Boiler Cutting Out

[goble]

Hi all, a few weeks ago the following 3 things started happing almost simultaneously.

1) Hot water became constantly boiling hot.
2) 3 port valve in airing cupboard starting making humming noises.
3) Boiler would cut out randomly and would need re-setting (Potterton Promax SL version 24).

First off I changed the thermostat on the tank to see if this stopped the boiling hot water and was a cheap fix, but this changed nothing.

A heating engineer came round and sorted the port valve (not sure what they did). This stopped the humming for a week or so and then it came back, it also then stopped working properly. We have now had the port valve changed.

The problem is we still have points 1 and 3 above after changing these items. Before we get someone out again to check everything I was just wondering if anyone could give any advice on what could be the problem.

Is the boiling hot water the reason why the boiler is cutting out as a fail safe or could they be unrelated?

I understand from looking up about the boiler it is not necessarily that good and a pain to find the fault codes and some people drill holes in the front casing to see the lights. Is this something you do without taking the casing off or not advisable to do at all?


Many thanks in advance

 

[ianmcd]

If you have an electric immersion heater as back up make sure it hasnt been switched on by mistake, a lot more common than you would think, are the radiators also a lot hotter than usual or just the HW

 

[goble]

If you have an electric immersion heater as back up make sure it hasnt been switched on by mistake, a lot more common than you would think, are the radiators also a lot hotter than usual or just the HW

Have checked and the immersion is not on. I think the radiators are getting hotter or at least the wife says so, but can't be 100% sure as we have only been in the house 6 months and I did not really notice how hot they got before this started.

 

[ianmcd]

Turn the flow temperature adjustment screw on the boiler down to about half way, for a few hours and see if things get cooler ( Rads) it could be a faulty thermistor

 

[goble]

Turn the flow temperature adjustment screw on the boiler down to about half way, for a few hours and see if things get cooler ( Rads) it could be a faulty thermistor

I turned the flow temperature down and it didn't seem to have any effect on the radiator temperature. This may be a silly question but how does the thermistor affect the hot water temperature, I thought it was the thermostat on the cylinder tank that controlled this?

 

[ianmcd]

The thermistor controls what temp the water leaves the boiler at, so say for arguments sake the boiler was set at 60 C then the hot water couldnt get higher than that without an external heat source immersion as mentioned, the water cant heat itself up higher than it leaves the boiler

 

[goble]

The thermistor controls what temp the water leaves the boiler at, so say for arguments sake the boiler was set at 60 C then the hot water couldnt get higher than that without an external heat source immersion as mentioned, the water cant heat itself up higher than it leaves the boiler

Okay thanks for the explanation ianmcd it is appreciated. I forgot to mention that after I adjusted the flow temperature and was monitoring the rads the boiler cut out but there were no fault codes on the boiler. Would a faulty thermistor give fault codes?

 

[ianmcd]

Okay thanks for the explanation ianmcd it is appreciated. I forgot to mention that after I adjusted the flow temperature and was monitoring the rads the boiler cut out but there were no fault codes on the boiler. Would a faulty thermistor give fault codes?

yes it should do

 

[goble]

yes it should do

So the boiler cut out again today and this time there were fault codes, but it was not the thermistor fault code but the Ignition Lockout code. I understand this could still be numerous things but any ideas?

I did also notice today that outside on the floor under the flue there is a wet patch, not sure if this is normal for this type of boiler.