worcester bosch 35cdi combi

[averagejoe]

I have had this boiler for 6 years over the last 6 months i have had nothing but problems with most of the guts of the boiler having been replaced. I am now suffering the problem that the boiler keeps cycling by that i mean turn on the hot water tap and it gets so hot that the boiler stops heating the water which then goes cold then switches back on heats up again and so on. The engineer says this is correct but it has never done this in all the time its been installed, now when having a shower which is off the boiler the water goes hot and cold, a nightmare. Having tested the temp with a digital tester the water just seems to go all the way up to 70c and then switches the boiler off.
It does seem to respond to the temp switch on the front of the boiler in so much as if you set it at postion 1 it just stops heating the water earlier position 2 slightly higher and so on. Before it would reach a temp say 40c and just stay at that temp no matter how long you ran the water for.
Any thoughts would be gratefully appreciated.
Ray H.

 

[bogstandard]

The answer is probably very simple. However I have the feeling you should be changing your heating engineer - like yesterday. Get a list of service engineers in your area from Worcester. Unfortunately the fact that someone is Corgi reg is quite meaningless or indeed that they have been approved by a manufacturer, one has to mostly learn the hard way.

 

[averagejoe]

well i should have mentioned that the engineer is a worcester bosch engineer and the boiler is under contract. He is passing me over to the technical dept. but i really need abit of extra help as he is saying that that is how its ment to work and i know from the last 6 years that its not
Ray H.

 

[Agile]

He should not be passing YOU to Worcester!

It seems pretty obvious to me that probably the temperature sensor has failed or just possibly the secondary heat exchanger is blocked.

Either get an independent engineer to fix it and charge the contract provider or express your displeasure to the contract provider and give them the opportunity to fix it and say that if they cannot then you will have to call a Worcester engineer and will look to recover the cost from them.

I am not sure that your understanding of the situation is necessarily correct. The maintenance contracts are operated by organisations and they use boiler maintenance firms at agreed rates and rarely use either the manufacturer's staff engineers or independent "Worcester approved engineers".

Most of the maintenance firms seem to use lower calibre people as we are often called in by householders after the maintenance contractors have failed to correctly diagnose the problem.

Tony Glazier

 

[averagejoe]

Thanks for the quick replies, just to clarify i have a maintenace contract with Worcester bosch to service and repair the boiler in any breakdown. It is their own engineer that comes to service it and is not contracted out to any third party.
I was thinking along the same lines as yourself but when i suggested to him that it may be the heat exchanger he said as it had been replaced within the last two years it couldn't be that, i think the sensor is linked to a small PCB which has already been changed, the boiler has suffered kettling recently and I was advised to put some Sentinal in which i have done and it has made it slightly better.
Ray H.

 

[Agile]

I would be very surprised if the Contract is really operated by Worcester!

I have examined the actual Agreement now ( edit ) and its with the holding company for Worcester which is unusual. There are severe limitations within the wording on coverage of sludge problems as yours seems to be. In my view its unlikely to be covered because the system was not properly cleaned when the boiler was installed.

Just because something was changed before does not mean it will not be blocked again.

I now expect that this fellow is totally incompetent and that its just a blocked secondary HE.

Call the contact number and say you have no confidence in this "parts changer" and request another more competent person.

Tony

 

[averagejoe]

Well i am absoulutly sure that he is a worcester bosch engineer and is employed directly by them. To make an appointment i have to phone worcester bosch and have spoken to him about working for the company.
Is there any way that i can prove that its the secondary HE that is at fault
Thanks for your quick reply
Ray H
I also need to add that the whole system was installed at the same time as the boiler that includes all and every piece of pipework, it would seem strange to me if it had got sludged up enough to stop the boiler from working in such a short period of time

 

[ollski]

sounds like a sludged up hx for sure, why was it replaced 2 years ago? that must also have been on the complete new system and also when it was 2 years cleaner.....if sludge in the system is causing a problem it will always do it as long as the cause of the problem is not adressed. Personally I would come with both sensor and hx and look at them both together, the fault will be obvious.

 

[averagejoe]

The heat exchanger was chalked up, i live in a hard water area, after the new one was fitted i put in an electrical gizmo that is supposed to stop it happening again, never had much faith in it actually.
The engineer can't believe that its gone again in such a short period of time perhaps he's right but for sure there's something wrong with the boiler and it's frustrating when they don't believe what your saying and try to convince you that "thats how they are supposed to work"
also to add is the flow rate should be 15 ltrs a minute which it is if the HX is blocked that figure would be reduced, is this correct?
Ray H.

 

[ollski]

No because it would be the other side which is blocked ie the heating water can't pass through the hx to heat up the hot water so reaches temperature quickly and the boiler cuts off until it cools down, meanwhile the water is passing the other side getting hot when the boiler is on and cooling down when it goes off. The problem you had before would have been indicated by a lack of hot water from the taps.

 

[averagejoe]

Ok understood thankyou all for your informed help, thank hevens for the internet hopefully when the tech guy gets to see the boiler i am forwarned as to what to expect.
As a footnote should the engineer have spotted this or is there an excuse to be made you know " sometimes can't see the wood for the trees"
Ray H.

 

[jiminblack]

Yes, he should have spotted it! I would put money on it being a W/W heat ex. I did three today on the 35CDi. Easy, pleasant job and nice customers today too. By the way i'm a WB engineer and parts changing is not my thing! It sounds as though you got a lazy, must beat the traffic home, couldn't care less, let someone else sort it out, poor excuse for an engineer...or a new guy who just needs guidance By the way the former is a still rare in WB.

 

[Agile]

Nice to hear that some W-B engineers also agree with both my assessments! ( System + engineer )

I know that it seems odd to those without experience of heating breakdowns and to some extent warranty calls but an uncleaned NEW system sometimes gives rise to more problems that most older systems.

The explanation is quite simple. Many installers add too much flux when soldering a joint as that can make soldering easier. Normally that would be of little consequence but if the system is not properly cleaned the hydrochloric acid dissolves the steel from the rads and ends up with a pretty lethal precipitate of iron oxides which will block everything.

I still think that your secondary HE is actually blocked on the primary side by debris in the system water. That is not really covered in my view according to the Agreement! But Worcester are pretty flexible because they realise that supporting installers is paramount even if they are somewhat lacking!

The electronic water descalers are pretty useless to be honest although the permanent magnet ones are somewhat effective and usually cheaper too. The former give a money back guarantee and know that hardly 10% of people ask for a refund because they cannot be bothered!

How to get your problem solved? Follow my advice unless any of the WB people can give any better suggestions.

Tony

 

[ChrisR]

Joe - there is scope for confusing the sides of the secondary heat exchanger.
Primary side, boiler water - prone to sludging up in dirty systems. Nothing to do with hard water. When blocked, gives the symptoms you have - hot/cold/hot water, so reduced hw if you measured it over time.
Secondary side, tap water, scales up with "chalk". To begin with it can give the symptoms you have then it will reduce the HW tap flow as well.

The boiler will "see" the water temp too high, whichever side it is, but can't regulate it quickly enough, because the response time is slowed down by the sludge or scale, so it can only turn off, turning your water cold.

If your boiler has been producing tap water over 65º (too bloomin hot), for whatever reason, it will quickly scale up like a kettle on the HW side. A case of one fault leading to another.
And 2 years between sludged primary problems is common too.


"when having a shower which is off the boiler the water goes hot and cold"
Thermostatic showers can cause a problem when the cartridge is getting old. If it sees the output too hot the valve reduces the HW inlet flow - which then makes the hw hotter, so it reduces the flow more, and so on until the boiler turns off.

Aren't combis great!

 

[Paul Barker]

Just to pick up on a point about service contract staff tony made, though I realise no longer strictly relevant to this thread.

I met a local contract engineer, wasn't impressed by his demeanor and then came the conversation. BAsically he does the least possible to get the boiler working, knowing full well there are many more problems which will precipitate another breakdown very soon ad infinitum. His response to that, good another call out later. He gets paid per job.

When an independent like ourselves comes to your boiler, we do our best to get it ALL right, because we hate call backs.

Of course this shouldn't apply to manufacturers' service contracts and I would be very surprised if it applied to any BBT engineers.

To get a proper diagnosis and a real attempt to SOLVE your heating problems, call someone who has a vested interest in getting it right first time. If you want repeated engineer visit, call someone who gets payed for every visit.