Biasi Riva Compact HW but no CH

[gregsy]

I have an M90E.24S Riva Compact, which I'm having a few problems with, the hot water is working fine but the central heating is turning on fireing up for a few seconds then switching itself off for a about 2.5 minutes before fireing up again for a few seconds then switching itself off this continues indefinately. I can feel the hot water just about reaching the input of the first rads but thats about it.

So far I have purchased a thermistor and swpped out both the CH and HW thermistors in turn but this made little or no difference, I have also changed the main PCB as these were the stepped advised in the service manual fault diagnosis table but the fault still remains. The CH system has been apart as I have fitted three radiators and also bled the boiler down twice when fitting the thermistors.

Where do I go from here, I'm thinking Diverter valve or possibly the pump. (Ive heard you can get hot water flow without a working pump on some boilers due to mains pressure)

I was going to unscrew the screw at the front of the pump and see if the pump is seized tomorrow, but it is getting quite hot. Anyway to clarify a diverter problem?

Any suggestions appreciated, as its now giving me a headache!

 

[rm1]

sounds like a faulty pump remove screw from front of pump and turn on boiler see if pump runs if it does not see if you are getting 240 volts ac at the pump terminals if you are then ump needs replaced

 

[gregsy]

Okey Cokey thanks rm1 I'll give it a go.

 

[gregsy]

Well the pump is running fine. But I missed the light on top of the dhw flow switch hall sensor was stuck on, which indicates dhw flow. So the boiler must be sensing a demand for hw hence no central heating. The worrying thing is when I pull the hall sensor away from the dhw flow switch the boiler just stops turning over rather than returning to CH function. The magnet was indeed jammed in the dhw flow switch group and I'm waiting for the repair kit but I'm slightly worried because pulling the hall sensor from the flow switch didnt turn the heating back on...which may indicate another problem??

 

[mboshier]

could be over heating.

 

[gregsy]

I have changed the flow switch group and the boiler has now stopped showing a constant demand for HW, but the boiler doesnt fire at all for CH. If I turn it off by the main fuse spur and on again the pump will turn over and the micro switch is activated, but the switch is then released and the pump stops working. Nothing more will happen unless I switch the spur on and off again which will activate pump and switch for a brief period each time.

DHW is working absolutely fine, I have swapped the new thermistor with both CH and DHW thermistor and it shows no change in symptoms, Ive changed the main control board. Ive opened up and checked the divertor valve and all seems well, nothing seized and diaphram intact, replaced the diverter valve motor, dhw flow switch group has been replaced. Pump and fan are both running fine with the HW which is working perfectly on demand. Have tried with internal clock connected and disconnected.

Really at a loss now, Ive run out of ideas... Anybody??

 

[Danny1983]

Hello Gregsy.

Did you ever managed to sort this out. Mine is hating the same issue. I had to disconnect the power to the diverter valve and lock it in the ch mode and then run the hot water which runs cold but does put heat the comes to the rads instead as a temp measure. But before this it showed all the same signes as yours above

 

[g60rge]

I have an M90E.24S Riva Compact, which I'm having a few problems with, the hot water is working fine but the central heating is turning on fireing up for a few seconds then switching itself off for a about 2.5 minutes before fireing up again for a few seconds then switching itself off this continues indefinately. I can feel the hot water just about reaching the input of the first rads but thats about it.

So far I have purchased a thermistor and swpped out both the CH and HW thermistors in turn but this made little or no difference, I have also changed the main PCB as these were the stepped advised in the service manual fault diagnosis table but the fault still remains. The CH system has been apart as I have fitted three radiators and also bled the boiler down twice when fitting the thermistors.

Where do I go from here, I'm thinking Diverter valve or possibly the pump. (Ive heard you can get hot water flow without a working pump on some boilers due to mains pressure)

I was going to unscrew the screw at the front of the pump and see if the pump is seized tomorrow, but it is getting quite hot. Anyway to clarify a diverter problem?

Any suggestions appreciated, as its now giving me a headache!

i have the same issue with a customers boiler, did you find out what it is? 30 secs on 2.5mins off cycle.

powerflush made no difference

biasi are telling me the boiler is working fine and i have a circulation issue, my gut tells me the main heat exchanger could be blocked and its time for a new boiler

 

[Rickster123]

i have the same issue with a customers boiler, did you find out what it is? 30 secs on 2.5mins off cycle.

powerflush made no difference

biasi are telling me the boiler is working fine and i have a circulation issue, my gut tells me the main heat exchanger could be blocked and its time for a new boiler

It was time for a new boiler the day it was fitted!

 

[g60rge]

It was time for a new boiler the day it was fitted!

i always swear when i hear someone has a biasi but on the other hand they have made me alot of money over the years hahahaha