VOKERA Mynute EHE Installation & Servicing Instructions Manual - page 4
2
SECTION 1
DESIGN PRINCIPLES AND OPERATING SEQUENCE
Fig. 2
1.1
PRINCIPLE COMPONENTS
●
A fully integrated electronic control board featuring elec-
tronic temperature control, anti-cycle control, pump over-
run, LED fault indicator, full gas modulation.
●
Low-water-content, copper heat exchanger.
●
Electronic ignition with flame supervision.
●
Integral high-head pump.
●
Fan.
●
Air pressure switch.
●
Expansion vessel.
●
Water pressure switch.
●
Two-stage gas valve.
●
Pressure gauge.
●
Safety valve.
●
Condense switch.
1.2
MODE OF OPERATION (at rest)
When the appliance is at rest and there are no requests for
heating and/or hot water, the following functions are active:
●
Frost-protection system – the frost-protection system
protects the appliance against the risk of frost damage.
Should the temperature of the appliance fall to 5 °C, the
boiler will function in the heating mode at minimum
power until it reaches 35 °C.
●
Anti-block function: the anti-block function enables the
pump to be energised for short periods, when the appli-
ance has been inactive for more than 19-hours.
1.3
MODE OF OPERATION
When there is a request for heat via the time clock/program-
mer and/or any external control, the pump and fan are
started, the fan will then prove the air pressure switch. 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;
●
a high limit thermostat that over-rides the temperature
control circuit to prevent or interrupt the operation of the
burner;
●
an air pressure switch that requires the fan to prove
operation before the gas valve is energised;
●
a pressure switch that interrupts the operation of the
appliance if the condense pipe becomes blocked;
●
a safety valve which releases excess pressure from the
primary circuit.
CH
return
CH
flow
safety valve
automatic
by-pass
pump
bottom
AAV
expansion
vessel
latent heat
collector
flue
outlet
air
intake
pressure
switch
main heat
exchanger
CH NTC
sensor
main
burner
gas valve
pressure
switch