Ferroli modena Boiler

[Bacumears]

Can someone help!!!!!!!!!!!
The boiler fires up for about 5 seconds, shuts down, fires up for approx 5 seconds shuts down etc,etc .Radiators all get hot, but it takes forever to as the boiler comes on and off too quickly. The pump has 3 speeds , but it doesn't seem to make any difference. That seems to be ok.
I thought I might have sludge in the system so I put a flush in the system for a week. During that week I shut all the rads down and opened 1 rad at a time to see if I could locate any blockage. Every time closing the hot rad off before starting on the next one. All radiators got red hot.
I had my system power flushed about 4 years ago. The system is a pressured system. I drained the flush out and opened the all rads until clear water came out, this took a couple of hours to do. I then put an inhibitor in. I am still getting this problem. do you think the boiler is the problem?

 

[bengasman]

Sounds like the boiler can’t get rid of the heat. As the system appears to be clear, you should check the pump. Are the flow and return valves on the boiler fully open?

 

[numpty1]

remove the outer case,pull one of the plastic bungs out of the combustion cover for only for a couple of minutes,if this helps you need a competent heating person to correct the fault.

 

[Bacumears]

I have checked that the flow and return valves on the pump and they are fully open.
Are there flow and return valves situated on the boiler and do they look like shut off valves?
Also, the pump is a Grundfos and is only about 4-5 years and when I switch the speeds, you can hear the water move quicker.

 

[Slugbabydotcom]

My ten bob says its a faulty ch thermistor

Pump should be on fastest speed BTW

 

[Bacumears]

Many thanks for all your advice, hopfully a engineer will be coming soon and I will pass the information on.

 

[JonB]

I have an 8 year old Modena 102.
The only problem I have had in that time is the hot water Thermister, they are best changed in pairs. Very easy to change & cheap.
JonB

 

[Bacumears]

To change a thermistor the manual says to drain off from the boiler to change the sensor.
Will the upstairs radiators need to be drained down to do this or is there a simpler way, ie shutting off the pump and water feed and shutting off the radiators etc

 

[JonB]

My 102 has shut off valves under the boiler on every pipe, no need to drain any rads.

 

[Bacumears]

I think the boiler I described is a Sigma and not a Modena. There is only 1 sensor and this pipe doesn't have a shut-off valve.

 

[JonB]

Sorry I thought the topic heading said Ferroli Modena