February 15, 2005
Electro-Boiler Small Zone Warning

Over the past year we have been encouraging the use of our zone controllers to improve the operation of the TS Series Boilers. Even with our encouragement, many installs are not using the zone controllers and experience follow-up service calls due to small zone cycling.

Available zone controller models:

EB-Z2P - 2 pumps
EB-ZTS - 4 or 8 zone valves/actuators
EB-ZC - 4 or 8 pumps or valves


Typical application seems to be 2+ zones with one or more of those zones being rather small in size. With a medium and small size zone both calling for heat, the water flow through the boiler is adequate for temperature sensing and the boiler can adjust accordingly based on output requirements. When the medium zone’s thermostat is satisfied and all that remains is the small zone, due to the shortage of water flow through the boiler on the smaller zone, the boiler tends to overshoot dramatically and may indeed hit the hi-limit. This causes less than desirable water temperature control.


When selling a boiler on a system that has 2+ zones and especially when one or more of those zones are small, we recommend installing an appropriate Electro zone controller. The zone controller immediately sets the boiler to the minimum stages/elements that are needed to adequately heat the zones that are calling for heat (example - 15,000 Btu/h is only one element on). These settings are preset by the installer at the time of installation as shown in the picture below. Using this function on the zone controller will eliminate the hi-limit overshoot and reduce the cycling of the boiler relays promoting long relay and element life and also better water temperature control, that meets the system's requirements.

Please contact us with questions or ordering information!