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[Solved] Vaillant Ecotec 186/3-5 Plus Condensing Boiler Hums During Operation - Solutions & Experiences

ptak01 10842 12
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  • #1 17054137
    ptak01
    Level 11  
    Posts: 37
    Rate: 8
    Has anyone encountered a boiler hum during boiler operation. I have a Vaillant Ecotec 186 / 3-5 Plus boiler and the boiler "hums" from time to time.

    During the service technician's visit, the problem did not occur, and the service technician stated that everything was fine, and the boiler hums from time to time (when the heating is turned on).
    After turning the boiler off and on again, in most cases the boiler does not hum, but after some time the problem returns.

    anyone have any ideas what it might be?

    Attached is a video with the sound of the boiler.


    [movie: 1ffc772742] https://filmy.elektroda.pl/32_1519239491.mp4 [/ movie: 1ffc772742]
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  • #2 17054281
    Darek A.
    Level 20  
    Posts: 542
    Help: 39
    Rate: 204
    Pump - bows.
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  • #3 17054864
    ls_77
    Level 38  
    Posts: 2440
    Help: 500
    Rate: 944
    You can remove the casing and put your hand on the pump. It will probably vibrate slightly. Either it is over or the debris has accumulated in it.
  • #4 17055598
    Darek A.
    Level 20  
    Posts: 542
    Help: 39
    Rate: 204
    Exactly, because in the gas boiler, apart from the pump, there are no mechanics that would emit a constant hum.
  • #5 17055629
    ls_77
    Level 38  
    Posts: 2440
    Help: 500
    Rate: 944
    Alternatively, the fan may also cause a hum, or more precisely, a muffler which draws air in.
  • #6 17056506
    ptak01
    Level 11  
    Posts: 37
    Rate: 8
    Darek A. wrote:
    Pump - bows.



    I was also thinking about the pump, but whether the pump should not make noise, regardless of whether hot water is being prepared or heating is working. Meanwhile (maybe it's a coincidence and a lack of careful observation), the hum only occurs when there is "active heating".
  • #7 17056568
    Darek A.
    Level 20  
    Posts: 542
    Help: 39
    Rate: 204
    The pump circulates a closed circuit of water in the radiators so that they all heat up, hot tap water flows into the boiler fresh, which simply pushes it with pressure without the need for a pump :)
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  • #8 17057034
    mauri_b
    Heating systems specialist  
    Posts: 1055
    Help: 109
    Rate: 528
    Darek A. wrote:
    The pump circulates a closed circuit of water in the radiators so that they all heat up, hot tap water flows into the boiler fresh, which simply pushes it with pressure without the need for a pump :)

    Go film man, don't spam.

    bird01, open the front cover and listen, for now it's reading coffee grounds.
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  • #9 17057041
    ls_77
    Level 38  
    Posts: 2440
    Help: 500
    Rate: 944
    Darek A. wrote:
    hot tap water flows into the boiler with fresh water, which simply pushes it under pressure without the need for a pump :)

    With hot water, it is like you write, but to heat this water, the water circulating in the boiler in the so-called short circuit, i.e. the pump pushes the boiler water to the main exchanger where it receives heat from the burner and flue gas, and then pushes it to the secondary exchanger where it gives the heat to the incoming cold water (it can be a plate exchanger in a combi boiler or a coil in a DHW tank).
    Perhaps there are greater resistance in the central heating installation here and the pump is more difficult to push the water than in this short circuit to heat the hot utility water.
  • #10 17058407
    kz61
    Level 27  
    Posts: 590
    Help: 108
    Rate: 314
    When there was a service technician, he probably removed the casing and nothing strange happened then. So the analyzer and checking what it sucks is one time, and the gas tightness check in the boiler (on the move) is two.
  • #11 17060778
    ptak01
    Level 11  
    Posts: 37
    Rate: 8
    at the moment there is silence, I am waiting for symptoms to appear
  • #12 17583152
    nickiel
    Level 12  
    Posts: 14
    Help: 3
    Rate: 8
    Buddy bird01 what came out with your boiler because mine started to rumble exactly the same ...
  • #13 17583846
    ptak01
    Level 11  
    Posts: 37
    Rate: 8
    nickiel wrote:
    Buddy bird01 what came out with your boiler because mine started to rumble exactly the same ...


    service diagnosis: pump to be replaced, but after replacing the pump, a symptom appeared after some time - and here the reason turned out to be clogged with stone "elbow 90 ° below the boiler.- and the pump had problems with pushing the water through.

    there was silence after cleaning the elbow,

    An interesting fact is that the filter on the boiler was clean ...
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Topic summary

✨ The discussion revolves around a humming noise experienced during the operation of a Vaillant Ecotec 186/3-5 Plus condensing boiler. Users suggest that the hum may originate from the pump, which can vibrate and cause noise, especially when the heating is active. Some responses indicate that debris accumulation in the pump or increased resistance in the central heating system could exacerbate the issue. Additionally, the fan or muffler may also contribute to the humming sound. A follow-up from the original poster reveals that after a service diagnosis, the pump was replaced, but the humming returned due to a clogged elbow fitting below the boiler. Cleaning the elbow resolved the noise issue temporarily.
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FAQ

TL;DR: On this thread, 1 confirmed fix came from cleaning a scaled 90° elbow; "there was silence after cleaning the elbow." Humming during heating often indicates pump load or flow restriction. Start by feeling the pump and inspecting the intake path. [Elektroda, ptak01, post #17583846]

Why it matters: For owners and technicians chasing a humming ecoTEC 186/3-5 Plus during CH, this FAQ pinpoints causes and safe first checks.

Quick Facts

Why does my Vaillant ecoTEC 186/3-5 Plus hum during heating?

Humming during CH often points to hydraulic stress or a pump issue. A confirmed case here traced the noise to a scaled 90° elbow. The pump struggled to push water through the restriction. Replacing the pump did not cure it until the elbow was cleaned. After cleaning, the boiler ran quietly. [Elektroda, ptak01, post #17583846]

How do I check if the circulation pump is causing the hum?

Remove the casing and place your hand on the pump. Expect slight vibration in normal operation. Excess buzz or resonance suggests bearing wear or cavitation. Compare sound with and without heating demand. If vibration matches the hum, investigate the pump and flow path. [Elektroda, ls_77, post #17054864]

Why does it hum in CH but not when running hot water (DHW)?

During DHW heating, the boiler circulates its internal water in a short loop. The pump faces low resistance there. Central heating sends flow through the full radiator circuit. Higher resistance can load the pump and amplify noise. That difference explains a hum during heating but not DHW. [Elektroda, ls_77, post #17057041]

Could the fan or air-intake muffler be the source?

Yes. Intake components can hum if the muffler or fan resonates. Listen near the air intake while the boiler runs. Remove the front cover and compare sound levels. If the hum localizes to the intake, service the muffler and fan. Check for blockage or damage. [Elektroda, ls_77, post #17055629]

The humming stops after I reboot the boiler—what does that mean?

Power-cycling temporarily stops the hum for some users. That suggests a state-dependent vibration or debris shift. It may reset pump speed or break resonance. If the hum returns under heating load, inspect the pump and flow path. Document when and how it reappears. [Elektroda, ptak01, post #17054137]

What fix actually solved it for the original poster?

In the confirmed case, cleaning a scaled 90° elbow solved the humming. The pump had already been replaced. The elbow was below the boiler and restricted flow. "There was silence after cleaning the elbow." In this thread, 1 of 1 confirmed fixes involved descaling that elbow. [Elektroda, ptak01, post #17583846]

How do I check and clean a clogged 90° elbow below the boiler?

Focus on the 90° elbow below the boiler and nearby fittings.
  1. Isolate and drain the section below the boiler; remove the 90° elbow.
  2. Inspect and descale the elbow; flush debris.
  3. Refit, refill, bleed, and test under heating load. If the hum disappears, the restriction was the cause. [Elektroda, ptak01, post #17583846]

The hum goes away with the cover off—what should I test?

Run a combustion analyzer check and inspect what the boiler "sucks" for air. Then check gas tightness with the unit operating. Cover-off silence points to intake resonance or leakage. Address air path restrictions or sealing issues. Schedule service if you lack test gear. [Elektroda, kz61, post #17058407]

Is a constant hum normal on this boiler?

In a gas boiler, only the pump can produce a constant mechanical hum. Continuous hum means the pump or its hydraulic load needs attention. Inspect for restrictions and verify pump condition. Then test under CH demand to reproduce the noise. "Apart from the pump, there are no mechanics that would emit a constant hum." [Elektroda, Darek A., post #17055598]

Does the pump run during hot-water production?

Yes. The pump circulates boiler water through the main exchanger and the DHW exchanger. The incoming cold water then gains heat across the plate or coil. That loop uses short piping and less resistance. Noise there is less likely unless components fail. Hum under CH load points back to the heating circuit. [Elektroda, ls_77, post #17057041]

My filter is clean—can a restriction still cause humming?

Yes. The filter can be clean while an elbow or valve is scaled. In this case, a 90° elbow below the boiler was clogged. The pump struggled until the elbow was descaled. Cleaning that elbow restored quiet operation. Inspect elbows and local fittings even if the filter looks fine. [Elektroda, ptak01, post #17583846]

How much pump vibration is normal?

A small amount of vibration is normal when touching the pump. Excessive buzzing or rattling suggests wear or cavitation. Use a mechanic’s stethoscope or screwdriver as a probe. Compare vibration with and without heating demand. Replace or service the pump if vibration increases under load. [Elektroda, ls_77, post #17054864]

What should I check before calling Vaillant service?

Open the front cover and localize the sound. Place a hand on the pump to detect abnormal vibration. Listen at the intake for resonance. Note whether the hum happens only in CH mode. Share these findings with the technician to speed diagnosis. [Elektroda, ls_77, post #17054864]
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