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NOTE ON ADDITIONAL OUTPUTS
The RC-90 has two additional outputs (B and O) for use with zoned heating and cooling systems. The B and O
terminals control the mode of operation (heating or cooling) of the zone control panel. The zone control panel
will recognize calls for heat (W) from the individual zones when the B terminal is energized, and calls for cool
(Y) when the O terminal is energized.
The RC-90 will energize (connect to R) the B terminal whenever the display shows "HEAT" or "HEAT AUTO"
mode, even if it is not calling for heat (W). Similarly, the RC-90 will energize the O terminal whenever the
display shows "COOL" or "COOL AUTO". Both B and O are Off when the display shows "OFF".
Therefore, the RC-90 can act as a Master to set the operating mode of the entire system (HEAT, COOL, or
OFF).
CONFIGURING THE BACKLIGHT ON THE RC-90B
The backlight on the RC-90B can be configured to one of three different modes: 1) on for 30 seconds when a
key is pressed, 2) always on, or 3) always off.
1)
To configure the display backlight to turn on when a key is pressed, then back off 30 seconds later, set
the “JP2” (Select Backlight Mode) jumper to the “TIMED” position (between the top and middle pin on
the connector) - See Figure 8.
2)
To configure the display backlight to always be on, set the “JP2” (Select Backlight Mode) jumper to the
“ON” position (between the middle and bottom pin on the connector) - See Figure 8.
3)
To configure the display backlight to never come on (always off), remove the “JP2” (Select Backlight
Mode) jumper from the connector - See Figure 8.
DISABLE KEYS
The keys on the thermostat can be disabled to prevent anyone from controlling the thermostat locally. To
disable the keys, solder a wire jumper across “JP1” (two holes on the circuit board) - See Figure 8.