Underfloor Heating Installation

Installing underfloor heating is not complicated, provided the design drawings are adhered to.

It is essential to install the correct linear meterage set out on the drawing. Keep to the pipe centres; never exceed circuit lengths as to do so may result in balancing problems.

There are a number of tools that are essential to install an underfloor heating system – a drill to fix the manifold to the wall, pipe cutter to cut the pipes to length and a spanner to tighten the nuts on the manifold.

Non-essential equipment; pipe decoiler (makes it much easier to pull off from a wheel than rolling a coil out), staple gun to clip pipes down into insulation (much easier on the back and fingers!).

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Most heating engineers and plumbers initially baulked at the idea of laying so much tube, but over the years, have now become accustomed to laying pipe. They may not be as fast as a dedicated underfloor heating installation team, but they do, in most cases, a good job.

Mount the manifold horizontally, in the position set out on the drawing, about 750mm from slab to top of manifold. This allows for the 90° bend on the pipe between manifold and slab. It is important to leave enough space to connect the heating supply pipes to the manifold.

Couple the coil end to the first circuit and fit the pipe support bend so that the pipe sits on the insulation square to the wall and floor. Proceed with laying the circuit return to the manifold. Fit another pipe support bend, cut the pipe at the right length, fit nut, olive and pipe insert and couple up to the manifold. This procedure is repeated until the manifold has been completely piped up.

After completing the underfloor heating installation, the pipework must be tested, either pneumatically or with water, normally up to twice the working pressure. Underfloor heating pipes are made to a high standard but failures do occasionally occur; i.e. damage in transit, or more commonly during or after the installation prior to the finished floor going down. It is far better to test prior to having the screed or floor put down!

Design drawings should have circuit settings listed out in a table. The majority of manifolds these days come with a flow metre which indicates the flow rates in litres. This is adjusted to suit.

Some underfloor heating manufacturers still work on the number of turns the return valve is unwound. Shut the return valve completely, then for each litre required, open the valve one revolution.

Connecting the manifold to the heating system is best left to a competent plumber or heating engineer, so too is the wiring – a qualified electrician will be needed.