What causes flow in the secondary piping when closely spaced tees are installed?

In the context of closely spaced tees in heating or cooling systems, the presence of a secondary circulator is critical for establishing flow in the secondary piping. Closely spaced tees are designed for the purpose of providing hydraulic separation between the primary and secondary systems while allowing efficient fluid transfer. The secondary circulator actively moves the fluid through the secondary loop, thus ensuring that heat is distributed effectively in that part of the system.

The secondary circulator's role is particularly important because it maintains proper flow rates and helps in balancing the system. In systems with closely spaced tees, the primary circulator may be responsible for moving fluid through the primary loop, but it is the secondary circulator that drives flow through the secondary tees and maintains the necessary flow conditions. This arrangement prevents unwanted flow paths and allows for better control of temperature and distribution in the system.

While gravity plays a role in some heating systems, it is not the primary factor in the functioning of closely spaced tees in a pumped system. A pressure differential can influence flow, but in this scenario, the action of the secondary circulator is the key driver of flow in the secondary piping, making it the most relevant choice in this context.