Our thermal oil heater system is with automatic control. It can control the working status and temperature automatically. 
There is expansion tank installed on the highest point of the system. It absorbs the expansion volume of thermal oil during heating from the thermic oil furnace, and compensate oil into the system when the heat is consumed and oil get cool and shrink.

So the expansion tank is a very important part of the system, keep the system working under a stable pressure condition.
How did the system works automatically? Please contact us to discuss about more details.