Boiler kittling again after 2 yrs of fixing.

[RayPlumb]

A bit of history first. 2 yrs ago visited a grant boiler with boiler and pipework kettling. I added SentX200 noise reducer.
It is standard open vented system S plan Also found there was no bypass and this was an external boiler with frost stat so boiler would start with no valves open... Client a few days later agreed it needed more work.
I then drained and installed an auto bypass also replaced the air separator and feed pipe (starting to fur) added 2 x sentinel X400 and allowed to clean for 8 days. Then drained and flushed through a few times added 2 x bottles X100 inhibitor. Returned a few days later to check header tank was checking water level to see if leaks as estate has history of screaded copper pipes leaking. Also why don't want to convert to sealed system.
At this point I added another bottle of X200 noise reducer.
All worked fine and quiet until today on a service I could hear it start to kettle again.. and the over heat had tripped.
Mag filter had a bit of sediment in it. I checked the boiler temp with a temperature probe in a spare probe pocket and at 1/2 temp dial setting the water temp would get to about 88deg then shut off then on as usual until hot water cylinder satisfied, when pump and boiler would switch off. The residual heat in the boiler would then rise from 88 to 104 deg and Kettling starts for a few minutes. Didn't trip overheat this time. I've turned the stat down a bit .
Q. Have I done anything above wrong for this to come back?
Q. Does the sentinel X200 noise reducer need topping up or is it meant to last...
Q. Could the temp stat be faulty, do they go out of sink? or could this be just boiler scale build up giving a delayed temp reading.
Any ideas feedback and suggestions welcome.

 

[Chuck]

It seems to me that the system has a leak and is continually topping itself up with fresh hard water in order to maintain the level. This will cause both scaling and corrosion, which is what's killing the system.

IME, the sorts of pressures involved in a sealed system don't cause leaks in sound pipework. Sealing a system will make pre-existing problems easier to spot.

 

[Chuck]

It's me again. Sorry, but I misread the original post and my answer above was written while under the impression that the scaling you found was recent not historical. So, probably not relevant.

You don't say which model boiler you are looking at but I would expect the water temperature dial to go from 40°C minimum to 80°C maximum. If we're talking about the same thing, your 88°C at the halfway setting seems too high to me, I'd expect that to be more like 60°.

 

[RayPlumb]

It's me again. Sorry, but I misread the original post and my answer above was written while under the impression that the scaling you found was recent not historical. So, probably not relevant.

You don't say which model boiler you are looking at but I would expect the water temperature dial to go from 40°C minimum to 80°C maximum. If we're talking about the same thing, your 88°C at the halfway setting seems too high to me, I'd expect that to be more like 60°.

Hi Chuck
Boiler is a Grant vortex ext 21-26.
I thought the temp should be as you say above but not sure if the stats go out of temp range? Ive only experienced a completely failed stat. Could a new stat help with the kettling.
There is no evidence of a leak but saying that all the plumbing downstairs (5 rooms) are in screed and under tiles so not easy to find. I could try a low pressure test with F&E capped just to see if a leak at all.
If im getting fresh limescaling from a topping up feed tank , whats the best descaler or is that now stuck in the boiler. Sentinel X400 i used is good for sludge...
Could I just add X200 noise reducer again until leak shows itself then convert to sealed system. ...

 

[Chuck]

According to the current boiler manual:

https://www.grantuk.com/media/5030/grant-vortex-eco-utility-and-utility-system-installer-uk-doc-0124-rev-20-july-2022.pdf

The boiler thermostat range is "50°–75°" so the flow temperature you've observed (88°C) with it set midway is significantly out of specification. 88°C is also above the maximum for the boiler, which is likely why you are getting kettling.

I'd check the thermostat sensor is snuggly installed in its phial. If that's not the problem, and it probably won't be, it's time for a new thermostat.

Sentinel do a X100 test kit so you can confirm the inhibitor levels in the system.

 

[exedon2]

As above check stat sensors are in place (right hand side of boiler) they only push in not held in !
At the temperature your recording plus kettling I would have expected over heat stat to work so check that as well.
If you need technical advice phone Grant they really are excellent.
Even out of warranty they still advise in stark contrast to some other oil boiler manufacturers.

 

[RayPlumb]

Thanks I checked the thermostats and securely in the phails. there is a 3rd one not used so put my thermostat in there so presume same temp as delivered to boiler stat. Ill look into changing the stats next time.

 

[John.g]

Hi Chuck
Boiler is a Grant vortex ext 21-26.
I thought the temp should be as you say above but not sure if the stats go out of temp range? Ive only experienced a completely failed stat. Could a new stat help with the kettling.
There is no evidence of a leak but saying that all the plumbing downstairs (5 rooms) are in screed and under tiles so not easy to find. I could try a low pressure test with F&E capped just to see if a leak at all.
If im getting fresh limescaling from a topping up feed tank , whats the best descaler or is that now stuck in the boiler. Sentinel X400 i used is good for sludge...
Could I just add X200 noise reducer again until leak shows itself then convert to sealed system. ...

Its easy to check for a leak, just tie up the ballcock for a few days, or if its dripping without the F&E overflowing then probably a leak.

Possibly pump or pump ports & impeller sludged up, are the rads heating up OK or very slowly, my OF Firebird (20kw) will get up to full operating temperature of 70C in ~ 20/25 minutes from cold and then the burner cuts out.
Any idea of the pump make/model/setting and the ABV index setting/.