT), trader_4
wrote:



Time to get a new tech. I've never had any thermostat go 2 deg lower
than set, nor would many people put up with that.


Things get fancier every year. My new Lennox will go up to 3 degrees
below the set point in order to lower the humidity. (That feature is
can be disabled and the number of degrees is a user setting).


Humidity control is important to comfort and not easy to control
economically. Some years ago my father was the maintenance engineer in
a printing plant. humidity control was more important that temperature
control. The plant was air conditioned for that reason, not for
employee comfort. On cool but rather humid days the AC did not run
enough to removed the humidity so they cranked up at least one of the
heating boilers to warm it up enough to run the AC.

I don't know the capacity of it, but I do remember walking into the
plenum with room to spare.

New Carrier AC runs past setpoint when I shut thermostatbacklight off
 

On Wednesday, August 16, 2017 at 12:57:01 PM UTC-4, Pat wrote:
On Wed, 16 Aug 2017 07:29:47 -0700 (PDT), trader_4
wrote:



Time to get a new tech. I've never had any thermostat go 2 deg lower
than set, nor would many people put up with that.


Things get fancier every year. My new Lennox will go up to 3 degrees
below the set point in order to lower the humidity. (That feature is
can be disabled and the number of degrees is a user setting).

That's a good point, who knows what features and settings it has.
I remember that being discussed here before, that if it has humidity
control feature, it can go lower than the set point if the humidity
is still too high.

But if it really takes 3 hours to lower the temp by 1 deg on a day
that's not extreme, seems something is wrong. Of course we don't
have all the info, like what the starting temp is, the desired temp,
how hot outside, etc. That would help. I think we'd all agree that
if it's 80 out, 77 inside, set to 74 and it takes 3 hours to go down
1 deg, something is wrong.

New Carrier AC runs past setpoint when I shut thermostatbacklight off
 

On Tuesday, August 15, 2017 at 10:56:20 AM UTC-5, JR wrote:
We have a new Carrier furnace/AC & Touch & Go thermostat.

1) The AC keeps running past the setpoint but only shows the setpoint as Actual temp. Set=73 Actual=73 but real temp is 71. 1st repairman said it was normal to run 3 hours for 1 degree & be 2 degrees colder than setpoint & this is how new ac works. Told him I set U2 backlight to OFF & U4 program to NP. Still told me nothing wrong. 2nd repairman replaced thermostat & it worked. That was until I set the Advanced Settings U2 backlight to OFF, that makes the AC run on. So I turned the U2 backlight back to ON & now it stops at set temp. Why is the backlight controlling the AC shutoff? Hoping someone can figure this out before I call for the 3rd time because we are stuck with the backlight on.

2) The Actual Temp drops 1 degree when you go to start the AC. Actual=74 & I Set=73, then Actual drops to 73 immediately & doesn't click on. You then have to go to 72 to hear the click on & reset to 73. So now I click down 2 degrees to 72 to hear the click & bump up 1 degree back to 73.

Anyone have this problem?


Ask you HVAC installer if he/she/it installed a gasket behind your thermostat to keep air from inside the wall from getting into your thermostat. Sometime the hole in the wall for the thermostat wire can allow air from the wall to throw off the thermostat. If it's an interior wall, it may not be insulated and there can be quite a bit of air flowing out the wiring hole. ヽ(ヅ)ノ

[8~{} Uncle AC Monster

New Carrier AC runs past setpoint when I shut thermostat backlight off
 

On Thu, 17 Aug 2017 16:00:31 -0700 (PDT), Uncle Monster
wrote:

On Tuesday, August 15, 2017 at 10:56:20 AM UTC-5, JR wrote:
We have a new Carrier furnace/AC & Touch & Go thermostat.

1) The AC keeps running past the setpoint but only shows the setpoint as Actual temp. Set=73 Actual=73 but real temp is 71. 1st repairman said it was normal to run 3 hours for 1 degree & be 2 degrees colder than setpoint & this is how new ac works. Told him I set U2 backlight to OFF & U4 program to NP. Still told me nothing wrong. 2nd repairman replaced thermostat & it worked. That was until I set the Advanced Settings U2 backlight to OFF, that makes the AC run on. So I turned the U2 backlight back to ON & now it stops at set temp. Why is the backlight controlling the AC shutoff? Hoping someone can figure this out before I call for the 3rd time because we are stuck with the backlight on.

2) The Actual Temp drops 1 degree when you go to start the AC. Actual=74 & I Set=73, then Actual drops to 73 immediately & doesn't click on. You then have to go to 72 to hear the click on & reset to 73. So now I click down 2 degrees to 72 to hear the click & bump up 1 degree back to 73.

Anyone have this problem?


Ask you HVAC installer if he/she/it installed a gasket behind your thermostat to keep air from inside the wall from getting into your thermostat. Sometime the hole in the wall for the thermostat wire can allow air from the wall to throw off the thermostat. If it's an interior wall, it may not be insulated and there can be quite a bit of air flowing out the wiring hole. ?(?)?

[8~{} Uncle AC Monster

Sometimes the holes are the size of a hammer head -- dang them drywall
guys. Fill the hole with drywall mud. Done.