Installation Instructions

Safety and Installation Requirements

Please ensure that these instructions are read and understood before starting any service work. Failure to comply with these instructions may cause product/property damage, severe personal injury and/or loss of life.

Working on the equipment

The installation, adjustment, service and maintenance of this product must be performed by a licensed professional heating contractor who is qualified and experienced in the installation, service, and maintenance of hot water boilers. There are no user serviceable parts on the boiler, burner or control.

• Ensure that main power to the equipment being serviced is off.
• Ensure that the main fuel supply valve to the boiler is closed.
• Take precautions to avoid accidental activation of power or fuel during service work.
• Do not perform service work on any component part without ensuring safe operation of the heating system.
• When replacing parts, use original Viessmann or Viessmann approved replacement parts.
• Refer to the Installation and Service Instructions applicable to this boiler.

Removing the Front Panel

Diagram showing the front panel of the boiler detached, with an inset view highlighting two screws labeled '2x' at the bottom, indicating they should be loosened but not fully removed.

• Loosen retaining screws (do not remove completely).
• Remove front panel.

Replacing the DHW Hydraulic Assembly

Image of the DHW hydraulic assembly unit.

• Protect the control from water damage.
• Disconnect piping, gas line, DHW supply/return and the heating supply/return.
• Disconnect wiring – flow sensor, temperature sensor, DHW sensor, pump connector (10 mm clip), pressure sensor, fan sensor, and the diverting valve.

Image showing a pipe being disconnected using a wrench, with text 'NATURAL GAS' visible on a label.

• Disconnect the gas line.
• Disconnect the return pipe mid connection (18 mm clip) at the bottom.

Image showing various wires and pipes connected to the boiler, with a hand disconnecting them.

• Disconnect the supply pipe (bottom and top).

Replacing the DHW Hydraulic Assembly (continued)

Image showing a hand holding a Torx T15 screwdriver, removing screws from the bottom of the heat exchanger assembly.

• Remove five screws from the bottom of the heat exchanger assembly (torx T15).
• Remove the DHW hydraulic assembly.

Image showing the DHW hydraulic assembly being carefully removed from the boiler.

Image showing a water hammer tube being detached using a clip, to give access to the plate heat exchanger screw.

• Remove the water hammer tube (10 mm clip) to give access to the plate heat exchanger screw.

Replacing the DHW Hydraulic Assembly (continued)

Close-up image of the flow limiter component, showing a brown orifice. A spare orifice is provided.

• Flow limiter is preinstalled with a 14 L/min orifice (brown). Spare orifice is provided.

Image showing a circulation pump being disconnected from the assembly using a screwdriver.

• Disconnect the old circulation pump and install onto the new assembly.

Replacing the DHW Hydraulic Assembly (continued)

Image showing the plate heat exchanger being disconnected, with a wrench attached to a fitting.

• Disconnect the old plate heat exchanger.
• Remove the plate heat exchanger protective cover (blank plate) (two screws).

Image showing the plate heat exchanger being installed into the assembly.

• Install the plate heat exchanger.
• Reinstall the DHW Hydraulic Assembly in reverse order onto the boiler using new gaskets and O-rings provided.

Reinstalling the Front Panel

Diagram illustrating the front panel being reattached to the boiler, with an inset showing screws being tightened at the bottom.

• Install the front panel.
• Tighten the screws at the bottom of the boiler.