Worcester 30cdi system pressure problem

[alexlindley]

Hi,

I apologise that my first post is about a problem but I wasn't sure who else to ask about this, so I would be really grateful if there was someone who could give me a bit of advice with my current situation. I did have a quick search on here but couldn't find anyone with a similar problem.*

I have a Worcester 30cdi combi which was fitted Aug 2009 and worked great until Dec 2010. I noticed that the Pressure was falling and even though I'd fill up the system the pressure would fall back down. This got progressively worse until it was dropping from 1.5 to just above 0 in a day. I called out the worcester-Bosch man as it has a 2-year warranty and he came and changed the heat exchanger saying he couldn't really see anything wrong but there may have been a small leak in the heat exchanger so he swopped it for a new one.*

This seemed to fix the problem as I kept an eye on the pressure after this and it didn't drop as it did before so I thought it was fixed. But then I checked it a week or two ago and noticed the pressure had dropped a little. I filled it up a little, bled the rads and there was a little bit of air in the attic rad. Thinking it mint be a small leak I added some leak sealer super concentrate and I've not had any air in the rad since then.*

I've had to top the system up every three days or so and it goes down much much quicker when it's in use than when it isn't. I really don't think it's a leak as I've put so much extra water into it I thought I would have been sure to see it somewhere by now?

There is no leak I can see from the boiler itself as it's in my kitchen above the worktop and the escape pipe outside is dry (I've had a bit of paper towl in there to make sure).*

I'm going to call out Worcester-Bosch again but they make a point of saying there will be a charge if no fault is found so I was hoping someone on here might have an idea of what it might sound like so I can get the guy to check everything as he seemed in a rush last time!

It just seemed really odd that it seemed fixed then within a month it is gettin back to being as bad as it was!

Sorry that was such a long description but thank you in advance for your time and help.

Alex

 

[Bartdude]

Is the pressure relief valve passing water?There should be a pipe coming out beneath the right hand side of the boiler which discharges outside,see if you can see water on the wall maybe,a sure way to check is to tie a plastic bag around it for a day or so and see if it fills at all.

Does the pressure rise to 3bar when the heating is on?There could be a problem with the expansion vessel.Did the guy from Worcester check it?

 

[alexlindley]

I have wondered if it's leaking before it gets outside but there doesnt seem to be any water around the wall. I will pull the pipe casing off so i can get a closer look.

I've only ever filled it up to 1.5 bar and when it's on it gets to 2. I could try over filling it to get to 3 bar?

Does the expansion vessell control the pressure release valve?

He didn't really say exactly what he checked but he did say it was likely to be a leak if what he did didnt fix the problem.

 

[Bartdude]

Don't fill it to 3bar,if it only goes to 2 then that's fine.

If the expansion vessel is faulty then the pressure relief valve operates,it has a washer that can fail.Can you find where it discharges outside?It will be a small copper pipe that should be facing down and against the wall.You need to check it outside,not inside. I didn't explain that too well!!!

 

[alexlindley]

Im pretty sure it's not coming out the release pipe outside because I put a piece of kitchen roll up there to see if it would get wet and after a few days it was still dry. I have wondered whether it could be leaking into the wall before it gets outside.

Is it easy for the boiler man to check this from the inside to see if the water is going down there or if the valve is faulty?

 

[Bartdude]

I doubt that it would be leaking in the wall,very unlikely.

There could be a leak on the heating system somewhere,I had a similar problem last week. I disconnected the heating pipes and rigged up a pressure test on the radiator pipework,which showed a leak. Finding it can be difficult sometimes,I got lucky and found it quite quickly!

Did Worcester suggest it could be the heating system?They normally do!

 

[alexlindley]

Yeah he said if what he did didnt fix if then it would be the system. I jus have no idea where it could be leaking as I thought I would have seen all this water by now. (i live in an old Victorian terrace). A pressure test on the system would be useful, wish they would do that before deciding to blame the system.

Thanks for the advice, I guess I need to do that test so I can be sure whether it's the boiler or the system, do the Bosch people ever do that test?

 

[gassafe]

Okay this is a long shot but maybe its a dodgy pressure gauge!? ... Could try fitting another one on the heating circuit if this is suspect! It seems rare a Worcester barely 2 years old is leaking!!! Keep us informed =]

 

[alexlindley]

It's a possibility but I've put extra water into the system so many times I'd have thought the pressure would have got too much by now?

If the heat exchanger was leaking would it only leak when the system is on or would it leak a little when the system is off too?

 

[gassafe]

It would leak all the time i wud have thought... Also a long shot on a worcester cdi i wud imagine!
To eliminate the boiler you could try putting the pressure up, noting where it is on the gauge and then isolating the boiler with the valves below the boiler (ch flow and return) if the pressure stays steady then the boiler is fine!? IF it drops when u open up the valves again must be a leak on the circuit!?
You wud have to turn the boiler off to do the above test mind, so u wud have no heat or hw on a combi.
Just a thought anyway!!

 

[Centralheatking]

Isolating the boiler from the heating circuit as gassafe suggests is a good way to locate the pressure loss area. Do it with the power to boiler off and do it when house is empty during the day.

If the boilers pressure stays constant it will be the heating side. Now a leak such as you describe on the radiator circuit might go undetected and undectable - such that the difference between 1.5 bar and 0.5 on a normal 7 rad sized system might only be a pint or so which can evaporate from a hot joint leaving no real sign. That sort of volume over a week or so is hard to spot.

centralheatking

 

[alexlindley]

That sounds like a good idea, at least I'll know where the problem is!

Just to get this straight I need to:
- Turn the boiler off
- Fill the system up to say 1.5, and take a note of where it is
- Isolate the boiler (I can see there are four pipes coming out the bottom of the boiler, the two outer ones have little pics of rads next to them so I guess they are the ones I want. They have flat head screwdriver turning screws so turn them so they are off)
- Leave it for a few hours and see if the pressure moves
- un-isolate the boiler by turning the flow and return back to how they were
- turn boiler back on

Then hopefully I'll have a better idea of whats going on. Are there any situations where the boiler would only be leaking when turned on? say if the boiler is leaking through the pressure relief valve will it still do this if the boiler is off?

Again, thanks for the help guys!

 

[alexlindley]

I did the test I describe above today and this is what I found...

I turned the boiler off let it cool for an 45/60mins then filled it up to 1.5 bar (see first pic), I isolated the boiler from the radiators by turning the inlet and outlet 90deg to the off position. I left it all day while I was at work (from 9am to 6pm) and when I got in I would say it had moved 0.1 bar (see middle pic). I then opened the outlet and inlet to the radiators and it dropped further to around 1.2 bar (see last pic).

Does this mean I've got a leak in the boiler and the system? 🙁

Or is it possible that the 0.1 bar lost in the boiler was just cooling over the day? Maybe I would have to experiment leaving the boiler isolated longer to see if it lost more than 0.1 bar?

If any one has any advice on this it would be great, as I still have no idea where this blumin leak is!

 

[mattwebbs]

Hi Alex, what was it in the end? I'm having exactly the same problem.

 

[alexlindley]

Hi Matt,
I followed all the piping around the house in close detail and then found a small leak under the floor in the attic. It definitely wasn't obvious but once fixed the pressure problem was no longer!
i hope you manage to get it sorted, I know how frustrating it all is!

Alex