System Pressure and Boiler Faults

[laikax695]

Hi all – would appreciate some advice please

I have a three year old Viessmann 26 kw system boiler – a Vitodens 100-W WB1B. As far as I know (and I have no reason to doubt it) it was installed properly by local tradesperson (Gassafe reg and all that sort of thing) to replace knackered old boiler. In process of installation the boiler was relocated to an attached garage. As far as I know and as far as I am concerned the job was done well, no hassles and no complaints – all the work is neat, tidy and as a lay person it looks like a proper job..

However, ever since install the pressure has been problematic. There are two pressure gauges,. one as part of boiler and one near the filling loop. Filling loop is in first floor HW Cupboard by HW Cylinder. As far as I know the filling loop uses some components from the old install and is a braided hose approx 12 inches long with a black plastic handle at one end to allow water to fill the system.

There are 13 radiators (approx ½ on the ground and ½ on first floor)

System pressure at new was 1.2 bar dead cold. Over a few weeks it rose to be 3 bar and I was advised to bleed rads and release air from HW circuit vent. Did so and very little air came out. Pressure down to about 1.5 bar. Was told it should be okay.

Noted that when we left went on holidays in July this year that pressure on leaving was approx 1.5 bar if cold and approx 2.2 bar hot. Boiler left in holiday setting for three weeks (i.e. Off). On return pressure was 3.2 bar stone cold. Fire up boiler and pressure rises and prv releases water – all settles down to about 2.8 -3.0 bar after a few hours.

Decided to get installer to do service and look into pressure issues. Told expansion vessel knackered which explains odd pressure issues and so the rest of Service done – Fermox filter cleaned etc, new chems added in service and new exp vessel ordered and fitted a few days later. Boiler fired up – checked and installer all okay with various readings (efficiency, temperatures, pressure etc). Pressure set on completion of everything was 1.5 bar at 47 C.

First question, does blown expansion vessel explain away pressure problems?

Within 24 hours pressure was up to 3.2 bar at 65.4 C and 2.6 bar at 29.8 C. Boiler is on program and so figures reflect the max and min values throughout the 24 hour cycle

This has pretty much been the case for last three weeks up to a couple of days ago when boiler threw a fault code F4 (see later on – I will get to this). Contacted installer – he is very busy so gave me some advice on going through and eliminating all air related issues that I can deal with and also on resetting boiler.

Started today at pressure of 2.8 bar stone cold (i.e. am pretty sure water temp was less than 20 C as boiler been off for over 24 hours. So today, bled every rad twice – started at lowest and furtherest from boiler and finished at highest and closest. TRV on every radiator fully open. All rads immediately discharged water so as far as I know that means no air in rads. Bled HW Circuit and tiny amount of air came out (really tiny amount). Pressure on completion 1.0 bar and topped up via a short fill from filling loop to 1.5 bar. That was around midday.

Tried to Restart boiler – went through 4 cycles attempting to start and then returned the F4 error. Noticed that when attempting to start that pressure rose about 0.2 bar (presumably as pump kicks in and cycles water around) and then drops by same amount when boiler finishes its failed start attempts.

So, boiler off – not working, everything stone cold and pressure now at 17.00 is 3.4 bar and PRV is releasing pressure!

I have been assured the filling loop is not passing water BUT i have no idea if I have any way of proving that for myself.

Second question, is there some method or trick that I can use to confirm the filling loop when closed is in fact closed and no additional water is entering system? As far as I know, the filling loop is fed from the rising main and I am pretty sure I was told our mains pressure was over 3 bar.

Third question, is it likely that the new expansion vessel has split or whatever and if so what causes these things to split / rupture / leak or whatever it is that they do?

The F4 issue – according to Viessmann literature this is “Burner in Fault State, No Flame Signal is Present and says under the measures column - Check the ignition/ionisation electrode and cables, check the gas pressure, check the gas train, ignition, ignition module and condensate drain.Press "Reset"”

Now – I know nothing about Boilers but was an aircraft engineer and logic says to me that message has nothing to do with system water pressure. However, I am prepared to accept that the fault code could be a “bad message” that is arising due to the water pressure issues.

I have discussed all this with my installer and he agrees that the pressure shouldnt be rising like this and that I should not be needing to bleed rads to keep the pressure under control. He is exceptionally busy and cant get to me for a few days but we do have a service request logged with Viessmann to come and deal with it.

I would like to decrease my state of ignorance in advance of that visit – so can anyone offer advice please? As I said earlier, I have no issue with the install or installer and he has been nothing but helpful and free with advice. But I am not understanding whats happening here and just want to get other views on what might be going wrong.

Thanks in advance.

 

[Dotty]

Disconnect the filling loop. You'll soon know that it's passing

 

[Dotty]

Disconnect the filling loop. You'll soon know that it's passing

If you buy a 15mm stop end, discard the big nut and copper/brass ring you'll have a thing looking like a threaded socket. Disconnect the filler loop on the heating side, possibly where the gauge is, move sharpish and fit the stop end (threaded socket) on the end of the filler loop.

Then dump some pressure out of your boiler through a radiator vent to 1.0-1.5bar.

 

[laikax695]

If you buy a 15mm stop end, discard the big nut and copper/brass ring you'll have a thing looking like a threaded socket. Disconnect the filler loop on the heating side, possibly where the gauge is, move sharpish and fit the stop end (threaded socket) on the end of the filler loop.

Then dump some pressure out of your boiler through a radiator vent to 1.0-1.5bar.

Thank you Croppie - I will try this tomorrow and post when done.

 

[laikax695]

Hi again -

I have done the following

Turned water off at rising main

Lowered pressure to 1.5 bar by bleeding highest top floor rad

Undone filling loop from fitting at rising main pipe - (black handle end in pic)

Attempted to disconnect filling loop at silver valve end but lots of water under pressure pi$$ing out so tightened it back up.

Loosened screw fitting slowly in silver end - nothing happened, so went a bit further and still nothing so did it back up and loosened fitting where braided hose joins valve end and removed - small amount of water from braided hose came out.

Had a good look at silver valve end and its fizzing slightly so suggests to me that valve is letting system pressure from the boiler side back past into the filling loop hose.

Given that its doing that I assume its leaking and also assume its supposed to be a non return valve to stop system water backflowing into household water system. If thats correct and its staying open then surely I should be getting decreasing pressure. So I figure the black handle end of the filling loop is also letting water by but as its a higher pressure it just flows into the system through the leaking non return valve.


As my installer cant come out at present I decided to fit an isolating valvebetween braided hose end and the existing silver valve. Logic being its a temporary repair and helps me prove the problem and stops the whole system constantly being over pressurised. Pic attached shows the end result (Yes I know its not ideal - but its a temporary repair based on what I had available in my box of bits and pieces in garage).

Once it was fitted in - mains water turned back on, no leaks (phew) and repressurised system allowing it to go up to 3 bar. Left it like that for 15 minutes - no leaks and so again bled system at radiator back down to 1.5 bar.
In the past the pressure readings on Boiler Gauge and on Gauge by filling loop would have risen after an hour or so by about 0.2 bar and so far they have not. Probably safe to say the whole filling loop is shot at both ends and needs to be replaced. Is that a reasonable conclusion?

BTW wasn’t ignoring your advcie re blanking plugs - just didn’t have any and couldn’t get any today. Will add some to box of bits when next out shopping.

I can’t see any problem with the temp repair apart from its ugliness and excessive number of parts and joints. AFAIK it stops mains pressure water flowing into boiler system unless I open both the Black handle end and the isolating valve and I think thats all the filling loop is supposed to do in any event.

Thanks for the advice.
Now all I need is for Viessmann to sort out the F4 problem and the boiler can be switched on again

 

[Ermintrude]

That's all good. Well done tidy job. When your installer is back get your expansion recharged as all that pressure may have flattened it abit. Water needs to be drained from heating side of expansion when recharging.

 

[Dotty]

Ugly is in the eye of the beerholder. Thanks for coming back and telling us how you got on.

 

[laikax695]

Thanks Ermintrude and Croppie for advice and feedback. I will make sure the installer knows what I have done and ask him to recharge the expansion and I guess also top up the chemicals he put in the system a few weeks ago as I imagine taking a lot of fluid out via the bleed process probably took most of the chems with them.

Anyways - pressure has held rock steady at 1.5 bar for 24 hours now and thats never happened before. Thanks again for the advice.

Laika