33
ELECTRICAL CONNECTIONS & INTERNAL WIRING
4. Relay Module: This fused module provides isolation
for the pump contacts on the main control board. The
maximum rating for each pump attached is 10 amps.
Since only two pumps will operate at any one time,
this limits the incoming power required for this
module to 20 amps. This separate power supply is to
be connected to terminals 27 and 28 on the right
terminal strip.
5. Integrated Primary Controls: There are two primary
ignition controls on the P
UREFIRE
®
PF-850 and
PF-1000 boiler. They are integrated controls that
supervise all of the ignition timing as well as the
burner modulation. The “managing burner” control is
located in the blower vestibule area and is mounted
adjacent to the top, “managing burner”. The
“dependent burner” control is located adjacent to the
lower “dependent burner.
6. Supply Temperature Sensors: The supply temperature
sensors provide input to their respective control which
use them to determine the input rate of each burner.
These sensors are 12kW NTC thermistors.
7. Return Temperature Sensor: The return temperature
sensors provide information on the boiler return water
temperature to prevent unsafe operation of the boiler.
These sensors are 12kW NTC thermistors.
8. Header Temperature Sensor: The header temperature
sensor provides the outlet supply temperature of the
boiler to the managing control to control the overall
boiler system operation. These sensors are 12kW NTC
thermistors.
9. Flue Temperature Sensor: The 12kW flue temperature
sensor provides the exhaust vent temperature to the
managing control to prevent unsafe operation of the
boiler.
10. Supply Limit Switches: The supply limit switches are
UL353 certified temperature switches that prevent the
boiler from exceeding 210°F (99°C) which is the
maximum operating temperature allowed by ASME
Boiler and Pressure Vessel Code, Section IV. These
switches along with the manual reset circuitry of the
primary controls meet the high limit requirements of
ASME CSDAFB (CSD-1).
11. Thermal Fuses: The thermal fuses located at the rear
of each combustion chamber prevent unsafe
operation of the boilers in the event of ceramic
deterioration in the combustion chamber target wall.
12. Condensate Drain Float Switch: This switch is
connected to the managing primary control and
prevents the boiler from operating if the condensate in
the condensate collector vessel exceeds its maximum
level.
13. Blocked Vent Pressure Switch: This switch is
connected to the managing primary control and
prevents the boiler from operating if the pressure in
the combustion chamber exceeds 4.5 in. w.c. (11
mbar). This will prevent the boiler from operating with
the condensate displaced from the trap due to
pressure.
14. Flapper Proof-of-closure Switches: These switches
transmit the position of the flapper to their respective
primary control. If the switch indicates that the flapper
is not closed on the inactive burner while the other
burner is operating, it will start the blower for the
inactive burner. This will assure a positive combustion
chamber pressure and prevent combustion gases from
back-feeding through the inactive burner in the event
of a flapper failure.
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