The ErP Directive does not change our cast iron boiler

If you think the ErP Directive meant the end of cast iron boilers, think again. Meet the Purewell VariHeat mk2 – your pre-mix, cast iron condensing boiler that complies with the Energy Related Products Directive (ErP)


Most people think ErP wiped out cast iron boilers under 400kW. But that is because cast iron is traditionally associated with atmospheric burners that are inefficient (you can read more about the history of cast iron here). However, we have a solution – an ErP-compliant condensing cast iron boiler that retains all the benefits of cast iron (longevity, robustness and tolerant of older heating systems) along with the high efficiencies of a condensing boiler.

Find out more about our customers’ favoured solution for refurbishment projects – discover Purewell VariHeat mk2.

Debunking the myths of cast iron boilers

#1: Cast iron boilers can’t condense

Technically, they are not designed to. But our cast iron boiler achieves condensing performance by returning system water through a copper/aluminium composite construction secondary heat exchanger that extracts the latent heat from the flue gases in the base of the boiler.

#2: Cast iron boilers use old fashioned technology

No, they don’t. The cast iron heat exchanger design has continually evolved. The heat exchanger has high density with well-defined fins to maximise heat transfer to the water. The waterways in a cast iron heat exchanger are also larger than typical lightweight wall-mounted boilers, making it more tolerant of older heating circuits.

#3: Cast iron boilers are not efficient

Ours is. The Purewell VariHeat boiler has gross seasonal efficiencies up to 96%. Plus, their life expectancy is much longer than other materials making them an ideal, long term investment. We have such confidence in the reliability and long life of our cast iron boiler we are happy to back it with a 10-year warranty on the primary and secondary heat exchanger.

#4: Cast iron boilers are heavy, so cannot be used in difficult to access plant rooms

Yes, cast iron is a heavy material. However, the Purewell VariHeat boiler design enables the heat exchanger to be dismantled into manageable sections or supplied to site unassembled. The sectional design also allows for simple replacement of a single section if required.

#5: Cast iron boilers are not compliant with the Energy-related Products Directive (ErP)

Most cast iron atmospheric boilers under 400kW do not comply with the ErP Directive. But we have the only ErP-compliant cast iron condensing commercial boiler available in the UK.