Mike the Boilerman 

Your independent Potterton 

Netaheat specialist covering Berkshire, Wiltshire & surrounding counties

For more information or to book your breakdown repair, call or text me on 

07866 766364 

Potterton Prima

This page is a brief side-note about the Potterton Prima, which is very closely related to the Potterton Profile. The Prima looks identical to the profile externally and shares all the same controls and electronics. It is so very similar to the Profile aesthetically but has one big difference technically. 

Although this is just a guess, the Prima was probably designed, produced and marketed following the emergence of data showing that positive gas pressure boilers such as the Profile are slightly less ‘safe’ than negative case pressure boilers. This is due to the remarkable ability of gas technicians to incorrectly replace the front cover leaving leaks, thus rendering a positive gas pressure dangerous to use. With a negative case pressure boiler an incorrectly fitted front cover does not make it dangerous, so this is an advance in safety. The Prima is a negative case pressure boiler unlike the Profile, which is positive case pressure appliance. 

To explain in more detail, with a positive case pressure (PCP) boiler the fan blows fresh air from outside into the boiler which then flows into the combustion chamber, supplying fresh air and oxygen to the gas burners. The burned gas then passes out through the flue propelled by the positive air pressure inside the boiler case, created by the fan. If the outer case of a PCP boiler is not assembled correctly and/or leaks, it is possible for combustion products to leak out into the room via the leak. With a negative case pressure (NCP) boiler, the fan is in the boiler flue duct and sucks the products of combustion out of the boiler causing the air pressure inside the boiler case to be lower than outside. If the case of a NCP boiler is not assembled correctly and/or leaks (due to a clumsy engineer or, say, corrosion damage) fresh air from the room gets sucked into the boiler through the leak instead, and there is less (or almost zero) chance of flue gasses being blown out into the room. 

For fault-tracing a Prima, most of my comments on the Potterton Profile page on this site apply except to say, by far the most common failure I ever see on a Prima is the fan. And a jolly awkward and time-consuming fan it is too to replace, annoyingly. There are two versions of the fan and I keep both in stock…