VOKERA LINEA 28 EXPERT REQ !!!

[clarkerothwell]

Constantly running at 42 degs on domestic hot water

Boiler fires on high rate cuts to low rate, water remains at 42 degs
never cuts out

Both thermisters changed
New Plate h/exch fitted

Not passing down diverter to htg

Water tempt Dial set to max - not broken spindle

ANYBODY HAD THIS FAULT
????

 

[clarkerothwell]

been informed its the non return valve in the right hand manifold of the domestic heat exch - bloecked or broken, part number - 2908 in vokera manual.

 

[petit_pablo]

PCB has gone into anti scald mode.
Needs new board.

If the NRV was blocked/broken you woudnt get consistant HW temp and the boiler would short cycle.

 

[45yearsagasman]

Nice one PP. In all my time I've not had one do that.It's never to late to pick up useful tips.

 

[Agile]

I have never heard of that before!

Is it mentioned in the manual or a BG laptop tip?

Does Vok tech help know about it?

What does it mean anyway? Can you explain what this anti scald mode is and why its apparently a fault?

I wonder if DP knows about it?

I would have been doing a thermal survey and looking at poor heat transfer into the DHW.

Tony

 

[petit_pablo]

Vokera tech do know about it.

They explained it on the phone a while back as i had the same issue on a linea. Basically the board software is the same for uk models as the Euro models. Apparently its a requirement on the continent that they have a method of preventing scalding. If it gets stuck in this mode theres no way of getting it back out.

I suspect its coupled with the HW thermistor failing and the board reacting to that but ive no proof of that.

 

[clarkerothwell]

CORRECT !!! Yes. you are spot on, changed the board and it sorted it, after i was mis informed it was the non return valve, which was fine.

The domestic thermisister was faulty too, so your totaly bang on.

Thanks for the advice.

 

[Agile]

Pablo, is this know throughout BG or is it just something you discovered by accident?

Have you or anyone else tried hard to make the PCB revert to the normal mode?

Presumably there is some initialising method to lock it into this mode which the manufacturers use for the EU ?

Suspicious/mean me would fiddle the DHW thermistor to overcome the probem by adding a series resistor to make the boiler limit the temp to say 46° C instead.

Thanks for that useful tip! Most interesting thing I have heard recently outside of Japan.

Tony

 

[petit_pablo]

Tony - i came across it by accident. A few other guys had given up and bounced the job to me to fix. On the face of it, the boiler operates fine. It just modulates right down at 42c and sits there. Ive not found a way to get it reset but time isnt on my side working for BG.