Baxi System / Potterton System pcb schematic Diagram

philthyballs · 6 Aug 2015

I drew this diagram to Repair this pcb board . Its a Baxi system Boiler but also a Potterton system boiler .Here it is if anyone needs it ..
I will upload this again with all components labelled on schematic.
There is a few different boards updated designs for this boiler I will upload these also.

baxi system pcb schematic 2.9 export 1 .png

This Pcb had open circuits on some tracks that where completely invisible.
Only when i used the Diagram i found the open tracks.
I,ve Repaired a few of these boards since then and found its usually the 230v side thats failing .Solder gone bad,capacitors, the big Resistors or Relays failing .

Sam Gangee · 6 Aug 2015

Excellent, thanks. What was wrong with the board?
I understand that the electrolytic capacitors usually fail.
http://www.satcure.co.uk/accs/low_ESR_capacitors.htm#heating

bernardgreen · 6 Aug 2015

The necked down ( thinner ) track to create a "fuse". If it has to be repaired use a single strand of wire as, depending on the thickness of the copper, that track is "equivalent" to a fuse between 3 to 5 amps maximum

The large pads to take the static weight of the mains transformer compared to the minimum sized pads ( in the black rectangle ) for the pins of the connectors which will have to withstand the vibrations that the cables bring the to PCB. It is no wonder the solder joints or the PCB track around those pins fail so often.

Sam Gangee · 6 Aug 2015

Interesting. I would repair the "fuse" track with thick wire and connect an in-line fuseholder externally as shown. This allows the use of a specific value fuse (e.g. 3, 4 or 5 Amps) and facilitates easy checking and replacement in the future.

As for the transformer, in similar equipment it's common to see a cable tie passed through two holes to secure it.

FiremanT · 7 Aug 2015

This is all a bit above my head - but I'm fairly sure it constitutes adapting a safety critical part.

Sam Gangee · 7 Aug 2015

Well it might but at least my method ensures that the fuse value is known and won't cause a fire whereas the "replace track with piece of thin wire" doesn't - not that it's any worse than the original design.

If I were called to court as Expert Witness, I know which method I'd choose. (I would also criticise the manufacturer for using a PCB copper track as a fuse - a cost-cutting design that could have serious consequences - such as encouraging someone who doesn't know better to repair it with wire. In addition, there is an ISO standards requirement to label the value of any fuse.)

Vic Spanner · 7 Aug 2015

That P.C.B (248074) was supersede by 5112380 a long time ago. Be careful what you wish for.

Agile · 7 Aug 2015

A fuse is there to protect the supply from overcurrents caused by faulty components somewhere.

If the fusible track has blown its because of an over current on the fan or pump or whatever it is supplying.

Better to concentrate on the cause of the over current.

I have never seen that track blown on any boiler ( yet ).

philthyballs · 8 Aug 2015

As Baxi customer support said this is the first pcb board(248074) produced for this boiler.

The new Board Baxi has produced is upgraded version from trial and error and would be better board.

One thing i have noticed of the new pcbs board 5112380 is that the Pcb Board checks the water flow switch twice before it will continue the firing up sequence which has Cought out me and a a lot of heating engineers .

Theres no mention of this in the new pcbs Notes.

In saying this ,In my opinion Baxi is one of the Top Boiler Manufactures And I recommend these Boilers over all other Manufactures .

Just giving my 5 Cents .
phil

Dan Robinson · 8 Aug 2015

philthyballs said:
Baxi is one of the Top Boiler Manufactures

bernardgreen · 8 Aug 2015

Fusible tracks can be designed in as a last ditch means of protection to equipment. It is considered OK to use them in the main supply line when there is the risk of an external fuse being changed for a higher amperage to stop the fuse blowing on transient faults. But this necked track ( assuming it is necked to act as a fusible track ) isn't protecting the whole board.

Agile · 8 Aug 2015

philthyballs said:
One thing i have noticed of the new pcbs board 5112380 is that the Pcb Board checks the water flow switch twice before it will continue the firing up sequence which has Cot out me and a a lot of heating engineers .

phil

Surely it is a continuous check that the flow switch is made? So that if it fails during firing the burner is cut off?

Tony

Gasguru · 8 Aug 2015

Don't we sometimes see melted venturis on these models? perhaps because of a failure to check primary flow.

philthyballs · 11 Aug 2015

Agile said:
Surely it is a continuous check that the flow switch is made? So that if it fails during firing the burner is cut off?

Tony first the water flow switch needs to be in the open position Boiler powers on the pump turns on for around 5 or so seconds (switch closes) then the pump stops where the switch must disengage then pump starts up again and the flow switch engages again .only then the boiler continues the firing sequence .

Baxi must want to be sure that the Boiler does not fire up without a flow of water in the heat exchange.

I had 3 pcbs there all coming up with pump fault indicator spent a few days trying to find a fault on all these boards when there was none . it was the flow switch rubber diaphragm just gone stiff.

baxi doesn't mention this in the replacement pcb Notes .

Cought me out ,And all them pcbs boards where from RGIs thinking there faulty .

Sam Gangee · 12 Aug 2015

philthyballs said:
it was the flow switch rubber diagram just gone stiff.

Were you able to sketch out a new diagram?

diynot

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Baxi System / Potterton System pcb schematic Diagram

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