I've my Nest Learning Thermostat connected to my boiler (Ideal Vogue C32 Gen2) in OpenTherm mode. There is also an Ideal Weather Compensation kit available, but given that my Nest already knows the external temp, is Weather Compensation not required?
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It's an external temperature sensor supplied by the boiler manufacturer, so presumably in cold weather it tweaks the flow temperature to keep the temp differential within the condensation parameters to maximise efficiency.
I'm speculating that the Nest stat does the same, but by the external temp from the Internet location.
It's been a while since this thread was last updated so I'll go ahead and lock this thread. If you're still experiencing problems, please feel free to start a new thread and we'll be happy to help.