boiler behaviour,please let me know your thoughts.

[MrPotts]

21 minutes ago, SimonD said:

 

You've basically got 2 options here. Buy the optional WB diverter kit with a DHW cyllinder sensor and then get a friendly gas safe person to come and fit it. Then you need to add some controls so either weather comp sensor, and/or WB Easy Control. With this option you can only run a single heating zone because the weird way WB have decided to implement their technology means that if you have zones you forefeit modulation and then have to run relay on/off heating.

 

The second option is to get a Nefit opentherm/ems converter from the Netherlands and wire this into the boiler along with an openterm controller. This can then be configured using EPH CH4 combipack control with the CP4 DHW control to provide priority hot water, so 2 flow temps. With this you can have up to 6 heating zones. Now, this is not an official thing, but the Nefit is made by Bosch Thermotechnic, and although it has worked for me, I've found one of two mentions online where it hasn't worked on a specific WB boiler - but I don't know whether this is because it hasn't been wired up properly as these mentions were diy stuff.

Thanks for the info. I dont want to go the diverter kit route as that, I believe, needs a 4 pipe system which I dont have or want. When I spoke to WB about the Easycontrol I was told that it won't give two flow temps on my boiler. I will look into the Nefit option, presumably this will also need the NC heating zone valve to be replaced with a NO zone valve.

Edited April 2 by MrPotts

[SimonD]

6 minutes ago, MrPotts said:

NC heating zone valve to be replaced with a NC zone valve

 

With the EPH controls you don't need to change your valves as it's managed through the controller wiring. So the 2 normally closed valves stay in place.

9 minutes ago, MrPotts said:

When I spoke to WB about the Easycontrol I was told that it won't give two flow temps on my boiler.

 

Not on its own it doesn't. It needs the option diverter kit which has the dhw cylinder sensor - this is what gives you 2 flow temps, but for boiler modulation you then need the Easy control or weather comp.

[marshian]

8 hours ago, Post and beam said:

I believe it is clear what the observed issue is.  I believe that to all practical standards it is not likely to be possible to detect if the CH water experiences the same pause to heating. And in any case the engineer has confirmed what he does observe and why. He said himself that opening TRV's ( at least one) does stop the issue at the hot water taps. He also agreed that changing our house heat behaviour, while effective, is not the answer to the problem and that the boiler should be able to cope with how we want/need to live.

But that Worcester Bosch would not be offering to replace the device for this scenario.

 

I agree it's very clear what the issue is............

 

Establishing if the issue affects CH is quite easy - just park yourself in front of the boiler when the house is up to temp and most of the TRV's have shut down.

 

Observation is often the key to seeing whats happening - it's almost certainly doing the same - it's just with a massively elevated flow temp the recovery time for the boiler from the fault timer isn't taking a long enough time to cause the house to cool down because the rads that are still in use have to cool down from 82 deg flow temp and that'll take a while.......

 

So the engineer has given an option that has been demonstrated to stop it happening - you don't want to take up that idea.

 

The "agreement" of the engineer that is shouldn't need you to change your house heat behaviour and the boiler should be able to cope with how you want/need to live is because he recognises you aren't going to change no matter what he says, You are convinced it's the boilers fault - it's his "get out of the situation" because he is unable to educate you out of the issue.

 

He knows full well WB wouldn't entertain replacement of the boiler for the situation you force the boiler to work under.

 

To be blunt - it's a situation of your own making.

[John Carroll]

I would take careful note of what SimonD said in one of his posts before ......"max boiler temp of 82C it would sometimes get to over 90C as the cylinder reached target temp and the diverter valve closed and the system then relied on the bypass only for flow. But never did the boiler block as such, just tripped the burner as would be expected."

Edited April 3 by John Carroll

[Post and beam]

11 hours ago, marshian said:

The "agreement" of the engineer that is shouldn't need you to change your house heat behaviour and the boiler should be able to cope with how you want/need to live is because he recognises you aren't going to change no matter what he says,

You were not there and you are incorrect. I did not express to him the views that i have here. He offered his own opinion that we should not need to alter our home to suit the boiler. Whether this is a good or bad strategy is another question.

[SimonD]

19 hours ago, John Carroll said:

Interesting, looking at their reply again they said the heat exchanger temperature and not the flow temperature so there could be a significent difference in these depending on where the sensor is attached, could be something as simple as a faulty or badly attached blocking sensor?

 

I was wondering about this. These boilers have the horrible drum hex with the high temp limit sensor at the back of the top of the hex. The flow sensor is separate on the flow pipe behind/next to the fan assembly. There could easily be a significant difference between these.

 

But to me it seems odd that the error being thrown is essentially a 'no flow' condition rather than low flow. Technically, the boiler shouldn't need an external bypass, but there is no mention of internal bypass built into this boiler.

 

I also wonder about whether the no flow situation might happen as the boiler switches over to DHW and this throws the sensor due to a brief moment of poor timing with the burner/diverter/pump  and resultant flow velocity? However, the blocking fault should automatically clear as soon as dhw flow happens and the flow temp reduces, which clearly doesn't happen and the result is cold shower..

 

So back to either a design or component fault I suppose as whatever causes the fault, it should clear itself..

[John Carroll]

20 hours ago, SimonD said:

 

I was wondering about this. These boilers have the horrible drum hex with the high temp limit sensor at the back of the top of the hex. The flow sensor is separate on the flow pipe behind/next to the fan assembly. There could easily be a significant difference between these.

 

But to me it seems odd that the error being thrown is essentially a 'no flow' condition rather than low flow. Technically, the boiler shouldn't need an external bypass, but there is no mention of internal bypass built into this boiler.

 

I also wonder about whether the no flow situation might happen as the boiler switches over to DHW and this throws the sensor due to a brief moment of poor timing with the burner/diverter/pump  and resultant flow velocity? However, the blocking fault should automatically clear as soon as dhw flow happens and the flow temp reduces, which clearly doesn't happen and the result is cold shower..

 

So back to either a design or component fault I suppose as whatever causes the fault, it should clear itself..

 

I spoke to WB technical and they agreed that the "2965" sensor should not reach 88C when the  flow temperature reaches  90C or more, the person I spoke to wasn't aware that a low flow as such should trigger it, he suggested that WB technical are again contacted.

[John Carroll]

Found this in one of the MIs so if this is the 2965 sensor then it looks like it must reach 120C to operate  and doesn't reset until it falls to 80C.

 

[marshian]

On 04/04/2024 at 16:35, John Carroll said:

Found this in one of the MIs so if this is the 2965 sensor then it looks like it must reach 120C to operate  and doesn't reset until it falls to 80C.

 

 

Yikes - that's a seriously hot boiler HE core to trigger that............