Ferroli Optima 901 Hot water issues

Hi guys,
You did a great job of helping me in 2004 when my Ferroli Optima 901 kept loosing pressure and a zero pressure expasion vessel.

I now have an issue with the Hot water supply from the combi.
When you turn on any hot tap in the house and let it run the water eventually gets up to temperature for a 10-20 seconds and then starts to come thru tepid. Then after another 20 seconds or so it returns to full temp and keeps repeating the cycle. Having a shower is becoming an artform.

Could it be somekind of protection on the boiler to protect it from overtemperature that is kicking in & out.

Our mains waterpressure isnt brilliant, our neighbour has even had the south staffs water out to check pressure and was told although on the lower end of their scale, it was within guidlines.

I'm wondering if the water flowrate through the combi is too slow allowing the water to heat too much and somekind of saftey device to kick in.

Thanks in anticipation
Phil

Phil

I had exactly the same symptoms with my 901. I had to replace a temperature sensor. There are two of them, from memory exactly the same, one for DHW and one for Central Heating. It cost me about a fiver and took about ten minutes to replace the DHW temperature sensor. The Ferroli part number was 800310.

Have a look on the Ferroli website and download the PDF installation instructions for the boiler. They show a diagram of the parts I needed.

And if you are at all unsure please consult an expert. My problem may not be the same as yours.

Sensors are the first thing I would be looking at and for the cost they are something I would eliminate before looking further.

Could also try removing flow restrictor

Thanks guys, it was the sensors as discussed, I decided to get a proper corgi guy in to change them and give the boiler a service as it hadnt had one for a couple of years.

There is still an outstanding problem.

The gas flow modulates (as it should if in water temp is +35 degrees to out temp, so corgi guy tells me)

This results in 20seconds of piping hot water then slight kettling then the flame can be seen to drop slightly resulting in a slightly lower temp water for 5-10seconds.

Plumber tells me it is modulating as if the water temp is too high, kettling could possibly provide a clue as to why it is doing it.

Have removed filter & restrictor to increase flowrate as we do have low water pressure.

Plumer spoke to ferolli, could be gadget that controls modulation has been told to check the voltage regulation on it if that is OK probably the heat exchanger.

Any other ideas, what are my options if it is the heat exchanger.

Thanks in advance
Phil

Thanks guys, it was the sensors as discussed, I decided to get a proper corgi guy in to change them and give the boiler a service as it hadnt had one for a couple of years.

There is still an outstanding problem.

The gas flow modulates (as it should if in water temp is +35 degrees to out temp, so corgi guy tells me)

This results in 20seconds of piping hot water then slight kettling then the flame can be seen to drop slightly resulting in a slightly lower temp water for 5-10seconds.

Plumber tells me it is modulating as if the water temp is too high, kettling could possibly provide a clue as to why it is doing it.

Have removed filter & restrictor to increase flowrate as we do have low water pressure.

Plumer spoke to ferolli, could be gadget that controls modulation has been told to check the voltage regulation on it if that is OK probably the heat exchanger.

Any other ideas, what are my options if it is the heat exchanger.

Thanks in advance
Phil

Thanks guys, it was the sensors as discussed, I decided to get a proper corgi guy in to change them and give the boiler a service as it hadnt had one for a couple of years.

There is still an outstanding problem.

The gas flow modulates (as it should if in water temp is +35 degrees to out temp, so corgi guy tells me)

This results in 20seconds of piping hot water then slight kettling then the flame can be seen to drop slightly resulting in a slightly lower temp water for 5-10seconds.

Plumber tells me it is modulating as if the water temp is too high, kettling could possibly provide a clue as to why it is doing it.

Have removed filter & restrictor to increase flowrate as we do have low water pressure.

plumber spoke to ferolli, could be gadget that controls modulation has been told to check the voltage regulation on it if that is OK probably the heat exchanger.

Any other ideas, what are my options if it is the heat exchanger.

Thanks in advance
Phil