7
OPERATIONAL INFORMATION
Five--minute Compressor Timeguard
The cycle timer limits the number of times the heating or cooling equipment can be energized in one hour. If option 1 is set to a value of 1 or
2, the equipment will be allowed to energize up to six times per hour. If option 1 s set to 3 or greater, then the equipment will be allowed to
energize up to four times per hour. This timer is defeated for 1 cycle when the desired temperature is manually changed. It can also be
defeated for 1 cycle by simultaneously pressing the FAN button and the INCREASE TEMPERATURE button.
Cycle Timer
This timer prevents the start of a heating or cooling cycle until at least 15 minutes after the last start of the same cycle. Its function is to assure
that equipment is not cycled more than 4 times per hr. This timer is defeated for 1 cycle when the desired temperature is manually changed. It
can also be defeated for 1 cycle by simultaneously pressing the FAN mode button and the INCREASE TEMPERATURE button.
Staging Timer
In multistage heating or cooling, this timer prevents any higher stage from turning on until the preceding stage has been on for 15 minutes.
This timer is defeated if the temperature error is greater than 5
_
F/3
_
C (usually due to a large change in desired temperature).
Three--minute Minimum On Time
In normal operation, when a stage turns on, it will not turn off for a minimum of 3 minutes.
Heat/Cool Setpoints (Desired Temperatures)
A minimum difference of 2
_
is enforced between heating and cooling setpoints. This is done by allowing one setting to “push” the other, to
maintain this difference.
Auto Changeover
When the auto changeover mode is selected, a change from heat to cool (or vice versa) will not occur until an opposite mode demand has
existed for 20 minutes. If the setpoint is changed, the 20 minute requirement is deleted. Auto mode may be disabled.
Emergency Heat Mode
When thermostat is configured as a heat pump and emergency heat mode is selected, all Y signals are locked out and W becomes energized
upon a call for heat.
Heat On and Cool On Icons
When a heating or cooling demand exists, the HEAT ON or COOL ON icon will either remain on or flash. If flashing, the equipment is
temporarily prevented from turning on by one of the timers (see above). While the icon remains on without flashing, the equipment is on.
Power On Check
When AC power is first applied, all segments of the display are turned on for a few seconds. Following this, the temperature display indicates
the model/configuration via the following 2 digit code: AC—1--speed air conditioner, HP—1--speed heat pump.
Error Codes
---- — If the thermostat cannot properly read room temperature, the display will indicate ---- (2 dashes) and all outputs (except the fan if on)
will turn off. This is to prevent operation of the equipment if the thermostat has failed.
E2 — If the AC line voltage drops below a minimum (brownout) level, all outputs are turned off and the display indicates E2. This condition
will remain for 15 sec after proper line voltage is restored. If the AC line voltage disappears completely, the display will immediately go
blank.
Thermostat Troubleshooting
SYMPTOM
WHAT TO CHECK
Blank LCD
Check for 24vac between R and C at terminal connections or battery.
“--- ---” (2 dashes) on temperature display
Temperature sensor reading out of range. Check sensor for damage. If
recycling power does not clear display, thermostat should be replaced.
“E2” on temperature display
Brownout condition or too low of voltage to thermostat. Double check
wiring and check for 24vac between R and C. E2 will clear 15 sec after
proper voltage is restored.
“SERVICE FILTER” on temperature display
After the selected number of hour of blower operation “FILTER” will display
on LCD. This is to remind the homeowner to “check” the filter. Press
RESET FILTER button to clear display and reset timer to 0.
Cooling will not come on
Select COOL mode. Set desired temperature to 10
˚
F below room temper-
ature. Simultaneously press FAN and INCREASE TEMPERATURE buttons
to defeat timers. Check for COOL ON icon and 24vac at Y (first---stage)
terminal. If present, thermostat is OK and problem is with equipment or
wiring. If not present, replace thermostat.
Heating will not come on
Select HEAT mode. Set desired temperature to 10
˚
F/6
˚
C above room
temperature. Simultaneously press FAN and INCREASE TEMPERATURE
buttons to defeat timers. Check for HEAT ON and 24vac at Y (first---stage)
terminal (with heat pump) or W (with air conditioner) terminal. If present,
thermostat is OK and problem is with equipment or wiring. If not present,
replace thermostat.
T2SN
