Velocity Shadow Series, Installation And Operating Instructions Manual

Page: 78 / 104

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FIGURE 14.0: HOLD SCREEN
FIGURE 14.1: SUSTAINED HOLD
Outlet (Supply)
Temp
Lockout Code
Alternate
Flash
Lockout
FIGURE 14.2: LOCKOUT SCREEN
“Hold”
Illuminated
Outlet (Supply)
Temp
Hold Code
Alternate
Flash
Supply Sensor
– The boiler control infers the supply temperature based on the resistance measured at the supply sensor. Table
14.8a shows this resistance as a function of water temperature. Because the control/supply sensor is used as the boiler’s water
temperature limit control, there are actually two “thermistors” in the supply sensor wired in parallel (Figure 10.5). The control
compares the resistances across these two thermistors and prevents boiler operation if there is a significant difference between the
readings.
Return Sensor
– The boiler control infers the return temperature based on the resistance measured across a single thermistor in
the return sensor. Table 14.8a shows this resistance as a function of water temperature.
Flue Temperature Sensor
– The boiler control infers the flue gas temperature based on the resistance measured at the flue
temperature sensor. Table 14.8a shows this resistance as a function of flue temperature. There are actually two “thermistors” in
the flue temperature sensor wired in parallel (Figure 10.5). The control compares the resistances across these two thermistors and
prevents boiler operation if there is a significant difference between the readings.
Outdoor Sensor
– The boiler control infers the outdoor temperature based on the resistance measured across a single thermistor
in the outdoor sensor. Table 14.8b shows this resistance as a function of temperature.