Hydronics & Boilers

Boilers and hot-water heat — circulators, zones, expansion, air elimination and the controls that run a hydronic system.

5 guides

• Boiler Types: Cast Iron vs Condensing
  The practical differences between a traditional cast-iron (non-condensing) boiler and a modern condensing (mod-con) boiler — how each handles flue gas, why return water temperature matters, efficiency, condensate, and what each one needs to live a long life.
• Circulator Pumps and Zoning: Zone Valves vs Zone Pumps
  How hydronic systems are split into independently controlled zones — the two common approaches (a zone valve per zone with one pump, or a dedicated circulator per zone) — plus how a circulator and its pump curve work, and how to troubleshoot a dead zone.
• Common Boiler No-Heat Diagnostics
  A systematic no-heat troubleshooting approach for hot-water boilers — splitting the problem into 'is it getting a call,' 'is it making heat,' and 'is it moving heat,' and walking the common stoppers in each branch from thermostat to ignition to circulator.
• Expansion Tanks and System Pressure in Hydronic Systems
  Why a sealed hydronic loop needs an expansion tank, how the bladder/diaphragm tank absorbs the volume change as water heats up, what cold-fill pressure should be, and how a waterlogged tank causes the classic dripping-relief-valve complaint.
• How a Hydronic Heating Loop Works
  An orientation to hydronic (hot-water) heating — how a boiler heats water, a circulator moves it through a loop to emitters, the water gives up its heat, and returns cooler. Covers the supply/return delta-T and why water moves heat so much better than air.

← All HVAC topics