Delta T (∆T) is often mentioned as the key problem in hydronic systems, and the term “Low ∆T Syndrome” is used to describe that the system is “sick” when ∆T is too low.
But what is ∆T, and why is it so essential to the system performance?
In a hydronic system we use water to carry energy from a heating/cooling source to the place where heating or cooling is needed. Water is a super-efficient carrier of energy, and for every degree Kelvin, the water contains a certain amount of energy that can be used for heating or cooling.
∆T is the difference between the inlet and the outlet temperature, and if you double the temperature difference you double the amount of energy transported. In other words, you can have half the flow and still deliver the same energy when ∆T is doubled.
Remember, the only reason for circulating water in a heating or cooling system is to transfer the energy to the place where the heating or cooling is needed. If we are not able to transfer the energy to the room, the temperature in the inlet is nearly the same as in the outlet. The energy stays in the circulated water and our system is not delivering the desired performance.
Dynamic valves (Pressure Independent Valves) work as flow limiters and always deliver only the amount of water to the thermal unit that it is designed for. Thereby it can secure a minimum ∆T and your system will never suffer from “Low ∆T Syndrome”.
