VOKERA Linea Max HE Installation & Servicing Instructions Manual Download Page 5

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SECTION 1

DESIGN PRINCIPLES AND OPERATING SEQUENCE

1.1

PRINCIPLE COMPONENTS

●

A fully integrated electronic control board featur-
ing electronic temperature control, anti-cycle
control, pump over-run, self-diagnostic fault in-
dicator and premix burner control

●

Low-water-content, aluminium heat exchanger

●

Electronic ignition with flame supervision

●

Integral high-head pump

●

Fan

●

Expansion vessel

●

Water pressure sensor/gauge

●

Two-stage gas valve

●

Condensate level sensor

●

Safety valve

1.2

MODE OF OPERATION (see section 7 for de-
tailed information)

When the appliance is connected to the electrical
supply, there are 5-possible modes of operation:

●

STANDBY- Heating and DHW functions are
disabled, however anti-freeze and anti-seize
functions are active*

●

WINTER - Heating and DHW functions enabled
with DHW pre-heat and SARA BOOSTER func-
tion active

●

SPRING - DHW only enabled, DHW pre-heat
disabled

●

SUMMER - DHW only enabled, DHW pre-heat
disabled, TSC function enabled

●

AUTUMN - Heating and DHW functions enabled,
DHW pre-heat disabled, SARA function active.

*Anti-freeze & anti-seize functions are active in all
operating modes.

1.3

MODE OF OPERATION (Heating)

When there is a request for heat via the program-
mer/time clock and/or any external control, the
pump and fan are started, the fan speed will
modulate until the correct signal voltage is re-
ceived 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 suc-
cessful ignition has been achieved, the electronic
circuitry increases the gas rate to 75% for a period
of 15 minutes (adjustable, see parameter 28, cap.
7.3.1). Thereafter, the boiler’s output will either
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 five-minute anti-cycle
(timer delay). When the request for heat has been
satisfied the appliance pump and fan may con-
tinue to operate to dissipate any residual heat
within the appliance.

1.4

MODE OF OPERATION (DHW)

When there is a request for DHW via a hot water
outlet or tap, 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 suc-
cessful ignition has been achieved, the electronic
circuitry increases the gas rate to maximum or will
modulate output to stabilise the temperature.
In the event of the appliance exceeding the de-
sired temperature (set point) the burner will shut

down until the temperature drops*.
When the request for DHW has been satisfied the
appliance pump and fan may continue to operate
to dissipate any residual heat within the appliance.
*When the appliance is in the SUMMER mode, the
burner will remain on minimum power even if the
set point has been achieved.

1.5

SAFETY DEVICES

When the appliance is in use, safe operation is
ensured by:

●

a water pressure sensor 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;

●

2 temperature sensors that control and prevent
the over-heating of the circuit, interrupting the
operation of the burner;

●

a differential temperature protection circuit which
interrupts the burner if the temperature differen-
tial is too high or inverted;

●

a fan speed sensor that checks the correct
operation of the fan, thereby allowing safe opera-
tion 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.

1.6

OPTIONAL ACCESSORIES