The PST system explained
- The PST (Primary-Secondary-Tertiary) system ensures long boiler life by keeping the boiler loop temperature high, ensuring constant flow and preventing the boilers from cycling.
- The PST system can safely provide lower heating zone send-out temperatures than other systems preventing overheating, saving energy in the spring and fall, and increasing resident comfort.
- The PST system can be used for multiple zones that require different temperatures and can be used to heat domestic hot water, thus saving capital and maintenance costs by eliminating separate boilers.
Boiler piping design that worked well in the times of monster boilers and cheap energy will not work for today’s small high-efficiency boilers. Our PST system is the solution. PST stands for ‘primary-secondary-tertiary’ pumping. This is a way to pipe the boilers that:
- Saves energy by eliminating overheating in the spring and fall ... up to 25% over conventional systems;
- Allows for different send-out temperatures for different zones;
- Allows for much lower send-out temperatures which prevents overheating in mild weather for energy savings and greater resident comfort;
- Keeps the temperature of the return water to the boilers high enough to ensure long life.
High-efficiency boilers require two things. They need a constant flow of water through them and they need return water temperature that is, in most cases, no lower than 130°F. The PST boiler system was designed to accommodate these needs.
This system has a boiler loop that always maintains a high temperature (typically 180°F to 220°F) and a constant flow . . . so that the boilers stay happy. Each distribution zone is a closed loop. The injection loop has a variable speed pump or 4-way valve to meter hot water from the hot boiler loop into the distribution zone as needed. This gives accurate and immediate control of the supply temperatures.
In the PST system, the distribution loop can be any temperature. In fact, different zones can be different temperatures. Because of this, we can use the one boiler plant to heat zones with different requirements. We can also use the same boilers to heat domestic hot water, rooftop makeup air units, garage ramps, heated walkways or any other hydronically heated device.