Installation Manual

3.5 BOILER SIZE SELECTION
The Qudos 28s will automatically adjust heat output and pump speed to match the system
requirements at any given time. Efficiency and combustion levels are maintained at
optimum levels throughout the possible output range. The Qudos 28s is therefore suitable
for all systems with a total heat load within the maximum range of the boiler.
3.6 GAS SUPPLY
A gas meter should be connected to the service pipe by the local gas region or their
contractor. An existing meter should be checked preferably by the gas region to ensure
that the meter is adequate to deal with the rate of gas supply required. Installation pipes
should be fitted in accordance with BS 6891.
Minimum/Maximum Gas Pressure:
Natural gas pressure before the gas valve must be maintained at between 18 mbar (7.2 in
WG) and 22 mbar (8.8 in) while the boiler is running.
LPG pressure must be maintained between 31.5 mbar (12.4 in w.g) and 37.6 mbar (14.8
in w.g) while the boiler is running.
Gas pressures above or below these levels will lead to problems associated with the gas
valve's internal pressure regulator.
Supply pipes to the boiler must not be sized less than the boiler inlet connection
(15 mm). Due consideration must be given to the supply pressure to other gas
appliances in the premises. Reduction in dynamic gas supply pressure will result in
intermittent ignition failures. Ensure gas supply pipe work is adequately sized for
the length of run from the meter to the boiler at a supply rate of 28.4kW (i.e. a natural
gas supply should be considered to be a minimum of 22mm diameter, reducing to 15mm
at the boiler. If gas runs greater than 12m, including the allowance for bends, are involved
the pipe size should be increased further).
3.7 WATER SYSTEMS
All piping must be installed in accordance with all applicable local and Water Supply
Bylaws for forced hot water heating systems.
Consideration must be given to pipe capabilities and pressure drop through the piping
when selecting pipe sizes. The primary pipe connections to the boiler must be sized
according to the system load, not dictated by the boiler connection sizes.
Water treatment must be carried out to BS 7593 : Treatment of Water in Hot Water
Central Heating Systems.
In IE the requirements given in the current edition of IS813 and the current Building
Regulations must be followed.
a The Keston Qudos 28s is designed for installation on sealed water systems only.
With fully pumped water circulation. The pump, an 8l expansion vessel and
associated safety devices are fitted within the boiler.
b Any system must be thoroughly flushed clean of grease, dirt and debris, prior to
connection with the boiler. A trap may be installed in the flow line to collect any
solder, or other debris, from the installation.
c All water systems must be constructed to comply with requirements of the Local
Water Authority.
d Always use a system complying with the requirements of BS 5449 and BS 6798.
e System design must ensure an open circuit is always available to ensure
circulation when the pump overrun function is operating after boiler shutdown.
f Isolation valves must be fitted on the flow and the return to enable isolation when
maintaining the boiler.
WD420/3/2007 Chapter 3 : Boiler Location The Keston Qudos 28s & Qudos 28sP Boilers
Installation & Servicing Instructions Page : 14