Mine also, my heating is often running at ~40° unless it's bringing it up from being off overnight or something. Recently I installed a Nest thermostat and doin

Mine also, my heating is often running at ~40° unless it's bringing it up from being off overnight or something. Recently I installed a Nest thermostat and doing reading around it suggested that in the US (I'm in the EU) OpenTherm may not be so common, so perhaps they don't tend to use systems that can do modulation much there.