Underfloor Heating Technology

Pipe Technology

PEX Pipe

The main component of a warm water underfloor heating system is its pipe. We use PEX high-density cross-linked polyethylene pipe. The pipe is installed in continuous lengths with no joints in each heating loop.

PEX pipe is specially designed for underfloor heating (UFH) systems and incorporates an oxygen diffusion barrier in the form of five polymeric layers around the outside wall of the pipe. This oxygen diffusion barrier is oxygen-diffusion tight to DIN 4726.

The barrier layer makes the pipes virtually impervious to oxygen. This means that metal components in UFH systems should not suffer corrosion from oxygen permeation as they might if the system utilised plastic pipes without the oxygen diffusion barrier.

This is particularly important in mixed systems where the radiators and UFH systems are supplied with the same water.

Safe Working Pressure

The safe working pressure and continuous temperature rating for the PEX pipe should be certificated to 6 bar at 90°C. However, the pipe can withstand higher temperatures for short periods of time. This means that there is an adequate safety margin to ensure that damage to the pipe should not occur in the event of a boiler thermostat failure.

Use of Corrosion Inhibitors

PEX pipe will not be adversely affected by corrosion inhibitors normally used in central heating systems. It will not be affected by accidental contact with linseed oil based sealing compounds or soldering flux.

The PEX pipe will not be affected by soft, hard or aggressive potable water. The pipe will not be attacked by constituents of concrete, screeds, mortars and is fully resistant to attack from micro-organisms.

Use of Antifreeze

PEX pipe is resistant to glycol-based antifreeze products. If a system is to be installed in freezing conditions, the hydrostatic pressure test should be carried out using the correct mixture of water and antifreeze solution. However, before system start up, the glycol mixture should be flushed out and disposed of carefully.

Manifolds

Manifolds are manufactured from dezincification resistant brass. The PEX pipe loops are secured to the manifold with compression fittings. Manifolds are supplied in pairs – flow and return.

They come in a variety of sizes from 2 port to 12 port. The flow manifold controls the on off valves to each circuit. An actuator or telestat can be fitted to each loop enabling thermostatic control to separate areas.

The return manifold is fitted with regulating or balancing valves. These valves allow flow rates to be adjusted as necessary, different pipe lengths require different resistance.

Insulation

Screed insulation is the key to an economical and efficient underfloor heating system.

Care should be taken in ensuring that the correct insulation material is installed prior to any pipes being laid. Complying with the new part "L" of the Building Regulations is the least you can do.