Page 4 of 4
before the boiler start; continue water flow for an adjustable cool down period after the boiler
has stopped; and ensure water is always moving past the remote system temperature sensor
even after the last boiler has been stopped. The pump shall immediately stop if any trips
occur during pre-purge, pilot, or main flame trial for ignition.
H Flue Gas Condensate Protection
Include alarms and control logic to help prevent corrosion in the boiler due to sustained flue
gas condensation. These features become increasingly important as we add energy savings
modulation and outdoor air reset functions. Provide a 4-20mAdc, 3 way mixing valve control
output based on PID control, measured boiler inlet temperature and minimum inlet
temperature setpoint and measured boiler inlet and outlet temperature difference and
differential setpoint. If the boiler inlet water temperature drops below setpoint or the
differential temperature is excessive the valve shall open to allow hot boiler outlet water to
blend with cold inlet water temperature. The valve repositions toward 0% recirculation after
inlet water temperature increases above setpoint. Low boiler inlet water temperature shall be
alarmed using an alarm message, indicating light and an alarm contact output. Excessively
low boiler inlet temperature events shall be stored with boiler historical data.
I Mixing Valve (when required by contract drawings)
In order to prevent low inlet water temperature, provide an electric actuated three-way mixing
valve with a 4-20 mAdc input control signal and slow (1 minute) travel time for each boiler. If
the boiler inlet water temperature is below 130 ° F (adjustable) or when boiler differential
temperature is above 40° F (adjustable), the valve shall slowly jog closed causing boiler
outlet water to blend with the inlet water. When the inlet water temperature and differential
temperature return to an acceptable range, the boiler outlet valve shall slowly jog open.
J Communication
Include an RS485 Modbus slave or peer-to-peer communications data highway on each
boiler control system. When peer-to-peer communication is enabled the data highway shall
allow the connected boilers to exchange signals as required to provide coordinated fully
modulating lead/lag functions. It shall not be required to wire individual control signals
between boilers. When Modbus communication is enabled the data highway shall allow
individual boiler limits, lockout, boiler and system temperatures and firing rate status to be
readable and water setpoint, boiler firing rate, and start/stop command to be readable and
writable. Provide all equipment capabilities specified in this paragraph, even if a connecting
SCADA (Supervisory Control And Data Acquisition system, typically a desk top personal
computer) system or Building Automation System (BAS) is not included in this project.
K Quality Assurance
The boiler control system shall be supplied as part of a factory assembled, tested burner
control cabinet.
(1 strony)
(1 strony)
Manymanuals.com
Manymanuals.de
Manymanuals.fr
Manymanuals.it
Manymanuals.pl
Manymanuals.cz
Manymanuals.es
Manymanuals-pt.com
Komentarze do niniejszej Instrukcji