Yet another Potterton Suprima question ...

[TheChump]

Hi

A year or so back I moved into a lovely home complete with a Potterton Suprima 80 boiler.

Yes, you know what's coming. Had the usual problems with it (having to press the Reset button every 20 mins), so I eventually bit the bullet and had the upgraded PCB installed. All fine for about a month, using hot water only coming on twice a day for 20 mins.

A week or so back, I thought I'd run the central heating, so switched that on - fine for a day or two, but then the dreaded red light (lockout) came back to haunt me. It now appears whenever I turn on either central heating or hot water for more than 10 or 15 mins.

Now, the installation manual states that if you press the reset button for 10 secs and release, you'll see a sequence of flashing lights to indicate what the fault might be. A sequence of 5 red flashes in 5 secs means the overheat cutout has kicked in. Fine, except I get 10 flashing reds over about 15 seconds - the sequence then halts for a couple of secs, then repeats itself. Needless to say the manual says nothing about a sequence of ten red flashes...

Does anyone know what the 10 flashes in a row means?

Also, any ideas what might be causing the system to lockout? The outflow pipe seems to get mightily hot, even with the boiler temperature set to the minimum, but I've not managed to find a way of measuring the temperature (it's meant to be 55c at its lowest).

The chap who installed the PCB suggested the heat exchanger might be clogged up, getting too hot and causing the cutout. Strange though how it worked fine for a good month before hitting a problem.

I've tested the thermistor and overheat sensor using the tests in the manual, and they appear to be OK.

Cheers.

 

[5544]

as a side issue, when you changed the PCB did you also change the temperature thermistor which is in the dry pocket. Manufacturers recommend that at the same time as the PCB. Do not have the manual to hand so would not be able to tell you what the light sequence means, but the Thrmistor does cause problems . i would spend a fiver and change that and see what happens.

 

[John Pederson]

are you an rgi?

let me thinka minute, flow pipe overheating then it locks out, hmmmmm
jp

 

[5544]

Yes I am registered. Yes I have changed a few o these PCB,s. And yes have discussed similar issues with the manufacturer who have recommended changing the thermistor at the same time as it can cause problems. This might have absolutely nothing to do with this fault, but still worth changing if not done.

 

[45yearsagasman]

I would have changed the thermistor and the overheat sensor with the pcb.
What should be checked before anything else is the temp rise across the heat exchanger and prove that circulation is correct. I've never changed a Suprima heat exch for being "clogged up". Do the basics.

 

[nickso]

Difficult for a suprima H/E to get clogged, the waterways are huge and it would sound like a steam train on full tilt long before it blocked.

As for changing thermistors and O/H stats at the same time as the PCB I think potterton are having a laugh here, it either works or it doesn't. I have changed several hundred Suprima PCB's, but only changed a handful of of thermistors and only one O/H stat. Pretty much the only thing that goes wrong with a Suprima is the PCB.

 

[5544]

would normally tend to agree, infact had that conversation with them. As it was, and sods law, when we did change the dry pocket thermistor after having exactly the same circumstances as this, it solved the problem. we put it down to a dodgy connection between the two strands that are joined together at the tip. probably a one off. do agree that this is normally always the pcb, but £5.00 is cheaper than £150.00. as bizarre as it sounds, i really like these boilers.

 

[TheChump]

Chap changed the thermistor and overheat sensor - made no difference, still getting lock out. Changed the PCB...and so far all's well four days later.

The clue apparently was in the solid red warning light coming on, though we never got to the bottom of what the 10 flashing reds meant when the reset button was depressed for >10 secs.

Anyway here's hoping the new PCB continues to do the job.

Cheers.

 

[Agile]

5544, did it not occur to you that you should have questiones that the OP was apparently opening the combustion chamber which a DIYer should never do?

The salient test is to accurately measure the flow and return temps to see why it may be overheating. Usually a blocked system or blocked or failed pump.

Those thermistors are dry pocket in the sense that they are not in contact with the water. But they rely on the pocket being filled with thermal transfer paste.

Most nupty boiler repairers dont even know this and dont carry the paste.

The first thing to do is to repack the pocket with new thermal paste. If this is not done then the repsonse time is very slow.

Tony

 

[ChrisOxford]

Most nupty boiler repairers dont even know this and dont carry the paste.

When I changed the 2 sensors on my old Worcester, I was amazed to find that each replacement came with a huge tube of RS (RadioSpares) thermal compound, of which about 1% was actually needed for the job. So even the meanest of repairers should have some knocking around.

 

[Agile]

You underestimate the nuptyness of some of those fixing boilers!

They would not even recognise it for what it is and would throw it away!

One of my ex-trainees called me about a problem with one of these boilers.

I explained that the NTC needed to be well surounded with paste. He would not accept this at first. Now you have to understand that he has an MSc and so is not that stupid. I persevered with my explanation of what I thought was probably wrong.

He called me back a few hours later with his pēnis between his legs!

My supposition had been totally correct!

Tony



PS the word "pēnis" is the latin word for "tail".

 

[ChrisOxford]

Scary stuff, Tony!