8
• Heat Exchanger Thermistor: Measures hot water temperature at heat exchanger outlet. If
water temperature reaches a predetermined limit, gas supply is stopped.
• Hot Water Delivery Thermistor: Measures hot water temperature at the outlet valve (i.e. the
‘mixed’ temperature).
• Flame Rod: Monitors combustion characteristics inside the combustion chamber. If the flame
fails, gas supply is stopped.
• Overheat Switch: Situated on the heat exchanger, gas supply is stopped when water
temperature reaches 97ºC for a number of seconds.
• Fusible Link: Situated on the heat exchanger, electrical power supply is stopped if the
temperature exceeds 150ºC.
• Water Pressure Relief Valve: Safeguards the water circuit against excessive inlet pressure.
Opens at 15 bar, closes at 12 bar.
• Electrical Fuse: (3A glass fuse) prevents against over-current. Surge Protector: prevents
against over-current.
• Boil Dry Prevention: If water flow sensor detects no flow, gas supply is stopped.
• Combustion Fan Speed Sensor: In case of combustion fan defect (no rotation of fan) gas
supply is stopped.
• Temperature Cutout: If the delivered hot water temperature rises above the required delivery
temperature for a number of seconds, the gas supply is stopped.
Sensors and Safety Devices
Combustion Specifications
The secondary gas pressure is set with the cover off the unit and a manometer measuring
the pressure from the gas valve (regulator) test point
Gas Type
Injector
size
(mm)
Primary
Pressure (mbar)
Secondary Pressure
(mbar)
Gas Input [Gross]
(kW)
Low High Low High
Natural Gas
(G20)
1.3 20 1.8 9.0 4.7 34.9
Propane (G31) 37 2.2 14.2 4.9 36.5
Damper
Nat Gas
LPG
To Next Page
Loading...
