New PCB - could it be faulty?

[gazhogg]

My boiler (Baxi 105e) broke down a few weeks ago, so I changed the PCB. The other day, the boiler completely clicked off and then fired up again a few seconds later. It has never done this since. Is it worth taking the PCB back and getting a replacement?

Thanks for any help you guys can offer

 

[Agile]

I am assuming that you are not a boiler engineer or even CORGI registered!

When a PCB is changed its necessary to check and adjust the gas settings on the boiler. I assume that you did not do that! In the worst case the boiler could be dangerous.

Because people cannot be trusted to know how to handle or fit PCBs they are not normally returnable! Sometimes a failed PCB is replaced with a new one only to blow immediately because there was an undiagnosed faulty pump, gas valve or fan.

Tony

 

[Balenza]

Agile wrote

Sometimes a failed PCB is replaced with a new one only to blow immediately because there was an undiagnosed faulty pump, gas valve or fan.

Why is the pcb not protected by relays ?.
So when a pump goes faulty or any other component for that matter or when an electrician wires something incorrectly a simple and cheap £1 relay blows instead of an expensive controller.

 

[ChrisR]

Why is the pcb not protected by relays ?.

Because it tisn't part of the design requirement that the pcb is FOOL proof.
Even if it were, relays are not protection devices per se. Take too much current and you weld or damage the contacts.

There's nothnig on a pcb which costs very much - more than £1 say, so it makes little difference what it is. Components are often damaged by incorrect connections far quicker than a fuse could protect them.

 

[Agile]

Why is the pcb not protected by relays ?.
So when a pump goes faulty or any other component for that matter or when an electrician wires something incorrectly a simple and cheap £1 relay blows instead of an expensive controller.

Why should the manufacturer not take advantage of an incompetent electrician to sell a new £120 PCB rather than design a more expensive circuit to protect it from idiots?

Many of the Baxi/Pott circuits use resistors which are designed to blow if subjected to an overcurrent. They would say thats to protect against overcurrents from a faulty gas valve or fan etc. Others might say its to sell a PCB as well if any other component fails!

Earlier Kestons had a fuse soldered onto the sealed PCB in series with the fan so that a stalled fan would make a sale of a PCB as well !

Tony

 

[micpwelsh]

gaz because you came here for help and not abuse il try to help you , i had the same problem with a pcb and it went on for ages and didnt break down ( a pcb is less hi-tech than a £4.99 wrist watch its not complicated )
, if its only done it once dont worry and if it breaks down dont repair it your self just call a plumber and wait in for 86 or more hours for him to come

 

[Balenza]

ChrisR wrote

Even if it were, relays are not protection devices per se.

Then why do controls engineers who manufacture custom built electrical panels use relays wholesale on their products ?
The onsite electrical engineer then wires everything back to the relay circuits.

 

[micpwelsh]

Gaz i just chatted to a mate have you reset the boiler after you changed the pcb ?

 

[gazhogg]

no i didnt should i have ? . agile were do you buy your pcbs ? £120 ? the one i got only cost £85

 

[namsag]

mcpwelsh, as you had trouble understanding how to locate thermostat knobs on your board i take it you must struggle setting your far more complicated watch
Gazhog it is not unusual to get a glitch on these boards which is part of the reason they have a reset knob on the boiler... So see what happens over next few weeks

Boards still come with a gtee providing an additional problem does not blow them and not heard of any fan or pump blowing a 105 board..
And the gas pressures on this boiler would not change by renewing the board

 

[micpwelsh]

gaz he knows what hes talking about trust me or rather trust him lol . and agiles pcb is more expensive because maybe its the mark up price maybe

 

[gazhogg]

Thanks for your help namsag and micp , i was starting to worry about gas settings after what agile said , anyway ty i feel better now . 1 last thing what would a plumber charge to change a pcb ? and is british gas cover worth it ?

 

[Slugbabydotcom]

The other day, the boiler completely clicked off and then fired up again a few seconds later.

It did this only once and you want to take the PCB back! I bet you would have fun trying now its been fitted.

Theres a load of causes for that from someone turning a tap on for a second to a faulty sensor, an APS or fan/ flue fault, power supply problem or even a freak gust of wind.

As Tony implies If you haven't checked the parts that could take out a PCB then you could be on your way to blowing another one. I'm not on your case for DIYing it, you have accomplished the mission of being 'warm for Christmas' and deserve a pat on the back IMO. I am just letting you know some of what you could be up against.

Gas settings on a 105e are done at the gas valve so unless you have done something really silly I can't see how it would be dangerous for you to change the pcb on this particular boiler.

 

[Corgigrouch]

Every now and then I do like to check out the boards that I have replaced and find out why it failed... I would say that in about 85% of cases it is the cheap and nasty relays that have failed, so adding more relays would only help in the sale of new circuit boards..

Yep the circuit boards are more simple than the average digital watch and just as cheap to make but they are also unique to the application and designed to be so.. It is the way that the boiler manufacturers get to make money... Making a board in China or where ever for a fiver and selling them for whatever the accountants think that they can get away with. if the gas man decides to sell at full retail then that is only fair.. Would you expect to walk in to ASDA and buy your stuff for what they pay for it?

 

[Agile]

The reset is only needed immediately the new PCB is fitted if it does not work at first.

As stated they sometimes give random lockouts during the first few weeks.

The gas settings should be checked and readjusted when a new PCB is fitted to ensure the boiler is working correctly. Its particularly important on that model because many lockouts arise as a result of the minimum gas setting being too low. The CH maximum power should also be set to match the system,.

Tony