Illegal radiators: what you need to know

There is growing issue of ‘illegal’ radiators that do not meet the legal requirements. Stewart Clements, director of MARC, highlights how to spot them and the consequences of installing them. 

What makes a radiator ‘illegal’? 

Hydronic radiators (including steel panel radiators, multicolumn radiators, designer radiators and towel rails) must comply with the test standard BS EN 442. This standard requires manufacturers, and importantly, importers, distributors and resellers acting as ‘manufacturers’ to ensure radiators have been tested in an accredited facility, and the heat output accurately measured and declared at ∆T50 and ∆T30.  

Under the Construction Products Regulation, every radiator placed on the UK market must be supplied with a Declaration of Performance (DoP), either in paper form or electronically. A radiator becomes ‘illegal’ if it does not meet these requirements. 

There are several indicators that a radiator may not be compliant: 

• Missing Declaration of Performance (DoP): If a radiator is supplied without a DoP, it is not compliant with the law. The DoP should be easily accessible, either included with the product or available for download. 

• Incorrect Delta T values: The most common issue is the misuse of Delta T (∆T) values. The legal requirement is for outputs to be declared at ∆T50 and ∆T30.  An output advertised at ∆T60 (or higher) should be a red flag, as this artificially inflates the stated heat output, making the radiator appear more powerful than it actually is under normal UK operating conditions. 

• Output not stated in Watts: The heat output must be clearly stated in Watts (W). Any deviation from this, or vague/unclear performance data, should raise concern. 

• Lack of independent testing evidence: If it can’t be demonstrated that the radiator has been tested by an accredited laboratory, the product may not comply. 

Why does this matter? 

Non-compliant radiators can undermine system performance, increase customer costs and potentially expose installers to risk.   

Accurate heat output data is fundamental to the design of the heating system. As highlighted in guidance from the Manufacturers Association of Radiators and Convectors (MARC) guidance, correct radiator sizing is critical, particularly as the industry transitions to lower flow temperatures (55°C and below). 

Installing a non-compliant radiator can lead to underheated rooms because the radiator fails to meet the heat loss requirements. For example, a radiator sized using inflated ∆T60 data will almost certainly underperform at lower operating temperatures.  Furthermore, energy bills may be higher because the system runs hotter and longer to compensate. For heat pumps in particular, where electricity costs are significantly higher than gas, system efficiency is critical to keeping running costs manageable. And carbon emissions can be increased too. 

To protect both your customers and your business, always use trusted manufacturers and suppliers with transparent data. Request and check the DoP before installation.