Worcester Bosch Greenstar CDi with opentherm

[snewb]

My Hive thermostat took a tumble and the display broke so was in the market for a new thermostat. Screwfix had a black Friday deal on a Nest so here we are. Wired it in binary on/off mode but read about the opentherm connectivity so as others in this forum have discussed I picked up Bosch/Netstats opentherm / EMS convertor from ebay. This is where my problems started. The Nest can see the boiler (it complains when I unplug the EMS connection from the boiler) so I know it's making a connection but the boiler is permanently on. CH water temp is the only control I have so I have reverted back to on/off for now. I've found a Technical bulletin for another model that talks about needing additional parts or a factory reset to tell the boiler to look for an external control. Any ideas and is this DIYable? If I try a reset is there a way to make a note of settings and re-enter them or is this a bad idea?

 

[harrythefurrysquid]

I think @Ranking Roger might have run into the same issue:

Heating Zone for Loft Conversion

Hi All, I'm in the process of getting quotes for a loft conversion for our bungalow. We currently have a Worcester-Bosch Greenstar 34CDi Classic combo boiler (installed 2013) which we have been told will be able to cope with the 2 additional bedrooms. It's installed in the garage, so if it...

www.diynot.com

I didn't have a solution for him, but pinging just in case he found one.

I used the same converter with a Greenstar 30i and it fired right up, but I'm starting to think I was lucky!
I presume you've done the obvious and turned it all the way off and on again.

[edit - my bad, you already linked the same bulletin. If it were me, I'd probably be trying that next. But obviously you're running the risk of breaking it in cold weather and needing a callout. That said, installation instructions are easy to find online, so you have the same info as a typical heating engineer would have, I think.]

 

[snewb]

Thanks @harrythefurrysquid. I'm a little wary of trying a factory reset. I'm imagining explaining to the wife and kids why when it was working I've messed it up.

Is there anything I can do to remove that risk from a factory reset? Is thre a good online source on the Greenstar menus? The manual is light in that area. Could nothing go wrong with a reset? Would my installer have changed much when putting it in or at its annual service? Thinking maybe I should just wait until the next service before trying again.

 

[harrythefurrysquid]

Thanks @harrythefurrysquid. I'm a little wary of trying a factory reset. I'm imagining explaining to the wife and kids why when it was working I've messed it up.

Is there anything I can do to remove that risk from a factory reset? Is thre a good online source on the Greenstar menus? The manual is light in that area. Could nothing go wrong with a reset? Would my installer have changed much when putting it in or at its annual service? Thinking maybe I should just wait until the next service before trying again.

I think that might be wise TBH.
I think OpenTherm only gives a few % extra efficiency at most so maybe better just to leave it in relay mode until the summer.

Also I think I'll stop mentioning that adapter. I have no idea why it worked for me straight out of the box but so far that's two separate people in a few days who have had basically the same show-stopper.

 

[snewb]

I think that might be wise TBH.
I think OpenTherm only gives a few % extra efficiency at most so maybe better just to leave it in relay mode until the summer.

Also I think I'll stop mentioning that adapter. I have no idea why it worked for me straight out of the box but so far that's two separate people in a few days who have had basically the same show-stopper.

Apparently there are numerous versions of the EMS bus. Maybe my boiler is incompatable with the opentherm adaptor's EMS version ‍

Did find this page though all about a little bit of kit you can buy to fiddle with the EMS bus. https://bbqkees-electronics.nl/wiki/gateway/how-the-gateway-works.html

If only I had more time although maybe I should start on smart light switches and ip cameras rather than the box in my kitchen that burns explosive gasses.

 

[MJN]

If only I had more time although maybe I should start on smart light switches and ip cameras rather than the box in my kitchen that burns explosive gasses.