User Guide

77
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signicant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uegastemperaturebasedontheresistancemeasuredattheue
temperaturesensor.Table14.8ashowsthisresistanceasafunctionofuetemperature.Thereareactuallytwo“thermistors”in
theue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signicant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.