Vaillant Ecotech F.75

[Ackoman]

Hello,

I've got the dreaded Ecotech F.75 error on the Vaillant boiler in the house which I only bought 3 weeks ago. As far as I can tell, there are no leaks anywhere, but each time I top up the system after a few hours the pressure has dropped again - there doesn't seem to be any coming out of the pressure relief pipe, so where could the water be going?

I've read that this can be a problem with the expansion vessel needing to be "topped up", and/or a faulty pressure sensor.

The digital pressure reading says 2.1bar, regardless of whether there is water in the system or not, so I'm thinking that the pressure sensor is faulty?

If there was a leak, but the pressure sensor itself was fine, would that present itself as a F.22 rather than as a F.75?

Any help would be much appreciated.

Thanks,

Ackoman

 

[Ackoman]

Hello,

I've got the dreaded Ecotech F.75 error on the Vaillant boiler in the house which I only bought 3 weeks ago. As far as I can tell, there are no leaks anywhere, but each time I top up the system after a few hours the pressure has dropped again - there doesn't seem to be any coming out of the pressure relief pipe, so where could the water be going?

I've read that this can be a problem with the expansion vessel needing to be "topped up", and/or a faulty pressure sensor.

The digital pressure reading says 2.1bar, regardless of whether there is water in the system or not, so I'm thinking that the pressure sensor is faulty?

If there was a leak, but the pressure sensor itself was fine, would that present itself as a F.22 rather than as a F.75?

Any help would be much appreciated.

Thanks,

Ackoman

Actually, just been outside and there is a slow drip drip drip from the pressure relief pipe................ so, totally confused now. Does that now cast doubt on it being due to a faulty pressure sensor? And if the pressure sensor isn't faulty, why does it always say 2.1 bar?

 

[hertsboilers]

You have got two problems at least, one for PRV leaking, another for pressure sensor being blocked.

Need a boiler repair engineer through.

 

[Ackoman]

Hi,

Thanks for your reply - I had a plumber come round and he replaced what he thought was the pressure sensor, however he seemed to be confused because when he took the cover off the boiler he found two things that looked like a pressure sensor - one on the left in the picture below (just to the left of the copper pipe coming down out of the boiler) and one to the right of the picture, up and to the right of the pump.

He changed the one on the left, to no avail. Around an hour after he left I got a F.75 again.

Should he have replaced the one on the right?

Thanks,

Ackoman

 

[St0rmer66]

Never seen one like that on the right! But if I was replacing either one I'd do the one on the right then disconnect the one on the left (leave it in to plug the hole). F75 is not low pressure, it's "no flow detected". When the pump starts the pressure needs to increase by at least 0.2bar otherwise you'll get F75. Hence why I say use the one on the right as it's closest to the pump.

It can also be caused by a weak pump but those type usually knock like hell when they're dying. New replacement version is a Grundfos instead of Wilo.

 

[Ackoman]

Never seen one like that on the right! But if I was replacing either one I'd do the one on the right then disconnect the one on the left (leave it in to plug the hole). F75 is not low pressure, it's "no flow detected". When the pump starts the pressure needs to increase by at least 0.2bar otherwise you'll get F75. Hence why I say use the one on the right as it's closest to the pump.

It can also be caused by a weak pump but those type usually knock like hell when they're dying. New replacement version is a Grundfos instead of Wilo.

Thanks for your reply, and yes it does seem logical that the one nearest the pump would be the one used to detect a pressure change when the pump comes on.

But, why would there be two?

Also curious to know why you recommend disconnecting the one on the left? Won't the system complain if it is expecting a signal from that one and doesn't get it?

Thanks,
Ackoman

 

[Agile]

Your plumber does not seem to have known what to do for the F75 fault.

There are three main things to do.

But it is not suitable for DIY repairs and so I cannot disclose what they are.

But most competent engineers should know what to do.

I fix one every few weeks and mostly without having to replace the pressure sensor if it is the later black one. Early ones were pink and they are better replaced.

Tony

 

[Ackoman]

Your plumber does not seem to have known what to do for the F75 fault.

There are three main things to do.

But it is not suitable for DIY repairs and so I cannot disclose what they are.

But most competent engineers should know what to do.

I fix one every few weeks and mostly without having to replace the pressure sensor if it is the later black one. Early ones were pink and they are better replaced.

Tony

Rest assured I am not going to do anything myself! But, I am guessing that one of the three things is recharge the EXV? I suggested that to my plumber but he ruled it out...
..


But could you at least offer your opinion on which of the two sensors in the photograph is the sensor that trips F.75 as a result of "no pressure change detected"?

Thanks,

Ackoman

 

[Agile]

Your plumber clearly had no experience of dealing with F75 faults. Probably little experience of boiler fault repairs in general.

Therefore there is only you left at the moment. You presumably took that photo!

But as a DIYer, you are not meant to even remove the cover which forms the room sealed feature of the boiler which ensures its safety.

If you get a competent engineer then he will know how to deal with F75 faults safely.

Tony

 

[Ackoman]

Your plumber clearly had no experience of dealing with F75 faults. Probably little experience of boiler fault repairs in general.

Therefore there is only you left at the moment. You presumably took that photo!

But as a DIYer, you are not meant to even remove the cover which forms the room sealed feature of the boiler which ensures its safety.

If you get a competent engineer then he will know how to deal with F75 faults safely.

Tony

I did indeed take that photograph, but I did it whilst the plumber here. He took the cover off, and put it back on - I have not touched it.

I call him a plumber, but he is a Gas Safe engineer - he installed a boiler for me in another property and did a good job. To be fair, I think you are being a bit harsh on him.

He changed the pressure sensor at my suggestion because I had read (on here) that 9/10 the pressure sensor is the reason behind a F.75 - what threw him was that when he took the cover off there appears to be two pressure sensors, and that does not match what the picture shows in the Installers Manual. As such, he is going to phone Vaillant today to get a better understanding of why the manual does not seem to match the reality. I took the photograph so that I could send to him, so that when he is on the phone to Vaillant he has got it in front of him. I didn't take the photograph specifically so that I could stick it on diynot.com!

 

[Ackoman]

Your plumber clearly had no experience of dealing with F75 faults. Probably little experience of boiler fault repairs in general.

Therefore there is only you left at the moment. You presumably took that photo!

But as a DIYer, you are not meant to even remove the cover which forms the room sealed feature of the boiler which ensures its safety.

If you get a competent engineer then he will know how to deal with F75 faults safely.

Tony

You mention that you don't feel you should disclose what the repairs should be for a F.75 fault, as a DIYer should not be doing them, however in this thread:

//www.diynot.com/diy/threads/yet-another-vaillant-boiler-with-an-f-75-error.357112/

you went into a quite a bit of detail regarding the EXV.

I am not going to do anything myself, but given that I have enlisted the help of a professional, who in this instance is not familiar with this particular fault, I am trying to do what I can to identify the likely causes so that he can concentrate on the most likely solutions.

 

[Agile]

Most would advise you to get another engineer who knows how to deal with common boiler faults like the f75.

We are not permitted to give advice on DIY gas related repairs.

If any registered gas engineer wanted advice on gas related all they have to do is to go to the Combustion Chamber part of this site which is only for gas registered engineers.

Tony

 

[AGAS]

why are you so worried when the engineer should be able to sort it ?, what are paying for ?? .

I did indeed take that photograph, but I did it whilst the plumber here. He took the cover off, and put it back on

I took the photograph so that I could send to him, so that when he is on the phone to Vaillant he has got it in front of him

your taking photo's of inside of boiler , just in case he needs to provide to vaillant at later date ????? ( why didn't he do that ? ) , you seem to be doing a lot of research for which should be a relatively easy fault to sort for the engineer .

 

[picasso]

Any chance you could post the boiler model ? I have not seen a vaillant with a sensor on that side.

 

[AGAS]

op you can take a picture of the label if you don't know the model , i think under the boiler left hand side . i can't remember seeing one there either tbh