5.4
Connecting the boiler with a closed central heating system
The use of a safety valve is obligatory (with a 2-3 bar threshold, depending on the power of the
boiler) and it must be mounted near the boiler.
It is essential to have a thermometer and a manometer installed to the system.
It is recommended to install an anticondensation valve on the return line. (3-way mixing valve).
It is also recommended to mount a filth catcher on the return line.
Depending on the position of the boiler in relation to the pipe-work and the radiators – the installation
can be carried out using one of two methods.
5.4.1
Installation method 1
If the boiler is positioned on the same level or higher than the pipe-work and radiators.
Each of the following items of equipment shall be fitted along the flow line:
1. Automatic air vent.
2. Safety valve (spring valve is recommended).
3. Expansion vessel.
4. Boiler valve.
The safety pressure valve must always be positioned and mounted close to the boiler. It
must be easily identifiable and allow for easy access. The safety pressure valve must be set to a nominal
pressure of 2.5 bar. The valve must open and operate smoothly at 2.5 bar. Diameter for the aperture
at the seat of the valve must be at least 15mm. Connecting pipework to the boiler must be as short
as possible. Welds, joints or any possible blockage to this pipe-work must be prevented. Bends in the
pipe-work should be avoided if possible. Unavoidable bends should be of a diameter r>3D (D = radius
of curvature) and less than
α
> 90 ˚C .
The closed expansion vessel shall be fitted close to the boiler. Connecting pipework should
be as short as possible. Fit the expansion vessel in horizontal alignment to the pipe to ensure equal
distribution of pressure. The volume of the expansion vessel is determined by the output/capacity of the
boiler. A ratio of 1 kW:1 litre should be used. The safety pressure valve and the expansion vessel should
be fitted in close proximity to each other, in the following order: expansion vessel closest to the boiler,
followed by the safety pressure valve.
In the event of power failure and the boiler fails to operate correctly – any sudden increase of
pressure will be controlled first by the expansion vessel, on any further increase in pressure the safety
pressure valve will open.
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