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Gas Safety

Exam revision materials for Plumbing Level 2&3 and ACS Gas Safety test

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Safety Devices and Controls

Safety Cut-off Devices

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Safety Devices and Controls

Air/Gas ratio valves

Appliances Controls

Flame Supervision Devices FSD

Gas Controls

Gas Meter Controls

Safety Cut-off Devices

Spare Part Identification


Open-vented System


Gas Appliances

Ventilation Sizing

Unsafe Situations

Dealing with Unsafe Situations

Emergency Notices and Warning Labels

Gas Leak




Tightness Test

Gas Performance

Gas Rate

Heat Input

Gas Supply

Gas Meters

Gas Pipework

Gas Fittings and Pipes

Gas Supply


New Installation

Pipe Protection

Pipework Sizing

Chimney and Flue


Flue Construction

Flue Inspection and Testing

Flue Terminals

Flue Types


Carbon Monoxide Poisoning

Combustion Process

Natural Gas

Portable Combustion Gas Flue Analysers


Components and Safety Devices

Multifunctional Control Valve

Multifunctional Control Valve Multifunctional Control Valve
    • Inside a boiler
    • Incorporates:
      • FFD with solenoid
      • Appliance regulator (governor)
      • Main gas valve
      • Ignition device
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Gas Tap

Gas tap

  • Integral gas flow control to at least perform an on/off function
  • Control of the heat input to the appliance
  • Correct lubricant is a molybdenum disulphide grease
  • Servicing Gas Tap :
    • Make sure that knitting components are not wrongly assembled, distorted or missing
  • Faults :
    • Lubrication between the valve plug and the barrel
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Safety Cut-off Valve

  • Fitted on free-standing cookers
  • Operated by a drop down lid
    • Turns off the gas supply as the lid drops
  • Faults
    • Broken spring
    • Dirt on the sitting
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Solenoid Valve

Solenoid ValveSolenoid Valve
  • Used in conjunction with an Electric Switch or Thermostat
  • Solenoid Valve controls the flow of gas
  • Valve is closed when the current is off
  • Can be operated on either AC (can be noisy) or D.C. suppliers
  • May be a stand alone device e.g. gas line
  • Commonly it is incorporated in a Multifunctional Control Valve
  • Often joined with FSD on a cooker oven with automatic cooking
  • Testing :
    • Use pressure gauge to ensure the gas is allowing full gas pressure through or closing
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Zero Governor

Zero Governor

  • Reduces the gas pressure to atmospheric on pre-mix burners
  • In domestic appliances the Zero Governor is built into the Multifunctional Valve
  • Has adjustable nut on the top
  • Similar to constant pressure governor (the spring is softer)
  • The outlet side of the zero governor is connected to the low pressure point of the venturi
  • Fan speed can be adjusted through the use of Potentiometer
  • Testing :
    • Zero Governors are preset and no adjustments can be made
    • Should be negative pressure reading prior to firing on the Multifunctional Gas Valve
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Gas Relay Valve

Gas Relay Valve

  • No longer used on domestic equipment
  • Similar in construction to a regulator
  • Relay Valve Faults :
    • Blockage in the Weep Tube
    • Blockage in the Thermostat
    • Blockage at the Burner
    • Damage to the Weep Tube causing a leak will cause the valve to stay open (fail safe relay valve overcomes this problem)
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