Honeywell Home ST9420C User Manual page 26

FAQ AND TROUBLESHOOTING
How reliable is 2-way RF communication?
The 2-way RF communication (also known as wireless communication) used by
Honeywell Home is extremely robust and reliable. When installed correctly the
Signal Strength test feature allows the Installer to locate the system components
where mutual signal reception is strong. During communication, signals are sent
several times to ensure receipt, and if any message is garbled, the error detection
software recognises this and ensures the message is repeated again.
What do I do if RF communication is lost?
Follow the steps in the Troubleshooting Guide on the next page. The most likely
cause for loss of communications is the DT92E batteries running low on power. This
will be indicated on the DT92E display by a flashing battery symbol, or the display
may even be blank. Simply replace the batteries (as shown on page 21) and wait a
few minutes for communications to become re-established.
If this does not resolve the problem it may be that the RF signal path between
the ST9420C and the DT92E is blocked by a metal object. Check the direct path
between the two devices and reposition any object that may be blocking the signal,
or move the thermostat.
How do I know when to change the batteries in the DT92E
room thermostat?
If the DT92E batteries need changing, the battery symbol will flash on the DT92E
display. DT92E will continue to operate for at least 4 weeks after the indicator begins
to flash. The ST9420C will also show the message 'SENSOR LOW BATT' and the
radiator symbol will flash. It is important to change the DT92E batteries as soon
as the low battery condition is indicated, as reduced battery power may affect the
RF signal strength and impair RF communications.
Can I override the Programmer from the DT92E thermostat?
As well as changing the set temperature from the DT92E, it is also possible to
override the heating system on or off from the DT92E. This is only possible if the
ST9420C is in AUTO or ONCE Modes. If ST9420C is in CONT mode it will not be
possible to switch the heating off from the DT92E. Similarly, if ST9420C is in OFF
mode, it will not be possible to switch the heating on from the DT92E. If these latter
overrides are required it is first necessary to change the ST9420C mode setting to
AUTO or ONCE.
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