Page 521 - 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

Filling

The procedure for filling central heating systems will again depend on the type
of system that is installed. We will look at two separate procedures here.

Open vented systems
Filling open vented systems is a fairly simple procedure. Having conducted a
pressure test at the installation stage, there should be no surprises when it
comes to system filling:

l Ensure that all radiator valves and radiator air release points are closed.
l Check the F and E cistern to ensure that all joints are tight.
l Temporarily replace the pump with a short piece of tubing. This will ensure
that no debris enters the pump.
l Ensure that all motorised valves are manually set to the open position for
initial system filling.
l Turn on the service valve to the F and E cistern and allow the system to fill.
l Starting with the furthest-away radiator on the downstairs circuit, open the
radiator valves and fill and bleed the air from each radiator. Work backwards
towards the boiler, downstairs circuit first, then the upstairs circuit. This will
ensure that air is not trapped in pockets around the system.
l Once the system is full, allow it to stand for a short while. Visually check for
leaks at each radiator and all exposed pipework and controls/valves, etc.
l Check the water level in the F and E cistern.
l Drain down the system. This will flush the system through, removing any
flux residues, steel wool, etc.
l Refit the pump and turn on the pump valves.
l Refill the system as before.

Sealed systems
The main difference when compared to the open vented system is that there
is no F and E cistern, so the system will have to be filled in stages or short
bursts via the filling loop. In other words, turn on the filling loop, fill the
system up to operating pressure, turn off the filling loop, bleed the air from
the radiators until the pressure has depleted and then restart the process
until the system is full. All other points remain the same as for open vented
systems, above.

Replace defective components
Maintenance of central heating systems takes many forms, from replacing
valves to replacing boilers. It can also include adding to or altering an existing
system.
In this part of the chapter, we will look at some of the more common
maintenance activities and the processes involved.
Some of the general maintenance activities include:

l pump replacement
l radiator replacement
l radiator valve replacement

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