Supplied By www.heating spares.co Tel. 0161 620 6677
3
1.1
PRINCIPLE COMPONENTS
A fully integrated electronic control board featuring
electronic temperature control, anti-cycle control,
pump over-run, self-diagnostic fault indicator, full
air/gas modulation.
●
●
●
●
●
Radial aluminium heat exchanger.
●
●
●
●
●
Electronic ignition with flame supervision
●
●
●
●
●
Integral high-head pump
●
●
●
●
●
Fan
●
●
●
●
●
Expansion vessel
●
●
●
●
●
Water pressure switch
●
●
●
●
●
Condensate level sensor
●
●
●
●
●
Pressure gauge
●
●
●
●
●
Safety valve
1.2
MODE OF OPERATION (at rest)
When the appliance is at rest and there are no
requests for heating or hot water, the following
functions are active:
●
●
●
●
●
2-stage frost-protection system – the frost-
protection system protects the appliance against
the risk of frost damage. The first stage enables
activation of the pump should the temperature
of the appliance fall to 6
o
C. Should the first stage
become active, the appliance will function on
m25% power until it reaches 35
o
C.
●
●
●
●
●
Anti-block function – the anti-block function
enables the pump to be energised for short
periods, when the appliance has been inactive
for more than 24-hours.
1.3
MODE OF OPERATION
When there is a request for heat and/or hot water,
via the programmer/time clock and/or any external
control, the pump and fan are started, the fan
speed will modulate until the correct signal voltage
is received at the control PCB. At this point an
ignition sequence is enabled.
Ignition is sensed by the electronic circuitry to
ensure flame stability at the burner. Once
successful ignition has been achieved, the
electronic circuitry increases the gas rate to 75%
of the MAX Heating (set by the corresponding HTG
trimmer) for a period of 15 minutes. Thereafter,
the boiler’s output will either be increase to
maximum or modulate to suit the set requirement.
When the appliance reaches the desired
temperature the burner will shut down and the
boiler will perform a three-minute anti-cycle (timer
delay).
When the request for heat has been satisfied the
appliance pump and fan may continue to operate
to dissipate any residual heat within the appliance.
1.4
SAFETY DEVICES
When the appliance is in use, safe operation is
ensured by:
●
●
●
●
●
a water pressure switch that monitors system
water pressure and will de-activate the pump
(when lockout condition is reached), fan and
burner should the system water pressure drop
below the rated tolerance;
●
●
●
●
●
fan speed sensor to ensure safe operation of the
burner;
●
●
●
●
●
a high limit thermostat that over-rides the tem-
perature control circuit to prevent or interrupt the
operation of the burner;
●
●
●
●
●
flame sensor that will shut down the burner when
no flame signal is detected;
●
●
●
●
●
a sensor that interrupts the operation of the
appliance if the condense pipe becomes blocked;
●
●
●
●
●
a safety valve which releases excess pressure
from the primary circuit.
Fig. 2
SECTION 1
DESIGN PRINCIPLES AND OPERATING SEQUENCE
expansion
vessel
CH
return
safety
valve
pump
return
temperature
sensor
main heat
exchanger
bottom
AAV
automatic
by-pass
pressure
switch
CH
flow
drain
valve