Building Performance Green Building Home Inspections Moisture & Pollution Renewable Energy Lighting Insulation / Air Sealing Windows Appliances Low-Cost Cooling Residential A/C Residential Heating Water Heating Water Conservation Mobile Homes Commercial Buildings Podcast

Servicing Your Boiler for Energy Efficiency

Boilers generally provide quiet, clean, and energy efficient heat. Boilers have low maintenance costs if they are installed properly. But there are a few important service procedures necessary to assure the safety and energy efficiency.

Boilers operate much like a large tea kettle, with a vessel of water that is heated by large burners. Most modern boilers heat the home by circulating water through radiators, convectors, or a radiant slab, though some older systems heat the home by circulating steam. The maintenance is different for each.

Hire a licensed serviceman to perform the following maintenance tasks. Ask to be shown which jobs you can safely perform yourself.

For hot water systems, identified by a pump that moves water through the piping:

The expansion tank allows water to expand and contract without creating excessive pressure. The air excluder traps air bubbles and the air vent releases the trapped air into the room.

Bleed the radiators of excess air periodically if necessary. When water comes out the bleed valve, there is no more air in the radiator.
Check the expansion tank for the correct air pressure, usually 12–15 pounds per square inch.
Clean the burners and heat exchanger if needed.

For steam systems, identified by a sight glass that shows boiler water level:

Drain the float chamber, and test that the low water control shuts the boiler off when the water level drops. Open the blow-down value and flush the sediment until the water runs clear.

Steam boilers have a sight glass to show the boiler water level.

After flushing the float chamber, confirm the proper operation of the automatic make-up water valve by checking the sight glass for proper water level.
With two-pipe systems, check the steam traps under each radiator to confirm that they pass only condensate, not steam.
Clean the burners and heat exchanger if needed.

A little maintenance goes a long way with these hydronic heating systems. A service visit every two or three years should be enough for most hot water systems, but steam systems need more maintenance especially when water treatment is necessary to prevent corrosion or scale.

See The Homeowners Handbook to Energy Efficiency or Residential Energy: Cost Savings and Comfort for Existing Buildings Chapter 6 for more information. For professional information about heating systems and energy efficiency see Saturn Mechanical Systems Field Guide.