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Installation Instructions

Once you have purchased your underfloor heating system, the next step is installation. Below we have laid out everything you should need to help you install and set up your underfloor heating system.

  • Pipe centres for concrete floors and timber suspended floors is 200mm. We recommend centres of 150mm if using a Heat Pump because of lower flow temperatures.
  • The pipe should be 100mm from all walls.
  • Maximum loop length should be 120m. We recommend two people fitting the pipe; one to lay the pipe and another to staple the pipe to the insulation.
  • Staple the pipe to the insulation with the clips provided. You need approximately 1 or 2 clips per metre of pipe, you will need to install more clips on pipe bends.
  • The manifold, wiring centre and control pack should be located as central as possible within the building.
  • Try to install the full amount of pipework as calculated with your underfloor heating kit. You will usually have some wastage from each loop. The pipe is marked every metre so you know when it is time to go back to the manifold. The loop lengths on the chart provided are only estimations on the information we have been given.
  • Piping isn’t generally laid under Kitchen units or Utilities, try to install pipe at closer centres near kitchen and utility units to ensure the full amount of pipe required for each room is met.
  • We recommend that you first install the manifold and the control pack. To fit the pipe to the manifold, cut the pipe end squarely using the plastic pipe cutter. Bevel the pipe end with the Bevelling tool provided, place the nut over the pipe, then the olive and finally push the insert into the pipe and attach to the manifold.
  • If the pipe is kinked when bending, it should be straightened and rearranged so that the location of the kink sits on a straight length.
  • Note the lengths of pipe fitted to each circuit, piping is marked every metre.
  • Note also the room to which each circuit applies.
  • Prevent people from walking over the pipes and keep tools etc away from the pipes.
  • The system should be filled with water and pressure tested before the screed is laid.
  • Screed or flooring should be laid as soon as possible after the pipe is laid in order to protect it.
  • Hardwood timber flooring must be conditioned before it is fixed in place.
  • Balance the loops as suggested in the instructions.

If the system is making noise, then it is possible that air is in the system. The air can be removed from the end caps on the manifolds, similar to a radiator system. Make sure that the system is operated for 24 hours before making any adjustments.

Note, the system should operate 24 hours a day during the heating season, this is the most efficient way to run it.

Room thermostats are normally fitted 1.5 m from the floor, located near to the light switch. Try to avoid positioning them in direct sunlight as it will affect their readings.

The maximum heat output for a underfloor heating system is 100 W/m2 for concrete floors and 70 W/m2 for timber suspended floors. For any underfloor heating system to work efficiently, the property needs to be built to current building regulations. Carpet and underlay together should not exceed 2.5 Tog.

If you are using a heat pump, please make sure that the heat pump company specify a pump that can cope with the underfloor heating duty as you might not need our control packs with heat pumps. Heat pumps should be supplied with a buffer tank (ask your GSHP supplier).

We recommend a minimum of 50mm of insulation for the underfloor heating system. This is very high quality insulation and can be used for both concrete and timber suspended floor constructions.

Note we do not supply the insulation. Any builders’ merchant will have Celotex or Kingspan insulation in stock. The quote is based on clipping the pipe direct to the insulation board. We do supply pipe clips. With concrete floors, we recommend 50mm – 65mm of screed on top of the insulation.

The screed must be allowed to dry for a minimum of 4 to 6 weeks before the heating is operated. The first time a system is used, the mixing valve should be set to minimum in order that any moisture in the screed dries out. Following this, the temperature should be increased by two degrees every day until the mixing valve is set at 45°C.

For stone and ceramic tiles, flexible adhesives and grout are recommended. With Vinyl, check with the manufacturer that it works with underfloor heating and laminate flooring should always have an expansion gap, to allow for movement.

One by one, the flow and the return valves are opened and closed, purging the loops of air. Ensure that all the red caps on the return manifold are closed. Open the upper ring on the end cap 2 to 3 turns. Open the first red cap and then open the return end cap. Wait until clear water is coming out and make sure that all the air is gone. Close the blue cap and do same for the next loop. Continue the process until all the loops are fully vented of all the air. Close the end caps when done.

The following is an approximate guide to how far each loop should be adjusted;

Size of Loop                                                  Percentage Open

10 – 30 metres                                    30 % open

40 – 60 metres                                    50 % open

60 – 90 metres                                   75 % open

90 – 100 metres                                   100 % open


Note, if there is a risk for the air temperature dropping below freezing, then you must protect the pipes and manifolds from freezing conditions. It is always recommended to lay screed on top of the pipes as soon as they have been pressure tested.