Potterton Promax System Boilers

25 Apr. 2019

Written by Neil Marsh MCIPHE RP RHP EngTech


In this article, we will be discussing the latest Pottern Promax System boilers, of which is pretty much the same as the Baxi Megaflo System boiler with a lower warranty …

Value For Money

For the home owner, we would advise that they spend a little more money and invest in the Baxi Megaflo warranty as it has a 7-year warranty, whereas the Potterton Promax System boiler is only 2-years. The slightly lower price is more appealing to home builders and renovators. 

Track Record

This boiler has been on the market around 3-4 years, but its design is the same as a boiler which is much older. 

Our Thoughts On The Overall Design

This is probably the best built system boiler on the marketplace and arguably one of the best system boilers ever made along with the Baxi Megaflo. Below is a Promax System boiler which is one year old, which we were servicing recently. As per the photo above, which is from Potterton’s website, there appears to have been some slight changes as of late. 

The layout of the boiler, as above, is very well thought out and it is easy to work on, which will help keep repair costs outside of the warranty lower due to reduced labour requirements where work is conducted on an hourly basis, or by an honest Gas Safe registered engineer who quotes fairly. 

The boiler has a stainless steel heat exchanger, of which we would strongly advise in all instances over aluminium.

For more information about issues with aluminium heat exchangers, click here!

The gasket used to seal the heat exchanger door is of a silicone variety, but we have never seen one deteriorate from heat damage and many of these boilers which are over 10-years still have the original seals, unlike some other boilers. 

The system water containing components are mostly brass and copper, of which the photo below shows. 

It is very easy to power flush with the boiler running.

More information about power flushing can be found by clicking here.

Criticisms: Build Quality Issues

We would have preferred a metal pump block instead of a plastic one. 

The wiring connection could be made better and the clips to hold the wires in place through the case can be flimsy. 

The heat exchanger is fused, as the outer part is made of plastic. Consideration needs to be given where the boiler is installed and could run dry briefly, such as being in a loft, as if the thermal fuse was to fail, then the main heat exchanger, which is a very expensive part, would need replacing. 


The boilers are on the larger side, so fitting into tight spaces is not always possible. Also, the off centre flue can make a straightforward combi swap more complicated, or even prevent its use in some instances. 

The Boilers Life Expectancy

So long as the heat exchanger is kept free from overheating, sludge and limescale and is serviced periodically, there is no reason in our opinion why this boiler could not last 18+ years with some modest part replacements. There are a number now that are not far from that age. 


In our opinion, the Promax System boiler for home developers and builders, is an excellent choice.

For home owners who are not selling their home immediately, we would recommend that a home owner spends a little more for the Baxi Megaflo with its 7-year warranty. 

For all your Potteron Promax System boiler installations in Cheltenham, Gloucester, Tekesbury and the areas around, you will not go wrong when you contract Forthright.