Service manual

16
Figure 15: Boiler Temperature Control (BTC 1)
8.3 SETTING THE APPLIANCE
TEMPERATURE CONTROLLER
Press and hold all three buttons
simultaneously for 1 second. Pressing the ITEM
key again will cause the last setting to be
accepted. Once all settings have been made
wait for 30 seconds for the BTC 1 to return to
normal operating mode. To re-enter the Installer
menu press and hold all three buttons
simultaneously for 1 second. In normal operating
mode the inlet temperature, outlet temperature,
∆T temperature and ON hours can be viewed by
repeatedly pressing the ITEM key. If you wish to
check the setting you will have to start again by
pressing and holding the buttons
simultaneously for 1 second, and then use the
ITEM key to scroll through the settings. After
checking the settings allow the BTC 1 to return
to normal operation on its own.
8.4 MODES OF OPERATION
Mode 1: Constant Temperature Control
This mode is designed for hydronic heating or
domestic hot water (DHW). Once a heat
demand is present, the BTC 1 turns on the
appliance pump and modulates the boiler burner
to maintain the boiler target at the boiler inlet
sensor. A heat demand is generated when a
24VAC is applied across CD (common demand)
and Ht D (heat demand). Once voltage is
applied, the BTC 1 turns on the Dem 1 segment
in the display.
If the inlet sensor is ½ (half) of the differential
below the BOIL TARGET, the BTC 1 then
changes the proportional modulation output to
the START modulation setting, the Stage
contact (pins 15 & 16) close to proceed to trial
for ignition. The burner remains at minimum
modulation until the flame is proved and then the
modulating output changes the boiler burner
output to maintain the programmed boiler target
temperature at the inlet sensor. If the inlet
sensor reaches ½ (half) of the differential above
BOIL TARGET setting, the burner shuts off.
Once the external heat demand is removed, the
BTC 1 turns off the appliance and operates the
boiler pump based on the PUMP DELAY setting.
The water temperature is controlled based on a
fixed setpoint (BOIL TARGET).The setpoint for
inlet water is pre-set to 120
o
F and the auto re-
set limit is set to 210°F and is fixed. In addition
to the auto reset limit the factory installs a
manual re-set limit set to 250°F.
Figure 16: Mode 1 Piping & Electrical Layout