I finally plugged in my OTGW device that has been sitting in the box for over a year. My set up is the Evohome OTB is plugged into the VR33 (OT <-> eBUS) on a Vaillant 438 boiler. For the last couple of days, I have the OTB passing through the OTGW before going to the VR33.

I have the OTGW set up as a Monitor only, which in theory is supposed to pass messages unchanged. However what I have noticed is the simple presence of the OTGW in the chain sets the max boiler flow requested temperature to whatever is set as a default on the OTGW. So I am no longer seeing the 90C heat requests on the boiler.

I have been lucky that the Vaillant has always allowed me to clip the max temperature based on the knob in the front. But I just thought that might be a solution for anyone wanting to use the Evohome OT Bridge but where the boilers are expecting the "Optional" Max temperature to be set, but the OTB doesn't set it. This causes those boilers to just ramp up as far as near 90C as physically possible.