Commissioning Underfloor Heating

Richard Kern, Technical Manager of Continental Underfloor Heating , explains to HPM readers the importance of following best practice procedures for commissioning an underfloor heating system.

Commissioning an underfloor heating system (UFH) correctly is just as important as the design and installation process. As such, it should always be considered during the planning stage and not simply as an afterthought at the end of the installation process. If possible, it makes sense for the person installing the UFH system to also commission it, as they will be aware of any potential issues that may occur and are familiar with the design and components used.

Even conventional heating systems using radiators, as their primary heat source, should be commissioned to optimise heating performance, however, in practice this simple task is rarely undertaken and could dramatically reduce any future issues that could potentially arise. There are several ways to commission a UFH system, but best practice procedures should always be followed to ensure that the system runs efficiently and at its optimum level.

Common faults can occur if the commissioning process is not properly followed, or if best practice procedures are overlooked. The following issues could arise:

• Over-warm floors
• Cold rooms
• Temperature differentials around rooms
• An inefficient heating system
• Reduction in energy savings
• Unhappy customers

Best practice commissioning procedures will ensure a UFH system meets its design specification and therefore the energy efficiency requirements of Building Regulations.

The following checks should take place before commissioning:

• Complete all safety checks relating to water connections, control wirings and boiler operations; these should be in accordance with the suppliers' instructions, warranty conditions and building regulations.
• The person carrying out the commissioning process should be competent and able to interpret readings and record data.
• Check all components. The UFH system may have been partially installed by other contractors so it is vital to check that all components are correctly fitted and free from obstruction.

Commissioning Procedure

Commissioning the UFH system is often overlooked until the time when it has to be turned on and fired up. A little planning at the initial design stage will help with this process. There are three main ways to commission a UFH system:

1. Thermometers
2. Lockshield Valves
3. Water flow meters

Thermometers measure the water temperature of every flow and return pipe; this has an influence over the water temperature decrease in the pipe circuit. This in turn is related to the flow rate of the circuit pipes. This method has several drawbacks, most notably the length of time taken by the floor screed to increase in temperature - this could take up to 3 hours per pipe circuit.

Lockshield Valves are an alternative solution. Fitted to every pipe circuit, these valves are able to be opened and closed by the person commissioning the UFH system. These are used in unison with valve charts to adjust the water flow-rates. This procedure, like the thermometer method, is also time consuming because the valve can be very sensitive and difficult to adjust, to ensure the correct flow-rate.

We recommend the water flow meter method as it is accurate, repeatable, quick and the most direct method to ensure the system is properly commissioned. The water flow meter method allows an instant visual display of the water rate. Flow meters come in two basic formats: the first being for mounting on top of the manifold valve or fitted to the underside of the circuit pipe return valve. By using this method, it can be repeated at any stage and easily accessed by the engineer.

It is also good practice to complete the commissioning report and inform the user how to operate their UFH system as they may be unfamiliar with this type of technology.