my bad Biasi Boiler

[Pumpsnip]

Hello Everyone,
Im new to this so please excuse my ignorance.
Our Biasi Prisma boiler is playing up!! The heating turns off and the red light comes on. sometimes it can stay on for hours and other times cuts out after 20 mins. If I turn it off and on again and press the button the red light goes out and it starts up again. But sometimes the red light wont go out and it wont fire up again and I have to turn it off and give it a rest for half an hour or more before giving it another go. Im assuming this is related but when running the hot water for any length of time (bath or shower) it also turns on and off. It will be hot for 20 seconds and then cold for the same before heating up again and sometimes cuts out completely as mentioned before. At which point I have to get out of the shower to press the button once again, shampoo in eyes and praying for it to fire up again.......nightmare!
I dont expect to ba able to fix this problem myself, but thought before I call for help Id at least have a crack at figuring out what the problem is.
PLEASE HELP!!
Tim

 

[twgas]

the water running hot-cold-hot-cold.... is normally due to dirt in the plate (domestic hot water) heat exchanger. the lock out light may be the result of overheating caused by poor circulation which is, very often, caused by the same dirt. you may well need a system clean and replacement plate heat exchanger.

 

[Boilerman2]

Oh! and all Biasi boilers are bad, not just yours!!

 

[caltrad]

If looked after, Biasi boilers are fine. No worse than a lot of other brands..

Did u resolve the issue? If not, I think it's the DHW temperature sensor or cabling to it has gone intermittent.

What happens is the sensor develops a fault such that it tells the control board that the water is cold. The boiler then fires up until the overheat cut out is triggered. The burners then cut out and the boiler cools down, the overheat cut out re-sets and the cycle starts again.

A new sensor will cost you about £8 and 20 minutes to fit. Remember to isolate and drain the boiler first.

 

[Mikefromlondon]

Biasi boilers are ecconomical and fairly reliable boilers, of course you get what you pay for, but i have seen some of the expensive ones failing, so there is no argument about this, remember murphy's law.

Your problem with red light coming on can be due to boiler failing to light up, may need looking at the HT circuit area (Spark module/circuit) and the ignition probes, remember, the new high efficiency boilers all have no permanent lit pilots, so they rely on burner lighting up each time the heat is required, when you are using heating, at some stage the radiators will have reached the set temeperature and the room state or the flow temperature sensor would shut the burners down completely. Bad or faulty spark probes can often start one minute and next minute they won't, so this could be likely cause of your problem as well as any overheating in the domestic heat excahnger or main heat excahnger due to flow problems. All needs to be checked and elliminated from diagnoses.

having said that, most boilers regulate the heat output by modulating the gas valve, so how much flame is being produced and what are the flow temeperature settings are, but it will reach a stage where the burner would cut off completely, and when it must re activate, then the ignition starting sequence starts all over again, and if the ignition fails to light the pilot then the boiler will shut down with a red warning light coming on.

On one Biasi boiler the fitter did not put the covers back on the electrical circuit compartment, because the place was still being refurbished, he left the covers off because he still had some wires to connect from the room state, but it had been working to provide heating for the workers using a loop in the room state terminals, it was a brand nerw boiler, but a mice had got in and done a piddle around the HT circuit, which made that new boiler come up with a red light each time an attempt was made to re-ignite it. The mice piddle had shorted the HT tarcks and caused the spark to jump across tracs rather than at the probes! The mice piddle did not evaportae for days but became a thick wet sticky substance and continued to stop the boiler from re-igniting, once the piddle was washed and the board dried and refitted all was well!

So most problems occur due to incompetent work by others and it is not the boiler itself.