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Bosch In tankless water heater with adjustments (C) Daniel Friedman Screaming Whistling Water Heater Noise
Bosch MiniMAXX tankless water heater noise diagnosis & repair

Causes & cures of whistling, screaming, shrieking or whining noises heard at or in a gas-fired tankless water heater:

Two diagnostic recordings of resonant whistling or shrieking water heater sounds are given here along with an explanation of the cause and cure for this unbearable noise. Humming and other noises have been reported for some Bosch water heaters.

This article series explains how to diagnose and cure noisy water heaters such as popping, hissing, crackling or banging. We describe the different types of sounds heard at a water heater, what they mean, their cause, and their elimination.

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- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Noise Diagnosis & Repair Guide for Residential Hot Water Heaters

Shrieking Bosch tankless water heater before repair (C) Daniel FriedmanHow to diagnose screeching or screaming water heater sounds - First step

In my OPINION Bosch makes high quality equipment of many varities including water heaters, but that has not made the company immune to an occasional screaming appliance - or customer. Here we go through steps in diagnosing the cause and cure of a loud whistle sound coming from a Bosch gas-fired tankless water heater installed in San Miguel de Allende, Mexico.

Before fooling around with the heater itself - which can be dangerous, take a close look for a partly-closed control valve at the water heater inlet or anywhere in the building piping system.

[Click to enlarge any image]

BOSCH MiniMAXX CALENTADOR de GAS Resonancia Shrieking WHISTLE NOISE DIAGNOSIS STEP 1 [MP4] 20MB. In this first whistling water heater sound recording we try to diagnose the cause of a loud, horrible screaming tankless water heater.

In this first video you'll see me partly-closing first the heater's outlet valve, then the heater's inlet water valve - no no avail. The sound is not unlike blowing across the top of a Negro Modelo bottle.

This step didn't work for us but it's where you should start.

Cause of shrieking screaming or whistling Bosch Compact MiniMAXX gas-fired tankless water heater

In addition to bangs and rattles (scale in water heaters) in 2017 we investigated and obtained repair help from Bosch for a shrieking tankless water heater installed in San Miguel de Allende.

We recorded the noise in part to convince the technicians that it was not imagined, but happily this resonant whistling water heater was, if nothing else, reliable at making the screech whenever we turned up the heater temperature or the water flow rate.

I called our supplier in San Miguel, Don Pedro, who were wonderfully helpful. Christian referred us to their Bosch trained service technicians Daniel y Rene for technical support. Daniel and Rene had in fact come across this problem before, and it's also known to Bosch who cites in the water heater's troubleshooting table as a last item:

Resonancia - el aparato emite un sonido anormal (vibracion), giving this advice: contactcar con un tecninco especializado y capacitado.

The sound was traced to a resonant frequency air or exhaust movement interacting between combustion air intake and exhaust flue outlet gases.

BOSCH MiniMAXX CALENTADOR de GAS Resonancia Shrieking WHISTLE NOISE vs Temperature Setting - DIAGNOSIS STEP 2 [MP4] 11MB - shown above. In this recording we show that setting the temperature up at the water heater causes loud shrieking.

This Bosch heater includes a variable-speed burner and fan that induces more combustion air and increases the tankless water heater's output either when the hot water usage rate goes up in the building or when the water temperature is set to a higher level.

Bosch In tankless water heater with adjustments (C) Daniel Friedman

At the increased demand or temperature settings as air and exhaust flow through the heater speeds-up, a high-pitched resonant frequency screaming ensues.

Partly covering the air intake at the top of the water heater stops the noise- confirming that the probable noise cause is right at that area of the heater.

The Bosch service technicians found and "fixed" the shrieking sound problem by a combination of re-sizing of the exhaust flue vent connector at the water heater and a partial blockage of the combustion air intake at the water heater top. [Second photo above and close-up photo below]

Cure for screaming tankless water heater in San Miguel de Allende (C) Daniel Friedman

Watch out: don't even think of trying to fix this noise yourself by blocking air flow in or out of a gas fired heating appliance. Making a mistake risks fatal carbon monoxide poisoning. Consult Bosch customer service if you are having noise problems with your tankless water heater.

Other shrieking screaming sounds in and around buildings are discussed at WATER SUPPLY PIPE WHISTLE NOISE
and also
at SCREAMING or whistling or shrieking A/C compressor/condenser unit sounds - warning about high pitched sound from the compressor/condenser unit

Other Reports of Bosch Water Heater Noises & Recommended Cures


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