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Potterton Suprima Gas Boiler Faults, Problems and Fault Finding
With a Potterton Suprima boiler which was repeatedly locking out and having to be re-set we expected to find that this was a circuit board problem as older Potterton Suprima boilers were famous for this. It's a problem which affects the old style Suprima circuit boards not the circuit board which Potterton eventually, and belatedly, had re-designed by Siemens for the Suprima boiler.
The boiler we saw was in a garage, not enclosed in a cupboard. It clearly still had the old style circuit board, in fact one of the earliest circuit boards fitted to the Potterton Suprima, with a membrane panel which has to be pressed to re-set the boiler if it locks out. Occasionally we find Suprima boilers where the membrane panel has been pressed so many times that the plastic membrane carrying the word "Reset" has broken away. The "99" on the lower right of the data plate in the photo is a manufacturing year code.
We removed the screw (top left in the photo) which allows the control panel to flip down and inspected the board, expecting to find the classical darkened scorch mark which is typical of Potterton Suprima circuit boards of this type. This board showed only very slight darkening.
Re-setting the boiler by pressing the Reset panel (you can also isolate the power temporarily to reset it) we watched to see if it would lock out. It attempted to go through the ignition cycle 3 times before locking out. This indicated an alternative likely cause for the lockout, a failing ignition lead.
We looked to see which type of ignition lead this boiler carried. The early leads were composed of a graphite core formed round glass fibre thread and covered with a red, rubberised insulation. These are the Suprima ignition leads which give lockout problems. The later, more conventional leads (translucent plastic round a metal core), are fine.
The problem with the red leads is that the carbon breaks away. The ignition lead in the photo had cracks through the carbon but often the carbon just beyond the red insulation (between the insulation and the spade connector) breaks away, leaving just the glass fibre core with carbon particles clinging to it.
When the high tension current is sent through the lead to create the spark, the very high voltages (maybe 10,000 to 20,000 volts) enable the current to jump the gap in the broken carbon conductor in the same way as it jumps across the ignition electrodes. This lights the burner
The red ignition lead serves a second purpose. When the burner has lit, and only when it has lit, a small low voltage flame rectification current passes along the lead and is sensed by the circuit board. This current indicates the presence of a flame and the circuit board allows gas to continue to pass from the gas valve. If the flame rectification current is not sensed by the circuit board the board will shut down the ignition sequence and go through the process again, three times in all. If the presence of a flame is not detected within three attempts the boiler will go to lockout.
When the carbon conductor is broken or substantially cracked, the low voltage flame rectification current is unable to jump the gap in the conducting path and the circuit board is not able to sense the current. After three attempts it locks out.
The remedy was a simple, just a replacement new style ignition lead, and the boiler worked fine.
We suspect that the reason this circuit board (printed circuit board, pcb) has lasted so long is that the garage that houses the boiler is shaded and very cool and there is lots of free air round the boiler. In our experience these early boards have a shorter life span if not cooled well.
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Potterton Suprima 80 Boiler Fault
Potterton Suprima boiler repeatedly locking out, then would not re-set
When we looked at the boiler the red light only was flashing twice per second. The fact that this Potterton Suprima boiler refused to re-set either by pressing Reset or by switching off and back on the mains power supply to the central heating system suggested that this was not a Suprima ignition lead problem.
The boiler we saw was in a tight enclosed cupboard with no ventilation. It clearly still had the old style circuit board, again one of the earlier circuit boards fitted to the Potterton Suprima, with a membrane panel which has to be pressed to re-set the boiler if it locks out. The data plate carried a "00" year code indicating it was manufactured in 2000.
We removed the screw which allows the control panel to flip down and inspected the board, finding the classical darkened scorch mark which is typical of Potterton Suprima circuit boards of this type.
This board was one of the most scorched Suprima circuit boards we have seen. Interestingly, the customer had fitted this "re-furbished" board about 5 years earlier after his previous Suprima circuit board had failed. This board carried a 1997 date code.
Fitting re-furbished circuit boards is certainly risky and almost certainly illegal though we can understand the temptation given the excessive amount Potterton charge for the new Siemens designed circuit board.
We fitted the new circuit board designed by Siemens for the Potterton Suprima, complete with chassis and wiring loom. An expensive repair but the boiler worked fine.
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Potterton Suprima 30 Boiler Fault
Potterton Suprima boiler shuts down after 15 minutes, then "dead" for hours with no lights before working again
We've added this fault because the way it presented was unusual. Our customer reported that the boiler would fire normally in the morning for about 15 minutes before shutting down. It would then refuse to do anything at all for several hours, firing again in the evening. The programmer was calling for heat and showing red LED's for both hot water and central heating circuits. The room thermostat was turned up to maximum.
We expected to find an external control playing up, possibly a motorised valve but the customer reported that the boiler wouldn't fire for either heating or hot water when it went dead and there were no lights at all. We knew this would be one of the earlier Enertech circuit boards as the customer confirmed that the small black reset button was circular, not square. (The new Siemens circuit boards have a small square reset button.)
Since the boiler was in a "failed" state when we arrived we were able to find the fault very quickly. Despite neither a red or green light on the circuit board, the programmer showed two red lights so the main fuse for the heating circuit was intact. We turned the mains switch off and on again to see if it would reset the pcb but it didn't work. We could, however, hear a relay clicking on the circuit board.
With the power turned off again we removed the on board fuse from the pcb and checked it for continuity. It was not blown. We refitted it and powered up again but still no lights. Using a multimeter we checked between permanent live and neutral and found 238 volts, fine. Checking between switched live and neutral we again found about 240 volts. This guaranteed that the fault was the Enertech circuit board. Checking for live with a neon is not enough as you don't know whether you have lost the neutral return path. Using a multimeter between live and neutral proves that the neutral is OK too.
We changed the circuit board for the new Siemens board and the boiler worked fine. The reason we added a report on this boiler is because we'd never seen a Potterton Suprima pcb go dead with no lights at all; normally you end up with a flashing or fixed red.
It’s possible that fault-finding may not sort out your problems or that the repair costs mean you should consider having your Potterton boiler replaced. For a replacement boiler or a new boiler installation we would recommend Worcester Bosch. Given current regulations and the work involved, boiler replacement is never cheap but sometimes a new boiler installation is the best option.
Why are Worcester Bosch our first choice for boiler replacement?
Worcester boilers are well made and the quality seems consistently high. Their technical backup is very good. The warranties on Worcester boilers are good and we’ve found that Worcester spares are readily when needed. We hardly ever have to wait long for spares.
Potterton Suprima 40 Boiler Fault
Potterton Suprima boiler shuts down during ignition; flashes red 3 times per second (Siemens pcb)
This Potterton Suprima boiler was locking out during the ignition sequence or immediately after the main burner had fired. The PCB fitted to the boiler was the newer, Siemens model, with the square ignition re-set button. There was a red light flashing, 3 times per second.
The Potterton Suprima Replacement PCB Kit manual says that flashing red 3 times/sec indicates an air pressure switch (APS) fault or a flow switch fault. We opened the boiler up to check if a flow switch was fitted (sometimes called a dry fire switch) but there was none on this boiler. This left us with the APS or, logically, the hoses connected to it.
With the combustion case removed, the cause of the fault was obvious. The air pressure hose between the fan and the air pressure switch (APS) was kinked (see the photo). Straightening the air pressure hose resolved the problem and the boiler worked normally.
