Biasi Riva Compact HE No longer firing...

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Hi,

Excuse the long post but hope to get as much detail in the first post :)

My son has a Biasi Riva Compact HE (model M96.24SM.C2) which was fitted nearly a year ago and has been running fine until I meddled :(

When it was installed there was no whole house thermostat so it relied on the TRV's in each room but it meant the boiler was always on an cycling and the cost of gas these days is a concern. Also it is in the airing cupboard which isn't easy for them to get to for changing the programmer.

From the manual I noted that a thermostat could be installed so I added a Centaurstat 7 day programmer. This was wired into the external controls panel by 2 wires to the inner and outer links. Removing the existing link. The boiler programmer was then switched to permanently on.

This worked fine for about a week but then they started having a problem with the boiler locking out which they didn't tell me but kept resetting. Now the boiler is dead.

I went to take a look last night and think I can see what has happened. When I pushed the control panel back into the boiler having wired the thermostat up one of the ignition electrode wires seperated at the joint.

The boiler has been running like this for a while and I have a suspicion that something in the ignition has been buggered as a result.

The boiler is currently doing the following.

Reset the lockout with it calling for heat via CH. The fan starts up and the circulation pump. The ignition electrodes start sparking and the gas does actually fire up and ignite. It burns for maybe 10-15 seconds before it all shuts back down again. Error lights are 2 outside green lights flashing. Middle light red and lockout light on. Manual suggests no ignition signal from the full sequence ignition device.

Kinda hoping it is just the flame detection electrode or has the wayward spark voltage made it's way to and destroyed the PCB?? Or has running it with one electrode disconnected done the damage? I measured the voltage on the detection electrode when it was firing up which showed .5V DC at peak. Is this normal? Any suggestions?

Thanks
Paul M
 
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ho ho ho :LOL:

you have cream crackered the pcb. the spark has to come back to the board by the correct path. most likely the spark have returned by the flame sensing circuit and spiked that part of the pcb.
had a tech bulletin about it a few weeks ago telling me to keep a eye out for incorrect wired spark wires


merry chrismas btw ;)
 
If you disconnect one ignition wire the supply becomes unbalanced.

Thats causes a very high voltage to be conducted through the burning gas to the flame sensing electrode.

This high voltage causes R39 on the PCB to go open circuit so that it no longer detects any flame.

However, in that case the flame should go out after just 5-6 seconds rather than the "maybe ten or fifteen seconds" you have quoted. In fault finding on boilers its essential to take exact measurements.

Tony
 
Thanks for the help and advice.

Engineer came today and replaced the main control board and it fired back up again. The electrode didn't need replacing. I did ask him about repairing it but he would only do a swap. I hung on to the old one just in case for future!

Cheers.
 
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R39 is just to the right of the ignition transformer and should be 1 Meg Ohm.

I expect yours is open circuit.

At about £158 its an expensive mistake for you to make.

It would have been better to have got a CORGI to do it for you!

Tony
 

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