Using The Room Thermostat For Specific Applications; Using The Special Features Of The Room Thermostat - Honeywell CM900 Installation Manual

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.
Specific Application:
HEATING Gas Boiler (<30kW)
Oil Boiler
Thermal Actuator
Zone Valve
Electric Heating
(resistive load <8A)
AIR-
CONDITIONING
Heat Pump / Air-
Conditioner
Fan Coil

4.4 Using the Special Features of the Room Thermostat

Special Feature: Description:
Optimisation The thermostat will adjust the start time in the morning/afternoon so the
(Variable Start desired temperature is reached by the start of the program period. The
Time) system will restrict the start time to a max of 2 hours.
Heating or Cooling This product can be used for heating or cooling applications. If you select
Operation cooling mode the control algorithm and factory default program will be
modified. You can independently modify the heating and cooling profile.
Summer/Winter This feature moves time automatically on the last Sunday of March and
Auto time change the last Sunday of October. The feature is factory enabled.
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.
Upper/Lower The normal upper temperature limit of 35°C can be reduced to 21°C
Temperature Limit to save the homeowner energy. The normal lower limit of 5°C can be
increased up to 21°C to protect inhabitants from cold.

Setting: What to change:
Cycle/ Minimum ON Note: All parameters listed below belong to category 2
Hour Time - System Parameters (see Installer Parameters Table)
6 1 No changes required
3 4 Set 1:Ot parameter to 4
Set 2:Cr parameter to 3
12 1 Set 2:Cr parameter to 12
6 1 No changes required
12 1 Set 2:Cr parameter to 12
Set 3:EH parameter to 1
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
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
as required.
3 4 Set 1:Ot parameter to 4
Set 2:Cr parameter to 3
6 1 No changes required
CM900 Wireless - Programmable Room Thermostat
buttons and ensure the cooling program is modified
Enable/Disable
To enable: Set parameter 8:
OP (category 1) to 1.
To enable: Set parameter 4:
HC (category 2) to 1.
To enable: Set parameter 3:
tC (category 1) to 1.
Set parameter 12:tO
(category 1) to the required
offset value.
Set parameter 6:uL (category
1) to the desired upper limit.
Set parameter 7:LL (category
1) to the desired lower limit.
and buttons
and