Underfloor Heating Manifolds Guide

Over the last 3 decades, underfloor heating has become increasingly popular with homeowners due to the realistic prospect of making significant savings on energy bills. An underfloor heating system, whether electric or water, can be up to 40% more energy efficient than a traditional home heating system.

A water-based underfloor heating system offers the highest cost savings over the long term, with much of the action centred on the system’s underfloor heating manifold. In this guide, we explain why this crucial piece of equipment is so important to the smooth operation of a water-based underfloor heating system.

How Does An Underfloor Heating Manifold Work?

The underfloor heating manifold consists of between 2 and 12 ports, to which flow and return pipes are attached.

1. Hot water is passed into the flow section of the manifold from the heat source, which could be a boiler or heat pump.
2. The water then passes through a blending valve, which regulates the water temperature.
3. Under pressure, the hot water is then pumped through the underfloor pipework and back to the lower section of the manifold, which is called the return.
4. The return section is controlled by actuators, which are responsible for controlling the flow rate through the loop of pipes. Actuators work in conjunction with the wiring centre and when they receive a signal, they can open or close to ensure the water temperature is evenly maintained by the flow rate of water.
5. A gauge will continuously monitor the pressure within the manifold and a thermostat will control the heat output.

Types Of Underfloor Heating Manifolds

Manifolds for underfloor heating come in various types and can be made from different materials, such as brass, plastic and stainless steel. However, there are 3 main types, which are generally used in the UK.

Type 1. This is the most basic form of underfloor heating manifold, which will have either manual or automatic air vents plus 2 ball valve isolators. Additional functionality can be added such as an integral differential pressure by-pass valve and thermometer controlled flow and return ball valves. Circuit isolators and flow meters can also be added. More information is available on low-profile water underfloor heating manifold kits

Type 2. A type 2 manifold has all the functionality required plus the option to have electro-thermic heads on the return rail. These components will allow you to use programmable or simple room thermostats for each room. More information is available on standard output water underfloor heating

Type 3. This is a type 2 underfloor heating manifold with the addition of a secondary pump, which is used for the longer pipe runs. It includes a temperature controller for reducing running temperatures. More information is available on high-output water underfloor heating manifold kits

Components Of An Underfloor Heating Manifold

A standard underfloor heating manifold consists of several components, each with a specific function. These include:

How To Install An Underfloor Heating Manifold

Underfloor heating manifolds are usually surface mounted and are available in 1” and 1¼” sizes. They come with 2 to 12 ports so ensure you have ordered or selected the correct size. They usually come fully assembled and ready to be mounted on brackets.

Starting from left to right, begin to connect to the flow manifold rail or flow bar. Make a note of which room or zone the loop serves on the manifold tag.

Once you have completed the loop, follow the same route back to the manifold and connect the pipe to the return bar. It’s recommended you make a note of the loop length installed on the manifold tag.

Complete the process for all the other loops, fill the system with water and then pressure test. Connect a pressure test pump to the fill port on the upper flow rail of the manifold. Next, open the valve fully anticlockwise using the square key on the cap. If necessary, vent the system of any residual air before increasing the pressure to 6 bar.