Central Heating Flashcards
Boiler must be fitted in accordance with…
Manufacturers instructions
Mounted on the wall where the boiler is to be installed and the pipework connections are made before the unit is attached. Means that pipework can be pressure tested without fear of damaging the sensitive parts of the boiler.
Boiler Jig
Location of pump in modern system and combination boilers.
Inside the casing as integral part of boiler
Location of pump for traditional boilers that are fed from a feed & expansion cistern.
Externally to the boiler on the system pipework.
At what stage should the pump be installed on a system fed from a feed and expansion cistern?
After the vent and cold feed pipes but before motorised valves and controls. Ensures that system does not pull air into the system via open vent.
Where/ when should the pump be fitted on a sealed system?
On the flow pipe from the boiler, before any motorised valves or controls.
Very Correct Position (VCP)
Vent Cold-feed Pump
Distance between vent and cold feed
150mm apart to maintain the neutral point
Where are motorised valves positioned?
After the pump and wired back to the central wiring unit.
Y Plan
1x 3 port mid-position valve
W Plan
1x 3 port diverter valve
S Plan
2x 2 port motorised valves
S Plan Plus
3X 2 port motorised valves
C Plan
1X 2 port zone valve installed on the grtavity primary flow or primary return
Position of expansion vessel
In many instances as part of the boiler package.
If external is necessary, usually fitted on the return pipe.
If installed on the flow pipe, it must be installed behind the pump on the suction side.
Where are TRVs required?
Every room except for where there is a thermostat.
Where should drain valves be installed?
At all low spots on heating systems and all radiators where pipe drops down from above.
Two types of decomissioning
Permanent decommissioning and temporary decommissioning
Permanent decommissioning
Performed when a system is no longer required.
Completely draining down the system and the removal of all pipework, fittings, clips and appliances. Cold water supply tap turned off at external tap. Internal stop tap capped off as near to stop tap as possible.
Temporary decommissioning
Conducted when a system is being serviced, repaired, renewed or extended. Isolating water supply to either whole property or a particular section of pipework.
Notify relevant people, isolate fuel/ electricity as appropriate, isolate water supply, apply warning notices, continuity bonding as required, temporary capping as required, alternative heat arrangements.
Factors that affect the selection of central heating systems
- Customer needs
- Building layout and features
- Energy efficiency
- Environmental impact
- Occupancy and purpose of the building
- Appliance location
- Cost
- Legislation
