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Purge Air Flow Switch

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									Purge Air Flow Switch




PSL - Differential Pressure Switch set to trip at 80% of the differential pressure
      generated with the boiler at high purge. The differential pressure is from the wind
      box to the boiler outlet.

AA – Test port
AB – Manual shutoff valve – Lockable in open position
Combustion Air Pressure Switch (Replaces combustion air flow switch) for Boilers with
Inlet Dampers or Inlet Guide Vanes on the Forced Draft Fan.




PSL -- Differential Pressure Switch set to trip at 80% of the differential pressure that
       exists across the fan with the boiler at high fire.

AA – Test port
AB – Manual shutoff valve – Lockable in up position
Combustion Air Pressure Switch (Replaces combustion air flow switch) for boilers with
discharge dampers on the forced draft fan.




PSL -- Differential Pressure Switch set to trip at 80% of the differential pressure that
       exists across the fan with the boiler at high fire.

AA – Test port
AB – Manual shutoff valve – Lockable in open position
Typical fuel supply systems and safety controls for gas burner.




A Safety shutoff valve, spring closing (NC)                                    Safety shutdown interlocks (not shown)
C Vent valve, spring opening (NO)
D Gas flow control valve                                                       Flame detector(s)
H Gas strainer                                                                 Excessive steam pressure interlock
I Closed position interlock on valve safety shutoff                             (excessive water temperature and pressure interlock
J Constant gas pressure regulator valve                                          For hot water boilers)
K Vent line manual shutoff valve for leakage testing (locked or sealed open)   Auxiliary low water cutoff (one required)
L Test connection                                                              Combustion air supply interlock
M Gas meter (optional)
N Drip Leg
Q High gas pressure switch
R Low gas pressure switch
S Pressure gauge
T Manual shutoff valve
X Low fire start switch
Y Manual shutoff valve – lock in open position
Note: NC = normally closed, de-energized
      NO = normally open, de-energized
Typical fuel and atomizing medium supply systems and safety controls for oil burner.




AA Test connection                                                     N Low atomizing medium pressure switch
AB Manual shutoff valve – Lock in open Position                        O Oil strainer
A Safety shutoff valve, spring closing (NC)                            P Atomizing medium flow interlock differential switch
B Oil recirculation valve atomizing (NO) (optional for unheated oil)   Q High oil pressure switch
D Oil flow control valve                                               R Low pressure switch
F Low oil temperature switch (not applicable for unheated oil)         S Pressure gauge
G High oil temperature switch (not applicable for unheated oil)        T Manual shutoff valve
I Closed position interlock on safety shutoff valve                    U Oil temperature gauge (optional for unheated oil)
J Atomizing medium differential control valve                          W Atomizing medium strainer
L Automatic atomizing medium shutoff valve                             Y Atomizing medium flow orifice
M Oil meter (optional)                                                 Z Check valve
Typical ignition systems for gas-/ oil-fired burner.




A Safety shutoff valve, spring closing (NC)
C Vent valve, spring opening (NO) (optional)
H Gas strainer
J Constant gas pressure regulator
N Drip Leg
R Low pilot gas pressure switch
S Pressure gauge
T Manual shutoff valve
Y Manual shutoff valve – Lockable in open position
AA Test Connection

								
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