Vaillant ecoTEC pro VUW 6/5-3 Series Installation And Maintenance Instructions Manual page 38

13.6.2 Replacing the fan or gas valve
1. Remove the air intake pipe.
2. Remove the plug from the gas valve (7).
3. Remove the plug from the fan motor (6) by pushing in
the latching lug.
4. Unscrew either the cap nut (2) on the gas valve or the
cap nut (8) between the gas pipes. Secure the gas pipe
against twisting.
5. Unscrew the three screws (2)-(4) between the mixture
pipe (1) and the fan flange.
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6. Remove the entire fan/gas valve unit from the product.
7. If you want to replace the gas valve, unscrew the cap
nut (2) if the gas pipe is still secured to the gas valve.
8. Unscrew both fixing screws (1) on the gas valve and
remove the fan from the gas valve.
9. Replace the defective fan or the defective gas valve.
10. Install the gas valve and the fan in the same position as
before. Use new seals.
11. Screw the fan to the gas valve.
12. If you had removed the gas pipe, screw the cap nut
of the gas pipe (2) only loosely to the gas valve. Only
tighten the cap nut on the gas valve after the installa-
tion work has been completed.
13. Refit the entire fan/gas valve unit in reverse order. You
must use a new seal (5) for this.
14. Ensure that the order in which the three screws are
screwed in between the fan and the mixture pipe cor-
responds to the numbering (3), (2) and (4).
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15. Tighten the cap nut (2) on the gas valve and the cap
nut (8) between the gas pipes. In the process, secure
the gas pipe against twisting. Use new seals.
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16. After you have completed this work, carry out a leak-
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tightness test (function check). (→ Page 31)
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17. If you have installed a new gas valve, adjust the gas
ratio setting. (→ Page 29)
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13.6.3 Replacing the heat exchanger
1. Drain the product. (→ Page 36)
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2. Remove the compact thermal module. (→ Page 34)
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3. Detach the condensate drain hose from the heat ex-
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changer.
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4. Remove the clamps (2) and (3) from the flow connec-
tion and the return connection.
5. Detach the flow connection.
6. Detach the return connection.
7. Remove two screws (1) on each of the two retainers.
8. Remove the lower three screws (2) on the rear section
of the retainer.
9. Swing the retainer to the side around the top screw (1).
10. Pull the heat exchanger downwards and to the right,
and remove it from the product.
11. Install the new heat exchanger in reverse order.
12. Replace the seals.
Installation and maintenance instructions ecoTEC pro 0020244995_04
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