Baxi solo 2 PF30

[bster]

On the job today we went to replace the PCB on the boiler, but still the boiler would not fire - (the pilot LED flashing fast),

checked polarity,
wires from PCB to gas valve - all connected\continuity
phoned Baxi and tech help said measure the resistance across the gas valve, pilot side and main valve side, he said should be 1.5mohm and 5mohm respectivly. we did and the readings were 0 and 5.3 - tech help said new gas valve.

my questions are

what happens to the elctrical cable that allows the resistance to drop and why is it important in relation to general electronics and the gas valve.

what voltage does the pcb send to the gas valve?

The fan started and sparking commenced (but no gas) when neutral on the pcb was bridged to the orange (pilot side of gas valve) why is this (polarity is wrong)?

 

[ChrisR]

1.5mohm and 5mohm

I don't think I believe that. I'll find one and measure it.
Would have expected a few k ohms not M ohms! (like 1.4k and 2.8k)

 

[bster]

might of been k not M but defo 1.5 for pilot side and 5 for main valve (or whatever you call it).


edit - just checked my work/learning notes (yes i really am that dedicated or sad ) and yes it was K ohms.

 

[Rob]

On the job today we went to replace the PCB on the boiler, but still the boiler would not fire - (the pilot LED flashing fast),

checked polarity,
wires from PCB to gas valve - all connected\continuity
phoned Baxi and tech help said measure the resistance across the gas valve, pilot side and main valve side, he said should be 1.5mohm and 5mohm respectivly. we did and the readings were 0 and 5.3 - tech help said new gas valve.

my questions are

what happens to the elctrical cable that allows the resistance to drop and why is it important in relation to general electronics and the gas valve.

what voltage does the pcb send to the gas valve?

The fan started and sparking commenced (but no gas) when neutral on the pcb was bridged to the orange (pilot side of gas valve) why is this (polarity is wrong)?

sounds like pilot solenoid shorted hence the 0R through the coil.
would imagine its fed 24v from pcb.?

dont understand you cable resistance question, cables/wires provide a voltage and current. the varied voltage i.e for modultaion valves is varied via PCB

also why are you trying to bridge out a gas valve solenoid, sorry this is what it sounds like? reversed polarity affects most boilers when it comes to flame rectification

rob

 

[bster]

I wasnt bridging the solenoid - checking for voltage with a Fluke voltage\resistance tester (bridging probably the wrong word).

What i meant by the resistance thing was if the resistance is meant to be 1.5kohms and its zero why has it become zero STOP. i think i get it! - the resistance is caused by the solenoid coil and hence if its shorted then it has a clear path and hence zero resistance.

is this a new gas valve then or repairable?

 

[bster]

edit - wrong thread

but whilst i'm here if the pilot solenoid is faulty wouldnt the fan still start on a demand being created?

 

[ChrisR]

Yes it wouldn't stop the fan coming on.
If you used the meter on a high scale you might have read the mod coil as 0 ohms if it's only 50 or so.

 

[bster]

i read it with a 1-1999 Kohm scaled Fluke 140 tester thing

 

[geoff@cetltd]

Who said modulation valve ?

there is no modulation valve on a solo 2

OP - you need to sort yourself out wrt kilohms and megohms, it's not a trivial difference

as for

but whilst i'm here if the pilot solenoid is faulty wouldnt the fan still start on a demand being created?

yes the fan should start - which then operates the pressure switch, which then starts the pcb to open the pilot valve and generate the spark to ignite it

 

[Rob]

Who said modulation valve ?

i did

there is no modulation valve on a solo 2

i know

 

[bster]

remember im only an apprentice.

 

[geoff@cetltd]

Oh sorry, I forgot ...

CORGI

 

[Agile]

Yes, but he is something of an overactive apprentice!

If only he had got a GCSE grade of A or B in electronics then I would have considered training him myself !

Tony

 

[bster]

i'd slow you down with all my questions.....look out for Trivial Pursuit 'Bster Edition' this xmas - though there are no answers cards yet