Viessmann 230V Cylinder Demand Terminal Box | 7574319

Description

The Viessmann 230V Cylinder Demand Terminal Box is a wall-mounted signal converter that allows a Viessmann boiler to work correctly with a third-party hot water cylinder wired on a conventional S-plan or Y-plan system.

It transfers the 230V AC switching signal from a standard cylinder thermostat into the low voltage signal that Viessmann boiler controls expect, bridging the gap between older-style wiring centres and modern Vitodens control electronics.

230V AC

Input signal

Low voltage

Output signal

4-pipe

System configuration

S/Y-plan

Compatible with

Wall mounted

Fitting type

PlusBus

Hard-wire option

🛈

Please Note: This terminal box is intended for use when a four pipe configuration is required alongside a third-party (non-Viessmann) DHW cylinder. For the newer PlusBus Vitodens 200-W, the boiler connection plug can be snipped off and the cable hard-wired directly into terminals 3 and 4 on the cylinder sensor connection block.

Converts conventional cylinder signals

Takes the standard 230V AC signal from a conventional cylinder thermostat (S-plan or Y-plan) and translates it for the boiler control.

Bridges third-party cylinders

Purpose-built for installations using a non-Viessmann DHW cylinder alongside a Viessmann boiler on a 4-pipe system.

Simple wall-mounted fitting

Installs as a standalone wall-mounted enclosure, keeping the conversion electronics separate from the main wiring centre.

Complete with fittings

Supplied complete with fixings and installation instructions for straightforward first-fix wiring.

PlusBus hard-wire compatible

On PlusBus-equipped Vitodens 200-W boilers, the factory connection plug can be removed and the cable hard-wired directly into the cylinder sensor block.

Keeps hot water demand accurate

Ensures the boiler receives a properly formatted demand signal, avoiding miscommunication between old and new control standards.

Specification

Function

Input

230V AC from conventional cylinder thermostat (S-plan/Y-plan)

Output

Low voltage signal for Viessmann boiler control

Application

Four pipe configuration with third-party cylinder

Mounting

Wall mounted enclosure

Compatibility

Boiler range

Viessmann Vitodens boilers requiring a 4-pipe DHW signal conversion

PlusBus (Vitodens 200-W)

Boiler connector plug can be removed for direct hard-wiring to terminals 3 & 4

When would I need this terminal box?

It's needed when a Viessmann boiler is being installed on a 4-pipe system with a third-party (non-Viessmann) hot water cylinder that uses a conventional 230V cylinder thermostat, rather than a Viessmann cylinder sensor.

Can this be used with an S-plan or Y-plan system?

Yes — its specific purpose is to convert the conventional 230V AC demand signal from an S-plan or Y-plan cylinder thermostat into the low voltage signal the Viessmann boiler control expects.

Does this work with the PlusBus Vitodens 200-W?

Yes, though the wiring approach differs slightly: on PlusBus boilers, the boiler connection plug is snipped off and the cable is hard-wired directly into terminals 3 and 4 on the cylinder sensor connection block.

Does the box come with mounting fixings?

Yes, it's supplied complete with fittings and installation instructions.

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