Saunier Duval F24e Combi Boiler keeps losing pressure

jps14 · Nov 30, 2014

Hi guys

Sorry to be asking a question without posting before but I can see you guys know your stuff so just wanted to pick your brains if you don't mind. I've tried searching but haven't managed to find out what the problem could be yet.

I have a Saunier Duval F24e combi boiler which is about 10 years old in my house. It warms up and works ok but then once it has cooled for the evening, it is not able to fire up again the following day. The bar level indicator is flashing with the minimum amount showing and the red fault indicator light flashes. If I turn the boiler off and on again it will try to fire up but then the light flashes again and nothing happens and does the same thing again straight away.

However, if I open the little blue valve at the bottom of the boiler for about 10 seconds, a tiny bit of water comes out and you can hear it is letting air out (or taking air in?) of the system and the pressure bar quickly fills back up again. Like I said this only takes about 10 seconds. Once I have done this and turned the boiler off and on again, it starts up absolutely fine and provides heating around the house. But once it has cooled down, I have to repeat this process the following day as the pressure bar drops to 0.5 and flashes. It has been like this for a couple of weeks now. It will work fine throughout the day when it is in use (I have a Nest learning thermostat) but once it hasn't been used overnight, this happens.

What do you think it could be that is causing this? It sounds like a fairly common problem with these but I am yet to find a solution before calling someone out 🙁

Thanks in advance

Josh

ambrosia · Nov 30, 2014

bleed the rads and once you filled the pressure again check the pipe which comes out the bottom of youre boiler and through the wall, is water flowing out of it

if the water is not coming out there check rads and visible pipework for leaks

anything beyond that youll need a gas engineer to further fault find

village idiot · Nov 30, 2014

I doubt it has anything to do with letting air in? Chances are the PRV is letting water by. There are other possibilities but this is the first thing I will check.

jps14 · Dec 2, 2014

Thanks for your replies guys. Ok so I just put a bag over the PRV pipe and erm....it filled up with filthy black water within half an hour of switching the boiler on :/ Does this mean I need new PRV/expansion vessel? I know this is bad but not sure what to do next. I'm trying to post a picture but it won't let me as I am new poster 🙁

jps14 · Dec 2, 2014

Thanks for the replies guys. I put a bag around the PRV pipe outside and within half an hour of turning the boiler on it was full of filthy black water :/ I'm guessing this is not a good sign....New PRV needed or something more serious?

townfanjon · Dec 2, 2014

theres something else to check first mate, you need one of us !!

Chalked · Dec 2, 2014

If you go ahead and replace the prv by yourself. Firstly it is illegal and dangerous. And secondly you are only curing the symptom, not the scorce of the problem. There are many reasons why your prv would pass and the only recommended way to cure this is a trained gas safe registered engineer.

jps14 · Dec 2, 2014

Thanks guys. Don't worry I was never going to attempt to fix it myself, I wouldn't have a clue! It's just got to know what you are dealing with so to have an idea before someone comes to have a look. Got someone coming round tomorrow so fingers crossed it's a simple fix. Cheers for your help.