Will this make it possible to control coolant temperature and have longer operation time than 1 hrs? I am planing to use a webasto thermotop c to heat radiators in a cabin far from civilisation.

Thank you for your question. This controller will not control the coolant temperature of you Webasto Thermo Top C. The heater controls the coolant temperature internally. The heater should cycle up when the coolant temperature drops to ensure your have warmth through your radiators. When the coolant temperature reaches the upper limit the heater will cycle down and be dormant until the coolant temperature drops again. The heater can be run continuously and cabin temperature is controlled through the thermostats on your radiators.