Combating heat pump vibrations with piezoelectric sensors

Heat pumps efficiently use ambient air to heat buildings and provide hot water. The outdoor unit, housing the fan and compressor, is particularly exposed to pollution, solar radiation, weather conditions and mechanical stress. Rotating components including fan and compressor generate significant vibrations. Highly sensitive piezoelectric sensors are used in monitoring for operational issues, ensuring system reliability and conducting timely maintenance. Through its partnership with Metra Mess- und Frequenztechnik (MMF), ASC Sensors sets new standards for demanding measurement and testing applications through incorporating lightweight IEPE sensors in its innovative inertial sensor portfolio.

Heat pump efficiency

An air-to-water heat pump uses the surrounding air as a heat source to supply an entire building. A built-in fan draws in the air and passes it on to a heat exchanger. Circulating in this is a refrigerant that changes its aggregate state even at low temperatures due to its thermal properties. As the refrigerant mixes with the supplied “warm” external air, the former heats up until eventually starting to evaporate. The vapor flows on to an electric compressor. This increases the pressure, which further raises the temperature. Once the refrigerant steam has reached the desired temperature, it flows through another heat exchanger. Here, it transfers the thermal energy transported to the heating system and condenses; the refrigerant cools down and becomes liquid again.

The efficiency of heat pumps is expressed through their COP value (Coefficient of Performance). This indicates the ratio between heat output and the energy required to produce that output. The COP is impacted by parameters including outside temperature, flow temperatures within the circuit and air humidity. Any mechanical issues, emerging imbalances of the fan blades, the effects of aging or material fatigue, too, may significantly reduce a heat pump’s efficiency, output and safe operation.

Extremely accurate, stable vibration monitoring

Depending on their amplitude and frequency, a heat pump’s vibrations are always a measure of proper operation. IEPE (Integrated Electronics Piezo-Electric) sensors offer particular sensitivity to adequately capture even tiny changes in a unit’s fan, its compressor or the behaviors of other critical parts.

Through its recent collaboration with MMF, the German inertial sensor specialist ASC is now able to deliver customized IEPE sensor systems, in addition to its own portfolio of capacitive sensor solutions.

In heat pump vibration monitoring, MMF’s KS903 triaxial accelerometers can be of particular value. With a total mass of 9 grams only, the compact KS903 design is of minimal impact on measurement results. They offer a wide, extremely high frequency range of up to 12 kHz to capture shocks and vibrations. High temperature resistance of up to +100 °C and precision over extended periods translate to excellent long-term stability and reliable results.

Therefore, these light, compact IEPE accelerometers are predominantly used in demanding test and measurement applications such as structural and modal analyses for automotive and railway testing, lightweight planes and other light constructions including heat pump design. They are typically used during product development, to ensure the appropriate specs and robustness of the various component parts, as well as in analyzing defects and understanding their root causes.