Wed Dec 13th 2006 23:38:33: Potterton Suprima Boiler
Right I'm bored, so I thought I'd publish what I learnt when my boiler went wrong a couple of weeks ago...
I have a Potterton Suprima 60 Boiler and it seems they have a terrible reputation for reliability. Just search on Google for "potterton suprima lock out" and you'll see what I mean. The symptom that is mostly seen is the boiler going into reset mode randomly. There can be many things that cause this, however one of the main ones seems to be poor pcb reliabilty. When I removed the PCB out of my boiler I found dozens of blatantly dry joints (look for cracks in the solder, especially around the big pins of the connectors).
Anyway that is the general problem with this product, however it wasn't the problem I had! My problem was that the boiler would work fine from cold and would remain that way for at least 10 minutes (yay hot water!). Then it would start making an electrical hum (like you'd hear from a large transformer). This would gradually get louder and louder and eventually it was making a horrible rattling noise. The boiler would then cut out. It would try to relight 3 times (with varying levels of success), however it would always end up giving up and require me to press the reset button.
The first thing I did was "recondition" all the dodgy looking solder joints on the PCB and replace the Littlefuse MOV which looked like it had been getting hot. Sadly that didn't fix the problem. I then checked all the peripherals. From various forums on the web I found out the following:
These all checked out so I was a bit stumped. I then noticed that the windings on the Gas Valve were getting really hot (much much hotter than the surroundings). Therefore when my plumber visited a few days later I asked him to replace the Valve with one I purchased from http://www.keeptheheaton.com. Make sure you shop around if you are buying a new valve - I found prices ranged from £30 on Ebay to £100 from keeptheheaton.com to £160 at my local boiler spares place! Sadly I couldn't get it off Ebay as I needed it the next day so I had it for when the plumber was coming!
Since the valve has been replaced the boiler has been working perfectly again. My guess is that the insulation in windings was dodgy, and started shorting when energised. Hence a low voltage resistance measurement did not pick up the problem. Replacing the valve was pretty easy, however I would recommend getting a plumber to do it as a) it's the law (!!) and b) you need to adjust the burner pressure which is a screw on the valve itself which requires a U-bend thingy. Also the plumber can check you've not got a gas leak once the new valve is fitted by testing at the meter with the U-bend thingy.
If you think your PCB is dodgy, however don't feel happy to repair it yourself, then check Ebay for reconditioned ones or pay a visit to CET ltd. Their business is part exchanging duff PCB's with reconditioned ones. I understand replacement PCB's from potterton have been redesigned and will set you back a few hundred pounds. Apparently Potterton deny they have a reliability problem with their PCB's and will tell you that you are the first person to call them about it.
My thanks to the poeple on the uk.d-i-y group for their advice! If anyone has any experiences or comments on this subject, feel free to email me or leave a comment below.
UPDATE 6/2/07: My parents rang me tonight to tell me to turn the TV on quick - BBC Watchdog were doing a piece about how unreliable Poterton Suprima Boiler PCB's are and how Potterton refuse to accept there is a problem with them. So much of their piece rang true from my experiences that it was scary!!