Honeywell ST9420C User Manual

26
BDR91T Controls Layout
Automatic Operation
The BDR91T relay box simply switches the boiler
on and off according to a wireless signal it receives
from the ST9420C. It is mainly used when the boiler
is installed in a remote location where it may be
difficult to run wires direct from the timer. The green
light indicates the status of the relay output:
Green light on = relay on
Green light off = relay off
Temporary Manual Override
In normal operation it should not be necessary to
interact with the BDR91T. However it is possible
to press the button and temporarily override the
current relay position. This will be cancelled as soon
as the Relay Box receives another signal from the
ST9420C, because automatic operation has a higher
priority than manual operation.
Loss of Wireless Communications
If the RF communication is lost for a period of 1 hour the red light will illuminate.
The Relay Box will then enter the failsafe mode as selected by your Installer (see
page 34).
When RF communication is restored, the Relay Box will automatically return to
normal operation.
OPERATING YOUR BDR91T RELAY BOX (IF INSTALLED)
Green LED
Red LED
Push button
Green light, relay status indicator
Push button
Red light, indicator for special modes
or loss of communications

Honeywell ST9420C Specifications

General

Model	ST9420C
Category	Thermostat
Display	LCD
Channels	2
Power Supply	230V AC
Mounting	Wall-mounted
Contact Voltage	230V AC
Contact Current	3A resistive, 1A inductive
Switching Type	SPDT
Type	Programmer
Programs	7-day programming
Compatibility	Compatible with most heating systems