Worcester 8000 Regular and PDHW

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This is about my uncle’s boiler. He recently got a Worcester Bosch 8000 Regular.

He’s thinking of getting a new cylinder which heats more quickly, and we were talking about PDHW. The manual is confusing because in a couple of places it talks about fitting a WB cylinder sensor to activate the HW button. But when I rang WB they said that is a mistake, and that the HW button has no function on the 8000 Regular. They said the button only works on the system version, and that PDHW can only be done with the system version, by fitting WB integral diverter valve and cylinder sensor. I’ve asked twice now and been told the same.

Anyway, there’s a short Youtube video of a gas engineer called Richard, from Mid Wales Plumbing & Heating Supplies (which I think is also the Intergas Shop), converting an 8000 regular to PDHW. The important bit seems to start at 1 min 38 secs. He says he’s fitted a 10k Ohm resistor where the cylinder sensor would go. Then he says something I don’t understand, along the lines of the boiler now thinks it’s 30 degrees. But having done this, he says PDHW is enabled, and can be controlled by any external controller.

He is using EvoHome, but he says any controller can be used. My uncle has an S-Plan with a normal cylinder thermostat. I’d like to know if this might be possible with my uncle’s set up. Here's a still from the video showing the resistor.


WB 8000 PDHW.png


 
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Obviously it does, WB won't want to admit to anything that they don't recommend. Do remember, any pi$$ing about with things that aren't covered by the company won't be covered by the warranty. I don't know why they would say the regular wouldn't enable HW though as I would presume they are exactly the same (regular and system), albeit it's without the EV and pump so it'll be shy a few settings etc.

In it's manual it does have the HW cylinder sensor referenced so again I don't know why they say it won't do HW and therefore PDHW

The resistor is just to fool the boiler into thinking that it has a WB cylinder sensor installed & that's reading 30deg and then using some clever wiring with a separate switching relay to switch the external controls over from CH to PDHW plus the OT system set to run as PDHW.
 
I hadn't actually thought about the warranty. It seems such a tiny thing to add a resistor. But, I've read that the electronics on boilers quite often go wrong. Are these connections part of the PCB? I can just imagine if that needs replacing they would blame this sort of thing.
 
The installation manual is confusing. In fairness, it does clearly state at one point that the Hot Water key doesn't work on regular boilers. Although, it makes you wonder why it is there, in that case? But then three times later it talks about fitting a cylinder sensor to control the DHW.
 
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Obviously it does, WB won't want to admit to anything that they don't recommend. Do remember, any pi$$ing about with things that aren't covered by the company won't be covered by the warranty. I don't know why they would say the regular wouldn't enable HW though as I would presume they are exactly the same (regular and system), albeit it's without the EV and pump so it'll be shy a few settings etc.

In it's manual it does have the HW cylinder sensor referenced so again I don't know why they say it won't do HW and therefore PDHW

The resistor is just to fool the boiler into thinking that it has a WB cylinder sensor installed & that's reading 30deg and then using some clever wiring with a separate switching relay to switch the external controls over from CH to PDHW plus the OT system set to run as PDHW.

I've had two email replies now, saying the same as the two phone calls.

One said this boiler can't do PDHW, as it can only provide flow at one temperature. The other one said that the settings below have been printed by mistake in the manual, and should only be in the system boiler manual. It's all a bit bizarre, because we have seen above that the cylinder sensor connection is present and active in this boiler, and that two different flow temperatures can be produced. I'd have thought this would be something they would want to promote.

8000 Life DHW control.jpg
 
Only way to be sure would be to enable it ... as suggested though, if you do and strange things occur then the warranty may be an issue.
 

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