HVAC systems as we all know play a central role in heating or cooling a designated space which could be your home or office. In the design of large office buildings, HVAC systems must be factored in from the word go so as to have an efficient and effective targeted heating and cooling solution. HVAC systems rely heavily on the movement of air from one space to another to achieve the required heating or cooling level. AC motors have traditionally been used for this function, but their efficiency has been criticized because they always run at full power. In their place, electronically commutated motors (ECMs) were developed to give residential and commercial property owners a great range of operability choices as well as minimizing noise.
The Basics of ECMs
Simply defined, ECMs are direct current (DC) motors which use a built-in inverter and a magnetic rotor to achieve greater efficiency in air flow systems. Even though AC current is plugged into the HVAC system, the internal rectifier inside the ECM converts it to DC voltage. ECMs have an efficiency level of 65 to 75% when operating at different speeds. Because of this, they have been voted as the most efficient in cost and energy.
In addition, ECMs do not overheat and as such no additional measures are put in place to offset the excess heat generated. This is contrary to permanent split capacitor (PSC) motors which overheat and has an efficiency that falls in the range of 12 to 45%.
In terms of maintenance, ECMs are generally low maintenance components. This is because they use ball bearings which cuts down the need for oily and thanks to their varied startup speeds, the stress on mounting hardware is minimal.
Because of the operating range, 1 ECM can replace 2 induction-style models and this simplifies the installation, maintenance, and replacement processes. The only downside, but also a benefit in the long run is their high initial cost.
Usage of ECMs in HVAC Systems
If the benefits above resonate well with you and you want to integrate an ECM in to your HVAC system. There are several factors that you must bear in mind. Even though ECMs are usually preferred in models that run at variable speeds, you could also select ECMs that run at fixed speed for condenser units. The fixed speed ECMs are not as efficient compared to the variable speed ECMs, but they are far much superior to PSC motors.
Compared to PSC motors which start and stop immediately as they attain full capacity, ECMs start slowly and when stopping they do so gradually. The benefit of this is reduced humidity. You can also vary air flow rates by tuning your ECM motor drives.
Depending on manufacturers specifications and settings, ECMs can go through a number of stages during operations. The first stage comprises the ECM running at a lower speed so as to remove humidity and in the next stage it reaches its designated peak speed and then lastly it stops slowly also known as a soft stop.