7
HEATING SYSTEM DESIGN
• The THEMA C 23 boiler is compatible with any type
of installation.
• Heating surfaces may consist of radiators, convec-
tors or fan assisted convectors.
• Pipe sectional areas shall be determined in accord-
ance with normal practices, using the output/pres-
sure curve (diagram 3). The distribution system shall
be calculated in accordance with the output require-
ments of the actual system, not the maximum output
of the boiler. However, provision shall be made to
ensure sufficient flow so that the temperature differ-
ence between the flow and return pipes be less than
or equal to 20°C. The minimum flow is 450l/h.
• The piping system shall be routed so as to avoid
any air pockets and facilitate permanent venting of
the installation. Bleed fittings shall be provided at
every high point of the system and on all radiators.
• The total volume of water permitted for the heat-
ing system depends, amongst other things, on the
static head in the cold condition.
The expansion vessel on the boiler is pressurised at 1
bar (corresponding to a static head of 5 m w.g.) and
allows a maximum system volume of 140 litres for an
average temperature of 75°C and a maximum serv-
ice pressure of 3 bar. This pressure setting can be modi-
fied at commissioning stage if the static head differs.
An additional expansion vessel can be fitted to the
system if required, see diagram 6.
• Provision shall be made for a drain valve at the
lowest point of the system.
• Where thermostatic radiator valves are fitted, not
all radiators must be fitted with this type of valve, and
in particular, where the room thermostat is installed.
• In the case of an existing installation, it is ESSENTIAL
that the system is thoroughly flushed prior to installing
the new boiler using a product such as Fernox or Sen-
tinel. Contact the product manufacturers for specific
details.
Filling the system
Provision must be made for filling the system at low
level. The use of a WRC approved filling loop is strongly
recommended, connected as shown in diagram 6.
DOMESTIC HOT WATER SYSTEM DESIGN
• Copper tubing or plastic Hep2 O may be used
for the domestic hot water system. Unnecessary
pressure losses should be avoided.
• The boiler may operate with a minimum supply
pressure of 0,3 bar but under a reduced flow rate.
Optimum performance will be obtained from a
supply pressure of 1 bar.
• The flow restrictor must be fitted in the cold wa-
ter inlet during installation.
BOILER LOCATION
Clearances
The position of the boiler must be such that there is
adequate space for servicing.
The recommended clearances are:
5 mm either side of boiler
300 mm above boiler
250 mm below boiler
450 mm in front of boiler
Fixing jig
The fixing jig comprises three parts:
1) The connecting plate which allows the connec-
tion and soundness testing of all the pipework be-
fore the boiler is fitted and helps support the weight
of the boiler.
2) The hook which supports the weight of the boiler.
3) The template which ensures the hook and con-
necting plate are correctly fitted relative to one
another.
• Place template on wall in required position, mak-
ing allowances for the necessary clearances etc.
Note: It is permissible to install the boiler with re-
duced clearances at the bottom and sides of the
boiler PROVIDING that adequate consideration is
given for Servicing/Repairs at a later date. If any
doubt exists, contact the Saunier Duval Technical
Helpline 01773 828400.
• Mark the position of the holes for the hook and
connecting plate.
• Drill, plug and fix the connecting plate and hook
to the wall using suitable screws.
• Check that both the hook and connecting plate
are level.
If the boiler is not installed immediately, protect the
various couplings to prevent any ingress of foreign
materials e.g. plaster, paint etc.
