I have a Suprima 70 which I suspect has a dodgy PCB. With the boiler stat set to about one third of maximum the boiler seems to run OK. If I wind it up to about two thirds it runs fine (sometimes for days), but intermittently I get banging from the boiler (water in it vaporising?). This seems to be worse when the boiler is only heating the HW but it does happen on CH or both as well. I have found that immediately after this happens (and I suspect just before), the pump has stopped running. I have confirmed with a meter that there is no power to the pump at this stage. The boiler does not lock out and will start up again with pump running after a minute or two. I have had the PCB out and inspected it with a magnifying glass and can see no sign of dry joints. Can I safely assume that the PCB is faulty or do the experts here have any other suggestions before I fork out the cash.
Another Suprima PCB query!!!
- Thread starter MacJ
- Start date
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Problem more likely to be poor plumbing layout, or slludge.
PCB probs don't usually cause overhating which you have. Could be temp sensor or slow/sludged pump.
Pump should run on when boiler stops hot - does it?
PCB probs don't usually cause overhating which you have. Could be temp sensor or slow/sludged pump.
Pump should run on when boiler stops hot - does it?
ChrisR
Pump has stopped after overheat, but I suspect that the pump stopping is causing the overheat. Difficult to find out for sure unless I sit by the airing cupboard for hours or even days!!! Pump runs perfectly fine otherwise. I am at home for a couple of days now so I will try to be more precise.
Pump has stopped after overheat, but I suspect that the pump stopping is causing the overheat. Difficult to find out for sure unless I sit by the airing cupboard for hours or even days!!! Pump runs perfectly fine otherwise. I am at home for a couple of days now so I will try to be more precise.
Turn a few rads off, put room stat up, boiler stat on max and it should all get effing hot. Turn room stat down, boiler should go out but pump should carry on until things cool down a little.
If it starts boiling while the boiler's still on (the pump WILL be on)then you have a circulation problem, or the boiler temp sensor's buugered. Check full of water eg at bleed point by HW cylinder inputs, and that there's water inthe header tank. Assuming it isn't a sealed (pressurised) system, that is.
I've forgotted the resistance of the sensor - someone remind me - or it's in the fine print on the partsarena.com\baxi site. Or is that a / ?
If it starts boiling while the boiler's still on (the pump WILL be on)then you have a circulation problem, or the boiler temp sensor's buugered. Check full of water eg at bleed point by HW cylinder inputs, and that there's water inthe header tank. Assuming it isn't a sealed (pressurised) system, that is.
I've forgotted the resistance of the sensor - someone remind me - or it's in the fine print on the partsarena.com\baxi site. Or is that a / ?
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I have done what you suggested ChrisR. Expansion tank has plenty of water. Turned off upstairs rads, set boiler to maximum, turned up room stat and ran heating for about 90 minutes. Everything got 'kin hot but boiler was fine. Turned down room stat, boiler stops but pump runs on. Switched CH off and HW on and the result was the same - no problem. I am going to leave the boiler on max and run the CH and HW normally and see what happens. However, sometimes it will run OK for a couple of days. This could be a long process!!!
Not sure if same boiler but,i went to potterton boiler last year which was playing silly buggers.Boiler would work o. k intermittently.Problem was the control panel was pushing against connector on pcb.Vibration was causing connector to bob about therefore causing boiler to work then not.If same boiler look for arcing on board whilst working.
fitz1 - thanks for the info I'll check it out, but could not see any heat damage on board when I inspected it last week.
Tonight's update follows!!!
CW and HW operating normally, with boiler set to max for about 15 minutes and then much crashing and banging from the system. I leg it upstairs to the airing cupboard and the pump is not running. Wait about a minute or so and it starts running again. I am pretty much convinced that the problem is that the pump is intermittently stopping, due to lack of volts from the boiler. Any further suggestions or similar experience would be very much appreciated.[/b]
Tonight's update follows!!!
CW and HW operating normally, with boiler set to max for about 15 minutes and then much crashing and banging from the system. I leg it upstairs to the airing cupboard and the pump is not running. Wait about a minute or so and it starts running again. I am pretty much convinced that the problem is that the pump is intermittently stopping, due to lack of volts from the boiler. Any further suggestions or similar experience would be very much appreciated.[/b]
have you got one of these ?
Is there a bypass on ur system and if so, is the valve cracked open slightly? Also should ur boiler be wired for pump over-run?Check instructions.
failing that check the valves the timer feeds the valves the valves feed the boiler
electrically that is
electrically that is
fitz1 and kevplumb - there is a bypass which is open quite a bit, boiler is wired for pump overrun, I am almost 100% certain that the timer is wired to valves and valves wired to boiler, but will double check.
The boiler is just over three years old and has been faultless since it was installed. Apart from replacing some rads well over a year ago nothing has changed with the system. The water in the system is clear, but there does sound like there is some air in the pipes, which I can't bleed via the rads or the bleed valve near the pump, however that air has always been in there (and wouldn't it just dissipate in the water when the pump runs).
As I said nothing has changed for well over a year, but suddenly this problem has occurred.
My thoughts are that when the boiler stat is up past a third of max, the boiler and hence the PCB is getting hotter and causing a malfunction which is stopping the pump running. Is this likely?
It would be much simpler if the bl**dy thing stopped working altogether!!!
Thanks for all your suggestions - keep 'em coming.
The boiler is just over three years old and has been faultless since it was installed. Apart from replacing some rads well over a year ago nothing has changed with the system. The water in the system is clear, but there does sound like there is some air in the pipes, which I can't bleed via the rads or the bleed valve near the pump, however that air has always been in there (and wouldn't it just dissipate in the water when the pump runs).
As I said nothing has changed for well over a year, but suddenly this problem has occurred.
My thoughts are that when the boiler stat is up past a third of max, the boiler and hence the PCB is getting hotter and causing a malfunction which is stopping the pump running. Is this likely?
It would be much simpler if the bl**dy thing stopped working altogether!!!
Thanks for all your suggestions - keep 'em coming.
MacJ - I have a 5 year old Suprima 50 which started intermittently doing the exact same thing about 2 weeks ago. Crash, bang, boiling water shooting out the vent pipe. The cause of the overheat was the pump not running, which on investigation appeared to be because of no power from the boiler. Inspection of the infamous PCB with a magnifying glass showed cracks in all the large soldered joints, especially where the pump live feed connects. I re-soldered these joints and the boiler has been OK pump-wise since. Too early to say if it's cured intermittent lock out as I normally only get that about once a month. Couple of years ago it was happening all the time, but I cured that with a spot of percussive maintenance!
On a serious note these faulty PCBs are dangerous. The vent pipe on my installation sticks out from the side of the house, and could have showered scalding water on anyone who happened to be underneath at the time.
On a serious note these faulty PCBs are dangerous. The vent pipe on my installation sticks out from the side of the house, and could have showered scalding water on anyone who happened to be underneath at the time.
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