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Gas Safety

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

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Boilers

Components and Safety Devices

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Safety Devices and Controls

Air/Gas ratio valves

Appliances Controls

Flame Supervision Devices FSD

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Spare Part Identification

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Gas Leak

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Commissioning

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Tightness Test

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Pipe Protection

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Chimney and Flue

Chimneys

Flue Construction

Flue Inspection and Testing

Flue Terminals

Flue Types

Combustion

Carbon Monoxide Poisoning

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Natural Gas

Portable Combustion Gas Flue Analysers

Boilers

Components and Safety Devices

Diverter Valve Working Principle

Diverter Valves in Gas Combi Boliers

Most combi gas boilers have a complicated hydraulic circuit with a circulator pump and a diverter valve. There are two types of diverter valves. The first is a mechanically operated valve powered by a motored diverter head (just like a normal y plan system). Either switches to hot water or heating depends on what is being called for. The second one found on the SPA combis is a hydraulic three way valve. These have diaphragms in that are connected to push rods which operate microswitches to fire the boiler up. They work off a pressure differental valve in hot water mode and in heating mode its the pump.

Function:diverter_valve_working
  • The valve piston moves inside the 3-way valve cartridge in the axial direction. The piston is operated by the lever arm (shaft), which is operated by the actuator.
  • Due to the special principle of the valve, the shaft seal is not dynamically loaded by axial movement but statically loaded by a tilt motion. This prevents deposits at the shaft and extended wear.
  • The actuator is usually a hydraulic diaphragmconnected to the HW
    supply system. Opening a tap causes a drop in pressure on one side of
    the diaphragm, which is pushed by the pressure on the other side,
    operating 3-way valve. There are electric diverter valves (e.g.,
    Honeywell) but they're far too slow for this application.

diverter valve operation diagram

section_through_diverter_valvediafragm_diverter_valve.jpg

 

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