OpenTherm bridge

[Luddite]

Can somebody please tell me what one of these does - why/when it is needed, and why/when not.

It's an element in the comms link between a controller/stat/programmer type device and an OpenTherm supporting boiler. Why can't whatever it does be done by the device?

[Richard]

This might help?

https://theevohomeshop.co.uk/content/21 ... me-with-it