Component Replacement - Heat Line Vizo 24 Installation, Servicing & User Instructions

18. Component Replacement

CAUTION!
While there are no substances harmful to
health contained within this appliance, some
component parts of the boiler (insulation pads,
gaskets and rope seals) are manufactured from
man made fibres. When damaged or broken
these fibres may cause a temporary irritation.
High dust levels may irritate eyes and upper
respiratory system. It is important therefore,
that sensible precautions are applied when
exchanging components.
18.1 Ensure that both the electrical and gas supplies
to the boiler are isolated before replacing any
component part.
18.2 To prevent the need to drain the entire heating
system when replacing the boiler's integral pump,
expansion vessel, safety relief valve and pressure
sensor, the boiler's hydraulic circuit may be isolated
from the central heating circuit by closing the boilers
isolation valves. Opening the discharge valve will
then drain the boiler's hydraulic circuit. Note clean
the valve seat to ensure it seals before re-filling the
25
boiler.
18.3 For replacement of the following components
it will be necessary to remove the boiler casing
panels as described in Section 17.
18.4 Domestic hot water sensor
The domestic

water sensor
located on the left
side of the hydraulic
block's hot
side. (figure 27)
Isolate the cold mains inlet, located at the cold

water inlet shown in figure 2b on page 8 and open
the hot water faucets to drain the system.
Carefully disconnect the

leads from the sensor.
Remove the sensor using

a 13mm spanner.
Fit the replacement sensor ensuring the washer is

correctly fitted, close the water faucets and open
the mains water inlet to the boiler.
Re-fit the leads to the replacement sensor

18.5 Central heating sensor
hot
is
water
Figure 27
Disconnect the leads from the sensor.

Fit replacement sensor.

Fit the leads and replacement the sensor

18.6 Fan Unit
Disconnect the electrical leads from the fan.

To remove the fan, disconnect the 90º bend from

the top of the boiler
Disconnect the electrical leads and air pressure

switch connection tube from the fan, remove the
fan screws and withdraw fan from fan hood with
its 56º bend. (Figure 24)
Fit the replacement fan unit in reverse order and

reconnect the electrical leads and sensing tube.
WARNING! Ensure that the earth lead is re-
connected.
18.7 Air pressure switch
The air pressure switch is located on the top of

the expansion vessel. (figure 29)
Remove the sensing

connections from the air pressure switch, noting
which tube is connected to which port.
Remove the air pressure switch by pulling

forward off its bracket.
Fit the replacement switch in reverse order of

removal.
vizo 24/28
The c/heating sensor is

located on left side of
the combustion
chamber on the outlet of
the primary heat
exchanger. (Figure 28)
Unclip the sensor from

the pipe.
tube and electrical