6) Trouble Shooting
6.1 Trouble Shooting Guide
50039987-003 A
© 2009 Honeywell International Inc.
Manufactured for and on behalf of the Environmental and Combustion Controls Division of Honeywell Technologies Sàrl, ACS-ECC
EMEA, Z.A. La Pièce 16, 1180 Rolle, Switzerland by its Authorised Representative Honeywell International Inc.
Honeywell Control Systems Ltd.
Arlington Business Park,
Bracknell, Berkshire
RG12 1EB
Technical Help Desk: 08457 678999
www.honeywelluk.com
Symptom (Fault
Message)
Possible Cause Remedy
The room thermostat
displays the
symbol but
the Relay Box relay does
not switch on.
This is normal operation. The Relay Box cycles
the relay on and off for times proportional to
the demand signal (0-100%) from the room
thermostat. The
symbol only indicates that the
demand value is greater than 0%.
Using the
button change the
temperature setpoint by a few degrees.
The Relay Box should switch the relay on
after a few seconds delay.
The Relay Box does not
react to setpoint changes
on the room thermostat.
The room thermostat and Relay Box are not
bound.
Reset the Relay Box by pressing and
holding the push button for 15 seconds.
Then follow the binding / rebinding
procedure as described in section 5)
Additional Installation Information.
After the binding procedure
the red LED is on and the
green one is flashing once
every 3 sec on the Relay
Box.
Incorrect or incomplete binding procedure.
Incorrect position of the room thermostat during
binding.
Repeat the binding procedure.
Repeat the binding procedure keeping
approx. 1 m distance between the Relay
Box and the room thermostat.
The red LED on the
Relay Box is illuminated
(Communication loss)
The Relay Box receives no RF messages from
the room thermostat:
RF signal is blocked due to wrong location of the
room thermostat.
Room thermostat batteries are exhausted.
Re-locate the room thermostat following
instructions in section 2) Installing the
CM900 Wireless System.
Replace batteries in the room thermostat.
6.2 Diagnostic Mode
The CM927/921 room thermostat has a user accessible mode that provides information useful to a remote
service person and a means of checking whether the boiler is working. To access this move the slider
switch to the OFF position then press and hold the button for 5 seconds. The room thermostat will enter
the user settings mode. Next press and hold the and buttons together. The room thermostat will hold
the relay on for 5 minutes and the following information can be viewed on the display by pressing the
or buttons. : model ID, date code (WW/YY) & checksum.
Hereby, Honeywell declares that this CM927/CM921 room thermostat and BDR91 Relay Box are in
compliance with the essential requirements and other relevant provisions of Directive 1999/5/EC, 2006/95/EC
and 2004/108/EC.
®
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