
20
F LCON
3.05 Connecting the central heating and domestic hot water circuits
Connect to the relevant connections as indicated in fig. 1.
Connect the pressure relief valve discharge pipe (15mm) to the outside of the building, where possible over a drain.
The discharge must be such that it will not be hazardous to occupants and passers-by or cause damage to external
electric components or wiring. The pipe should be directed towards the wall.
To ensure long life, the heating circuit should be correctly sized and fitted with all the controls necessary to ensure
correct functioning and operation. The differential between the boiler flow and return pipes should not be more than
20°C. You are advised not to use the boiler with return temperatures of less than 50°C in order to prevent patches of
condensation forming and having a corrosive effect on boiler components.
3.06Boiler water characteristics
If the water is harder than 18clarke degrees, the water used should be treated to avoid possible scale in the
boiler caused by hard water or corrosion by aggressive water. It should be remembered that as a result of its low
thermal conductivity, even scale of just a few millimetres thickcan lead to considerable overheating of the boiler
walls, resulting in serious problems.
IT IS ABSOLUTELY VITAL THAT THE WATER USED IS TREATED IN THE FOLLOWING CASES:
a) Extensive systems (containing large quantities of water);
b) Frequent additions of water to top-up the system;
c) Domestic hot water circuits
If the system requires partial or total emptying, you are recommended to refill it with treated water.
3.07Filling
When cold, system pressure should be about 1 bar. If while running venting off of air dissolved in the water causes the
pressure of the central heating system to drop below the minimum level described above, the user must utilise a filling
loop to bring it backto the original value. During operation, water pressure in the boiler when hot should be about 1.5
- 2 bars. After filling, always close and disconnect the filling loop.
Note -If there is a possibility of air pockets forming in certain points of the central heating system flow and return pipes,
you are recommended to fit an air vent valve at these points.
Note -When the boiler is installed below the level of the central heating a system, single checkvalve should be fitted
in the flow to prevent gravity circulation around the heating system.
3.08Gas connection
Gas connection should be carried out using a rigid pipe.
The flow at the gas meter should be sufficient for the simultaneous use of all appliances connected to it. Connect the gas
supply to the boiler according to current regulations. The diameter of the gas tube leaving the boiler is not the determining
factor in choosing the diameter of the pipe between the appliance and the meter. This must be selected in relation to
length and pressure drop and in any instance should not be less than 22mm.
The whole ofthe gas installation including the meter should be inspected and tested for soundness and purged
in accordance with BS6891-1988.
N.B. -The filling loop will be fitted by the installer at the time of installing the system. It is NOTa part
ofthe boiler.
3.09Electrical connection
The boiler must be connected to a single phase 230 V50 Hz electricity supply with a 3Amax. fuse and a bipolar switch
with contact opening of at least 3mm fitted between the boiler and the electricity supply. The boiler must always be
connected to an efficient earth installation. Under the electrical box, there is a 3pole terminal board for connecting
the boiler to the mains (230 V50 Hz) and a 2 pole board for connecting a room thermostat (RT). To connect, undo
the screws fixing the terminal board box and connect the wires, ensuring correct polarity of the terminals. It should be
noted that there is low voltage (24V) between the room thermostat contacts.
When the boiler is connected to an electricity main, it is essential TOOBSERVE CORRECT POLARITIES (LIVE: brown
cable, NEUTRAL: blue cable, EARTH: yellow-green cable).
All wiring must conform to current I.E.E. regulations.