Evohome, Vaillant 637 s plan and opentherm
Posted: Mon Jan 08, 2024 4:54 pm
Hi everybody
I note that this is a fairly quiet part of the forum so I am not holding out much hope, but it bugs me so I need to try!
My set up is as follows:
- Vaillant Ecotek 637 plus system boiler
- Unvented hot water tank
- S plan set up with one BDR91 doing the central heating circuit via an actuated valve and a second BDR91 doing the hot water system via a second actuated valve controlled by a hot water kit with the thermocouple in the thermowell on the tank.
- I have two control panels, one controlling downstairs rads and the hot water, and the other controlling the upstairs rads. I guess both are bound with the heating BDR91.
- Each rad has a HR92.
Reading up, there are simpler ways of setting it up but, it works fine as set up and I am happy with it. I use a lot of gas so any fractional improvement is of benefit.
My boiler is about to end its 7 year warranty. I want to explore whether my system can use opentherm. I know as standard, that Vaillant boilers in the UK cannot work with opentherm but I am willing to get the VR33 to modify the boiler. My question is, is it possible to have opentherm for this S plan design, and if so, how does the boiler know to go to a higher temperature for water reheat vs. heating flow temperatures. Also, how does it get wired, do I remove the actuated valve for the heating system? I looked a while back and couldn't find any obvious circuit drawings to understand how it would be set up. I think I would get a R8810 to replace the BDR91 on the heating valve and remove the valve (?), but retain the hot water BDR91 with valve, but if so, how does the boiler know to increase temp for hot water.
Thanks very much for anybody that can point me in the right direction. It would be fine to say "you can't do it" as it can put a stop to me looking into it and wasting my time!
I note that this is a fairly quiet part of the forum so I am not holding out much hope, but it bugs me so I need to try!
My set up is as follows:
- Vaillant Ecotek 637 plus system boiler
- Unvented hot water tank
- S plan set up with one BDR91 doing the central heating circuit via an actuated valve and a second BDR91 doing the hot water system via a second actuated valve controlled by a hot water kit with the thermocouple in the thermowell on the tank.
- I have two control panels, one controlling downstairs rads and the hot water, and the other controlling the upstairs rads. I guess both are bound with the heating BDR91.
- Each rad has a HR92.
Reading up, there are simpler ways of setting it up but, it works fine as set up and I am happy with it. I use a lot of gas so any fractional improvement is of benefit.
My boiler is about to end its 7 year warranty. I want to explore whether my system can use opentherm. I know as standard, that Vaillant boilers in the UK cannot work with opentherm but I am willing to get the VR33 to modify the boiler. My question is, is it possible to have opentherm for this S plan design, and if so, how does the boiler know to go to a higher temperature for water reheat vs. heating flow temperatures. Also, how does it get wired, do I remove the actuated valve for the heating system? I looked a while back and couldn't find any obvious circuit drawings to understand how it would be set up. I think I would get a R8810 to replace the BDR91 on the heating valve and remove the valve (?), but retain the hot water BDR91 with valve, but if so, how does the boiler know to increase temp for hot water.
Thanks very much for anybody that can point me in the right direction. It would be fine to say "you can't do it" as it can put a stop to me looking into it and wasting my time!