The Heatmiser UH4 is a versatile wiring center designed for controlling heating systems, specifically tailored for use with Heatmiser 230V thermostats. Its primary function is to manage up to four heating zones and a hot water zone, making it suitable for both underfloor heating and radiator systems.

Function Description

The UH4 acts as a central hub for your heating system, receiving signals from thermostats and activating the appropriate components such as actuators, valves, boilers, and pumps. It is designed to control any actuator or valve that requires a 230V AC signal to open. For mid-position valves or those needing a closing signal, a changeover relay is required, which the UH4 can accommodate.

One of its key features is the ability to operate a boiler or other heat source through a volt-free output. This ensures compatibility with a wide range of heating systems. Additionally, the UH4 includes a dedicated pump/valve output, which is standard for underfloor heating systems and typically operates a manifold pump or manifold valve.

The hot water (H/W) output provides a 230V enable signal to the hot water valve, with auxiliary wires connected to the Gr & Or terminals. This allows for integrated control of your domestic hot water supply.

A unique aspect of the UH4 is its flexibility regarding Zone 4. This zone can be configured as either an isolated radiator zone or an underfloor heating zone via a Yes/No switch.

If the switch is set to "NO," Zone 4 will activate a radiator zone valve and the boiler when it calls for heat, but it will not enable the underfloor heating pump/valve output. This is ideal for systems with mixed heating types.
If the switch is set to "YES," Zone 4 will function as an underfloor heating zone, activating the actuator, boiler, and pump/valve outputs. This provides adaptability for different room requirements.

Any output not required by your specific system can simply be ignored, offering a streamlined setup.

Usage Features

The UH4 is designed for straightforward installation and integration into your heating system. It can be mounted directly to a wall using four screws or, alternatively, can be DIN rail mounted for a more organized installation within an electrical enclosure. For DIN rail mounting, two clips are provided on the back of the unit. These clips are positioned in the middle and slide down, with points A and B locating into corresponding holes to lock the unit in place. The UH4 is then located onto the DIN rail from the top, the clip is pulled down, and the bottom of the UH4 is pushed onto the DIN rail. Releasing the clip locks the unit securely. To remove the UH4, both clips are pulled down, and the unit is removed from the DIN rail.

The wiring connections are clearly marked for ease of installation.

Mains Supply: The power supply to the UH4 should be fused at 5 amps. Connections are marked L (live/phase 230V AC 50/60Hz), N (neutral), and E (earth).
Heat Enable: This is the main call for heat for the system, with three connections: LS (live supply), E (earth), and LR (live return). This is a volt-free switch, meaning whatever supply is placed on the LS connection is fed to the LR connection when there is a call for heat.
H/W (Hot Water): This output controls a hot water valve via a cylinder thermostat. Connections are L (live), E (earth), N (neutral), Gr (grey), and Or (orange). The auxiliary wires of the hot water valve (typically grey and orange) are wired to the Gr and Or terminals.
Zones 1-4: Each zone output is clearly marked with L (live out to actuator or valve) and N (neutral to actuator or valve). All L terminals are internally connected, as are all N terminals. Each zone output corresponds to the thermostat wired in at the top of the PCB.
Manifold Pump/Valve: This output is used for an underfloor heating manifold pump and/or valve. Connections are L (live), E (earth), and N (neutral). When an underfloor heating zone calls for heat, the live and neutral output will supply 230V to the manifold pump/valve. It is recommended that this output be fed through a high limit switch placed on the heating manifold to protect against mechanical failure of the manifold's temperature control.

The manual provides detailed wiring diagrams for various configurations, including:

UH4 to neoStat for 3 underfloor heating zones, 1 radiator zone, and hot water (with manifold valve & pump connections). This diagram illustrates connections for live, switch live, neutral, earth, end switch, and boiler enable, showing how the main supply, boiler enable, heat enable, manifold pump/valve, UFH valve, and UFH pump are integrated. It also details connections for neoStat thermostats for each zone, hot water valve, and hot water stat, including the crucial "Zone 4 Manifold Pump Control Switch" to select between underfloor heating and other systems.
UH4 to Heatmiser 230V Thermostat Wiring, showing connections for UFH zones with DS1 and Slimline thermostats. This diagram further clarifies how different thermostat models integrate with the UH4 for underfloor heating control.
UH4 with Touch, neoStat, and SmartStat thermostats for UFH, heating, and hot water applications. This comprehensive diagram demonstrates the versatility of the UH4 with various Heatmiser thermostat models, detailing connections for each zone, hot water valve, and boiler. It also highlights the importance of connecting the hot-water valve live feed through the cylinder high limit thermostat for safety.

Maintenance Features

The UH4 is designed for reliable operation with minimal maintenance.

Fuses: The unit includes a 5-amp, 20mm anti-surge fuse (Fuse 1). This fuse protects all 230V outputs from the board, specifically safeguarding the zone and pump/valve outputs. In case of an electrical fault or overload, this fuse will blow, protecting the internal components and connected devices. Replacing a blown fuse is a straightforward maintenance task.
Installation Guidelines: The manual emphasizes that the equipment should be installed by an appropriately qualified/registered electrician. This ensures correct wiring and adherence to safety standards, which is crucial for the long-term reliability and safe operation of the device.
Warranty: The warranty does not cover damage resulting from improper wiring or installation, reinforcing the importance of professional installation.
Troubleshooting: While not explicitly detailed as a maintenance feature, the clear labeling of connections and detailed wiring diagrams aid in troubleshooting any issues that may arise, allowing electricians to quickly identify and resolve problems.

Overall, the Heatmiser UH4 is a robust and adaptable wiring center, providing comprehensive control for modern heating systems with a focus on ease of installation and reliable performance.

Heatmiser UH4 - Support and Resources; Compatible Thermostats

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