Suprima problem (not lockout)

[craig]

Hi,

I have a Potterton Suprima 80 which in the past has had all the usual lockout problems. I bought a replacement PCB from CET Ltd a couple of years ago and have had no problems since, until now. However, what I'm now seeing is different from the lockout problem I had previously.

The most common symptom now is that the thermostat will call for heat, the LED will flash green and the boiler will light as normal. However, after only a few seconds it will switch off again and the LED will revert to solid red. If I keep cycling the thermostat down then up to cause it try again it will eventually stay lit for a while (normally). Sometimes though, no matter what I do with the thermostat or power cycling the boiler etc it won't even try to light - the LED will remain resolutely solid red.

So, do you think that the PCB is playing up again, or are there other things I should investigate before ordering a new one? I don't know if it's relevant or just sod's law, but it is worse when the outside temperature is particularly cold (contraction of dodgy solder joints?).

Thanks,

Craig

[John Stumbles]

Green OFF and red ON indicates that the boiler isn't getting a call-for-heat from the controls. You need to check whether there really is a call signal - if there is one up to the boiler then either there's a wiring fault between the boiler's terminals and the PCB or there's a fault on the PCB (what do you expect with these cheap refurbs from that dodgy fella? ;-))

OTOH if it's going to green flashing 2Hz and solid red it's probably a circulation issue - pump or blockage.

[craig]

Thanks for that John - it's definitely solid red, which implies that it's not seeing the call for heat as you say. Do you know where I can get a schematic for this PCB, so that I know where to put a meter to see if it's getting that far? All I have at the moment is the 'Installation and Service Instructions'.

[geoff]

In message , craig writes

Do you have a red or black HT lead ?

If it's red, then "the boiler will light as normal. However, after only a few seconds it will switch off again" is a classic flame sense failure problem.

Otherwise, you could have a blockage or pump failure which means that the water isn't getting the heat out of the heat exchanger quickly enough, and it's going into overheat

If neither of these, ring me, the number's on the CET website, and I'll see if I can diagnose the problem

[geoff]

Ha !

[geoff]

You will never get a schematic for the pcb

All you can do is look at the interconnection diagram in the installation manual (which is what I presume you mean you have) and check that you have mains on the switched live when there is a call for heat

You do seem to be indicating that there is more than one fault here

[John Stumbles]

Wouldn't it go either into 16Hz flashing green trying to relight, or lockout?

AIUI you'd have solid RED accompanied by 2Hz flashing green in that case (boiler temp satisfied).

However I'm going by the codes I have for the Suprimas I've come across but I know that there's a different design of PCB. Do you know if it has different diagnostic codes? The codes I know are as below:

Suprima LED Indicators

NORMAL INDICATION

Green Red Status

OFF ON Mains ON Only

2Hz ON Ext. Call for Heat (Boiler set to STNDBY Temp. Cont set to 'O' Off)

2Hz OFF Ext. Call for Heat (STNDBY switch to ON Temp. Cont to Max.)

16Hz OFF Ignition (i.e. Gas & Sparks ON)

ON OFF FLAME Detected

2Hz ON Boiler Temp Control Satisfied

FAULT INDICATION ON 2Hz Blocking - Mains Freq incorrect or Air Switch Fault > 1 min. or Reset button held in to force a restart

2Hz 2Hz Earth Fault or Mains Reversal

OFF 2Hz Lockout

[geoff]

Well, er yes

What it actually does is spark 13 times, then stops turns the fan off, sequences again , and then a third time , then goes into lockout

I must be getting rusty

It's several years since I actually worked on one myself

I spend most of my time answering the phone and doing paperwork now, It's too dangerous for me to do bench work, as when I get called away to the phone, I might have forgotten to do part of a test, therefore, with certain exceptions, I don't go near a soldering iron anymore