Baxi Bermuda random lockouts and a screaming She Devil

[pm1961]

Hi chaps, new to this so treat me gently please

I've got a Baxi Bermuda 45/3E in a completely conventional fully pumped 2 zone valve system.

At completely unpredictable/unrepeatable times, the boiler decides to lockout as indicated by the normally green neon on the PCB turning orange.

If either stat is calling for heat, the relevant zone valve remains open and the pump continues to run until SWMBO finds either there's no hot water left or she's freezing her bits off.

The cure is to turn off the mains, pause 2,3,4, and turn it back on and voila; it works again....... until the next lockout..... 1hr......1 day.....1 week away...........

It's had a new PCB and gas valve.

*The sensor that controls the boiler stat, the potentiometer and the gas valve solonoids all measure in tolerance. (edited to answer the next post)*

The electrical reset thing screams "PCB problem" to me. Have I been unlucky and got another duff PCB? Have I missed a trick somewhere?

Baxi won't talk to me because I'm not registered yet. I'm sick of ringing guys up who um and argh and don't convince me that they will do anything other than randomly change components hoping they get lucky....... at my expense.........

Does anybody have anymore detailed info on the PCB logic and lockout modes?

All help gratefully received. Thanks guys.

Paul

 

[Agile]

Thats odd, I did not even think that it had one thermocouple let alone two or more!

What is the "tolerance" for a thermocouple?

I dont understand why you think that you might have got "another duff PCB". Surely a brand new PCb in the manufacturers wrapping have a very high expectancy of being in good working order?

Tony

 

[pm1961]

..... The components that could be checked as in tolerance were ok. i.e. the thermocouple sensor on the boiler stat, the potentiometer that controls it and the solenoids in the gas valve..........

Tolerance as in its resistance in ohms at any given temperature was within the specs quoted by Baxi.........

The "new" PCB was bought as "New Old Stock" from a trader on fleabay........... draw whatever you want from that........

As I explained, because interupting the power supply works to get it going again my focus returns to the PCB. What is your take on it?

 

[Agile]

I still dont think your boiler has a thermocouple and in any case you measure their voltage not resistance!

Did your dogey "new" PCB look really new in a sealed wrapper?

Tony

 

[pm1961]

Shall we settle for a sensor that changes resistance with temperature?

A thermistor then?

PCB was in a manufacturers box and looked fine, as in, clean undamged with no obvious burn marks or scorching.

 

[Agile]

An NTC thermistor! That sounds much more likely!

Manufacturer's PCBs are usually sealed in a plastic bag to show if they have been tampered with. Warranty ends when you open the bag!

Tony