Page 523 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 7 Central heating systems

extension will need to be fitted. It is desirable, when replacing a radiator, to
replace the valves as well, as they will probably be as old as the radiator you
are replacing. If this is the case, then all or part of the system will need to be
drained. We will assume that the radiator is downstairs, requiring complete
system drain down.
Before attempting to remove the radiator, the electricity should be isolated
at the switched fuse spur to the system and the fuse retained to prevent
accidental switching on of the circuit. The system should also be cold. It may be
a good idea to ask the customer to turn the central heating off before you get to
the job. Before you begin, make sure you have protected carpets and furnishings
with lots of dust sheets.
1 Isolate the F and E cistern at the service valve. If it is a sealed system, this
will not be necessary.
2 Locate a suitable drain valve, attach a hose and drain the system. Take care
that the system contents are disposed safely to a drain as they will probably
be very dirty, especially if the system is an old one. The black water will stain
all it comes into contact with.
3 As the system drains, open the air release valves on all radiators, starting
upstairs, then working to the downstairs.
4 When the system is drained, carefully loosen the two radiator valve
compression nuts and remove the radiator. It is a good idea to leave the
valves on the radiator and to turn them off before removal. This will help
in preventing any residual dirty water from leaking from the radiator. If
possible, turn the radiator upside down (turn the air release valve off first!)
as this will further prevent accidental spillage.
5 The new radiator should be dressed and hung as previously described.
6 Reconnect the pipework, ensuring that the old compression nuts and olives
are removed first. If the old olives have crushed the pipe too much, then the
pipe may have to be replaced.
7 Ensure all radiator unions and compression nuts are fully tight.
8 Turn off the drain valve. It may be a good idea to replace the drain-off valve
washer at this stage. Drain valve washers quite often go stiff and brittle with
the heat from the water.
9 Turn off all air release valves.
10 Turn on the service valve to the F and E cistern or (if applicable) reconnect
the filling loop and refill the system.
11 Bleed the air from all the radiators, starting downstairs then upstairs. Leave
the new radiator isolated at this stage. This will be the last radiator filled.
12 Open the valves to the new radiator and bleed the air from it. Check for
leaks.
13 Replace the fuse in the fuse spur and run the system to full temperature to
ensure that the new radiator is working perfectly.
14 If corrosion inhibitor had been added to the system in the past, this will
need to be replaced. It must be replaced like for like. If this is not possible,
the system should be flushed several times to ensure removal of all previous
inhibitors.

511

9781510416482.indb 511 29/03/19 9:04 PM