Underfloor Heating Problems & Their Solutions

Provided a high quality system has been chosen and installed correctly, new underfloor heating systems should not have any problems. However, as the first two conditions of this statement are not always strictly adhered to, niggles can occasionally crop up. The best way to combat any potential issues with your underfloor heating system is to be aware of the main problem areas from the outset.

Air In The Loops

One of the most common problems with any warm water underfloor heating system is air in the loops. When installed, the system should never be filled from the boiler filling loop – believe it or not, people have tried this. When filling the system each loop needs to be flushed out individually to make sure that there is no air in the pipework. Always read not only your quote but also the ‘installation instructions’ that are provided with each order.

Debris In The Pipes

The heating engineer that is installing the heating source e.g. boiler, or connecting up the system to the heat source, must flush through the pipework feeding the underfloor heating system. If this is not done, the manifold and pipe system will be injected with iron oxides that can cause the mixing valve to malfunction. The pump can also get damaged, hence it’s crucial that a qualified plumber connects the system up. The standard installation can of course be done yourself but qualified tradesmen should take charge of the electrical work and connecting up to the boiler.

Underfloor Heating Manifold

Incompatible Floor Finish

Something to look into before laying your floor finish, is that carpet is fine for underfloor heating as long as the combined TOG value for both carpet and underlay does not exceed 2.5. If wooden boards are fitted over underfloor heating systems, use only one layer of wood, for example 20 to 21 mm thick engineered (oak) boards are a very popular choice. Always check with the manufacturer or supplier of any floor finish about its suitability with underfloor heating. It is not recommended to use rugs on floors with underfloor heating and you should also ensure that any open fire place isn’t causing cold air over the system.

Incorrect Set-up

The pump should be operated at speed 3, which is generally the default factory setting. The mixing valve should typically be set at 45°C for concrete screeded floors and 55°C for timber suspended floors. These are only approximate guidelines but should give you an idea. The installer would normally leave the mixing valve at the minimum setting (35°C) as per instructions, the temperature should then be increased by one degree per day until you have reached your required setting e.g. 45°C.

Check that the flow and the return are correctly fitted from the heating source to the mixing valve. There have been a small number of situations where the plumber has connected the pipes the wrong way, which obviously means the system will not work correctly.

Another potential problem that can arise is the manifold actuators being operated by the wrong room thermostats. This would result in the wrong rooms being set, which could waste time, effort and energy. This issue can go unnoticed for years, especially if the thermostats are programmed at similar temperatures. Check that the correct room thermostat is operating the correct underfloor heating loop(s). The installer will always mark up each loop at the manifold so that it is clear to the electrician which actuators should be controlled by each thermostat.

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