dscoll Posted January 10 Share Posted January 10 Hi So im getting an intermittent (once a day ish) F75 on my 2014 ish vaillant ecotec 831. Heating is on, all fine, for minutes -> hours then F75 appears and heating goes off. When I turn the boiler switch off and back on it goes away, HW and heating ok, then it comes back. Checked the electronic pressure sensor, it was always 3.8, so I changed it. New sensor works fine but intermittent F75 still present. Then I noticed the off the pressure was creeping up by about 1.5 bar a day, so I removed the handles from the inlet valves and tightened the valve with a screwdriver, problem solved, pressure stable at 1.6. But intermittent F75 remains. So im stuck any suggestions appreciated. Link to comment Share on other sites More sharing options...
Temp Posted January 10 Share Posted January 10 (edited) Google says... The Vaillant F75 error code will display when your boiler can't register a pressure change when the pump turns on. This usually happens because of a faulty pump or if there's a problem with the water pressure sensor. So perhaps check the pump or wiring to the pump. Edited January 10 by Temp Link to comment Share on other sites More sharing options...
dscoll Posted January 10 Author Share Posted January 10 (edited) 48 minutes ago, Temp said: Google says... The Vaillant F75 error code will display when your boiler can't register a pressure change when the pump turns on. This usually happens because of a faulty pump or if there's a problem with the water pressure sensor. So perhaps check the pump or wiring to the pump. 48 minutes ago, Temp said: Google says... The Vaillant F75 error code will display when your boiler can't register a pressure change when the pump turns on. This usually happens because of a faulty pump or if there's a problem with the water pressure sensor. So perhaps check the pump or wiring to the pump. The pressure sensor reads correctly and I can hear the pump working, that's why i'm confused. It appears not to be a normal F75 problem. Also the rads get hot which confirms the pump is ok. Edited January 10 by dscoll Link to comment Share on other sites More sharing options...
Temp Posted January 10 Share Posted January 10 I wonder if the pump just fails to start occasionally? Link to comment Share on other sites More sharing options...
dscoll Posted January 11 Author Share Posted January 11 thats what i thought but it doesn't sound very likely. i posted the question here to see if anyone else had seen this behaviour Link to comment Share on other sites More sharing options...
Ivo Posted January 15 Share Posted January 15 (edited) On 11/01/2024 at 10:04, dscoll said: thats what i thought but it doesn't sound very likely. i posted the question here to see if anyone else had seen this behaviour This exact behaviour happened to me today. Did you manage to find the root cause? Edited January 15 by Ivo Link to comment Share on other sites More sharing options...
marshian Posted January 16 Share Posted January 16 https://www.urbanplumbers.co.uk/vaillant-f-75-error-code-full-boiler-repair/ Issues discussed in the blog above - might help? Link to comment Share on other sites More sharing options...
dscoll Posted January 17 Author Share Posted January 17 On 15/01/2024 at 23:04, Ivo said: This exact behaviour happened to me today. Did you manage to find the root cause? Not yet Link to comment Share on other sites More sharing options...
dscoll Posted January 17 Author Share Posted January 17 13 hours ago, marshian said: https://www.urbanplumbers.co.uk/vaillant-f-75-error-code-full-boiler-repair/ Issues discussed in the blog above - might help? Thanks for that. The blog suggested there could be an issue with the expansion vessel, so I checked it and it was full of water ie when I pressed the schrader valve water spurted out. Also, when the boiler runs the pressure goes up to 3 and because of this water has been coming out of the overflow pipe These 3 points (the internet tells me) suggest a punctured expansion chamber, so i'm going to replace the EV. Link to comment Share on other sites More sharing options...
Temp Posted January 17 Share Posted January 17 59 minutes ago, dscoll said: Thanks for that. The blog suggested there could be an issue with the expansion vessel, so I checked it and it was full of water ie when I pressed the schrader valve water spurted out. Also, when the boiler runs the pressure goes up to 3 and because of this water has been coming out of the overflow pipe These 3 points (the internet tells me) suggest a punctured expansion chamber, so i'm going to replace the EV. Good catch. I've found that once a pressure relief valve opens they tend to leak by even after the cause of the over pressure has been fixed. Think they get bits of scale in them? So I think there is a good chance you will need to replace the PRV as well as the EV but do the EV first. I wouldn't put corrosion inhibitor back in until its been running for a few days just in case the PRV does need doing. Link to comment Share on other sites More sharing options...
dscoll Posted January 17 Author Share Posted January 17 1 hour ago, Temp said: Good catch. I've found that once a pressure relief valve opens they tend to leak by even after the cause of the over pressure has been fixed. Think they get bits of scale in them? So I think there is a good chance you will need to replace the PRV as well as the EV but do the EV first. I wouldn't put corrosion inhibitor back in until its been running for a few days just in case the PRV does need doing. Ok, thanks , i'll keep an eye on the PRV but my guess is it's ok because the pressure when the system is on is 3 bar, which is the level that the PRV kicks in at. Link to comment Share on other sites More sharing options...
marshian Posted January 17 Share Posted January 17 3 hours ago, dscoll said: Thanks for that. The blog suggested there could be an issue with the expansion vessel, so I checked it and it was full of water ie when I pressed the schrader valve water spurted out. Also, when the boiler runs the pressure goes up to 3 and because of this water has been coming out of the overflow pipe These 3 points (the internet tells me) suggest a punctured expansion chamber, so i'm going to replace the EV. No problem - I follow his blog - he's a very clever chap and when I saw that I thought it might be worth a link Link to comment Share on other sites More sharing options...
dscoll Posted January 24 Author Share Posted January 24 Update - I changed the EV and it's working fine now. No water out the overflow pipe, ON pressure = 2.2 bar 2 Link to comment Share on other sites More sharing options...
marshian Posted January 24 Share Posted January 24 2 hours ago, dscoll said: Update - I changed the EV and it's working fine now. No water out the overflow pipe, ON pressure = 2.2 bar Excellent news Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now