Misrepresentative output values for radiators remain a serious issue – despite action from regulators and industry groups. Here, Richard Lister looks at why it’s so important to have the correct information, what manufacturers are legally required to provide and how to avoid misleading claims of performance.
The correct specification of radiators is essential to ensure heating systems will perform as intended. However, the process largely relies on the correct sizing of the radiators, which in turn is based on the stated output of the radiator at a specific Delta T.
Incorrectly sized radiators result in rooms that are harder to heat, with poor performance and higher energy bills. Also, as the UK drives towards net zero, it is more important than ever that heating systems perform correctly to minimise the carbon contribution. Where radiators are sized incorrectly, the use of the wrong Delta T in the manufacturer’s information is where the issue often lies.
Why is Delta T so important?
The Delta T is the difference between the water temperature in the heating system and the target ambient room temperature.
The bigger the difference between the water temperature and the target room temperature, the faster the heat will transfer. Therefore, the output for a radiator, typically stated in either Watts or British Thermal Units (BTU), will be calculated at a specific Delta T.
What are the issues?
Under the Construction Products Regulation 2011, ‘manufacturers’, which includes importers, distributors and resellers, are legally required to determine and supply the thermal performance of the radiator. Specifically, all hydronic radiators, including towel rails, must be tested and comply with the BS-EN 442 standard.
The tests should be carried out by an accredited independent laboratory, and the manufacturer must then state the heat output in Watts at both Delta T50 and Delta T30 in the Declaration of Performance (DoP) for each radiator. Delta T50 is the standard value while Delta T30 is used for low temperature systems.
The issue is that some manufacturers and resellers, either intentionally or inadvertently, state an output on the DoP that is based on a Delta T of 60 or greater, which assumes higher system water temperatures. The result is that heating professionals will get an exaggerated picture of the radiator’s output. Using this as the basis of heating calculations means the radiators will be undersized, causing higher energy usage and bills for consumers.
Poor performance also has the potential to unfairly impact consumer confidence in modern heating systems such as heat pumps. This is because correct heat outputs are more critical with heat pumps due to their lower operating temperatures. If the heating does not perform as designed and fails to provide the required heat, the consumer will often assume the heat pump is responsible for the poor output. This in turn can impact the customer’s perception of the installer’s capabilities, negatively affecting the chance of recommendations and future work.
Making an informed decision
Given its importance when it comes to system performance, incorrect Delta T values is an issue that the industry is attempting to address.
The Manufacturers’ Association of Radiators and Convectors (MARC) is working with the Office for Product Safety and Standards, the body that enforces the Construction Products Regulation, to stop unscrupulous manufacturers providing misleading performance values. MARC has been raising awareness of the issue, seeking to ensure that both installers and consumers understand the problem and are well informed about what they should look for.
To avoid system performance issues, it is advisable that products should only ever be sourced from manufacturers who can back up their product information with the legally required product testing. Under both UK and EU law, there is a legal obligation to supply a Declaration of Performance for each radiator if requested, either in paper or electronic form. If a DoP is not available, the product should not be used.
However, it is also important to check the DoP to ensure the test data has been independently verified by a notified body such as BSRIA. The DoP should contain details of the organisation that carried out the tests. In addition, membership of MARC is a good indication of reliability and credibility for further reassurance.
Remember, the devil is in the detail. Always check the Delta T and ensure you are clear and confident in what is being provided before undertaking your own calculations, to ensure radiators are correctly sized and systems will work as intended.
www.theradiatorcompany.co.uk/marc
Richard Lister is National Sales Manager at The Radiator Company.
