8
CM900 Wireless - Programmable Room Thermostat
4.3 Using the Room Thermostat for Specific Applications
The CM927/921 RF room thermostat is a versatile controller that can be used to control many different
applications. For most typical applications, like wall-hung gas fired combination boiler control or zone
valve control, no adjustments from the factory settings are required. For other applications, like controlling
an oil burner, the best system performance can be achieved by modifying selected parameters of the
room thermostat in the Installer mode. The table below lists the most common settings used for specific
applications.
4.4 Using the Special Features of the Room Thermostat
Special Feature:
Description:
Enable/Disable
Optimisation
(Variable Start
Time)
The thermostat will adjust the start time in the morning/afternoon so the
desired temperature is reached by the start of the program period. The
system will restrict the start time to a max of 2 hours.
To enable: Set parameter 8:
OP (category 1) to 1.
Heating or Cooling
Operation
This product can be used for heating or cooling applications. If you select
cooling mode the control algorithm and factory default program will be
modified. You can independently modify the heating and cooling profile.
To enable: Set parameter 4:
HC (category 2) to 1.
Summer/Winter
Auto time change
This feature moves time automatically on the last Sunday of March and
the last Sunday of October. The feature is factory enabled.
To enable: Set parameter 3:
tC (category 1) to 1.
Temperature Offset
If the thermostat is located in a particularly hot/cold location for reliable
signal transmission reasons then the measured/displayed temperature
can be adjusted by +/- 3°C. This is useful if the homeowner wants the
reading to match another appliance temperature display.
Set parameter 12:tO
(category 1) to the required
offset value.
Upper/Lower
Temperature Limit
The normal upper temperature limit of 35°C can be reduced to 21°C
to save the homeowner energy. The normal lower limit of 5°C can be
increased up to 21°C to protect inhabitants from cold.
Set parameter 6:uL (category
1) to the desired upper limit.
Set parameter 7:LL (category
1) to the desired lower limit.
Specific Application:
Setting:
What to change:
Cycle/
Hour
Minimum ON
Time
Note:
All parameters listed below belong to
category 2
- System Parameters (see
Installer Parameters Table
)
HEATING
Gas Boiler (<30kW)
6
1
No changes required
Oil Boiler
3
4
Set 1:Ot parameter to 4
Set 2:Cr parameter to 3
Thermal Actuator
12
1
Set 2:Cr parameter to 12
Zone Valve
6
1
No changes required
AIR-
CONDITIONING
To enable switching between cooling and heating
modes adjust parameter 4:HC in category 2 (0 =
disabled, 1 = enabled). Now you can switch between
these modes by pressing the
and buttons
together for 5 seconds in any of the product operating
modes (
AUTO
,
MAN
or
OFF
). Explain to the end user
how to switch between these modes using the
and
buttons and ensure the cooling program is modified
as required.
Heat Pump / Air-
Conditioner
3
4
Set 1:Ot parameter to 4
Set 2:Cr parameter to 3
Fan Coil
6
1
No changes required
