Since the inductance of the windings of an electric motor standing still is much lower than at rated speed, a 2-3 times larger capacitance is required to obtain the necessary phase shift in them. Therefore, at the time of start, additional starting capacitors are connected in parallel with the working capacitors, with dimensions (due to a 3-fold voltage margin) and the price of which is mainly limited by the power of single-phase machines.

The start of the fans is soft: at the first moment there is practically no load, the magnetic field has to overcome only the inertia of the rotor and the impeller, and the air resistance becomes noticeable only when the speed is set, when the first force has practically no effect. A quick entry into the nominal mode (say, half a second instead of ten) is also uncritical. So, by and large, such installations can be operated without starting capacitors at all (especially if the capacitance of workers is slightly increased), saving not only money and dimensions, but also a fundamentally unnecessary element - a starting relay, which is often a source of malfunctions.

But in practice, two more significant forces can act during start-up - static friction in the motor bearings, which increases as a result of wear of the latter, poor condition of the lubricant or its mismatch with temperature, and a significant imbalance of the moving part due to the same wear or mechanical damage to the impeller. Therefore, starting capacitors in HVAC systems, as a rule, are still used, but their capacity is chosen less than for motors with a loaded start.