Copyright 2018, Michael Bryant
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The Potterton Suprima comes in a wide variety of versions, issues and sizes. These comments are broad-brush comments about the original Suprimas from the late '90s. In particular they do not apply to the Suprima 120 (a completely different boiler inside the same case), or current Suprima range, which are condensing boilers.
The Suprima is a strikingly small boiler. Neat and compact with the controls hidden behind an unusual vertical hinged panel on the right hand side.
I like the Suprima. It's a classic boiler from the 1990's. It's fully electronic (i.e. no pilot light), fan-flued, cast-iron heat exchanger, small and quiet, extremely quick and simple to service, and easy to fault-diagnose and repair. Is it a 'regular' boiler and does not come in a combi version.
Fuel efficiency is quoted on the SEDBUK database as between 76.6% and 78.7% depending on the exact model you have, so pretty good for a non-condensing boiler.
It was a very successful product for Potterton, and was only killed off by the change in Building Regulations making condensing boilers compulsory.
As the model had grown older though a major drawback has become clear. it's electronic control board is the weak point and VERY prone to failure. Failure of the original board presents as the boiler 'locking out' and needing to have the RESET button pressed. This will happen occasionally at first, then become more and more frequent until the user is driven to call an engineer.
A number of board redesigns failed to fix this problem and a complete redesign of the control board was undertaken. The current replacement board is an upgrade kit that replaces the metal chassis and the whole wiring loom, and is shockingly expensive.
Sadly, the new board seems no more reliable than the old versions. The new board (now made by Siemens) seems to fail in a different way. The boiler starts and appears to run correctly, but shuts down again long before the selected water temperature has been reached. The boiler produces warm water, but rarely HOT. Occasionally it will run up to full temperature but most of the time it shuts off prematurely. Some users report 'short-cycling' too, where the boiler fires for just a few seconds, shuts down for a short while, fires again, shuts down, etc etc. The fix for this is yet another new control board.
The Suprima suffers from no other major faults. I encounter the occasional gas valve failure or thermistor (heat sensor) failure, and I've seen three leaking heat exchangers, but otherwise if I get a call to repair a Suprima I can be reasonably certain it will be a circuit board failure. It will be a superb boiler if they ever sort out the electronics!
P.S. The Suprima 120 is a completely different boiler from the others. None of my comments above apply to the Suprima 120.
P.P.S. Potterton now market a condensing boiler called the Suprima HE. Once again, this is a totally different boiler having virtually nothing in common with the vanilla Suprima. None of my comments above apply to the Suprima HE.
Common faults and fixes:
Control board failure:
The control board (PCB) is the weak point on this boiler. There have been multiple revisions of the design but even the current version control board is not bomb-proof. A typical failure will be the red ‘lock-out’ light coming on and the user needing to press the reset button. The boiler will then run for a random length of time then the lock-out light comes on again. A new control board is straightforward to fit (if rather time consuming as sometimes when wiring loom has to be changed as well).
The thermistor is the semiconductor heat sensor in the flow pipe, which tells the control board the temperature of the water leaving the boiler, so the control board can turn the gas flames on or off to regulate that temperature. When the thermistor fails the boiler will usually run for a minute or two then turn OFF even though only Luke warm. A new thermistor is quick and easy to fit.
The flue fan expels the products of combustion through the flue to outside. When the fan fails the boiler remains silent with no sign of activity, then after a minute or so the red light flashes. Again the flue fan is straightforward to replace, if rather expensive.
Gas valve failure:
The fan runs and the boiler sounds for all the world as though it is running, but no flame is visible through the viewing window. The red light usually flashes fast. A new gas valve takes about an hour to fit, test and adjust.
If you’d like me to fix your Suprima, context me here
First written 2017
Last updated 30th July 2018