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Vokera's fault finder is telling me to replace the PCB ...but many of the outcomes on this fault finder give that guidance...
I am of the view that a new PCB will NOT solve this issue. Unless it is a total coincidence with the fault following a drain/refill. I need someone who is very experienced at diagnoses here; I am really at my wits end. I am pretty good with plumbing & electrical work but have finally run out of talent. My patient and supporting family are now looking at a cold Xmas if I can't get this sorted. A long post but i've added all the detail I have.
The TL;DR
NOT getting 24vdc at 8.3 – 8.5 (NTC to APS terminals) but just 4.5vdc. Not sure why NTC is relevant at this stage (like this recent post) https://www.diynot.com/diy/threads/vokera-compact-he-29-brainstorm-help-needed.514908/
Full details:
Boiler: Vokera Compact 25 HE (B band).
I installed a Fernox Omega TF1 on return 22mm copper line near Combi. When I refilled, I started the system before full pressure reached (bad boy, I know) and somehow “broke” something - there was lots of sloshing, wooshing, and noises increasing in pitch. Since then have now tested a lot with the Vokera Compact HE installation and servicing manual and replaced/cleaned parts.
Current status of what works:
Pump:
When a heat or DHW request comes in, the pump starts. In subsequent drain/refills, I took off the pump, rotated it by hand, cleaned the fins a little. It easily took the system back to 1.5-2.0 bars (and systems hold pressure fine). Also there is 240v at the PCB connector. So I think it works well enough (and even if it was weak, how would this prevent fan from operating?).
The AAV:
I checked this (drained down) cleaned too aggressively & broke! and then replaced (this a.m. fr.plumber's merchant 24quid). Also when the system was drained down I topped up the expansion vessel back to 1.1bar (it looses 0.1 in a few weeks).
Water pressure switch and the condense pressure switches:
The next leg of “Boiler Ignition / Sequence of operation” (acc to Vokera) is 24vdc through white/black of water pressure switch then black/white of condense pressure switch. I think this is happening. Both items (the water pressure switch and the condense pressure switch) show continuity (i.e. switch=closed) 1.separately, 2.coupled (as they are on this combi) and 3.show continuity for each switch wire back to PCB connector. A further test to ensure it is neither water pressure not condense switch; I bypassed these component (jumped either side of the wires at the PCB connector) nothing further happens.
At this point the fan should come on. It does not.
There is zero voltage measured at PCB fan connector. If I jump across from a 240v live (brown), the fan starts just fine (but thereafter no ignition, presumably as PCB is not ready to call for ignition sequence).
From here, Vokera's Fault finder asks to check 0vcc and then 24vdc at CN 8.3 to CN8.5 (supply wire to the heat thermistor and supply wire to APS). I don't know how to check vcc on this board but moot as yes=”replace PCB” but no=next check (24vDC) and fail=replace PCB.
The APS shows infinity (no continuity) with wires disconnected (i.e. NO position) but at the PCB (whether on / off at mains) there is 17kOhms reading. The wires show full continuity and, so, read 17kOhms across the APS when wire re-connected normally.
What else can I do before running out on Christmas Eve and dropping 250 quid on a new PCB?? Can I bypass/dummy the NTC (I do not know how to check this). In a 2011 post, Tony talks about properly testing the APS “not measured on a high range” - what does that mean? Alternatively. can I repair the PCB?
Should I get a new boiler instead? House is small. DHW not used for showers (electric). Although we live in v.soft water area DHW heat exchanger is prob a bit clogged (running DHW cycles on and off, lessened by lowering DHW temp dial); unclogging this was the rationale behind Ferox filter. We might move house in a few years.
Really appreciate constructive thoughts here
Davie
I am of the view that a new PCB will NOT solve this issue. Unless it is a total coincidence with the fault following a drain/refill. I need someone who is very experienced at diagnoses here; I am really at my wits end. I am pretty good with plumbing & electrical work but have finally run out of talent. My patient and supporting family are now looking at a cold Xmas if I can't get this sorted. A long post but i've added all the detail I have.
The TL;DR
NOT getting 24vdc at 8.3 – 8.5 (NTC to APS terminals) but just 4.5vdc. Not sure why NTC is relevant at this stage (like this recent post) https://www.diynot.com/diy/threads/vokera-compact-he-29-brainstorm-help-needed.514908/
Full details:
Boiler: Vokera Compact 25 HE (B band).
I installed a Fernox Omega TF1 on return 22mm copper line near Combi. When I refilled, I started the system before full pressure reached (bad boy, I know) and somehow “broke” something - there was lots of sloshing, wooshing, and noises increasing in pitch. Since then have now tested a lot with the Vokera Compact HE installation and servicing manual and replaced/cleaned parts.
Current status of what works:
Pump:
When a heat or DHW request comes in, the pump starts. In subsequent drain/refills, I took off the pump, rotated it by hand, cleaned the fins a little. It easily took the system back to 1.5-2.0 bars (and systems hold pressure fine). Also there is 240v at the PCB connector. So I think it works well enough (and even if it was weak, how would this prevent fan from operating?).
The AAV:
I checked this (drained down) cleaned too aggressively & broke! and then replaced (this a.m. fr.plumber's merchant 24quid). Also when the system was drained down I topped up the expansion vessel back to 1.1bar (it looses 0.1 in a few weeks).
Water pressure switch and the condense pressure switches:
The next leg of “Boiler Ignition / Sequence of operation” (acc to Vokera) is 24vdc through white/black of water pressure switch then black/white of condense pressure switch. I think this is happening. Both items (the water pressure switch and the condense pressure switch) show continuity (i.e. switch=closed) 1.separately, 2.coupled (as they are on this combi) and 3.show continuity for each switch wire back to PCB connector. A further test to ensure it is neither water pressure not condense switch; I bypassed these component (jumped either side of the wires at the PCB connector) nothing further happens.
At this point the fan should come on. It does not.
There is zero voltage measured at PCB fan connector. If I jump across from a 240v live (brown), the fan starts just fine (but thereafter no ignition, presumably as PCB is not ready to call for ignition sequence).
From here, Vokera's Fault finder asks to check 0vcc and then 24vdc at CN 8.3 to CN8.5 (supply wire to the heat thermistor and supply wire to APS). I don't know how to check vcc on this board but moot as yes=”replace PCB” but no=next check (24vDC) and fail=replace PCB.
The APS shows infinity (no continuity) with wires disconnected (i.e. NO position) but at the PCB (whether on / off at mains) there is 17kOhms reading. The wires show full continuity and, so, read 17kOhms across the APS when wire re-connected normally.
What else can I do before running out on Christmas Eve and dropping 250 quid on a new PCB?? Can I bypass/dummy the NTC (I do not know how to check this). In a 2011 post, Tony talks about properly testing the APS “not measured on a high range” - what does that mean? Alternatively. can I repair the PCB?
Should I get a new boiler instead? House is small. DHW not used for showers (electric). Although we live in v.soft water area DHW heat exchanger is prob a bit clogged (running DHW cycles on and off, lessened by lowering DHW temp dial); unclogging this was the rationale behind Ferox filter. We might move house in a few years.
Really appreciate constructive thoughts here
Davie
