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Central Heating

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

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Circulating Pump

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Heating system water analysis



Circulating Pump

Heating System Controls

Minimum Requirements

Room Thermostats



Heat Emitters

Heat Loss Calculation

Radiator Sizing



Fully Pumped Hot Water and Central Heating

Gravity Hot Water and Pumped Central Heating

Gravity System

Open-vented System

Pipework Sizing

Pipework Systems

Sealed Systems

System Layout

Underfloor Heating


Boiler Sizing

Flue Types

Gas Boilers

Heat Pumps

Oil Fired Boilers


Solid Fuel Boilers

Pump Location

pump locations

  • Pump circulates water around the heating and hot water circuits
  • NO pump is allowed between cold feed and primary vent pipe
  • Static Hydraulic Test - replace pump with temporary piping
  • MAX 1L/sec for small-bore and 1.5 L/sec for micro-bore to avoid nose in the system
  • 5-6m head delivers most of the pumps
  • Should be fitted on a vertical pipe and pump upwards
  • Neutral Point - where pressure turns to negative pressure
    position of the pump neutral point
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Boiler Interlock

  • required by Document L1
  • the boiler and pump wired in such a way that when there is no demand for heat they are switched off
  • achieved by the correct installation of a room and cylinder stat
  • TRVs alone do not meet this requirement
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Pump Sizing

  • You need to know the required Flow Rate
  • Index Circuit - the pump requirement is based on the individual pipework circuit with the highest pressure loss
    • add the pressure loss through the boiler
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