Ravenheat Flue Boiler Installation And Servicing Instructions - page 12
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Fig. 6C
Schematic ‘S’ plan
4.8.3
The water through the appliance heat
exchanger circuit must exceed the min.
1.84 gals/min. (503 It/h) when the burner is
firing. It is important to ensure that this rate
is achieved when sections of the system
are shut off either manually or by automatic
controls. Therefore a by-pass must be fit-
ted to the system (15 mm min.) (Fig. 6A).
If the volume of circulating water is too low,
the boiler water temperature will rise too
rapidly. This could cause noise in the system
or even cause the safety thermostat to trip.
4.0.4
Draining tap
These must be located in accessible posi-
tions to permit the draining of the whole
system. The taps must be at least 15 mm
nominal size and manufactured in accor-
dance with BS 2870 1960.
4.8.5
Air release points
These must be fitted at all high points where
air will naturally collect, and must be sited to
facilitate complete fitting of the system.
4.8.6
The appliance has an integral sealed
expansion vessel to accomodate the
increase of water volume when the system
is heated, It can accept up to 1.5 gal (7 Its)
of expansion water. If the appliance is con-
nected to a system with an unusually high
water content, calculate the total expansion
and add additional sealed expansion
capacity as appropriate (Fig. 7).
In general modern systems will present no
problem.
4.8.7
Mains water feed: central heating
There must be no direct connection to the
mains water supply, even through a non-
return valve, without the approval of the
Local Water Authority.
4.8.8
Permissible methods of filling
Cistern method (Fig. 8).
The system may be filled by one of the fol-
lowing methods. Through a cistern used for
no other purpose, via a ballvalve perma-
nently connected directly to a service pipe
and/or cold water distributing pipe. The sta-
tic head available from the cistern should
be adequate to provide the initial system
design pressure.
The cold feed pipe from the cistern should
include a non-return valve, and a stop-valve
with an automatic air vent connected be-
tween them, with the stop valve being locat-
ed, between the cistern and the automatic
air vent. The stop valve may remain open
during normal operation of the system, if
automatic water make-up is required.
Booster pump method (Fig. 6).
The system may be filled through a self
contained unit comprising of a cistern pres-
sure booster pump if required and if neces-
sary an automatic pressure reducing valve
or flow restrictor. The cistern should be sup-
plied through a temporary connection from
a service pipe or cold water distributing
pipe. The unit may remain permanently con-
nected to the heating system to provide lim-
ited automatic water make up.
Mains topping up method (Fig. 9).
Here the temporary connection is supplied
from a service pipe, or distributing pipe,
which also supplies other draw-off points at
a lower level.
Fig. 6