Vaillant – Demirdöküm Milenyum Combi Boiler Water Flow Turbine (with Sensor Board) – 178988 Compatible

The Vaillant – Demirdöküm Milenyum water flow turbine is the part that senses the flow of water in the boiler's hot water circuit when a tap is opened. As water passes through, the turbine in the body spins; the sensor board on it converts this rotation into a signal and sends it to the boiler PCB, which switches to hot water mode and fires the burner. The Vaillant spare part code is 178988; it is also used in Demirdöküm Milenyum and Protherm combi boilers.

Fault Symptoms

• The boiler does not switch to hot water when the tap is opened, or fires late.
• Hot water comes intermittently; the boiler goes out at low flow rates.

The common cause of these symptoms is the turbine seizing due to limescale or sediment accumulated in the body, or failure of the sensor board.

Compatibility

• Vaillant — spare part code 178988. According to customer reviews it has been used in the Vaillant turboTEC pro boiler.
• Demirdöküm Milenyum and Protherm combi boilers.
• It is the equivalent of the part with codes Saunier Duval S5720200 / 57202 and Glow-worm 2000801910 / 801910.

Before ordering, compare the connection ends, clip seat and sensor connector with the removed part.

Package Contents

• Turbine body with sensor board
• 3 O-rings
• Wire retaining clip

Points to Note When Replacing

• Switch off the power and the cold water inlet to the boiler; open a hot water tap to relieve the pressure in the line.
• Pull the wire clip to remove the old turbine. Use the new O-rings in the package when fitting the new one.
• The connector type of the sensor board may differ according to the boiler model. If the connector does not fit, the old sensor board can be transferred to the new turbine body; one of our customers solved the problem this way.
• In hard-water areas, the use of a filter or scale inhibitor at the boiler inlet is recommended so that the turbine does not clog again.

Technical Specifications

• Product type: Combi boiler hot water flow turbine (with sensor board)
• Body: Black plastic, clip-on push-fit connection
• Sensor: Sensor board with connector on the body
• Compatible OEM code: Vaillant 178988
• Package: Turbine + 3 O-rings + wire clip

Frequently Asked Questions

Is the turbine sensor board included?

Yes. The sensor board comes fitted to the turbine body.

Which boilers does it fit?

It is used in Vaillant (178988), Demirdöküm Milenyum and Protherm combi boilers; in Saunier Duval and Glow-worm it is the equivalent of the part with codes S5720200 / 2000801910. Order after comparing with the removed part.

Should the O-rings be replaced?

Yes. To avoid leaks, the new O-rings in the package should be used instead of the old ones.