Linea 28 keeps going to combustion mode error CO

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Max2020

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I have a problem with my linea 28, the engineer just replaced the Domestic hot water heat exchanger and the Main PCB (old one was fried).

The PCB was changed first and then it was intermittent cold and hot water, he suggested the domestic hot water heat exchanger be replaced which he did, everything ran fine for a day then it keeps going in to Combustion Mode error CO and has to be reset every 2 hours.

he has checked and the combustion mode knob is not stuck.

any ideas please?
Thanks
 
When he has fitted the replacement PCB the control knob is not located properly, it is 180 degrees out, and it is not combustion mode CO means control override , it ignores the thermistors to allow the boiler to run at full pelt , untill hi Limit cuts in, absolutetly nothing to do with combustion
 
ianmcd said:
When he has fitted the replacement PCB the control knob is not located properly, it is 180 degrees out, and it is not combustion mode CO means control override , it ignores the thermistors to allow the boiler to run at full pelt , untill hi Limit cuts in, absolutetly nothing to do with combustion
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Thanks for your reply, he did reopen the PCB to see the control knob(I am assuming it’s the black one that sits behind the white cap that can be screwed off). Or is it something else that I should tell him?

He pressed the black knob once with a screwdriver and the CO shows up on the screen, then he reset it but it’s appearing every 5-6 hours. When it appears the central heating goes full blown hot and there is no hot water.

Edit: I understand the control knob now, he never opened the control knob PCB he replaced the main PCB before the heat exchanger and it was working fine without errors but when he replaced the heat exchanger this error popped up?

when he did the replacement of the plate heat exchanger there was a leak and he refitted the new o rings, could that leak might have damaged the PCB behind the control knob? (Although it only happened for a few mins).
 
It does sound like a faulty PCB then, although never seen that fault except with the control knob being fitted wrong, what external controls do you have ?
 
So to put the things in order of repair/replacement

1. Main circuit board (everything worked fine after that but the water wasn’t getting very hot and the boiler was cutting out @39 degrees for hot water which then prompted him to change the plate heat exchanger).
2. Domestic hot water heat exchanger.
 
Sorry for being out of it.

The hot water is not working well and the radiators are getting very hot even with the switch turned to hot water only.

I have to turn the heating off from the thermostat to stop that from happening or turn the boiler off altogether.

when I switch on only hot water, the two pipes coming out of the boiler are getting extremely hot.

With no hot water running the temperature on the display reads 70 degrees even with CH off.

the PCB Was never changed (Sorry for using the wrong word earlier) the main circuit board was changed.

Any ideas ?
Thanks
 
PCB means printed circuit board...on this boiler you have 3 of them. The large main circuit board, a smaller ignition control board and a similar sized user control/display board.
What was the original problem with the boiler before it was looked at.
This is sounding more like a basic diverter problem and the pre-heat mode is heating up the radiators...pre-heat is whereby the boiler keeps itself warm 24/7 in order to give a quicker hot water draw-off.
If the diverter is playing up you'll have either continuous or intermittent heating even when hot water only is selected on the front.
Also be aware that the control knobs fail and don't always turn the spindles..
 
Gasguru said:
PCB means printed circuit board...on this boiler you have 3 of them. The large main circuit board, a smaller ignition control board and a similar sized user control/display board.
What was the original problem with the boiler before it was looked at.
This is sounding more like a basic diverter problem and the pre-heat mode is heating up the radiators...pre-heat is whereby the boiler keeps itself warm 24/7 in order to give a quicker hot water draw-off.
If the diverter is playing up you'll have either continuous or intermittent heating even when hot water only is selected on the front.
Also be aware that the control knobs fail and don't always turn the spindles..
Click to expand...
thanks for your kind reply,

the original problem was no power to the boiler and the guy suggested the main circuit board had fried and he installed a new one, then no hot water and CH worked fine. Hot water only worked if I twisted the knob for the hot water temperature very slightly and it gave hot water at 38 degrees. He then suggested the DHW heat exchanger was blocked and needed changing or servicing, he replaced that and it worked fine for a day then the boiler kept going in to CO (Control Override as I am being told now).
 
Max2020 said:
Hot water only works if I keep the hot water temperature at

thanks for your kind reply,

the original problem was no power to the boiler and the guy suggested the main circuit board had fried and he installed a new one, then no hot water and CH worked fine. Hot water only worked if I twisted the knob for the hot water temperature very slightly and it gave hot water at 38 degrees. He then suggested the DHW heat exchanger was blocked and needed changing or servicing, he replaced that and it worked fine for a day then the boiler kept going in to CO (Control Override as I am being told now).
Click to expand...
I forgot to mention there was a slight leak after he installed the DHW heat exchanger which was coming from behind the diverted valve, he fixed it after the leak was identified (almost after 30 mins). Could that have damaged the diverted valve and main circuit board again?
 
I guess you've lost confidence in the original "engineer" and from the sound of it he's not that great.
We don't really know what the original problem was and more problems appear to have been introduced by the multiple repair attempts.
Have you paid him?
 
Gasguru said:
I guess you've lost confidence in the original "engineer" and from the sound of it he's not that great.
We don't really know what the original problem was and more problems appear to have been introduced by the multiple repair attempts.
Have you paid him?
Click to expand...
I have for the first repair but I have bet for the rest. There is another guy coming and he thinks it’s a diverter valve issue and thinks the leak might have damaged the control knob PCB as well. As you rightly said about the “faith being lost” I just need to be sure by getting some information from here to match up with what he says.
 
Max2020 said:
I have for the first repair but I have bet for the rest. There is another guy coming and he thinks it’s a diverter valve issue and thinks the leak might have damaged the control knob PCB as well. As you rightly said about the “faith being lost” I just need to be sure by getting some information from here to match up with what he says.
Click to expand...
What you are calling the control knob PCB is actually called the display PCB, no matter though we know what you mean, I have never seen a water damaged one, only ones I have changed have been phsically damaged, by forcing in the control knobe in the wrong position, but yes your symptoms do point to that PCB somewhere, very easy to change
 
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