Pumps and Zone Valves

Heating system circulators, or pumps, move heated water from the boiler to distribution units (radiators, radiant floors, baseboard, or hydro-air heating coils) and then back to the boiler again. When we design a heating system, we select a circulator that can move the maximum amount of heat- carrying water needed by the building (or portion of the building served by the pump) on the worst day of the winter. But pumps do not come in an infinite number of sizes and also do not come in very small sizes, so we often have to choose one which has more capacity than necessary. Also, the heating needs of a space change depending on many things, including the outside temperature and time of day so the maximum capacity of the pump might only be required a few days or hours a year. Until recently, the pump could only draw electrical energy at one level when it was on- the maximum, over-sized level.

This overuse of energy gets even worse in systems with multiple zones, each served by its own pump. The zones are often small pieces of the whole space’s heat loss, and the smallest pumps available are capable of covering the whole system, so each zone multiplies the overuse of electrical power.

Pumps are now available with ECM (electrically commutated motors), which allows them to change their electrical draw according to the demands of the heating system. When all zones are calling for heat, the pump uses as much energy as necessary to circulate the large load. As zones are satisfied and drop out, the electrical draw also drops. The pump is essentially customizing itself to the system. In a multiple zone set-up, the ECM pump can save thousands of dollars in its lifetime. This is why we choose to pipe our customers’ zoned systems using a single ECM pump and zone valves, rather than pumps on each zone.

Zone valves are motorized valves which open and shut when the zone thermostat instructs them to. They are available with easily replaceable operators and have good reliability. Manufacturers like TACO make relay boxes which allow all the wiring for zone valves to be organized in one place with the proper transformers. The boxes have indicator lights that allow us to track the progress of a call for heat in each zone.