Worcester Highflow 400 RSF Installation And Servicing Instructions page 41

screws are correctly engaged. Replace the "O" ring seals and refit
the pressure pipe. Ensure the securing clips are fully engaged in
the locating holes.
Reconnect the electric cable to the control board and replace the
strain relief bush. Replace the circulating pump as described in
Section 15.3-20.
Open the valves, fill and repressurise the system as described in
Section 12.2. Reassemble the appliance in the reverse order.
22. Water to Water Heat Exchanger. See Figs. 16, 41, 45, 46, 47,
48, 49, 51 and 52.
Check that the electricity supply to the appliance is turned off.
Remove the cabinet front panel, place the facia and control box
in the Service Position and lower the expansion vessel into the
Service Position, as described in Section 14.2 a, b and c.
Drain the heating circuit as described in Section 15.2 a.
Drain the hot water circuit as described in Section 15.2 b.
WARNING: The weight of the water to water heat exchanger is
2 kg. approx. A quantity of water will remain in the heat
exchanger and pipework. Follow the procedure as described in
15.2.
Remove the circulating pump as described in Section 15.3-20.
Remove the water diverter valve as described in Section 15.3-21.
NOTE: i). It is not necessary to disconnect the electrical cable
from these components. The length of cable is sufficient to allow
them to rest on top of the appliance cabinet. Do not allow them
to be suspended by the cable. Secure the pump head and
diverter valve.
NOTE: ii). Unless otherwise stated all water joints are sealed
with "O" rings. To disconnect twist the pipe and / or ease the
joint apart. When re-connecting the joint a new "O" ring must be
fitted. Silicone grease must be applied to the "O" ring.
Remove the pressure relief valve and manual air vent assembly
as described in Section 15.3-27 and retain. See Fig. 51.
Unscrew locating screw No.1 in the bottom manifold two full
turns. See Fig. 47.
Unscrew the flat faced union fitting below the flow switch.
Remove the sealing washer and discard. See Fig. 52. Move the
cold water inlet pipe to the left to clear the flow switch. Ease the
pipe upwards, 10 mm approx. and remove from the bottom
manifold. Retain the pipe.
Unscrew the union fitting below the cold water inlet valve and
remove the flow switch and water filter assembly. See Fig. 52.
Place the flow switch and water filter assembly on top of the
appliance cabinet and secure.
Unscrew locating screw No. 2 in the top manifold two full turns.
See Fig. 47. Ease the heating return pipe downwards 10 mm
approx. into the slip joint in the bottom manifold.
Move the pipe to the left to clear the top manifold. Ease the pipe
upwards 10 mm approx. and remove the pipe from the bottom
manifold. Retain the pipe.
Remove the heating control thermostat phial as described in
Section 15.3-14. See Fig. 41. Place the phial to one side.
If the appliance is fitted to an open vent system unscrew the
open vent union connection and remove the washer. See Fig. 45.
Remove the flat clip securing the pump inlet pipe to the pump
lower support plate. Retain the clip. See Fig. 45.
Remove the two screws Nos. 3 and 4 securing the pump inlet
pipe support plate and remove the plate. See Fig45.
Unscrew two full turns locating screw No. 5. See Fig. 47. Ease the
pump inlet pipe upwards 10 mm approx. and remove from the
bottom manifold. Retain the pipe, plate and screws.
To access the water to water heat exchanger the top manifold
must first be removed:
Unscrew locating screw Nos. 6, 7 and 8 in the top manifold two
full turns. Unscrew and remove screws Nos. 9 and 10 securing
the manifold to the water to water heat exchanger support
bracket. Retain the screws. See Fig. 47.
Unscrew the flat faced union securing the manifold to the inner
casing pipework. See Fig. 47.
Remove the sealing washer and discard. See Fig. 47.
Ease the manifold assembly downwards, 10 mm approx., until
clear of the heating flow and return pipes and hot water outlet
pipe. See Fig. 47.
Remove the top manifold clear of the appliance and retain.
Unscrew locating screws Nos.11 and 12 two full turns. Unscrew
and remove screws Nos.13 and 14 securing the bottom manifold
to the water to water heat exchanger support bracket. See Figs.
47 and 48. Retain the screws. Unscrew the bracket supporting
the domestic drain from the left hand side of the gas valve. Using
long nose pliers remove the clip securing the drain pipe to the
bottom manifold. Ease the drain pipe downwards out of the
manifold and remove. See Fig. 48.
Retain the clip, screw, bracket and drain pipe.
Ease the bottom manifold and water to water heat exchanger
upwards 10 mm approx. until clear of the heat bank flow and
return pipes. See Fig. 48.
NOTE: It may be necessary to push down on the flow and return
pipes to release the "O" ring fittings. Before entering the heat
bank the flow and return pipes are fitted into slip joints. The
joints are sealed with "O" rings and allow some movement
forwards or backwards when removing the bottom manifold and
water to water heat exchanger. See Fig.48.
Ease the water to water heat exchanger and bottom manifold
from the support bracket and clear of the appliance.
Release screw No.15 and remove the bottom manifold off the
locations on the water to water heat exchanger. See Figs. 47 and
48. Discard the heat exchanger. Retain the fixing screw.
Remove the two "O" ring seals from the rear of each manifold
and discard.
IMPORTANT: Two new "O" ring seals must be fitted to the rear
of each manifold. See Fig. 49.
If the flow and return pipes to the heat bank have been disturbed
when removing the water to water heat exchanger the "O" ring
seals must be replaced :
Ease the heat bank flow pipe out of the front slip joint and return
pipe out of the rear slip joint and clear of the push in elbows. See
Fig. 48.
Remove and discard the "O" ring seals from each pipe. Replace
with new "O" ring seals.
Pull out the flat clip from the front push in elbow and remove the
elbow. Retain the clip and push in elbow. See Fig. 48.
To release the rear elbow reach under the water to water heat
exchanger bracket and push in fully the flat plate clamp
mechanism. Remove the rear push in elbow and retain. See
Fig.48.
Remove and discard the elbow "O" ring seals. Replace with new
"O" ring seals.
Re-assemble the rear and front push in elbows. Ensure the rear
clamp mechanism is engaged and fully pulled into the location.
Engage the front flat clip into the slot correctly.
Re-assemble the flow and return pipes into the slip joints. The
pipe lengths are not identical, the longest pipe is the rear/return
pipe. See Fig. 48.
Re-assemble the bottom manifold to the replacement water to
water heat exchanger. Ensure the heat exchanger is located
correctly with the internally threaded boss fitting through the
fixing hole in the manifold and the raised section on the manifold
port fitting into the bottom right hand port on the heat
exchanger. See Fig. 49. Replace screw No. 15 and tighten.
Fit the replacement water to water heat exchanger and bottom
manifold assembly into the support bracket. Ensure the heat
bank flow and return connections are fully engaged. Secure the
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