Circulator pumps (C) Daniel FriedmanHeating System Noise Sources
How to Diagnose, & Repair Heating System Noise Problems

  • HEATING SYSTEM NOISE DIAGNOSIS - CONTENTS: How to find, diagnosue & fix heating system noises. Heating System Noises & Building Temperature-Change Noises. Heating System Noise & Sound Isolation methods
    • Heating System Noise Cause Diagnosis List & Articles. Troubleshooting heating system noises traced to chimneys and vents. Troubleshooting heating system noises traced to thermal expansion/contraction
  • POST a QUESTION or READ FAQs about how to diagnose and fix heating system noises, rattles, bangs, hisses, clanking, and other sounds

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Diagnosing heating equipment noises:

This noise control article discusses the diagnosis and cure of heating system noises, including heating equipment noise, heat piping or ductwork noises, radiator noises, steam pipe banging, and steam radiator vent noise control.

We describe just about every single noise that might come from or have to do with building heating systems.

We describe the heating system noise, where that noise usually originates, and what to do about it.

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Heating System Noises & Building Temperature-Change Noises

Curing or controlling noises traced to building heating systems is divided naturally into two topics that should to be addressed in this order:

  1. Identify the source and cause of noises traced to the heating system or its components. Some heating system noises are normal and are thus not a worry.

    But other heating system noises (rumbling, buzzing, banging) might be a sign that the heating system needs repairs, that it is not operating efficiently (costing more than necessary for heat), or the heating system may be unsafe. To rule out heating system operating problems, review the Heating System Noise Cause Diagnosis Articles we list just below in this document.
  2. Isolate heating system noises, or prevent heating system noise transmission through the building. Once we are confident that the heating system noises themselves are normal, we can focus on keeping those noises out of the rest of the building. You will still need to identify specific heating system noise sources, since some noise control steps focus on specific heating system installation details.

    Once those noise and sound problems have been addressed, normal building noise transmission and sound control measures, such as sound insulation, can be applied to the room where heating equipment is located. See Heating System Noise & Sound Isolation in this article - below.

Watch out: while adding sound control barriers and insulation around a mechanical room be sure that you do not interfere with proper combustion air supply or you risk making the heating system work poorly or you may make it unsafe, risking carbon monoxide production and even death.

Heating System Noise & Sound Isolation

Examples of steps that reduce noise transmission from heating systems include

HVAC Duct noises: review and fix loose HVAC duct components, check that vibrations from the mechanical systems are not being picked up and carried through the building by metal duct vibration.

HVAC Ducts & Privacy: Sound from any source can also be transmitted between building areas through the ductwork itself. The author, politely smooching his girl friend in her family basement rec-room,was jolted by her father's sudden loud voice: "Joanne! time to come upstairs!!" - her dad just shouted down through the air ducts into the basement, leaving the couple to wonder if their private sounds had been transmitted up to Joanne's parents' bedroom.

Oil piping vibration transmission: as we cite at Heating System Noise Cause Diagnosis Articles, clamping heating oil piping to the underside of floor joists converts the floor above to a speaker cone to transmit vibrations from the oil burner into the space above.

Mechanical room sound isolation: once specific sound sources have been addressed, what remains is the isolation of mechanical room sounds from the rest of the building. See the sound control articles beginning at NOISE / SOUND DIAGNOSIS & CURE

Heating System Noise Cause Diagnosis List & Articles

Circulator pumps (C) Daniel FriedmanHeating systems and building heat as a source of indoor noises and sounds include air bubbling in piping, shrieks (bearings), bangs (puffbacks), rumbling (air noise, mechanical noise), grinding noises, and other mechanical noises.

  1. For hot water heat see OIL BURNER NOISE SMOKE ODORS

  2. For steam heat see STEAM HEATING SYSTEMS and If your steam pipes or radiators are making a horrible hammering, pounding or banging noise,

  3. For warm air heat see FURNACES, HEATING

    and DUCT SYSTEM DEFECTS. Steam heat can also produce (normal) hissing sounds as air escapes from steam radiator valves.
  4. Since heating system malfunctions that result in un-wanted noise may also produce smells,

  5. All heating systems can cause creaking or popping noises as heating system and piping or ductwork expand (and contract) through the heating cycle, though meticulous installation or repair can usually stop those sounds.

Troubleshooting Noisy mechanical system components and moving parts

  • Electric motors on oil burners or blower fans -

  • Banging pounding clanking heating pipes or radiators, especially steam heat:

  • Blower fans and air handlers: can induce vibration into building HVAC ductwork if a vibration isolator or vibration dampener is not installed.

    See VIBRATION DAMPENERS for a discussion of devices used to isolate noises produced by HVAC air handlers such as air conditioners and furnaces.
  • Bubbling or rumbling heating system noises in hot water heating piping can be caused by air in the heating lines. If the amount of air becomes excessive the heating system may be unable to circulate hot water and extra steps to bleed unwanted air will be required. See
  • Buzzing sounds and vibration at oil or gas fired heating boilers, furnaces or water heaters can be caused by a variety of problems such as a control cover touching a relay switch, control unit transformer failures, bad motor bearings, or loose mounting hardware.

    Buzzing and similar vibration sounds may also be traced to fuel oil piping that is not properly mounted, is in contact with building surfaces, and is transmitting vibrations from the heating appliance or oil burner to the building. We also trace buzzing sounds to a failing low voltage transformer such as the transformer that may power zone valves, thermostats, and some other heating system components.

    Buzzing heating system controls & relays: our photos below illustrate how a trapped aquastat relay buzzing problem can happen. Our measuring tape is stretched across the two steel ends of the aquastat control. The red arrow points to a relay in this control. You can see that there will be very little clearance between the relay's moving head and the an aquastat control cover that is pressed tightly in place.
Buzzing aquastat relay (C) D Friedman Buzzing aquastat relay (C) D Friedman

If the control cover is lightly touching the relay switch the control may simply buzz when the relay is trying to move. On some controls this clearance is so tight that the relay or is trapped solid so that it cannot move - leading to a no-heat servicer call. Simply pulling off the cover to let the relay move freely can immediately discover and "fix" this buzzing heating control problem.

So if you notice that the control cover on your aquastat (or on a cad cell or stack relay) has been bent slightly convex, or has been left slightly ajar (our photo, above right) think twice before jamming it on tightly. Thanks to oil heat service technician Bob at Bottini Oil for this service tip.[3]

  • Circulator pump noises: circulator pupms on hot water hydronic heating systems range from quiet to producing a mechanical whine or hum, or if failing bearings, grinding, or if failing electric motor, humming and vibrating. In our experience Taco-brand circulator pumps are usually so quiet that we can tell that the circulator pump is running only by feeling for a temperature change the pipes entering and leaving the pump.

    See CIRCULATOR NOISES for a catalog of heating zone circulator noises & their common causes.

    But if a circulator pump and hydronic heat piping contain unwanted air, cavitation in the pump itself due to the presence of air can make a pump abnormally noisy as well as making a bubbling or gurgling sound in the building hot water heating pipes, baseboards, or radiators. Eventually air leaking into a heating system (or low water volume in the hot water heating system) leads to loss of heat.

    Also see AIR BLEEDER VALVES for a catalog of air purging procedures for hot water heating systems.

    And see AIR SCOOPS SEPARATORS PURGERS for an explanation of the equipment intended to get rid of un-wanted and noisy air in hot water heating systems.
  • Clanking heating system pipes or sharp snapping noises may be heard as a normal consequence of expansion of metals during the heating cycle. These noises can often be eliminated or reduced by careful routing of piping and by allowing room around heating pipes for expansion, but probably not eliminated in the case of hot water baseboards.

  • Hissing heating system sounds such as air escaping from radiators or the piping where air bleeder valves are installed are normal but should be brief and uncommon. If you constantly hear air hissing from radiator bleed valves double check that you understand what kind of heat you have - hissing from bleeder valves on steam heat radiators as heat is coming up in the building is normal.

  • Mechanically driven motors such as the oil pump (fuel unit) on oil burners - see OIL BURNER NOISE SMOKE ODORS
  • Oil burner noises: could be normal motor noise or could be a sign of serious and even dangerous heating system conditions - see both

    and OIL BURNER INSPECTION & REPAIR for details. Additional noises at the oil burner may be due to a problem with the oil burner fuel unit (oil pump) such as a bad or slipping coupling between the burner drive motor and the fuel unit. Air in the heating oil supply piping can also cause noises in the fuel unit.

    Those problems are detailed at OIL BURNER FUEL UNIT.
  • Oil piping noises: buzzing or vibrating sounds may be transmitted from an oil burner fuel unit through flexible copper oil lines to the building, especially if the oil lines are hard-mounted to the basement ceiling (the bottom of floor joists for the floor above.

  • Radiator Noises: Watch out: If the radiator continually makes noises (whistling or wheezing) at the steam vent, there is a problem that needs to be fixed: a bad steam vent, steam piping problem, steam pressure set too high, or boiler oversized for the heating distribution system.

    See our diagnostic articles at RADIATORS and s

  • Steam pipe noises: see BANGING HEATING PIPES RADIATORS for the causes and cures of banging, clanging, hammering steam pipes as well as sounds from hot water heat piping.
  • Steam radiator vent hissing or other noises: steam vents should quiet down after steam has entered the radiator and the radiator and its vent have become hot.

    See Steam Vent Noise.
  • Whining, grinding humming: bearings in electric motors or other mechanical devices (whining, grinding, vibrating, maybe humming)
  • Zone valve noises: sometimes a zone valve motor makes a small grinding or whining noise when the motor is operating. In many cases that's normal. If the heating zone valve motor is getting louder we suspect it's failing.

Troubleshooting heating system noises traced to chimneys and vents

  • Heating flues, chimneys: Noises associated with heating system exhaust, including
    • Chimney noises:
      see Chimneys & Chimney Fires. Watch out for roaring freight-train sounds - indicating an immediate emergency - a very dangerous chimney fire may be happening - call the fire department and get out of the building. Wind blowing over a chimney can produce howling or whistling sounds -
    • Draft inducer fan noises, usually on oil-fired heating equipment.
      See DRAFT INDUCER FANS for details.
    • Gas burner noises at gas fired heating boilers or furnaces:

Troubleshooting heating system noises traced to thermal expansion/contraction

  • Thermal expansion/contraction: Noises associated with thermal expansion or contraction of heating system components
    • Hot water baseboard piping or radiator piping makes creaking or crackling sounds as the piping expands or contracts, particularly where piping passes through tight openings in walls or floors.
  • HEAT LOSS in BUILDINGS, how to determine and calculate heat loss from a building (or heat gain in a cooling climate), how to evaluate building insulation, & how to insulate buildings
  • Humidity: moisture changes can also cause creaking or ticking noises in buildings. See How Low Should You Keep Indoor Humidity to Avoid a Mold Problem discussed

In this NOISE / SOUND DIAGNOSIS & CURE article series we discuss how to locate the source of, identify and correct various building sounds and noises indoors or on occasion, noises from outside that penetrate indoors at annoying levels.


Continue reading at AIR CONDITIONING & HEAT PUMP NOISES or select a topic from the More Reading links shown below.

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