Replacing The Gas Valve; Combi Boilers: Checking The Plate Heat Exchanger; Replacing The Expansion Vessel; Replacing The Prv - Worcester Greenstar 4000 Installation And Maintenance Instructions Manual

Replacement parts
9.7

Replacing the gas valve

▶ Close the gas isolator.
▶ Unscrew the union nut [1].
▶ Remove the connector [2].
▶ Unscrew the union nut [3].
▶ Remove the union nut and hose connection [4] from gas valve.
▶ Remove the 2 screws [6].
▶ Remove the gas valve [5].
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Fig. 94 Removing the gas valve
▶ Install the gas valve in reverse order, and check the gas/air ratio.
9.8

Combi boilers: checking the plate heat exchanger

▶ Check the strainer in the cold water pipe for contamination
( Chapter 9.4, page 65).
▶ Descale the plate heat exchanger with scale removal agent approved
for stainless steel.
-or-
▶ Remove the plate heat exchanger [1] and replace.
▶ Remove the screw [2].
▶ Remove the plate heat exchanger [1].
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Fig. 95 Removing the plate heat exchanger
▶ Install the new plate heat exchanger in reverse order.
– Make sure that the lugs are fully inserted into the retaining points
on the right.
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9.9

Replacing the expansion vessel

▶ Disconnect the pipe union nut [3].
▶ Slacken the screws on the clamps, top [1] and bottom [2] of the
expansion vessel.
▶ Slide the expansion vessel [4] towards you to remove.
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Fig. 96
▶ Replace the expansion vessel in the reverse order
9.10

Replacing the PRV

▶ Unscrew the knurled nut of the PRV discharge pipe.
▶ Disconnect the PRV discharge pipe prior to removing the PRV.
▶ Remove the PRV in the sequence shown.
– Release the clip.
– Pull the PRV forward to release.
2.
Fig. 97 PRV removal
▶ Replace the PRV in the reverse order
Greenstar 4000 – 6 720 891 161 (2020/09)
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