Vaillant DN65 connecting pipe for PHE C up to 360 kW

Vaillant DN65 connecting pipe for PHE C up to 360 kW

Vaillant plate heat exchangers from the PHE S and PHE C series are among the key components of large professional boiler rooms, cascade connections of condensing boilers, and industrial heating hubs. Their role is to hydraulically and thermally separate the primary circuit (heat source – boiler, boiler cascade, heat pump) from the secondary circuit (distribution system, underfloor heating, radiator circuits, domestic hot water heating), with heat transferred between the circuits exclusively through a set of stainless steel plates – without any direct mixing of media. This principle is used in practice wherever it is necessary to prevent mutual hydraulic interference between the circulation pumps of individual circuits, to equalize different flow rates, or to separate circuits with different quality, pressure, or composition of the heat transfer medium (e.g. glycol mixtures in a solar or heat pump circuit from standard heating water in distribution).

The DN65 connecting pipe is an original Vaillant flanged component designed to connect plate heat exchangers of the PHE C series up to 360 kW (PHE C 240-40 and PHE C 360-70) to the boiler room's piping system. It is a pre-shaped fitting with a main flanged connection and several side ports, which allow direct installation of additional fittings – an air vent valve, a drain valve, a temperature sensor, or a pressure gauge – directly at the point of connection to the exchanger, without the need for additional T-pieces or branches in the main distribution system.

Technical data

Overview of the entire Vaillant PHE series (official manufacturer's technical data)

Plate material: stainless steel. Operating temperature (plate material range): -196 °C to +200 °C. The PHE S model has a screw (threaded) connection of 1 1/4", the PHE C models have a flanged connection. Source: Vaillant installation manual "Externer Plattenwärmetauscher PHE S, PHE C", document 0020196730_00.

Design and function of the side ports

In addition to the main flanged connection to the exchanger and to the main distribution system, the DN65 connecting pipe also includes several smaller-diameter side ports. These are used in practice for installing an air vent valve (needed when filling and venting the system according to the commissioning procedure), a drain valve (needed for servicing/draining the exchanger), and possibly temperature or pressure sensors for control and monitoring of the boiler room's operation. Because these ports are integrated directly into the connecting pipe, there is no need to additionally cut or drill into the main piping distribution at the point where the exchanger is connected.

Installation

Installation principles (according to the official Vaillant installation manual 0020196730_00)

• Installation only in areas without risk of freezing.
• Ensure sufficient space for operation, servicing, venting, and draining of the exchanger.
• Connections are always routed to the side, never from below the exchanger.
• To minimize pressure losses, a vertical mounting position is recommended.
• The PHE C model must always be additionally anchored to a floor bracket with height-adjustable feet (10 – 55 mm) – it must never be left hanging only on the pipe connections.
• The flow of the primary and secondary sides is routed in counter-flow – this ensures the highest heat transfer efficiency.
• Maximum permissible forces and moments at the connections: tensile force T, transverse force F, bending moment Mb and torsional moment Mv – see the table below to prevent mechanical damage to the connections during pipe installation.

Why choose a prefabricated connecting component instead of assembling from fittings

An alternative to using the original DN65 connecting pipe would be to assemble an equivalent unit from individual fittings (elbow, T-pieces, reducers, flange adapters) from various manufacturers directly on site. Such a procedure is not only more time-consuming, but also carries a higher risk of leaks at each individual joint in the assembly and usually requires more space than a compact, single-piece cast or welded original component. The prefabricated Vaillant component, on the other hand, comes as a single compact unit with pre-verified geometry and dimensions of the side ports, significantly shortening installation time and reducing the number of potential leak points in the entire assembly.

Comparison of DN65 and DN100 variants

Typical usage scenario

A typical application is a boiler room with a cascade reaching up to 360 kW – for example, an apartment building, office building, or school with the PHE C 240-40 or PHE C 360-70 model. In such a setup, the DN65 connecting pipe serves as a transition and branching component between the exchanger flange and the main distribution system, while the side ports allow for the installation of additional fittings without the need for further intervention into the main pipe.

Commissioning

1. While filling the system with heating water, the exchanger is continuously vented via the air vent valves of the flow and return.
2. To avoid water hammer caused by trapped air, the pumps are first started against closed flow and return shut-off valves.
3. The flow and return shut-off valves are opened simultaneously and slowly until the operating temperature is reached.
4. The primary circuit is always commissioned first.
5. After start-up, it is verified that no pressure surges act on the exchanger – if necessary, calming (dead) sections are added to the piping and the shut-off valves are closed.

Service, cleaning and care

If signs of limescale buildup or contamination appear (typical with hard or contaminated water), the exchanger is cleaned as follows: the system is taken out of operation, the exchanger is drained and removed. Only agents suitable for stainless steel and copper are used for cleaning – unsuitable cleaning agents may permanently damage the exchanger. Flushing with the cleaning solution is carried out against the normal flow direction, after which the exchanger is flushed with clean water, reinstalled, and it is recommended to check the water hardness before restarting. In the case of high water hardness, treatment of the heating water is recommended according to the documentation of the other system components – atria.sk offers, in the category chemical and physical water treatment, corrosion inhibitors and cleaning products from the SENTINEL and ULTIMA ranges for this purpose, which extend the lifespan of the exchanger and the entire boiler room.

In case of temporary shutdown (repair, service, longer outage), it is recommended to completely drain and clean the exchanger to prevent damage from frost, aggressive media, or biological fouling. When permanently decommissioning, the primary circuit is closed first, then the secondary circuit, followed by draining and disassembly.

Compatibility and related accessories

The DN65 connecting pipe is designed for the PHE C 240-40 and PHE C 360-70 models. For complete insulation of the entire connecting assembly (not only the exchanger body itself, but also the adjacent piping), we recommend adding the original insulation for the connecting pipe (code 0020248930) and thermal insulation for the respective exchanger model (codes 0020248923 to 0020248927, depending on the specific model) – all available separately in this category on atria.sk.

Why choose an original Vaillant connecting pipe

• Precise dimensional and flange design corresponding to specific models of the PHE C series.
• Integrated side ports for additional fittings without the need for further interventions in the distribution system.
• Simplified and faster installation compared to piecemeal assembly from universal fittings.
• Preservation of warranty conditions for the entire assembly when using original accessories.

Summary

The DN65 connecting pipe is a practical solution for installers and designers who want to connect a plate heat exchanger PHE C 240-40 and PHE C 360-70 to the boiler room's main distribution system quickly, reliably, and with a minimal number of additional joints. Combined with thermal insulation of both the exchanger and the pipe itself, it creates a complete, safe, and energy-efficient assembly in line with the manufacturer's recommendations for professional installations.

Ordering and design preparation

When designing a boiler room with a PHE C series exchanger, we recommend including the DN65 connecting pipe in the project documentation right at the design stage, not only later during implementation – this allows for more precise planning of space requirements in the plant room (including maneuvering space for operating the side fittings) and avoids improvised solutions on site. The component is ordered separately according to the exact type designation of the exchanger to which it is to be connected to the pipe – if there is uncertainty in choosing the correct variant (DN65 vs. DN100), we recommend checking the output of the planned boiler cascade against the threshold value of 360 kW mentioned above, or contacting the technical support of the supplier WINTNER s.r.o. or directly the atria.sk customer support, which can advise on choosing the correct variant based on the specific project and the type designation of the planned exchanger.

Frequently asked questions