Common Flow temperature reading

[Chameleonclaude]

Hi all,

I have clamped a pipe thermometer to the common flow immediately emerging from the boiler.

With a return temperature of 40 I still only get temperatures of 60 max on the flow with the boiler pemeprature set to max. According to WBosch a 15ri max temp ought to be 82.

I bought some themal paste to improve the conductivity to the thermometers. Does any one know if these types of thermometers tend to underread temperatures?

Thanks