Boiler won't heat

The boiler does not fire, or fires without delivering heat to the zones.

Hydronics

high

Possible cause

Zone Valve and Zoning
Component
How zoning delivers heat only where it is called for, using valves or multiple circulators.
Circulator Pump
Component
The pump that moves water through a hydronic loop, how it is sized, and why head matters more than pressure.

Affected equipment

Boiler
Equipment
How a hydronic boiler heats water and distributes heat, and the difference between conventional and condensing designs.

Local Code Notice

HVAC installation, venting, combustion air, ventilation air, gas piping, clearances, termination locations, electrical requirements, permits, and equipment requirements vary by jurisdiction and equipment. Always verify the applicable local codes, adopted code edition, regulations, permits, and manufacturer installation instructions before installation or service.