Polypipe Zonal Regulation Unit 2/3 Circuit ZRU Complete with Manifold

The Polypipe Zonal Regulation Unit (ZRU) is a complete, self-contained underfloor heating control unit that allows a single room or extension of up to 30 m² to be connected to an existing wet central heating system — with no costly hydraulic alterations, no new wiring centres, and no changes to the existing boiler or radiator circuits. It bridges the temperature gap between a radiator system (typically 70–80°C flow) and the lower temperatures required for underfloor heating (30–55°C) using a built-in thermostatic blending valve. A dedicated pump within the unit provides the correct flow rate for the UFH loops independently of the existing system pump. The PB970028 variant includes a built-in 2-circuit manifold as standard; a third circuit can be formed by adding two 15mm spigot elbows and two 15mm tees (sold separately).

• Connects single rooms or extensions up to 30 m² to any existing 2-pipe wet heating system
• No hydraulic or electrical alterations to the existing heating system required
• Built-in thermostatic blending valve blends flow water to the correct UFH temperature (30–60°C)
• Dedicated integral pump boosts flow — UFH loops are not dependent on the existing system pump
• Built-in pipe thermostat senses available heat — pump only runs when boiler water exceeds 45°C
• Optional volt-free room thermostat or wireless sensor connection for precise air temperature control
• 2-circuit manifold built in as standard — expandable to 3 circuits with standard 15mm fittings
• Can operate the UFH zone independently of the rest of the heating system when used with a zone valve
• Also suitable for low surface temperature (LST) radiator applications where water temperature control is needed
• Wall-mounted in the heated room or positioned elsewhere in the property — fully flexible siting
• Suitable for domestic and commercial buildings
• Compatible with all Polypipe UFH systems: Overlay™, Overlay™ Lite, MHP, solid screeded floors, and more

The ZRU forms a low-loss header between the existing heating circuit and the UFH loops, managing temperature and flow automatically. The six-step operational sequence is:

1. Boiler fires: Heating water circulates from the boiler through the existing system pipework and enters the ZRU via the Heating Flow connection.
2. Pipe thermostat activates: The built-in pipe thermostat senses that heating water is available (≥45°C) and sends a live signal to the ZRU pump.
3. Room thermostat calls for heat: If a room thermostat is fitted and the room temperature is below setpoint, the pump starts and draws water into the UFH circuits.
4. Thermostatic blending valve regulates temperature: A mixture of hot flow water and cooler UFH return water is blended to the correct underfloor temperature (adjustable 30–60°C) before being pumped into the loops.
5. Room thermostat satisfied: When the room reaches setpoint, the thermostat breaks the signal to the pump — the UFH pump stops, but the existing heating system continues to run normally.
6. Boiler shuts down: As the boiler switches off and main flow water cools below 45°C, the pipe thermostat breaks the pump signal and the ZRU goes to standby.

1. Pre-fill UFH pipework: If the ZRU is to be installed after floor screed or coverings are laid, fill and pressure-test the UFH circuit beforehand. Temporarily cap the pipes and keep them full of water (under pressure where possible). Take precautions against freezing in cold conditions.
2. Select mounting position: Ideally mount in the heated room at 100mm above finished floor level to allow pipe connections to exit the floor correctly. The ZRU can alternatively be positioned elsewhere in the property if more convenient. Ensure 80mm minimum clearance to the left of the unit for mixing valve access.
3. Fix to wall (Step 1): Tape the supplied fixing template to the wall. Mark and drill fixing holes. Insert wall plugs and screw the ZRU body firmly to the wall. Do not over-tighten fixings.
4. Connect heating pipework (Step 2): Connect the Heating Flow and Heating Return ports to the existing 2-pipe system via isolation valves. The preferred connection point is the main 22mm distribution pipework. Alternatively connect to the nearest existing radiator. Do not connect from any pipe smaller than 15mm.
5. Connect UFH circuits (Step 3): Connect the underfloor heating flow and return loops to the ZRU manifold ports using isolation valves. For 2 circuits, use the built-in manifold ports. To add a 3rd circuit, fit 15mm spigot elbows to the underside exit points and use 15mm tees off the manifold. Blank off any unused ports with spigot blanking plugs. Use PolyPlumb elbow fittings to exit pipes from floor level; cover elbows in polystyrene before screeding to allow future access, or enclose within a PolyPlumb Junction Box.
6. Wire electrical connections (Step 4): Connect 240V mains supply via a 3A fused spur to the ZRU wiring block as per the wiring diagram in the installation guide. If a room thermostat is being fitted, connect the volt-free contacts to the designated terminals and remove the shorting link from the wiring block. If no thermostat is fitted, leave the link in place — the ZRU will run purely on pipe thermostat control.
7. Fill and commission: Fill the complete system (boiler, radiators, and UFH circuits) and bleed any air. Check all connections for leaks. Set the thermostatic blending valve to the desired UFH flow temperature (typically 35–50°C depending on floor construction). Fire the boiler and confirm the ZRU pump starts when flow temperature exceeds 45°C. Verify correct operation of the room thermostat (if fitted).