Vaillant TURBOmax plus - code F.28 and pressure loss

[dpm_dpmartin]

I have some good (young and naïve) kids at a property I let out with this Vaillant boiler and they told me late last week that "it wasn't working". I attended on Saturday afternoon and saw it had F.28 displayed on the LCD and the BAR needle was down at zero.

I have the boiler manual so quickly realised F.28 is failure to ignite - but I wasn't sure whether it had failed to ignite because of low pressure - or because of something else - lack of gas, gas value, condensate etc. - so I started out by re-pressurising the boiler with the internal mechanism (two screws on the underside) - a task that takes around 30 minutes.

Once it was at about 1.5 BAR I reset it and it ignited - I got the Tenants to call for heat and the radiators got nice and hot in a very short while - the pressure needle remained constant and I was happy to leave - saying that they might consider bleeding the radiators at some point (maybe I should not have said that).

Apparently they did bleed the radiators on Sunday... but on Tuesday (last night, two days later) they said it was showing F.28 again and the bar needle was back at zero! I've re-pressurised this boiler before and I know that it lasted many, many months - so this news surprised me, and worried me - why on earth would it lose its pressure so quickly (I started to think about a leak somewhere - but why would that suddenly have occurred?)?

What I don't understand - as I'm not there to watch it - is whether the F.28 happens first and that then causes the pressure loss... or whether the pressure loss happens (leak? pressure relief valve? something else?) and then that results in a F.28.

I remotely talked them through re-pressurising it last night and they're back up and running, but I'm now trying to schedule-in a Heating Engineer to go and look at it - the last GSC was in March 2019, so it's annoyingly just before the next one is scheduled on the 11th March... but I can't risk waiting that long to get the GSC and Service done, I think, it annoys Tenants when they do not have a working boiler - fair enough.

The Tenants have a pre-pay meter (boo!) and one thing I've learned today is that one of the "most common causes" of F.28 is a lack of gas supply... I have mentioned this to the Tenants before so I doubt it's the case again... but there's a niggle at the back of my mind - this boiler is supposed to be built like a tank! When I'm there it seems to behave itself fine - then bang!

I'm not working on this any more myself - I've done all I can, I'll get someone in. I'm also going to have an external filling loop installed (to speed things up) and a magnetic filter. But, for my own knowledge and awareness - would anyone be able to answer my question about the combination or pressure loss and F.28?

Does the boiler fail to ignite at some point, give up and show F.28 and then that results in an eventual loss of pressure, with the needle eventually going down to zero? Or... is it the pressure loss (and who knows why that might be?) that eventually causes the F.28 as it (slowly, I assume) drops from over 1 BAR down to zero?

 

[ianmcd]

If your tenants bled the radiators that would cause pressure loss, when was the boiler serviced ? not a Landlords gas safety check ? as for the safety check due in March you can have the inspection done up to two months early now and keep the same date, so just get it done now and get a proper service done at the same time and the expansion vessel and pressure relief valve checked

 

[dpm_dpmartin]

Thank you... the radiators being bled can lead to the pressure loss I think I instinctively knew, but it's good to get that confirmed as to the possible "why". I am hopefully getting someone in on Friday and taking an oil radiator around early this evening as a backup. They have an electric shower so it's not as urgent as some situations I suppose. The boiler was actually serviced last year too. I am starting to suspect it's fine... but upon talking to the Engineer who will visit Friday he's asked me to try check for leaks with toilet paper when I visit tonight.

 

[ianmcd]

Thank you... the radiators being bled can lead to the pressure loss I think I instinctively knew, but it's good to get that confirmed as to the possible "why". I am hopefully getting someone in on Friday and taking an oil radiator around early this evening as a backup. They have an electric shower so it's not as urgent as some situations I suppose. The boiler was actually serviced last year too. I am starting to suspect it's fine... but upon talking to the Engineer who will visit Friday he's asked me to try check for leaks with toilet paper when I visit tonight.

when you visit tonight set the pressure on the boiler at around 1 Bar cold then turn the heating on and leave for abot 20-30 mins then recheck the system pressure , if it has went up to around 3 Bar then you have an expansion problem, sadly not many so called engineers properly check expansion vessels when servicing boilers, this is the most common cause of pressure loss in a boiler

 

[dpm_dpmartin]

Thank you. I will try and do exactly that. Although they are up and running at the moment now. If they're at over 1 BAR running, I don't even know how to reduce down to 1 BAR - well... I do! ...bleeding radiators!

 

[ianmcd]

Thank you. I will try and do exactly that. Although they are up and running at the moment now. If they're at over 1 BAR running, I don't even know how to reduce down to 1 BAR - well... I do! ...bleeding radiators!

being between 1-2 Bar when hot is not a problem, there is a pressure releif valve inside the boiler that opens at 3 Bar to protect the boiler and releases water to outside , if this is operating because of and expansion problem, then when the boiler cools there will be no pressure

 

[dpm_dpmartin]

OK - work booked in for Friday is:

Gas Safety Check
Filling loop supply & install
Magnetic Filter supply & install
Leak seal supply & install
Inhibitor Supply & install
Expansion vessel visual check (Engineer to confirm)... fingers-crossed, ey? If the expansion vessel is kaput there was mention of a temporary fix "topping it up?" until a date for a replacement could be gotten.

 

[Gasguru]

Auto air vents on these seem to leak more than other boilers...it's a standard part and only a fiver.
F28 is a failure to light...a design fault on these models is that the ignition burner pressure is the same as the minimum burner pressure.
It's always worth getting the minimum pressure upped a little (ie. ignore the book value) to improve ignition.
A temporary bodge for a failed expansion vessel is to part drain down a non essential rad (leaving air at the top) and close off one valve.

 

[ianmcd]

Leak seal supply & install

Dont it causes a lot more problems than it will ever fix

 

[dpm_dpmartin]

I was talked through this on the phone and persuaded it was a good idea in this case, where pressure loss might be caused by a minor leak in the system, somewhere. Please bear in mind I'm just a dumb user / owner... and getting conflicting advice is always a worrying thing. Especially when someone is telling me it's "magic juice" and another telling me it'll cause further problems... to be sure, I don't want further problems.

I don't even want these problems.

 

[dpm_dpmartin]

F28 is a failure to light...a design fault on these models is that the ignition burner pressure is the same as the minimum burner pressure. It's always worth getting the minimum pressure upped a little (ie. ignore the book value) to improve ignition.

Thanks. This sounds like experience accumulated over years of war-weary engagements... and extremely valuable to boot, but how on earth do I justify (if anything bad happens in the future) deliberately asking my Engineer to go against the "book value" (I assume that means the manual? maybe the installation one?) if something / anything goes awry? I did not select this boiler (as with so many people) I inherited it... but I was kinda pleased with it - sure, it looks rather old and clunky, but reputation says it's a workhorse and will just keep going and going and going... I like that. It appeals to me.

I will mention "ignition burner pressure is the same as the minimum burner pressure" to the Engineer tomorrow and see what his reaction is. You know how it'll be - he'll ask me where I got this and I'll say "a forum" and he'll raise his eyebrows at me.

 

[ianmcd]

I was talked through this on the phone and persuaded it was a good idea in this case, where pressure loss might be caused by a minor leak in the system, somewhere. Please bear in mind I'm just a dumb user / owner... and getting conflicting advice is always a worrying thing. Especially when someone is telling me it's "magic juice" and another telling me it'll cause further problems... to be sure, I don't want further problems.

I don't even want these problems.

Leak sealer causes problems on modern boilers, they have lots of very fine waterways and the leak sealer blocks them, if you have a leak find it and fix it dont turn the system water to mud hoping it will stop a leak

 

[dpm_dpmartin]

Genuine question, not being facetious - but is this Vaillant TURBOmax plus considered "modern" - sold around 2000 to 2005 is my understanding?

 

[ianmcd]

Genuine question, not being facetious - but is this Vaillant TURBOmax plus considered "modern" - sold around 2000 to 2005 is my understanding?

yes it has small waterways, some manufacturers will void warranty's if leak sealer is used, it is snake oil for lazy inexperienced cowboys, I have never and will never use it

 

[dpm_dpmartin]

Well... warranty is not a concern, that's for sure. I wish, right? I'll talk to the Engineer when we're face-to-face... and gauge his comments. I suspect part of the issue here is - a leak in the system might be the reason for the pressure loss, and it might not be - but tracking it down (if under floorboards etc.) could be difficult - so not necessarily inexperienced, maybe more pragmatic and time-aware?

As a layman, hearing this, I did do some Googling on whether to use leak sealer - there are firm objections to it on some sites I visited, but - strangely enough - they were leak detection service companies... so you would kinda expect that, right?