Baxi bahama not heating
- Thread starter tws750
- Start date
well it doesnt fire, and it doesnt sulk, well not temporarily anyway.
for hot water the dhw switch works just fine, and removing the actuator makes the ch switch work.
Other than that, on CH demand nothing works, pump doesnt start and burner doesnt fire.
So whatever it is that starts the pump cant be working.
Unfortunately it looks like i have all the right inputs, but no output to the pump. And the bit in the middle is the pcb.
I guess i could connect an external supply to the pump, ie bypassing the pcb and it would work. No worse than a constantly running tap, but maybe i wont.
for hot water the dhw switch works just fine, and removing the actuator makes the ch switch work.
Other than that, on CH demand nothing works, pump doesnt start and burner doesnt fire.
So whatever it is that starts the pump cant be working.
Unfortunately it looks like i have all the right inputs, but no output to the pump. And the bit in the middle is the pcb.
I guess i could connect an external supply to the pump, ie bypassing the pcb and it would work. No worse than a constantly running tap, but maybe i wont.
tws750 said:
yes sounds like a pcb fault, i'm just saying that if the dhw flow swich is sticking in the closed circuit temporarily after a hot water demand that will prevent anything from happening in ch mode and the boiler will go into a 10 minute sulk mode.
It appears the dhw switch is behaving itself. (am i the only one never to have needed to replace one??)
As for the thermistor, ive swapped the connections and there is no difference. However, the resistance measured is off the scale (2.3 Mohms) on a hot pipe. Hot because ive had the tap running to get some heat in here.
So it would appear this could well be faulty, but given the scale in the manual this would indicate a water temp of well below 10 degrees so if its function is to monitor whether the water is hot enough, in its current state it would be asking for heat. (????)
(10 deg= 19900 ohm, 100deg = 680 ohm)
As for the thermistor, ive swapped the connections and there is no difference. However, the resistance measured is off the scale (2.3 Mohms) on a hot pipe. Hot because ive had the tap running to get some heat in here.
So it would appear this could well be faulty, but given the scale in the manual this would indicate a water temp of well below 10 degrees so if its function is to monitor whether the water is hot enough, in its current state it would be asking for heat. (????)
(10 deg= 19900 ohm, 100deg = 680 ohm)
If your pump isn't running don't worry about the thermistor, that will only come into play after the flow switches and pump, ie demand, check dhw flow switch open circuit, power to pump, main flow switch goes closed circuit, thermistor then ignition.
NTC sensors work 'back-to-front' so that resistance goes DOWN as temperature goes UP.
If you're seeing high resistance with the sensor hot, it's broken. But if this really is the CH sensor, in CH mode the boiler should fire up, run until overheated (because the sensor stays at high resistance) then cut out on the limit stat. But that's not what's happening. Anyone know: does this boiler have a 'sanity check' for open-circuit sensors?
If you're seeing high resistance with the sensor hot, it's broken. But if this really is the CH sensor, in CH mode the boiler should fire up, run until overheated (because the sensor stays at high resistance) then cut out on the limit stat. But that's not what's happening. Anyone know: does this boiler have a 'sanity check' for open-circuit sensors?
looks like the pcb then, everything except the thermistor seems to check out.
Not sure why the CH flowswitch should operate on 5vdc when the DHW gets 19vdc but i guess thats irrelevant as they both work.
Pressure switch? or does this come into effect after the pump and ignition and therefore causes shutdown. In which case its not that.
Pump works on HW so again its not that.
timer and roomstat seem ok.
Short of any other inspiration, and thanks to all so far, i think i'll be looking for a pcb tomorrow. Oh and a pressure gauge cos i've upset mine and now its dangling above a bucket!!
Not sure why the CH flowswitch should operate on 5vdc when the DHW gets 19vdc but i guess thats irrelevant as they both work.
Pressure switch? or does this come into effect after the pump and ignition and therefore causes shutdown. In which case its not that.
Pump works on HW so again its not that.
timer and roomstat seem ok.
Short of any other inspiration, and thanks to all so far, i think i'll be looking for a pcb tomorrow. Oh and a pressure gauge cos i've upset mine and now its dangling above a bucket!!
I would suggest that you isolate flow and return connections to the boiler , isolate electrical supply , drain water from boiler thro the internal drain valve and remove and inspect the condition of the c/h flow switch and spring .Ninety percent of the time , the fault which you describe , is caused by the c/h flow switch . Also , if you eventually have to obtain a new p.c.b. , try asking any of the regular guys on this site , I an certain they will be of help .
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tws750 said:
The hot water would use the pump flow switch so cant be that anyway
my moneys on the pcb
what version do you have honeywell or sit with the silent H
as it makes a big differance how the boiler works
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