2
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.
●
Low-water-content, copper heat exchanger.
●
Electronic ignition with flame supervision
●
Integral high-head pump
●
Fan
●
Expansion vessel
●
Analogue pressure switch (PAD)
●
Water pressure switch
●
Two-stage gas valve
●
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 7
°
C. The
second stage becomes active when the
temperature has dropped to 3
°
C. Should the
second stage become active, the appliance will
function on minimum power until it reaches
30
°
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 19-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%
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,
fan and burner should the system water
pressure drop below the rated tolerance.
SECTION 1
DESIGN PRINCIPLE AND OPERATING SEQUENCE
●
a high limit thermostat that over-rides the
temperature control circuit to prevent or
interrupt the operation of the burner.
●
an analogue pressure switch (PAD) that
checks the operation of the fan and flue thereby
allowing safe operation of the burner.
●
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
Flue Outlet
Air Intake
A
B
Expansion
vessel
Latent Heat
Collector
PAD
AARV
Main Heat
Exchanger
Main
Burner
Gas Valve
Pressure
Switch
Automatyc
by-pass
Safety
valve
Pump
Condense
trap
