Underfloor Heating – Circuits & Manifolds

Underfloor Heating – Circuits and Manifolds

This page outlines the function of circuits and manifolds in Underfloor Heating (UFH). This description will help to contrast a major difference between UFH and the radiator type of hydronic heating. UFH Water based systems are covered by BS EN 1264 Parts 1, 2, 3 (Design) and 4 (Installation).

Besides tubing / pipework the other primary components of UFH are the manifolds,  and associated flow and temperature controls.

Manifolds provide for individual supply and return pipework for each room / area. The typical manifold has a temperature controller and possibly a pump, to ensure that water is at the correct temperature for the underfloor heating circuits, and that there is sufficient flow for the greater length of pipe used than in the case of radiator type circuits. In UFH, water typically circulates at temperatures between 35 to 50 degrees Celsius.

Courtesy MULTIBETON UK

Each thermostat in the UFH case can be mounted in an optimum position rather than a TRV (Thermostatic Radiator Valves) which has to be fitted directly to a radiator at low level. The use of a thermostat per room/area makes it much easier to create ideal comfort levels and can prevent the unnecessary heating of unoccupied rooms which can improve the energy efficiency of the building by up to a third.

In the radiator type of hydronic heating, with water circulating between 65 to 75 degrees Celsius, the typical configuration is that of a ring circuit with a TRV generally on each radiator. This approach has the problem of thermostats identified above, as well as that of one radiator producing heat well before another because of the speed at which the last radiator on a ring circuit receives its hot water (and the temperature of that water). This sequential warming of radiators can be somewhat address by balancing, but this approach can be tricky.

The advantages in the use of manifolds include:

  1. Manifolds provide extra control, especially  independent flow and return and temperature control. This reduces installation, commissioning and maintenance effort.
  2. There is little or no requirement for tees and elbows – more saving on installation time
  3. The number of joints are limited to those around the manifold, limiting potential leaks
  4. In the unlikely event of a leak, it is possible to isolate that circuit
  5. They avoid the problem of the “last radiator” (see above).

And the disadvantages? More pipework/tubing – not really a significant problem, but pipework design is important.