SECTION 1
INTRODUCTION
1.1
The Ravenheat CSI System boiler is for the
use of central heating wich incorporates a
circulation pump, expansion vessel, safety
valve, pressure gauge and electronic
ignition.
The boiler is equipped with a front cover
which can be removed for servicing. The
data badge with technical data is placed
on
the lower right hand side of the frame.
1.2
Fig.1.
Illustrates the general layout of components.
Fig. 2.
Illustrates the operating scheme described
in section 2.
SECTION 2
2.1
DESCRIPTION OF CONTROL SYSTEM
AND SEQUENCE OF OPERATION
2.2
Domestic hot water mode.
When the appliance is in rest mode with
the mains neon switch on.
2.2.1
The boiler will function in the following
sequence:
the pump starts,
the control board sensors,
the fan operates via the pressure switch and
sends a signal back to the ignition board that
the fan is running at maximum speed.
2.2.2
The spark ignition system is powered which in
turn commences the spark igniter to operate
and light the burner.
At this point the ignition board opens the gas
valve to light the burner.
2.2.3
When the electrode/sensor senses the
signal of the burner, the spark igniter stops.
2.2.4
From the minimum gas rate setting the
boiler increases to the maximum permissible
pressure over a period of 3 to 4 seconds
and will remain at its maximum required
power until it reaches maximum regulated
temperature.
2.2.5
When the domestic hot water tap is closed
the diverter valve goes back into rest mode,
the main burner is shut down along with the
pump and fan which are also switched off.
The pressure switch returns to its rest
mode.
2.2.6
Central heating mode
2.2.7
If the switch is positioned on
with a demand for heat to supply radiators,
with the heating circuit fully pressurized so
as to operate the low water sensor device
the boiler will start in the same way in
domestic hot water mode but with slightly
differing time delay.
6
In that it will start on minimum and remain
at this level for about 1 minute. After which
the fl ame will lift to its maximum setting as
governed by a potentiometer which range
rates the heating circuit between maximum
and minimum power. As the heating sensor
reaches temperature the gas burner
power modulates down, the fan speed
will also reduce to minimum fan speed.
When starting, the fan will always start at
maximum speed.
2.2.8
The boiler is fi tted with an anti-cycling device
on the control board. This delays the boiler
from re-fi ring over a 2/5 minute period when
in heating mode. The domestic hot water will
always take priority and is unaffected by the
anti-cycling device.
2.3 SAFETY
DEVICE
In both central heating and domestic hot
water mode safe operating is ensured by:
2.3.1
A differential pressure switch which shuts off
the main burner if the fan stops or the fl ue or
combustion air intake duct is obstructed.
An overheat cut off thermostat set slightly
higher than the high limit thermostat acts
to turn of the burner to resetable “lockout”
(Fig. 36) item 3.
2.3.2
A safety valve is fi tted on the central heating
circuit set at 43 psi (3 bar).
2.3.3
A heating circuit (low water) pressure switch
is set at 0.4 bar.
Summary of Contents for 780 Series
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