Boiler repair gone wrong
- Thread starter duffy78
- Start date
Sponsored Links
I'm just going to put the kettle on 
hi all,
thanks for the comments.
i was very gentle with the aps, didnt disconnect it, only removed the air hose from the venturi and gently, very very gently blew into it to see if it was stuck open as someone said it might be.
where i am at present is i think the pcb is at fault. i have disregarded what the plumber said as i think it is biasing my fault finding. i got the fault finder diagram from the si and started from scratch.
I ignored all the gas checks as i dont really want to be messing with any of that side of it and concentrated on the electrics, whilst fault finding i found the following to be true, there is 240v at the switched live from the programmer. There is 240v at the 3 way switch and then from there at the hi and low thermostats, the thermostats are both fine with 240v back to earth at both terminals. there is 240v at the pcb live connection, there is nothing at the fan terminals. i have checked the wiring flow diagram and also traced the wires through the boiler and on the back of the pcb to see what is in sequence for the ignition to happen.
i think it is as follows, call for heat comes, 240v goes to boiler over heat stat, switch is closed if boiler is not over heating, then next inline is the fan, fan spins up and thus closes the aps, this switch then sends 240v back to the pcb which then goes to the ignition side of the pcb and the boiler ignites.
in my boiler when the call for heat comes the boiler over heat stat does not have 240v across or at either terminal. i have tested and the stat is ok. The pcb circuit board does not have 240v across or at either of the boiler over heat stat points. therefore i think there is some fault in the pcb in relation to the boiler over heat stat part of the sequence.
to test my theory i put 240v to the boiler overheat stat and the boiler fired up.
I have ordered a replacement pcb, i thought it cant hurt to spend £120 to try and save £1600.
i will report back how i get on.
thanks for the comments.
i was very gentle with the aps, didnt disconnect it, only removed the air hose from the venturi and gently, very very gently blew into it to see if it was stuck open as someone said it might be.
where i am at present is i think the pcb is at fault. i have disregarded what the plumber said as i think it is biasing my fault finding. i got the fault finder diagram from the si and started from scratch.
I ignored all the gas checks as i dont really want to be messing with any of that side of it and concentrated on the electrics, whilst fault finding i found the following to be true, there is 240v at the switched live from the programmer. There is 240v at the 3 way switch and then from there at the hi and low thermostats, the thermostats are both fine with 240v back to earth at both terminals. there is 240v at the pcb live connection, there is nothing at the fan terminals. i have checked the wiring flow diagram and also traced the wires through the boiler and on the back of the pcb to see what is in sequence for the ignition to happen.
i think it is as follows, call for heat comes, 240v goes to boiler over heat stat, switch is closed if boiler is not over heating, then next inline is the fan, fan spins up and thus closes the aps, this switch then sends 240v back to the pcb which then goes to the ignition side of the pcb and the boiler ignites.
in my boiler when the call for heat comes the boiler over heat stat does not have 240v across or at either terminal. i have tested and the stat is ok. The pcb circuit board does not have 240v across or at either of the boiler over heat stat points. therefore i think there is some fault in the pcb in relation to the boiler over heat stat part of the sequence.
to test my theory i put 240v to the boiler overheat stat and the boiler fired up.
I have ordered a replacement pcb, i thought it cant hurt to spend £120 to try and save £1600.
i will report back how i get on.
i am due back in blighty in a couple of weeks
e mail me if you want an unbiased opinion (e mail in profile)
alright smoggy
e mail me if you want an unbiased opinion (e mail in profile)
alright smoggy
Sponsored Links
its a 3 switch mate. i think the aps gets its power at the same time as the fan. the boilerover heat stat comes before them both in the wiring flow diagram.
i think the stat is ok as there is continuity across it with the terminals removed. what it doesnt have is any voltage going to it when the call for heat comes. i removed the terminals from it and tested for continuity and the wires are ok. i then went back to the pcb and checked across the terminals there and again there is no voltage there. hence me thinking the pcb is at fault.
Before going to the expense of replacing a boiler PCB its most cost effective, and essential if repairing boilers commercially, to eliminate external devices first.
All you have done to the APS is to blow into one of its tubes. That checks nothing.
What you can do ( but shouldn't really ) is to disconnect the common and measure the contact resistance between common and NC and when blowing towards the +ve air tube, common and NO. In each case it should be less that one ohm.
If the APS did check out OK then you could follow the PCB circuit back from the o/h stat to see where it gets its power from. There may be a relay with an OC coil or badly oxidised contacts.
Tony
All you have done to the APS is to blow into one of its tubes. That checks nothing.
What you can do ( but shouldn't really ) is to disconnect the common and measure the contact resistance between common and NC and when blowing towards the +ve air tube, common and NO. In each case it should be less that one ohm.
If the APS did check out OK then you could follow the PCB circuit back from the o/h stat to see where it gets its power from. There may be a relay with an OC coil or badly oxidised contacts.
Tony
N
namsag
And of course we believe therre is an RGI looking at this boiler and the guy is not doing it all himself
hi.
it was the pcb. replaced it and all is well.
thanks to everyone who posted on the thread, i've thanked you all individually as well.
regarding all the "you're not a rgi, you're just diy" I intentionally stayed away from all the gas workings of the unit. Before going near any of the other parts i spent a bit of time researching them so as to not cause any damage to the unit or any undue risk to myself. I spent 2 years studying electronics at college so about 10 years ago i would have been able to interegate the circuit itself and wouldnt have just replaced it. Therefore i considered myself more than competent to look for any damage in the loom, which of course led me to the final conclusion of replacing the board.
thanks again. top site.
it was the pcb. replaced it and all is well.
thanks to everyone who posted on the thread, i've thanked you all individually as well.
regarding all the "you're not a rgi, you're just diy" I intentionally stayed away from all the gas workings of the unit. Before going near any of the other parts i spent a bit of time researching them so as to not cause any damage to the unit or any undue risk to myself. I spent 2 years studying electronics at college so about 10 years ago i would have been able to interegate the circuit itself and wouldnt have just replaced it. Therefore i considered myself more than competent to look for any damage in the loom, which of course led me to the final conclusion of replacing the board.
thanks again. top site.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
