WB Greenstar boiler technical info required

[Mister Banks]

I have a Worcester Bosch Greenstar 24i system boiler (GC Nr 41-311-68 NG), I am searching for technical information regarding exactly how this boiler works specifically how the various connectors on the PCB communicate with external controls. The installation and commissioning manual has some info but it is very sparse.

Thanks for any info.

 

[CBW]

It should be in the mi’s, but will only tell you what and where to connect with what voltages. Probably better if you ask us what exactly do you want to know and trying to achieve?

 

[Mister Banks]

It should be in the mi’s, but will only tell you what and where to connect with what voltages. Probably better if you ask us what exactly do you want to know and trying to achieve?

I’m investigating changing from an s plan to a PDHW system. I can see on the boiler PCB that the connectors I need to use are ST10 and ST8 and I can see where the Bosch Easycontrol plugs in but there is no information on how these connections electrically communicate with each other or how the Easycontrol controls boiler temperatures.

 

[MNW67]

Is it possible that your version of the boiler is too old to do PDHW? For example, I can't see the second switched live which the new version of this boiler has.

 

[Mister Banks]

Is it possible that your version of the boiler is too old to do PDHW? For example, I can't see the second switched live which the new version of this boiler has.

My boiler was installed in 2015 so It is possible, or likely, that my boiler can’t control the change to flow temp but maybe the Easycontrol can tell the boiler to change via EMS. I have asked Bosch support but not heard anything from them.

If the boiler can’t change the flow temp itself or via Easycontrol then I can still go to a PDHW system in preparation for changing the boiler and HW cylinder in the near future.

 

[Mister Banks]

I'm getting somewhere now. ST8 is the connection for the cylinder stat, when the stat is closed will it prompt the boiler to increase the flow temperature as it is calling for heat? ST10 is the connector for external controls, LR is a switched live connection but there is no indication if this is a switched live to the external controls of from the external controls.

You would have thought the installation instructions would explain all this but its no help at all.

Edit: I have found a wiring guide, ST10 LR is an input.

 

[MNW67]

I'm getting somewhere now. ST8 is the connection for the cylinder stat, when the stat is closed will it prompt the boiler to increase the flow temperature as it is calling for heat? ST10 is the connector for external controls, LR is a switched live connection but there is no indication if this is a switched live to the external controls of from the external controls.

What is the date on the installation manual you are using? I have found four different versions for your gas code. Is it 2013/12? Then there was a new model, with a different gas code, from 2015.

You would have thought the installation instructions would explain all this but its no help at all.

I've found that all the WB manuals seem to be like this with PDHW. They seem to want to force you to go down the route of using their proprietary solution i.e. the integral diverter valve.

 

[Mister Banks]

I'm using the 2013/12 manual. Looks like i won't be able to get my boiler to manage the changes in flow temp but maybe the Easycontrol will do it. I need to speak the WB about their Easycontrol as there is next to no info online.

I now have a wiring guide but WB only want us to connect the boiler to an inefficient s or y plan.

 

[MNW67]

Don't you have Drayton Wiser? What's prompted the change?

 

[Mister Banks]

Don't you have Drayton Wiser? What's prompted the change?

I'm just looking at improving the efficiency of the boiler by possibly using load or weather compensation. PDHW looks like a good way of doing this. The Wiser is just an on/off control which works well enough given its limitations.

 

[MNW67]

I'm just looking at improving the efficiency of the boiler by possibly using load or weather compensation. PDHW looks like a good way of doing this. The Wiser is just an on/off control which works well enough given its limitations.

I've been trying to understand how the WB approved method for your boiler works. Presumably the signal from the Cylinder NTC or Cylinder Stat triggers a voltage from the ST17 connector to the WB diverter valve? That sounds a bit like how Intergas do it (I think!). I wonder whether it is possible to redirect that signal to your S-Plan valve, instead of the WB diverter valve. Would it be the right voltage? This is just a bit of fun at the moment!!

 

[Mister Banks]

I have produced a wiring diagram that converts an s plan to a PDHW system using my Wiser as the controller. I would need to replace the CH normally closed zone valve with a normally open zone valve and connect the DHW and CH zone valve brown connections together and connect these to one side of the cylinder stat which takes a switched live feed from the Wiser hub.
Using the Wiser DHW timer a live feed goes to the cylinder stat which, if heat is required, will be closed. This then sends the live feed to the CH zone valve (closing it) and the DHW zone valve (opening it) and the DHW zone valve fires the boiler.
If the cylinder stat is open then the DHW zone valve will be closed and the CH zone valve will be open by default so in this scenario i will have room heating if the room stats request heat.
The issue with this method of connectivity is that I have no means of increasing or decreasing the boiler flow temps hence why I am investigating how Bosch Easycontrol works.

 

[Exedon]

I have produced a wiring diagram that converts an s plan to a PDHW system using my Wiser as the controller. I would need to replace the CH normally closed zone valve with a normally open zone valve and connect the DHW and CH zone valve brown connections together and connect these to one side of the cylinder stat which takes a switched live feed from the Wiser hub.
Using the Wiser DHW timer a live feed goes to the cylinder stat which, if heat is required, will be closed. This then sends the live feed to the CH zone valve (closing it) and the DHW zone valve (opening it) and the DHW zone valve fires the boiler.
If the cylinder stat is open then the DHW zone valve will be closed and the CH zone valve will be open by default so in this scenario i will have room heating if the room stats request heat.
The issue with this method of connectivity is that I have no means of increasing or decreasing the boiler flow temps hence why I am investigating how Bosch Easycontrol works.

What you are describing is fairly much what is described as X plan.
We use it on Ideal Vouge system boilers, on multi zoned systems you feed all the healing zone valves through the normally open valve.
The Vouge of course automatically rates up to 80c when wired for hot water priority.

 

[Mister Banks]

What you are describing is fairly much what is described as X plan.
We use it on Ideal Vouge system boilers, on multi zoned systems you feed all the healing zone valves through the normally open valve.
The Vouge of course automatically rates up to 80c when wired for hot water priority.

Yes, an X plan. My issue is can I get my Greenstar boiler to automatically increase the flow temp for hot water. I know this cant be done with Wiser controls but maybe the Bosch Easycontrol can do it?

 

[Mister Banks]

My other conundrum is....why is a Honeywell NO zone valve 3 times more expensive than a Honeywell NC zone valve!