biaisi combi cycling when timer off?

[Agile]

You remove four screws UNDER the PCB box and then it slides forward. You can pull out the sliding knob on the right from the groove to get the last cover screw off.

The three diagnostic LEDs are on the front left and the left green one is visible through the front panel.

To put it into diagnostic mode, move the right hand dip switch towards the front and then back.

Use the book to decode the sequence or very clearly describe to me what they are doing, on/off, flash together/alternate etc.

Tony

 

[jime17]

Hello Tony.

Had it in diagnostic mode.

3 leds. green red green. Left is visible through viewing window as you previously stated.

when heating on. the two greens flash together in sync on/off every second.

when hot water being called for they flash at the same rate, but alternately. ie not in sync.

sometimes when running hot water, leds stop flashing and right one becomes constantly lit and red middle one flashes at about 1 cycle per sec. this corresponds with the gas switching off and the water from the tap cooling. (I assume that this is because the water is being heated too much as when I turn the flow up from the tap, the leds revert to the green flashing and the gas fires up again)

this also happens sometimes when the ch is on.

The random firing seems to occur after the boiler has been fired up for a while (heating either ch or dhw) and is switched off. When the pump starts randomly the right hand green led glows and the middle red flashes. This only happens for maybe 1 sec as a rule and is in most cases not long enough for the gas to start flowing and the ignition to fire.

On the occasion I was watching this, I ran the hot tap for a while, then turned it off. Then after about 10 sec, the pump started for a sec and the right led came on constantly and the red led flashed. then the pump switched off the red led remained lit. then about 30 sec later the pump started again for a sec and when it switched off the only led on was the left green one which was flashing as is the norm.

does any of this make any sense?

cheers,

jim.

 

[Agile]

This indicates that the DHW NTC sensor is open circuit.

It sounds as if it is becoming o/c just when it gets hot.

I cannot explain why the boiler is coming on but thats probably under the influence of the built in frost protection, although the diagnostics are not showing that, but perhaps its a short transient as the fault in the NTC arises.

NTC should measure 10K-13K when hot falling to 2K-3K when hot.

NTC about £13 and easy to change after draining water from the boiler. before changing check the connector is not wet and slowly pull plug off and on a few times possibly with a little WD40 in case the connectors are slightly oxidised and not making proper contact.

Tony Glazier

 

[jime17]

Hi Tony.

Thanks for all your help. Changed the DHW NTC last night and seems to be working fine now touch wood.

I spoke to biasi service helpdesk the other day to run it past them (they agreed with your diagnosis) and they were very helpful. I had expected them to say that I shouldnt touch it and to let a registered biasi agent deal with it at great expense presumably.

Am I being a bit over sceptical or did I just get lucky and got a bloke who was having a good day?

Jim.

 

[Agile]

I am glad that its all OK now.

Dont know why you wanted to call the manufacturers though after I had told you what was wrong with it ! They only answer telephones and dont actually fix boilers! They are not even CORGI registered !

Tony Glazier

 

[jime17]

I didnt realise that at the time. Sorry I'll trust your every word next time. thanks again for your help.