Vaillant DHW Plate Heat Exchanger 178973 (20-Plate)

Genuine Vaillant secondary (DHW) plate heat exchanger for ecoTEC Plus combi boilers. This 20-plate unit transfers heat from the primary circuit to your domestic hot water for fast, stable hot water performance.

• Manufacturer: Vaillant
• Part type: Plate heat exchanger DHW (secondary)
• MPN: 178973
• GTIN / EAN: 4024074477540

Compatible boilers (examples)

Used on selected ecoTEC Plus models (model/year dependent). Common fits include:

• ecoTEC Plus 824, 831, 837
• VUW 246/3-5 & 316/3-5 (including R1 variants)

Always confirm against your boilers data plate/parts manual using MPN 178973 before ordering.

What this part does

The DHW plate heat exchanger keeps boiler (primary) water separate from tap water while efficiently transferring heat, ensuring reliable hot water at your outlets.

When to replace

• Fluctuating or lukewarm hot water
• Poor flow due to internal blockage/scaling
• Confirmed internal leak or cross-contamination

What’s in the box

• 1 Vaillant 20-plate DHW heat exchanger 178973 (OEM part)

Installation & safety

Must be installed by a qualified Gas Safe engineer. After fitting, flush/clean the system as required, renew seals, and check DHW temperatures and operation.