RTH2520
69-1867EF—04 03-11 3/8
3.2 Fan Operating Mode
Use the selector switch to set the fan to automatic
mode (AUTO) or continuous mode (ON).
Note
: This switch is not used in a 2-wire installation
as the fan is not connected to the thermostat in this
type of installation.
3.3 Displaying the Temperature
The actual temperature is normally displayed. To view the setpoint,
press once on one of the
buttons. The setpoint is displayed for
5 seconds along with the icon.
Note
: Pressing either of the
buttons more than once will
change the setpoint.
3.4 Setting the Temperature
Press one of the
buttons until the desired temperature is dis-
played.
3.5 Backlight
The display illuminates for 12 seconds when the backlight button or
either of the
buttons is pressed.
3.6 Thermostat Control Mode
3.6.1 Manual/Permanent Hold Mode
Maintains the temperature at a fixed setpoint. To place the thermo-
stat in this mode, press
[ Mode ]
. The house icon will disappear.
3.6.2 Programmable Mode
Maintains the temperature according to the energy-saving sched-
ule. To place the thermostat in this mode, press
[ Mode ]
. The cur-
rent period will be displayed. The four possible periods are:
To see the default program settings, see section 5.3.
Temporary Bypass
If you modify the setpoint (using the
buttons) when the thermo-
stat is in Programmable mode, the thermostat will use the new set-
point for the next 2 hours. The house icon flashes during the
bypass. Afterwards the thermostat will return to the temperature set-
ting of the period currently underway.
3.7 Filter Replacement Indicator
After 500 hours of operation, an icon appears to indi-
cate that the filter needs replacement. Once the filter
is replaced, press
[ Filter ]
for 3 seconds to remove
the icon and reset the counter.
3.8 Battery Replacement Indicator
Install fresh batteries immediately when the icon starts
flashing. The icon flashes for 120 days before the bat-
teries are depleted. You should replace batteries once
a year or before leaving home for more than a month
even if the icon has not appeared.
After replacing the batteries, set the time, day and date (see sec-
tions 5.1 and 5.2). However, the temperature and program settings
are saved and do not need to be re-entered.
Warning
: Before removing the batteries, place the
system switch on the thermostat to Off. Otherwise, the
heating/cooling unit might still be running even after
the batteries are removed.
To access the configuration menu, press the backlight button
for 3 seconds.
To go to the next parameter (menu item), briefly press the back-
light button.
To modify a parameter, press
.
Repeat steps 2 and 3 if necessary.
Press the backlight button for 3 seconds to exit the configura-
tion menu.
5.1 Setting the Time and Day
Press
[ Clk ]
. The hour flashes.
Set the hour using
.
Press
[ Clk ]
. The minutes flash.
Set the minutes using
.
Press
[ Clk ]
. The day flashes.
Set the day using
.
(MO: Monday, TU: Tuesday,
WE: Wednesday, TH: Thursday, FR: Friday, SA: Saturday and
SU: Sunday).
Press
[ Exit ]
to exit.
5.2 Setting the Date
The date is needed for automatic daylight savings changeover.
Press
[ Clk ]
for 3 seconds to display the year.
AUTO
The fan operates only when the heating or cooling sys-
tem is On (typical setting).
ON
The fan operates continuously. Use this setting to
improve air circulation and air cleaning.
Wake up
Leave for work
Return home
Sleep
4. Configuration Menu
DISPLAY
DESCRIPTION
DEFAULT
OPTIONS
Temperature display
°F
°C or °F
Time display
12 h
12 h or 24 h
Early start
1
Off
On or Off
Automatic daylight savings
changeover
2
Off
On or Off
Heating cycles per hour
3
4
2, 3, 4, 5 or 6
4
Cooling cycles per hour
3
4
2, 3, 4, 5 or 6
5
1
When Early Start is On, the thermostat determines when to start heating or cooling
so that the desired temperature is reached at the set time.
2
When this function is On, the thermostat automatically switches to daylight savings
time on the second Sunday of March and to normal time on the first Sunday of
November (see section 5.2).
3
Use the Heat/Cool selector switch to switch between the heating parameter and the
cooling parameter.
4
For optimal heating control, use the setting that matches your system as follows:
2=30 min (steam, gravity), 3=20 min (hot water, 90%+ high-efficiency furnace), 4=15
min (gas or oil), 5=12 min (alternate setting for gas or oil), 6=10 min (electric).
5
The corresponding cooling cycle lengths are: 2=30 min., 3=20 min., 4=15 min.,
5=12 min., 6=10 min.
5. Programming
