Potterton Suprima Boiler Problems

This article gives a short overview of the Potterton Suprima boiler problems. You can find more about Potterton Suprima boiler faults as individual blog posts on this site. Use the Search icon or for mobiles use Menu→Search.

We tried to find when the first Potterton Suprima boilers came out. We looked online and, strangely, there doesn’t seem to be any mention of the Suprima on Potterton’s “A History of Potterton” page. It must have been their biggest selling boiler too. I know I was fitting them as early as 1996 and they may have been around a year or two before that. I suspect that the boiler isn’t mentioned in their “History” because Suprima boiler faults damaged their reputation.

The Suprima is a very compact boiler. They seemed amazingly small when they first came out and they looked like they had been designed from scratch, not just modified from earlier boilers. The Suprima followed the Potterton Profile and Potterton Prima F which were good boilers so things looked promising. In many ways I like Suprima boilers but from very early on they had problems.

The biggest problem with Potterton Suprima boilers was the circuit boards. I don’t know if Potterton owned the company ENER-TECH ELECTRONICS, whose name was on all the early PCBs. I also don’t know who designed or specified the boards. Either way, components on the PCB (printed circuit board) would overheat and the board would fail. The material of the board itself would scorch in a characteristic area. At the time, I was told that these overheating components were Zener diodes but I’m not an electronics engineer. Over time, iterations (minor changes) were made to the circuit boards. Each time a change was made, the label on the PCB would show a change in the Issue Number. I have a photo which shows that by Week 11 of 1997 the PCB was already on Issue 05 .

Scorched Potterton Suprima PCB
Potterton Suprima ENER-TECH PCB showing typical scorch marking

One of the iterations was to stand some of the components on longer legs. This will have allowed them to cool more easily and the matrix of the board showed less scorching. This still didn’t sort things out. We were seeing ENER-TECH boards with Issue Numbers up to 11 before the numbering system was changed, possibly because it was becoming embarrassing.

Suprima boilers which were in a cool, well ventilated space seemed to last longer before the PCB failed. The longest-lasting ENER-TECH board we saw was in a boiler where the central heating pump was not drawing its power from the circuit board. This was wrong in installation terms (the instructions say the pump should be wired from the boiler) but it seemed to have extended the life of the circuit board. This makes sense. Pumps draw a significant amount of electrical current and current has a heating effect as it passes through most electrical components. With much less current passing through the board, there were no signs of scorching.

While the early PCBs were the main technical problem, the way Potterton handled the problem made things worse. We were a tiny company fitting only a few Suprimas but we had enough problems to make me ring Potterton Technical to ask if they had problems with this boiler. I was assured that they had not heard of any problems. This was implausible since the boilers were failing within the first year. After modifications to the circuit board design the lifetimes of the boards improved slightly, so that they didn’t commonly fail within the guarantee period.

Potterton had invested a huge amount of money in the Suprima, at a time when profit margins for boiler manufacturers were very small. It’s easy to see why they hoped small modifications to the ENER-TECH PCB design would sort it out.

Meanwhile, now that Suprimas lasted longer than the guarantee period, installers started fitting them in large numbers. They were cheap to buy, as Potterton tried to retain market share. They were simple to fit and they were very small and relatively light so they were easy for one man to fit. Over the next few years they were fitted in huge numbers but the circuit board problems hadn’t gone away. Eventually, Potterton had a completely new PCB designed and manufactured. It was made by Siemens and could be retro-fitted to the Suprima. It required replacement of the controls chassis and wiring loom too.

Potterton Suprima Siemens PCB kit
Replacement Siemens PCB kit for the Potterton Suprima boiler

The new Siemens PCB kit proved to be more robust and, under pressure, Potterton themselves retro-fitted them to many boilers free of charge. Not all boilers were included and many owners were angry. If you want to know more about that, Google it. It was all over the Internet and other media. Our experience of the Suprima Siemens PCB shows it is much better than the ENER-TECH PCBs. There are occasional faults but seemingly no more than with most other boiler PCBs.

The biggest problem with the Siemens PCB kit was the price. Currently (2022) they cost about £295 including VAT for the part alone. For years, customers were paying well over £300 to have Suprima circuit boards changed. Now the price to have a genuine new Potterton board fitted will be closer to £400.
There are refurbished PCBs on the market and these are much cheaper. Both the Siemens PCB and the old ENER-TECH PCB can be found refurbished. We can understand the temptation to fit these circuit boards as they are much cheaper but it is risky and may be illegal. The Gas Safe Register (Technical Bulletin 116) says that anyone fitting these components may be breaking the law. I suspect that it may also invalidate insurance policies.

Potterton took a financial hammering over the Suprima PCB problem. However, given the amount that is charged for the genuine new manufacturer’s part, and the huge numbers sold, they may have been paid back handsomely!

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