Baxi Solo 3 PFL 50

nearlypastit · 15 Nov 2006

I am getting a chattering noise from the PCB area. This happens when the boiler has reached temp on either C/H or water. After the boiler switches off it will be ok for maybe 20 mins then the noise starts up. If I switch off the boiler at the stat the noise is still there. The only way to stop it is turn the power off at the switch. Would welcome any sensible suggestions.
I am a retired domestic appliance engineer (Bosch, Neff & Siemens).

Vic Spanner · 15 Nov 2006

nearlypastit said:
I am getting a chattering noise from the PCB area.

What power head on your motorised valve do you have,as certain ones can cause this fault on the P.C.B..New board normallay sorts it out

nearlypastit · 15 Nov 2006

Thanks for replying. At the moment I'm not sure about the motorised valve. If I am looking at the right component it is a Honeywell Type VR460IT. P.Max 60 M.Bar.
I thought the problem might be solved by fitting a new PCB but at a cost of £103 I wanted someone else's opinion.
I know it is difficult for you without seeing the boiler, just wanted an educated guess.

geoff@cetltd · 15 Nov 2006

poxi said:
nearlypastit said:

I am getting a chattering noise from the PCB area.

Click to expand...

What power head on your motorised valve do you have,as certain ones can cause this fault on the P.C.B..New board normallay sorts it out

and how do you work that out ?
there is no connection between the MV and the PCB

... capacitors

nearlypastit · 17 Nov 2006

What do you mean when you say CAPACITORS? Are the capacitors faulty or has something else caused them to fail? Do I replace the PCB?

HarrogateGas · 17 Nov 2006

raden said:
poxi said:

nearlypastit said:

I am getting a chattering noise from the PCB area.

Click to expand...

What power head on your motorised valve do you have,as certain ones can cause this fault on the P.C.B..New board normallay sorts it out

Click to expand...

and how do you work that out ?
there is no connection between the MV and the PCB

... capacitors

Of course there is....the orange wire will go directly into the switched live on the pcb.

He could be on the right track, Ive had this problem before when the mod pos valve was only sending about 190 votls to the pcb....it chattered more than the wife. Changing the mid pos valve sorted it.

If you speak to baxi they say to check this first.

Mike4 · 17 Nov 2006

I'd change the circuit board. They fail commonly on this boiler. Commonly enough for me to keep two in stock.

The comment about the power head on the MV is a red herring. The boiler doesn't care what make it is providing it is delivering a 240v 'call for heat' signal to the boiler. (Mind you I saw a Siemens MV yesterday only delivering 190v on the orange wire. Fooled me for a while!)

The gas valve on the Solo II/III sometimes buzzes annoyingly. This isn't what you mean is it? Use a long screwdriver as a stethoscope to listen to it.

Cheers, Mike

ChrisR · 17 Nov 2006

We had a discussion in this direction recently and I don't think it was resolved. The Orange wire should only ever get the chance of 0V or full mains on it, surely?
The grey wire can get a funny voltage back from the diode/resistors on the 3 port internals, but that doesn't go to the boiler.

Nearlypastit - the VR4xxx is the gas valve. The motorised valve is the water diverter valve, poss in the airing cupd or elsewhere.
Honeywell ones look like

this

Mike4 · 17 Nov 2006

HarrogateGas said:
Of course there is....the orange wire will go directly into the switched live on the pcb.

He could be on the right track, Ive had this problem before when the mod pos valve was only sending about 190 votls to the pcb....it chattered more than the wife. Changing the mid pos valve sorted it.

Haha so you've found the same then! Mine was really puzzling at first. A Suprima that started properly when DHW was calling for heat but stalled half way through the igntion sequence on call for CH only.

Neon screwdriver showed a call for heat present on the SwL terminal in both situations, yet the boiler started in HW but not CH. Measuring the voltage at the SwL showed up the difference, and was easily traced to the MV. I soldered in a new circuit board robbed from a new valve. Quicker than draining down as the head doesn't come off a Siemens dry like all other makes. (Stupid to make 'em like that or what?!)

Cheers, Mike

Mike4 · 17 Nov 2006

ChrisR said:
The Orange wire should only ever get the chance of 0V or full mains on it, surely?

Hi Chris,

Correct, but 'should' is the significant word.

I now know that Seimens valves are capable of delivering 190v out on the orange wire to the boiler. It 'should' have been 240v but it wasn't!

Cheers, Mike

HarrogateGas · 17 Nov 2006

ChrisR said:
We had a discussion in this direction recently and I don't think it was resolved. The Orange wire should only ever get the chance of 0V or full mains on it, surely?

this

Well you have two proofs here that is does happen......im not an electronics whizz to say how but it does and certainly sends the baxi pcb into all sorts of stragne things.

HarrogateGas · 17 Nov 2006

ChrisR said:
We had a discussion in this direction recently and I don't think it was resolved. The Orange wire should only ever get the chance of 0V or full mains on it, surely?

this

Well you have two proofs here that is does happen......im not an electronics whizz to say how but it does and certainly sends the baxi pcb into all sorts of stragne things.

geoff@cetltd · 18 Nov 2006

nearlypastit said:
What do you mean when you say CAPACITORS? Are the capacitors faulty or has something else caused them to fail? Do I replace the PCB?

I repair the pcbs

believe me, I have more of a clue than some here - yes your pcb is CORGI'd

nearlypastit · 18 Nov 2006

Can I just confirm what is happening with the boiler. The chattering starts when the controls are all set at off. No demand on the boiler to start for any reason. Would the orange wire have a supply at that point?
I am retired but still capable of changing a PCB (my Wife says that she will be the judge of that).
If the valve is at fault I don't think I will get involved.
Thanks for all your comments, suggestions etc.

Mike4 · 18 Nov 2006

nearlypastit said:
Can I just confirm what is happening with the boiler. The chattering starts when the controls are all set at off. No demand on the boiler to start for any reason. Would the orange wire have a supply at that point?
I am retired but still capable of changing a PCB (my Wife says that she will be the judge of that).
If the valve is at fault I don't think I will get involved.
Thanks for all your comments, suggestions etc.

The boiler should be off and silent when the external controls are set to 'OFF'. The next thing to do is to rule out an external controls problem by measuring the voltage on the 'call for heat' terminal on your boiler while the chattering is going on.

The terminal is labelled "SwL" on a Baxi Solo (IIRC). The voltage should be zero. (This is also the terminal to which the orange wire from the motorised valve is connected.)

Check the polarity of the permanent live supply into the boiler at the same time. Provide polarity is correct and SwL is at zero potential while the chattering is going on, then PCB failure is the only cause I can think of, and a new board will almost certainly fix it.

Cheers, Mike

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Baxi Solo 3 PFL 50

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