VOKERA Linea Service Manual download pdf (Page 30)

Linea

If the temperature continues to rise and exceeds

the set-point by 6

C, the burner will shut down

and the boiler will perform a three-minute anti-

cycle (timer delay).

A new ignition sequence will be enabled when

the 3-minute anti-cycle has been performed and

the temperature at the primary thermistor has

dropped 6

C below the set-point.

NOTES

The timer delay can be de-activated by the inser-

tion of a ‘jumper’ on the PCB or by isolating the

appliance from the electrical supply for 30 sec-

onds.

Any DHW request will always have priority over

the heating request.

When the request for heating has been satisfied,

the appliance pump and fan may continue to cir-

culate to dissipate any residual heat within the

appliance.

7.2.6 DHW MODE

With the selector switch in the Heating & HW

position, or HW only position, and a DHW outlet

is opened, the appliance will operate in the HW

mode. The valve actuator will motor to the HW

position (if a heating request was active) and the

pump and fan will be active. The operation of the

fan causes the analogue pressure switch (PAD)

to deliver a signal voltage to the control PCB. If

the signal voltage is sufficient a slow ignition se-

quence is enabled, whereby the current supplied

to the gas valve modulating coil is progressively

increased from minimum to maximum over a pe-

riod of 8-seconds. During this period the ignition

electrode sparks continuously even if the burner

has ignited.

NOTE

If the spark/sensing electrode does not sense

ignition the appliance will then go to lockout.

Ignition is sensed by the electronic circuitry to

ensure flame stability at the burner. Once suc-

cessful ignition has been achieved, the electronic

circuitry modulates the appliance output in order

to achieve the DHW set-point (the position of the

DHW temperature selector) as measured at the

secondary thermistor.

When the set-point has been reached, the appli-

ance will begin the modulation phase whereby

the fan and gas valve will continuously modulate

to maintain the set-point.

If the temperature continues to rise and exceeds

the set-point by 5

C, the burner will shut down

until the temperature drops to set-point + 4

whereby a new ignition sequence will be enabled.

When the request for heating has been satisfied,

the appliance fan may continue to operate to dis-

sipate any residual heat from within the appliance.

7.3 CHECKING AND ADJUSTING BURNER PRES-

SURE (see fig. 19)

Although the burner pressure is factory set, it is

necessary to check it during servicing or if the

gas valve has been removed.

Isolate the appliance from the electrical supply

and attach a suitable manometer to the gas valve

outlet test nipple.

7.3.1 SETTING THE MAXIMUM BURNER PRES-

SURE fig. 41

Light the boiler as described in 5.7 and compare

the reading on the manometer with the value de-

scribed in 2.3. If adjustment is required, remove

the protective cap from the gas valve modulating

coil assembly and turn the outer (10mm) nut

clockwise to increase, or counter-clockwise to de-

crease the burner pressure.

Fig. 41

NOTE

Always check and/or adjust the minimum and

maximum gas pressures whilst the appliance is

in the HW only mode. Ensure a DHW outlet (pref-

erably the bath) is fully open, and that the HW

temperature selector is at maximum

7.3.2 SETTING THE MIMIMUM BURNER PRES-

SURE fig. 42

Once the maximum burner pressure has been

checked and/or adjusted, remove one of the grey

wires from the modulating coil. Compare the read-

ing on the manometer with the value described

in 2.3. If adjustment is required, turn the inner

(red) crosshead screw clockwise to increase, or

counter-clockwise to decrease the burner pres-

sure, whilst ensuring that the outer (10mm) nut

does not move. When checking and/or adjust-

ment has been completed, isolate the appliance

from the electrical supply, replace the protective

cap, refit the grey wire to the modulating coil, re-

move the manometer, and tighten the outlet test

nipple.

IMPORTANT, A GAS SOUNDNESS CHECK

MUST BE CARRIED OUT.

Fig. 42

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VOKERA Linea Service Manual Page 30

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