Nightmare time with Worcester Bosch repairs

[Millsy 82]

Every time you do work on a boiler you allow air into the system. If you fully drain a boiler it can take a few weeks for it to settle back down again and get rid of all the air. So a 1.5-1.3 drop the day after they have carried out.

Just leave the boiler alone don't do any isolation tests tissue tests anything for a couple of weeks and let the air settle then look again.

The chances are with everything you say they have done to your boiler it WONT be on your boiler.

 

[Cazza]

Thanks for the information. I'll leave it then for a couple of weeks.

 

[John.g]

If you could shut off the air vent like in this interesting thread it might tell something but you probably can't if the auto vent is inside the boiler casing (not GSR).
Pressure drops when AAV open

 

[Millsy 82]

If you could shut off the air vent like in this interesting thread it might tell something but you probably can't if the auto vent is inside the boiler casing (not GSR).
Pressure drops when AAV open

I wouldn't advise that as it's inside the boiler.

 

[Riley]

If you could shut off the air vent like in this interesting thread it might tell something but you probably can't if the auto vent is inside the boiler casing (not GSR).
Pressure drops when AAV open

Yes please be careful on what you post!

 

[Aire]

A 0.15 bar pressure drop isn't IMO just a drop of water from a boiler that's isolated.
If one assumes a 8 litre expansion vessel with a pre pressure of 0.5 bar and a filling (test) pressure of 2.0 bar, then the boiler will lose 0.21 litres of water. If the pre pressure above is 1.0 bar then the boiler will lose 0.28 litres of water for the same 0.15 bar pressure drop.

Quoting specific amounts of water lost is a little daft given that the amount of water it takes to drop pressure varies more on system volume than the size of the expansion vessel. I know the 2 go hand in hand but the standard vessel within the boiler is good for up to around 100 litres of water. Has op specified how many rads she has? A 5 rad system running at around 50 litres is going to show a much bigger pressure loss with a cup full of water compared to a 10 rad system running at 100 litres. I've had a system where the combi was in the loft in a bungalow, and bleeding a cup full of water out a radiator was enough to drop the pressure to nearly zero. So in my opinion, depending on the size of OPs system, yes a few drops from the isolation valves at the boiler is enough over a week, to drop 0.2bar of pressure.

 

[Cazza]

Thanks for all your thoughts everyone. I have 10 radiators. 4 of them are only a 1.5 foot wide tho. There is a large 4ft one, two 3ft, and three 2ft.
I did not know it takes 2 weeks for any air to vent out of the boiler. That changes everything. Perhaps this was accounting for the pressure loss I saw shortly after the recent repairs, on top of the isolation leaks. No one from Worcester told me this. After they came out the first time it went from 1.5 bar to 0.5 bar within 2 weeks. I doubt that was just air venting. But maybe after they re-pressurised the deflated expansion vessel that fixed that and then any continuing drops in pressure (0.4 bar a week) was just air venting from the boiler. I think i'm going to have to let it settle. If it is still dropping in 2 weeks time then i will run another isolation test. But now I am wondering how reliable isolation tests are if there is auto air venting. I will have to run the test without filling it back up with water (as that would put air back in the boiler)

 

[Cazza]

I forgot to say I only use 5 out of those 10 radiators tho. Keep the other 5 off.

 

[John.g]

I wouldn't advise that as it's inside the boiler.

I did point that out in my post above and IMHO the Bosch service man should have shut off the air vent, stayed around for a few hours and if the pressure increased slightly then vent again.
I spent many years running and maintaining large industrial boilers and various pressure vessels and carried out many pressure tests for leakages, some of these vessels had auto vents but in all cases once all the air was expelled then the auto vents were shut until the pressure test was completed.

Yes please be careful on what you post!

Double post.(above, mine)

 

[J Davies]

I find all the above interesting as someone trying to decide between a WB Highflow 550 and a Viessmann 222F. One installer who quoted for me (and who installs both makes) told me that WB customer service was really good, which was making my decision difficult as for various reasons I prefer the Viessmann boiler over the WB. The comments by Rob F now make me wonder if there is another reason the installer wants me to choose WB and not Viessmann. Perhaps a better profit margin, or maybe Viessmann customer service is worse than WB. Are WB easier to install than Viessmann? Decisions, decisions!

 

[Cazza]

I don't know anything about Viessmann but I was speaking to a boiler service man a year ago and he said he only now installs Valliant boilers as he has had too many problems going wrong with the WB. In my first house I had a Valliant and it was fine (but I was only there 7 years). I don't think i'd get WB again. Although the new WB ones come with a 10 year guarantee, but even still if you can't trust their service men to get to the bottom of any issues what good is their guarantee, just a load of stress.

 

[Millsy 82]

I did point that out in my post above and IMHO the Bosch service man should have shut off the air vent, stayed around for a few hours and if the pressure increased slightly then vent again.
I spent many years running and maintaining large industrial boilers and various pressure vessels and carried out many pressure tests for leakages, some of these vessels had auto vents but in all cases once all the air was expelled then the auto vents were shut until the pressure test was completed.




Double post.(above, mine)

How long do you think they get at each job? They are probably limited to say an hour per job then may have to travel inbetween.

 

[Cazza]

I was told they get two hour slots

 

[Riley]

But I think the point is that not all jobs take two hours and anyone would be naive to think otherwise. That’s not a stab at you cazza im just saying. The expectation and demand on these engineers is sometimes unrealistic

 

[Millsy 82]

I was told they get two hour slots

You will get a 2 hour slot they will have to drive from the last job in that 2 hours if they hit traffic that could affect their time on site.

 

[Cazza]

Yes this is true and must affect their ability to be thorough. The crazy thing is because of their system of trying to save time on visits and repeat visits end up actually spending more time and money in the long run. If they had spent more time diagnosing and finding the isolation valve leak they wouldn't have replaced a heat exchanger! Perhaps Bosch should allow their engineers more time on a job (a stitch in time saves nine). I did find though all the Bosch men that arrived in pairs spent a lot of the time chatting between themselves about personal stuff, rather than fully concentrating on the job.

 

[Millsy 82]

When my dad was in hospital the nurses talked about their holidays to each other, when I go to a shop all the staff chat to each other about personal stuff. Everybody speaks about personal stuff.

I charge a fixed price for diagnosis because on average I spend about 20 minutes on breakdowns but sometimes a leak is extremely difficult to find.

 

[John.g]

If you suspected a boiler leak then with the apparent view that isolation valves don't hold, its obviously going to take longer than 20 minutes if you have to start blanking off.

 

[Cazza]

I've been in hospital before and seen patients wanting nurse attention ignored because nurses were too busy chatting. But yes of course colleagues will chat to one another and they should, what I meant was they didn't seem that motivated to fully diagnose the pressure loss. I think the ideas given in this thread says the Bosch men could have done more, things like test the isolation valves for leaking or block the airvent and see if there was a pressure rise. But they just seemed to want to do the bare minimum as quickly as possible, not to come back and move onto the next client. Even shouting at me almost that they can't come out again and saying I could have my money back, rather than get to the bottom of the issue as they promised they would if the gauge showed a drop in pressure, which it did.

 

[sammathias]

If half of your radiators are 'turnt off' then how can you test for a pressure loss successful?

 

[Cazza]

Hi. I'm not an expert, I'm no plumber and don't understand why this would make a difference as there is still water sat in the pipes. All the radiator valves have been checked for leaks (about 5 times) and there aren't any. The pressure loss test carried out by Bosch with the large gauges was on a (so say) isolated boiler and also on the radiator system at the same time. So at least it shouldn't have made any difference to the boiler test?

 

[John.g]

No it shouldn't but with "proper" isolation and two pressure gauges it should differentiate between the two systems, with both gauges falling together it certainly points to isolation valve(s) passing but doesn't tell which system is leaking.

 

[Riley]

This to and fro is kind of going in circles. If the OP gets nowhere with WB following this latest fix and contacting CEO then they will need to enlist an independent. Simplest option would be cut two ISO’s into the F & R temporarily if the ISO’s on the boiler are suspect. By the sound of it they’ve been replaced so I’d be dubious as to their failed functionality so soon . If you already have a primary filter on the return then you could isolate there.

 

[Cazza]

I'm going to leave it now for 2 weeks, to allow air to vent. If it drops down as low as 0.9 bar (from 1.3) then I will run an isolation test. If it still drops, then with it still isolated I will drain 250 ml from a radiator and watch the gauge to test the new isolation valves. If no further drop then I will assume its the boiler.
If the isolation valves are leaking I will assume it is the pipes (as my boiler sits higher than the radiators being on 2nd floor; so where the last isolation test showed both boiler and radiator leak I doubt a boiler leak would have shown up as a radiator leak).
The previous isolation test was done with a new right isolation valve, and an old left isolation valve. Now both are new. So I can't rule out the previous test had an isolation valve leak.
Thanks for all your thoughts everyone, I will put a note on my calendar to update this thread in a couple of weeks as so many have been interested. Feel free to comment further, but apologies if I don't reply as I need a break now from thinking about it ;-)

 

[sammathias]

Open 'all' the radiators...vent all the air out of radiators, when system is cold put pressure upto 2bar then isolate boiler....no drop over a day or 2 then boiler is fine, when isolation is turn back on and there's a drop then it's your rads or pipework.

 

[Cazza]

I will open all the radiators but I didn't want to put the pressure back up to 2 bar as by doing this aren't I adding air back into the boiler (which I would have just taken 2 weeks to let vent)? This would give a false pressure drop reading. I was just going to test it with 0.9 bar pressure.

 

[johnduffell]

around 50 litres is going to show a much bigger pressure loss with a cup full of water compared to a 10 rad system running at 100 litres

That's not true as water is incompressible for all practical purposes. The only bit that can expand when water is lost is the air in the expansion vessel.

I've had a system where the combi was in the loft in a bungalow, and bleeding a cup full of water out a radiator was enough to drop the pressure to nearly zero. So in my opinion, depending on the size of OPs system, yes a few drops from the isolation valves at the boiler is enough over a week, to drop 0.2bar of pressure.

That will have been a specific case where the expansion vessel no longer had any water in it. At the moment when the last water leaves the ev, the ev is full of air, so the air pressure has no effect on the system. This means the pressure on the boiler is the static head of water above the boiler. Which would be practically zero if the boiler is at the top of the system.

If the air in the ev was unconstrained, the pressure would carry on dropping smoothly.
Hope that is useful, even though irrelevant to the op.

 

[John.g]

I will open all the radiators but I didn't want to put the pressure back up to 2 bar as by doing this aren't I adding air back into the boiler (which I would have just taken 2 weeks to let vent)? This would give a false pressure drop reading. I was just going to test it with 0.9 bar pressure.

Just to be sure that we are talking about the same thing, pre pressure is the pressure at the air end of the E.vessel when its unconnected at the other (water) end, the filling (or test) pressure in your case is the pressure as shown at the boiler panel, you say you have a pre pressure of 1 bar, so if you just pressurised the system until exactly 1 bar then you will have no water (reserve) whatsoever in the E.vessel and theoretically if you drained a eggcup full of water from the system then that pressure will fall to 0, so how are you proposing to test the boiler at 0.9 bar?.
As stated above, assuming a prepressure of 1bar, a filling pressure of 2 bar will give you 2.67 litres of water (reserve) in the E.vessel, you will have 2.18 litres remaining when/if pressure falls to 1.75bar, 1.6 lires @ 1.5bar, 0.89 litre @ 1.25bar and 0 litres @ =or< 1.0 bar.

 

[Cazza]

Thanks John. I thought a Bosch guy said to me the gauge on the front of the boiler is showing you the water pressure, that the 1 bar pressure of air in the expansion vessel you can only measure with a meter connected to the expansion vessel. So I was thinking the two are separate and the gauge just measured the water sat in the heat exchanger part of the boiler. If I add water to the system until its 2 bar then I am adding air into the heat exchanger as well as water which will auto air vent and drop the pressure. I thought water only goes into the expansion vessel as the heat exchanger heats and expands the water, giving it somewhere to go.

 

[John.g]

The E.vessel contains a rubber "bladder" (called a diaphragm) like a heavy duty baloon, this is pumped up with air to whatever pressure is required, ie 0.5 bar to 1.0 bar depending on the E.vessel duty. The diaphragm will then be resting hard up against the opposite end of the E.vessel where the water connection is attached so in this state will contain 8 litres of air or whatever its capacity is.
You then open the filling valve and no water will be admitted to the E.vessel until the water side pressure is > than the prepressure, in your case (if it has been pumped up properly) 1 bar, the E.vessel will contain a certain amount of water based on this differential pressure and will compress the air on the opposite side of the bladder. Again in your case a 8 litre E.vessel with 1 bar prepressure and 2 bar filling pressure will contain 2.67 litres of water. As the boiler/system water heats up then the expanded water will be forced into the E.vessel and add to the existing 2.67 litres and the E.vessel (+boiler) pressure will rise further. There is no mixing of water and air in the E.vessel.

 

[Cazza]

Thanks for your reply John. I am still not sure what the gauge on the combi boiler is showing me exactly. Is it just the water pressure or boiler pressure (i.e. air in the expansion vessel plus the water pressure in heat exchanger and expansion vessel) ? Or is it just measuring the expansion vessel pressure water ?

 

[johnduffell]

Just to pick up where the other John left off, under normal working conditions the two will be identical. It's only setting the initial charge that it needs to be only air in there. Once your charge is set correctly and confirmed correct, you only need to worry about the overall system pressure.
The guage measures the water pressure though, hence when when the ev becomes empty it no longer reads the air pressure.

 

[Cazza]

So if the boiler gauge is only reading the water pressure and I'm doing an isolation test with the boiler off (so no water going into the ev) then I should be able to start the test with 0.9 bar water pressure

 

[Riley]

I am not being rude but this is getting needlessly complicated

 

[Cazza]

Can you not just answer my question Riley?