VOKERA Linea Max HE Installation & Servicing Instructions Manual - page 6
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LINEA MAX HE
2
SECTION 2 DESIGN PRINCIPLES AND OPERATING SEQUENCE
2.1
Fig.1 illustrates the general layout of compo-
nents. Fig.2 illustrates the operating principles
described below.
2.2
Central Heating Mode
2.2.1
When the various switches and controls impose a
demand for heat, the pump is started. The flow of
water from the pump operates a flow switch. This
in turn energises the electronic circuitry. The fan
is started, the gas valve is energised at an inter-
mediate rate and the electronic ignition goes
through an ignition attempt.
2.2.2
The burner ignition is checked by the electronic
circuitry to ensure correct ignition of the burner.
Once successful ignition has been achieved, the
electronic circuitry increases the gas rate to 75%
for a period of 15 minutes.
2.2.3
As water temperature increases this is sensed by
the temperature sensor on the flow pipe which
modulates the burner to match the heat output to
the heat requirement of the system.
2.2.4
Depending on the load, either a) the water tem-
perature will continue to rise and the burner will
continue to modulate down until the maximum
setting is reached at which point the burner is
switched off, or b) the water temperature will fall
and the burner will return to a higher output to
match the demand.
When the request for heat has been satisfied the
appliance pump and fan may continue to operate
to dissipate any residual heat within the applian-
ce.
2.3
Domestic Hot Water Mode
2.3.1
The appliances incorporate a hot water preheat
facility. The appliance will therefore ignite periodi-
cally to maintain heat within the appliance.
2.3.2
The appliance will operate in domestic hot water
mode whenever the mode selector switch is on
regardless of mode selector switch position and
any demand for central heating.
2.3.3
The diverter valve will automatically energise into
the hot water position after central heating
demand, or will stay in the hot water position after
hot water demand. Opening a draw off tap will
energise the pump and fan sending primary
water to the domestic hot water heat exchanger.
2.3.4
Temperature control is transferred to the dome-
stic hot water thermostat (potentiometer) which
modulates the burner output between high and
low flame to maintain an average heat input to
suit the dhw output required.
2.3.5
An overrun is incorporated in the boiler in both
c/h & dhw modes. The fan overruns until the boi-
ler water cools to approximately 80°C (176°F).
This drawing is indicative only and does not accurately
represent pipe positioning.
2.4
Safety Devices
2.4.1
In both central heating and hot water modes safe
operating is ensured by:
a. Differential pressure unit in the primary circuit
which prevents burner operation if water flow
rates are too low.
b. An electronic device that checks the primary
pressure unit for activation. Failure results in
deactivation of the pump, after approximately
10 minutes of operation.
c. A safety thermostat, which interrupts the con-
trol circuit shutting off the gas valve. At the
same time the fan will still operate.
d. A Pressure differential switch in the flue
system to check the fan's operation before
allowing ignition.
e. A primary store safety thermostat with manual
reset, wich interrupts the mains electricity sup-
ply
2.4.2
A safety valve is provided to relieve excess pres-
sure from the primary circuit.
2..5
Frost Thermostat
The appliance has a built in frost protection cir-
cuit. Should the boiler temperature sensed at the
primary thermistor fall below 5°C, the boiler will
operate in central heating mode and continue to
operate until the primary thermistor reaches
approximately 40°C.
KEY:
A
Gas
B
Hot Water Outlet
C
Cold Water Inlet
D
Central Heating Flow
E
Central Heating Return
Fig. 2
flue outlet
air intake
2
4
39
7
11
9
16
A
B
C
D
E
21
26
37
38
22
24