Ask the Expert: HVAC Heating

Question: How can I improve the energy efficiency of my facility’s heating system?

Answer: HVAC heating issues, which include problems with component maintenance and temperature control, can take several forms. An energy audit will typically identify energy inefficiencies in one or several of the following areas:

  • Air inlets or outlets are dirty or obstructed
  • Boiler combustion efficiency is not tested on a scheduled basis
  • Boilers are not maintained on a scheduled basis
  • Multiple boilers or heaters fire simultaneously
  • Stack temperature appears excessively high (greater than 400 degrees Fahrenheit plus room temperature)
  • Water in heating system is heated when there is no need
  • Condensate from street steam is being discharged to sewer drain
  • Heating pilot lights are on during cooling season
  • Steam radiators or other steam equipment fails to heat, or is operating erratically
  • Steam, condensate and heating water piping insulation is in disrepair or missing
  • Operation of oil burner is accompanied by excessive smoke and sooting
  • Soot and odors are detected in areas where they are not expected
  • Evidence indicated faulty or inefficient boilers or furnaces
  • Air is humidified
  • Burner short-cycles
  • Combustion air to boiler/furnace is not preheated
  • Hot water radiation units fail to operate
  • Radiators, convectors, baseboards and finned-tube heaters are not providing sufficient heat
  • Condensers and cooling towers are not maintained on a scheduled basis
  • Circulating pump operation is manually controlled

The suggested HVAC operations and maintenance (“O&M”) improvements and HVAC facility improvement measures (“FIM”) will vary based on your facility’s unique mix of inefficiencies, but what follows are some general guidelines.

Suggested HVAC Heating O&Ms:

  • Clean inlets/outlets, remove obstructions and remove access covers to inspect turning vanes, fire dampers and splitters.
  • Prepare combustion efficiency testing schedule and log of test results. Conduct tests.
  • Perform boiler maintenance per manufacturer’s instructions.
  • In situations with multiple boilers, adjust controls so that boiler #2 will not fire until boiler #2 can no longer satisfy demand.
  • Ensure the proper amount of air for combustion is available in the furnace room.
  • Examine and clean air intake filters.
  • Perform flue gas analysis on a regular basis to ensure proper air to fuel ratio.
  • If furnace is over-firing, verify that spuds and nozzles are properly sized. Also check that fuel pressures are not too high.
  • Turn off boiler, pumps or heat source when no need for heat.
  • Turn pilots off during cooling season.
  • Check the temperature of the pipe on the downstream side of steam traps. If it is excessively hot, the trap probably is passing steam. This can be caused by dirt in teh valve, a valve off the stem, excessive steam pressure, or worn trap parts (especially valves and seats). If the pipe is moderately hot (as hot as a hot water pipe), it probably is passing condensate, which it should do. If it’s cold, the trap is not working at all, and should be replaced or repaired. Initiate a steam trap maintenance program.
  • Clean or replace thermostatic control valves on radiators.
  • Check the air vent valve. If it’s not operating properly, replace.
  • If thermostatic trap is malfunctioning, clean or replace bellows element.
  • Water pockets may be obstructing steam flow. Correct by re-pitching or rerouting pipes.
  • Inspect pipes for broken or missing insulation. Repair or replace as needed.
  • Inspect burner nozzles for wear, dirt and incorrect spray angles. Clean and adjust as necessary.
  • Verify that oil is flowing freely and that oil pressure is correct.
  • If burning heavy oil, check oil temperature.
  • If steam atomizing burners, check steam-oil differential pressure.
  • If soot and odors detected, then heat exchanger may have burned out or stack draft may be inadequate. Replace, or clean and correct, as necessary.
  • Check operation of furnace draft controller and boiler setting for leaks.
  • Remove scale deposits, accumulation of sediment and boiler compounds on water side surfaces. Examine and treat rear portion of boiler (the area most susceptible to scale formation).
  • Remove soot from tubes.
  • Observe the fire when the unit shuts down. If the fire does not cut off immediately, it could indicate a faulty solenoid valve. Repair or replace as necessary.
  • Inspect all boiler insulation, refractory, brick work and boiler casing for hot spots and air leaks. Repair and seal as necessary.
  • Discontinue or reduce humidification where possible.
  • If the burner is short-cycling, the start-stop limit switches may be set too closely or the thermostat may be faulty. Reset as required or replace if necessary.
  • If hot water radiator units fail to operate, then the radiators may be air locked. Open air vents and bleed off air until water appears. Bleed off water in pneumatic air lines if necessary. Check for air leaks. Check to see if hot water pump or booster pump is malfunctioning. Repair or replace as necessary.
  • Repair or replace faulty thermostats.
  • Establish a systematic cleaning schedule.
  • Remove items obstructing discharge grills.
  • Repair faulty valves.
  • Prepare a maintenance schedule per manufacturer’s recommendations.
  • Develop an operating schedule.

Suggested HVAC Heating FIMs:

  • Purchase and install automatic staging controls, if applicable.
  • Purchase kit for flue gas analysis if frequent testing is anticipated.
  • Install control to automatically shut down heat generating device when outside air temperature reaches 60 degrees Fahrenheit.
  • Replace worn units with new electronic ignition models to avoid unnecessary fuel consumption.
  • Install additional pipe insulation in accordance with design specifications and energy conservation codes.
  • Purchase new oil burner nozzles or tips.
  • Replace dangerous or ineffective units with more efficient modular type units. Do not install oversized units.
  • If applicable, install baffle type devices in the tubes to improve efficiency.
  • Employ a control specialist to adjust controls.
  • Utilize heat from flue gas to preheat combustion air by means of a heat recovery device.
  • Consider an economizer to transfer heat from flue gas to feed water.
  • Consider heat recovery from continuous blowdown.

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