Technical information

Combi 70 & Combi 90 Oil Boilers
18
Water connections
3.12
Sealed central heating system
3.13
For additional protection of either the entire heating
system, or the boiler and localised pipework, it is
recommended that a frost thermostat be installed.
Refer to section 10 for connection details.
To protect the heating system the frost thermostat
should be sited within the house in such a place that it
can detect any rise and fall in the ambient air
temperature, i.e. in a room with a radiator.
Where the frost thermostat is installed outside the
house (to protect a boiler installed in an external boiler
room or garage) or in an attic, it is recommended that
it be used in conjunction with a pipe thermostat to
avoid unnecessary and wasteful overheating of the
property. The pipe thermostat should be located on the
boiler return pipe, and set to operate at 25°C. Refer to
section 10 for connection details.
1 The boiler must stand on a surface that is firm and
level. It does not require a special hearth as the
temperature of the boiler base is less than 50°C.
2 Sufficient clearance must be allowed around the
boiler for the following:-
Access above the boiler to remove the Combi 70
baffles for servicing.
Access at the front of the boiler to remove the
burner and Combi 90 baffles.
3 It is preferable to allow access to the top of both
models to allow for removal and replacement of
components. The boilers may be installed under
a work surface, (the section above the Combi 70
must be removable).
4 If the boiler is to be installed with a side against a
wall, allow a nominal clearance of 20 mm for the
plug for the heating return connection. Water
connections may be taken from one side only if
required.
Note: Water connections may be from the left or
right hand side. If using low level side exit flue, the
flue must be on the opposite side to the water
connections. See Fig. 17 or 19 for flue/water
connection arrangements.
3 - GENERAL BOILER INFORMATION
Frost protection
3.10
Boiler location
3.11
1 Combi 70: Three push-fit elbows connections are
supplied with the boiler for connection of the
heating flow pipe (22 mm), cold water mains inlet
pipe (15 mm) and domestic hot water outlet pipe
(15 mm) to the three open pipe ends in the boiler.
See Fig. 16.
The safety valve outlet has a 15 mm compression
fitting for connection of the discharge pipe.
2 Combi 90: A kit of pre-formed copper tubing (to
BS 2871) connecting pipes is supplied with the
boiler for the heating flow (22 mm), cold water
mains inlet (15 mm), domestic hot water outlet (15
mm) and safety valve discharge (15 mm). These
pipes are suitable for use with compression or
soldered fittings. See Fig. 18.
3 A low level heating return connection (1" BSP) is
provided on each side of the boiler. See Fig. 1.
4 The heating return connections have been
temporarily sealed with plastic caps to prevent any
residual water (from factory testing) leaking from
the boiler during transit. Both caps must be
removed before connecting any fittings.
Plug the unused connection.
5 A drain tap is provided at the bottom on the front
of the boiler.
See Fig. 12
1 The boiler is only suitable for use with a sealed
system complying with the requirements of BS
5449.
The maximum temperature of the central heating
water is 85°C.
Design notes - when designing the system, the
pump head, expansion vessel size, radiator mean
temperature, etc. must all be taken into account.
2 The boiler is supplied with the following items
factory fitted:-
a 12 litre diaphragm expansion vessel complying
with BS 4814, pre-charged at 1.0 bar.
b System pressure gauge, with an operating range
of 1 to 4 bar.
c Pressure relief safety valve complying with BS
6759 and set to operate at 2.5 bar. The
discharge pipe must be routed clear of the
boiler to a drain, in such a manner that it can be
seen, but cannot cause injury to persons or
property.