Manifolds act as the central control hubs of water underfloor heating systems, managing water flow-rates, temperature regulation and pressure. In this guide, we explain exactly what a Manifold is and how it works to circulate optimally heated water through the underfloor heating circuits to provide thermally comfortable, energy-efficient heating to each zone of the system.

In this guide we explain:

  1. What a Manifold is
  2. The Components of the Manifold
  3. How a Manifold works
  4. The best location for a Manifold
  5. The cost of a Manifold
manifold for underfloor heating explained blog

What is a Manifold?

Manifolds are a key part of hydronic underfloor heating systems, they connect the underfloor heating pipework (also known as floor circuits) to the heat source and act as the termination point for these circuits. Manifolds are responsible for circulating heated water from the boiler or other heating source through the underfloor circuits whilst controlling the pressure, flow-rates and, if using a mixing unit, controlling the circuit temperature too.

Water underfloor heating systems commonly comprise of pipework installed either within a freshly laid screed or directly within custom underfloor heating insulation boards or panels. The pipework can be laid in various patterns forming circuits; a single circuit could be for an individual room or area or multiple circuits could be used for larger rooms or open areas – these are known as zones. Each floor circuit connects to a centrally located Manifold which allows independent control of the zones. Manifolds can control multiple circuits concurrently, warming different rooms to different temperatures at different times – each zone is typically controlled by a zone-specific thermostat, which is installed within the heated area.

Warmup’s S3 Manifold can control the underfloor heating for up to 12 circuits, which can each have up to 120 meters of pipework connected whilst maintaining a consistent and even distribution of the water around the floor circuits at the correct temperature, pressure and flow-rate.

Warmup’s S3 Manifold Components

The S3 Manifold by Warmup is a market-leading piece of technology produced from a single piece of high-quality ‘304’ stainless steel. The S3 is available in a range of sizes and configurations with the ability to control between 2 to 12 zones, making it suitable for a wide variety of hydronic systems at different scales; from a small apartment to a large commercial project. The circuits of each zone are connected to the Manifold by ports on the Manifold’s Flow and Return arms. Warmup’s S3 Manifold also comes with a 10-year warranty for your peace of mind.

1. Air Vents and Drain Valves

Air Vents can be found on the ‘flow’ and ‘return’ arms of the Manifold and are used to remove air from the underfloor heating system. The Drain Valves are used for the initial filling and draining of the system.

2. Taconova Flow Gauges

The Manifold’s Flow Gauges are mounted to the flow arm, one per circuit. They are set during the installation to configure the correct flow rate for the circuit and to provide the designed heat output for that circuit – which is determined by the floor build-up and heat losses of the area. These flow gauges also provide a visual indication of the flow rate through each of the floor circuits.

3. Thermometer / Pressure Gauge

Directly attached to the Manifold is a dual-purpose thermometer and pressure gauge for ease-of-use and accurate control.

4. Manifold Mixing Unit

The Warmup S3 Mixing Unit blends water from the heating source and the floor circuits to maintain the designed temperature for the system. An S3 Mixing Unit is required with Warmup’s S3 Manifold where the heat-source cannot constantly maintain design temperature. The Mixing Unit allows optimised water temperature regulation of between 20 – 60 Degrees Celsius, the ideal temperature range for water underfloor heating systems and much lower than typical radiator-based central-heating systems. The Mixing Unit is formed of three parts: The Lower Arm, Upper Arm and Circulator.

warmup manifold mixing unit

5. Manifold Isolation and Commisioning Valves

Connected to the Manifold arms, or the Mixing Unit (if used), the Isolation Valves allow the Manifold to be isolated and tested without affecting the primary floor circuits. The Commissioning Valves control the water flow through the individual floor circuits, allowing the system to be filled, drained and pressure tested. The Commissioning Caps are removed and replace with Actuators, to provide individual circuit control.

6. Actuator

Attached to the Manifold’s Commissioning Valves, electro-thermic Actuators connect to the Wiring Centre – where the zone thermostat can control when the Actuators open and close each circuit, allowing the water to circulate through the system.

7. Wiring Centre

The Wiring Centre controls the electrical aspect of an underfloor heating system and facilitates a connection between the Manifold and its components with the heat source and thermostat. Typically connected to the Actuators and Thermostats, the Wiring Centre coordinates the operation of the heating system.

How does a Warmup S3 Manifold work?

The Manifold connects the heat source – a boiler, heat-pump or other – with the water underfloor heating circuits, regulates the incoming water temperature via the Mixing Unit and distributes this warm water throughout the floor circuits for an energy-efficient heating system. Once successfully installed and the pipework connections made, the underfloor heating circuits are initially filled and purged with water.

Warmup manifold for underfloor heating

Connecting the Circuits to the Heat Source

Connection to the heat source is made via the primary heating circuit. The heat source supplies water to the Manifold via the Manifold’s Mixing Unit to guarantee designed water temperature (this can be set between 20 – 60 Degrees Celsius). However, if the heat source can constantly provide the necessary water temperature for the system without over-heating then a Mixing Unit may not be required.

The Mixing Unit regulates the water temperature by means of an Actuator-controlled Mixing Valve and blends the heated water from the primary heating circuit with cooler water from within the floor circuits to achieve the ideal design temperature. This temperature is configured during the installation process to match the designed heat requirements; which is determined by heat losses, floor construction, heat outputs and other variables.

Setting the Flow Rates

Through the Mixing Unit’s Circulator, the heated water’s flow pressure is set and maintained throughout the underfloor circuits. Manifold’s can support up to 120 Metres of underfloor heating pipes per circuit so before the water is delivered into these pipes, the flow rates for individual circuits are set via the Flow Gauges to suit the specific circuit’s needs. When correctly configured, this ensures heated zones will evenly heat the space, even where different floor finishes have been used.

Distributing the Heated Water

The optimally heated water, with the correct flow pressure and flow rates, is delivered from the Manifold into the floor via the Manifold’s Flow Arm and after circulating the floor circuits, the water re-enters the Manifold via the Return Arm. The Return Arm features Circuit Valves that are commonly mounted with Actuators which open and close when instructed by the thermostat (via the Wiring Centre) – thus allowing water flow into the floor circuits and warming up or cooling down the underfloor heating system.

Controlling the Manifold

The Manifold and its electrical components are efficiently controlled by the Wiring Centre. This forges a connection between the Manifold’s Actuators, Circulators and any Zone Valves with the Thermostat and heat source. When a thermostat calls for heat in a specific heated zone, the Wiring Centre will supply voltage to the relevant Actuator (or multiple, if using more than one circuit per heated zone) which opens the Commissioning Valves and allows warm water to flow through the circuits. The Wiring Centre also simultaneously calls the boiler for more heat, opens any Manifold zone valves and operates the Mixing Unit Circulator.

Using a Smart Thermostat by Warmup to control the floor heater ensures energy-efficient heating with long-term cost-savings on your heating bills.

Best Location for a Manifold

Manifold placement is key to ensuring an efficient underfloor heating system. The best location for Manifold placement is central to the heating zones; by mounting the Manifold centrally, pipe lengths will kept to a minimum ensuring the heated water reaches the heated area evenly and efficiently.

For larger projects, more than one Manifold may be required. If underfloor heating is to be installed across multiple floors, we recommend installing a sperate Manifold on each floor. Warmup also offer Manifold Cabinets to conceal the Manifold and its associated pipework.

where to install a manifold

How much does a Manifold cost?

Warmup’s S3 Manifold offers expert design at a competitive price. For the simplest two port option without a Mixing Unit, the Manifold retails at £128.93, rising in cost with additional ports and components.

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