Yet another Vaillant boiler with an F.75 error!

[ianmcd]

Yes you are correct that you have one EV for your system water and one for your Domestic water these two never meet, and the system expansion vessel should be checked for the correct charge every time the boiler is serviced but to honest this is commonly missed as the big guys today can FGA a boiler and it dismisses the need for proper servicing according to them, it does sound as though the EV needs re-charging , sticking your finger in the Schraeder valve means nothing whatsoever IT MUST be carried out correctly there are posts in the WIKI on here telling you how to do it but you MUST follow all instructions if you think you can do it without leaving a drain point open like most people do then no point whatsoever in even trying

 

[Milleniumaire]

I did turn the boiler off tonight, let it cool down until the analogue gauge was almost fully to the left (only just in the grey area) and then connected my tyre gauge to it. It read 0.8 bar, which seems perfect according to the manuals recommended 0.75 to 0.9 bar, but I suspect this reading is wrong due to the boiler still having water in it - as you say the water pressure is still affecting the expansion vessel.

To do this properly I guess I would have to drain the boiler to remove pressure (if I understand the procedure correctly) and this is more than I'm willing to do. I was very familiar with my old system, but not so much the new one, which seems to have twice as many pipes

Hopefully, if I do manage to get a plumber round, I'll watch what he does and get more of an understanding.

 

[ianmcd]

Exactly what I asked you NOT to do, the easiest way for a non professional is open a rad valve that bleeds the rad hold a pan or other container to collect the water, wait till the water stops then you start pumping the EV up while someone else holds the pan to collect the excess water that will come out , more water will come out of the rad once the water has stopped and you have the correct reading on your foot pump then you have re-charged the EV, you can not do it any other way !!!!!!!!!!

 

[Bunnyman]

Sorry to jump in here but agile has given u all u need an u just keep blabbing on about the f75 problem ffs! There is no problem only google warriors who say there is one ! I suspect your ex vessel is flat, I also suspect is never been serviced properly as agile says these must be refilled an checked at every service the same as all modern boilers, obviously I can't be sure but all your info points this way an the boilers just protecting itself . If you keep filling it without getting it drained an refilled properly u will probably stretch the hoses (if it's an older one) then you be saying u have the leaking hoses fault! Get it done quick by someone who knows

 

[ianmcd]

Sorry to jump in here but agile has given u all u need an u just keep blabbing on about the f75 problem ffs! There is no problem only google warriors who say there is one ! I suspect your ex vessel is flat, I also suspect is never been serviced properly as agile says these must be refilled an checked at every service the same as all modern boilers, obviously I can't be sure but all your info points this way an the boilers just protecting itself . If you keep filling it without getting it drained an refilled properly u will probably stretch the hoses (if it's an older one) then you be saying u have the leaking hoses fault! Get it done quick by someone who knows

Cheers Bunny but it was me that said all that ha ha ha do I need to go to Tonys school of competence before I am allowed to comment on Bunnys if I do then the Bunny is coming off the van and the key ring is getting sent back big ears

 

[gaswizzard]

Have an additional vessel fitted , the 10 ltr won't cope especially on a 37kw load.

 

[Agile]

Initially the OP said he had an external EXV. Later he decided that it was for the UV cylinder instead.

The internal EXV in the boiler is quite small and for larger water content systems needs to be augmented with an external one.

But first the internal one needs to be set up correctly. A DIYer should not be accessing it because the cover is the combustion chamber seal.

Tony

 

[mickyg]

There is no fault with the boiler re:F75 they are sensitive to dirt, which is why there is a kit to move it to prevent it getting blocked up so easily, nut essentially if the system is clean and properly maintained you will not get any F75 errors. I have never used/needed the kit even in 4yrs working for vaillant. As GW has said you have a 37kw load and a 10l vessel......oh dear....

 

[Agile]

I have never needed that kit either when dealing with F75 errors.

Tony

 

[bell824]

so now from being "another f.75 vaillant error" we have established you are relieng on just the boiler expansion vessel, you have had it serviced as per the manual? (this does state check the vessel!!),

the reason it is probably showing f.75 instead of f.22 is you will probably have magntide in your system and this has blocked the boiler pressure sensor, check when the manual gauge show's no pressure what the digital one say's (press - button) i bet it shows above 0.8bar,

so now you need the expansion vessel checked and the sensor done as well.

Oh well another f.75 problem cured because the boiler was not serviced properly and the google warrior found an issue by typing in a code,

sorry if my post seems abusive but it annoys when someone searches for a code from any manufacturer (or any other piece of equiptment for that matter) and find's a "few" frpom many have experianced a problem.

 

[Milleniumaire]

bell824,

The boiler was serviced in November 2012 by the person who installed it. At the time of installation (3 years ago) he was a registered Vaillant installer and lived locally. I got his name from the Vaillant website. As far as I'm aware he was very competent.

Did he check the expansion vessel or pressure sensor during the service? I've no idea as I didn't stand over him to ensure he did everything he should have done. I paid him to service the boiler and I expected him to do it properly.

Is the current problem the result of a poor service? I don't know as I'm struggling to get a plumber out to look at the problem and have one arranged for Monday (got his name from the Vaillant website).

"Oh well another f.75 problem cured because the boiler was not serviced properly".

It seems you are also making assumptions that the installer didn't do a good job of servicing the boiler and blaming "one of your own".

Put yourself in my shoes. I paid a LOT of money for a new boiler and unvented cylinder to be installed after having many pressure problems with my previous boiler. I chose Vaillant as I believed they provided good quality equipment. I have paid for the boiler to be regularly serviced. In short, I have done everything I can to ensure the boiler and system continues to work at its best.

Then I start to get F.75 errors and I do a little research and find that this appears to be a common problem. Can you blame me for getting a little irritated?

The boiler isn't even 3 years old. I don't expect problems with it just yet. I'm beginning to suspect this is why Vaillant only offer a 2 year guarantee!

Hopefully, the problem will be fixed on Monday and it won't cost me too much.

It's interesting that reading through these forums I see examples of "experienced plumbers" telling "diyers" that they should pay for "experts" to resolve problems and to not attempt to fix them themselves, and yet I also see postings, like yours, where you blame these same "experienced plumbers" for not doing their job properly. In fact, you seem to be having a go at me and other plumbers in a single post!

Are you surprised that diyers want to try to fix the problems themselves?

In the case of this posting, I have received some good feedback and having done my own research I've learnt something new about the boiler I have and the purpose of the expansion vessel. This will (hopefully) help me discuss the issue with the plumber and understand what he intends to do to investigate the problem and fix it.

 

[The831Bunny]

Hi Milleniumaire

Unfortunately the variation from one engineers knowledge and experience to another's is a widespread problem. Advice given to you from the likes of Bell824, mikeyg, Bunnyman et al is spot on. They are dealing with these appliances day in, day out. They are also giving you plenty of expert advice in their own time and for free.

Your plumber may have been on a manufacturers course, but does he appreciate why these items, like the expansion vessel check, are required and are important. Incidentally expansion vessel operation and principles apply to all sealed heating systems, and are a basic heating concept. I'm sure a quick look in the FAQs on expansion vessels on the DIYnot site will be helpful, and hopefully your plumber won't be offended if you 'guide' him in that direction.

FYI the ecotec plus range now comes with a 7 year warrenty if installed by an approved Vaillant installer, this is up from 5 years which it has been for some time. Obviously this has T&C, the major ones being the system is clean and inhibited and the boiler is regulary serviced following the manufacturers schedule. System dirt and lack of servicing are an all to common occurrence that contribute to the majority of boiler breakdowns.

To sort your problem the plumber needs to check: expansion vessel sizing against your system volume, the internal charge of the boiler vessel and any new vessel fitted, check the PRV is not passing, clean/replace the pressure sensor if blocked with debris, check & clean the canoe filter if dirty, look to clean/flush/inhibit the whole system if it is contaminated with magnetite.

You may be back to Groundhog Day if not...

Hope that helps.

 

[Milleniumaire]

Just thought I would update with the solution after a plumber visited today.

They emptied some water from the system using a drain cock at the bottom of one of the return pipes, which reduced the pressure and waited for the pipes to cool down, then they let all the air out of the expansion vessel - no sign of water, so it doesn't appear to be broken.

At this point the analogue gauge was showing 0, but the digital gauge was showing 1.5 bar, which seemed a little strange to me!

They then recharged the expansion vessel (while the drain cock was still open). This forced out more water. They then closed the drain cock and allowed water in until the digital gauge was reading 1.7 bar. The analogue gauge was just into the grey.

They then turned the boiler on full and waited until it heated up to about 70 at which point the digital gauge was showing 2.2 bar, with the pump running. He explained that the pump could add around 0.4 bar so he was happy with that.

The charge was £54 (including VAT) and hopefully everything will continue this way and the issue is resolved.

I queried Vaillant on why, when the analogue gauge was showing 0, the digital gauge was showing 1.5. The response was that the digital gauge was more accurate - so no explanation really!

Thanks to everyone who contributed to this topic.

 

[gaswizzard]

Just thought I would update with the solution after a plumber visited today.

They emptied some water from the system using a drain cock at the bottom of one of the return pipes, which reduced the pressure and waited for the pipes to cool down, then they let all the air out of the expansion vessel - no sign of water, so it doesn't appear to be broken.

At this point the analogue gauge was showing 0, but the digital gauge was showing 1.5 bar, which seemed a little strange to me!
.

So are you saying the vessel was charged with 1.5 bar showing on the digital gauge with boiler empty? , seems to me it was a wasted visit along with the £54 , was the pressure sensor removed and checked/cleaned/replaced? , i would say analogue gauge would be correct due to gauge showing a pressure drop/rise on emptying/refilling (tube not blocked).

 

[The831Bunny]

So close, yet so far...