Worcester WM 12 Installation And Servicing Instructions Download Page 24

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11.3 Reassembling the Appliance

From the outside of the property carefully insert the external

duct into the wall mounting duct with the oil connection block on
the bottom edge of the duct.

The wall thickness determines how far out of the outside wall

the external duct protrudes. Set the external duct position by
using table 6, fig. 4 and 23.

For a non-standard wall thickness which does not correspond

to table 6, fig. 4 and 23 proceed as follows:

Cabinet depth in the standard 315mm position

(a) Non-standard wall thickness within the range of 121 to
313mm the overall distance

(X),

as shown in fig. 25, from the end

of the wall mounting duct inside the property to the end of the
external duct outside the property should be set at 630mm.

(b) Non-standard wall thickness within the range of 314 to 460mm
ensure the external duct protrudes from the property by 45mm.

Cabinet depth in the optional 285mm position

(a) Non-standard wall thickness within the range of 151 to
343mm the overall distance

(X),

as shown in fig. 25, from the end

of the wall mounting duct inside the property to the end of the
external duct outside the property should be set at 630mm.

(b) Non-standard wall thickness within the range of 344 to 460mm
ensure the external duct protrudes from the property by 45mm.

Pack the external duct in the desired position to prevent move-

ment in assembly. Check the external duct is level or slightly
sloping downward towards the outside of the property using a
spirit level. In the event of an oil leak this will prevent oil entering
the property.

Place the wall trim 'U' section over the top of the external duct

as shown in fig. 3. Bend the tabs at the top of the 'U' section if
loose to ensure a tight fit. (See fig. 3.)

Insert the N

6 screws provided into the remaining section of

wall trim.

Place the bottom section screw side down in behind the 'U'

section, slide the screws into the slots and tighten the screws to
secure in place.

Mount the external cover onto the external duct ensuring that the

tabs fit over the lip of the external duct. Check that the cover fits cor-

rectly. Make any necessary adjustments to the external duct. Remove
the cover and wall trim being careful not to move the external duct.

NOTE: Ensure a minimum gap of 5mm (see fig.6) between the
external cover and wall trim to allow sufficient air to enter the
appliance for combustion .

To fasten the external duct to the wall mounting duct use the

locating holes in the back of the external duct to drill four 3mm
holes into the wall mounting duct (see fig. 25). Using the N

6 screws

provided, screw the external duct to the wall mounting duct. Check
that the external duct when fastened in place is level or sloping
downwards towards the outside of the property, using a spirit level.
In the event of an oil leak this will prevent oil entering the property.

NOTE: It is important the external duct is level or sloping
slightly downwards towards the outside of the property.

10.

Using the sealant provided, completely seal the joint on all

four sides between the wall mounting duct and the external duct
from the inside of the property (see fig. 25).

NOTE: It is imperative that the joint between the wall mount-
ing duct and the external duct is completely sealed to pre-
vent oil or combustion gases entering the wall cavity in the
event of a leakage.

11.

Slide the internal control box back into position, ensuring

the wall mounting duct earth lead is connected back into the
internal control box. Connect the earth lead to the earth spade
connector. The main harness is routed up the left hand side of
the internal control box in the gap between the control box and
the wall mounting duct (see fig. 2). Screw the internal control box
to the wall mounting duct using the two screws provided.

12.

Using the two screws provided fasten the facia to the internal

control box.

13.

Connect the earth lead to the service switch assembly and

using the two screws provided fasten the service switch to the
external control box on the external duct (see fig. 3).

There are two grommets on the main harness, slide the ‘D’
shaped grommets along the cable, fit one into the ‘U’ shaped slot
on the rear of the external control box and the other into the ‘U’
shaped slot on the wall mounting duct. It is imperative that the
‘D’ shaped grommet is pushed fully in position on the wall
mounting duct as failure to do so might cause damage to the
main harness when the heat exchanger is mounted on the appli-
ance. Ensure that the main harness does not sag by pulling gen-
tly on the cable when in position to take up the slack (see fig. 25).

14.

Take up any slack on the main harness inside the wall

mounting/external duct by gently pulling the main harness at
position shown in fig. 25.

WARNING: It is imperative the main harness inside the wall
mounting/external duct is not sagging. This will prevent the
main harness being trapped behind the insulation box.

15.

Put cloth or cardboard on the inside on the external and wall

mounting duct to protect the surface while installing the heat exchanger.

16.

Check the wall mounting duct seal as shown in fig. 25. It is

important that this seal is in good condition, replace if damaged.

17.

Pick up the heat exchanger and place inside the duct.

18.

Lift from the bottom so that the flow and return tapings clear

the top of the duct. Push onto the two studs at the top of the
wall-mounting duct so they protrude through the two holes in
the heat exchanger. Screw a M6 nut and washer onto each of
the top two studs, do not tighten.

19.

Push the bottom of the heat exchanger onto the two bottom

studs and screw the remaining two M6 nuts and washers onto
the bottom studs. Tighten the four nuts to secure the heat
exchanger to the wall mounting duct.

20.

Replace the thermostat phials in their original positions tak-

ing care not to kink the capillaries. They must be positioned so
the application or removal of the cabinet won't damage the capillaries.

21.

Position the boiler drain tube which is connected to the drain

valve down the back of the internal control box.

Distance External Duct Protrudes

Table 6. With the external cover removed the minimum
distance the external duct protrudes from the external
wall for standard wall thickness.

Wall Thickness

(mm)
102*

229
296
460

(inches)