VOKERA RAIN 24 Installation And Servicing Instructions - page 4
2
24/28/bi
24/28/bi
24/28/bi
24/28/bi
24/28/bi
SECTION 1
DESIGN PRINCIPLES AND OPERATING SEQUENCE
Fig. 2
1.1
PRINCIPLE COMPONENTS
●
A fully integrated electronic control board fea-
turing electronic temperature control, anti-cy-
cle control, pump over-run, self-diagnostic fault
indicator, continuous gas modulation.
●
Low-water content copper heat exchanger.
●
Electronic ignition with flame supervision.
●
Integral pump.
●
Fan.
●
Expansion vessel.
●
Differential air pressure switch.
●
Water pressure switch.
●
Two-stage gas valve.
●
Pressure gauge.
●
Safety valve.
1.2
MODE OF OPERATION
When there is a request for heat and/or hot water
via the programmer/time clock and/or any exter-
nal control, the pump and fan are started, the fan
proves the differential air pressure switch which
in-turn allows an ignition sequence to begin.
Ignition is sensed by the electronic circuitry to
ensure flame stability at the burner. Once suc-
cessful 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 tem-
perature the burner will shut down and the boiler
will perform a three-minute anti-cycle (timer de-
lay).
When the request for heat and/or hot water has
been satisfied the appliance pump and fan may
continue to operate to dissipate any residual heat
within the appliance.
1.3
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 pres-
sure drop below the rated tolerance.
●
A high limit thermostat that over-rides the tem-
perature control circuit to prevent or interrupt
the operation of the burner.
●
A differential air pressure switch that checks
the operation of the fan and flue thereby allow-
ing safe operation of the burner.
●
A safety valve which releases excess pressure
from the primary circuit.
CH
return
CH
flow
automatic
by-pass
flue outlet
air intake
pressure
switch
main heat
exchanger
CH water drain tap
main
burner
gas valve
pressure
switch
safety
valve
pump
bottom
AAV
expansion
vessel
primary
NTC sensor
fan