Using ECM Motors in HVAC Systems
In recent years Air conditioning systems for your home and light commercial have been using a new type of motor, Gone with Capacitor type motor and in with the new motor Called a ECM (Electronically commutated motors )
ECM Basics
Most ECMs are DC motors that function using a built-in inverter and a magnet rotor, and as a result are able to achieve greater efficiency in air-flow systems than some kinds of AC motors. (Although AC current is used for ECM, the ECM’s internal rectifier converts the current to DC voltage). Permanent split capacitor (PSC) motors, often used in conjunction with electronic SCR motors, are somewhat inefficient when used in air control systems, Study’s have shown that a PSC motors have a efficiency rating of less than 45%, ECM motors are far more efficient, up to 75%.
ECMs are also relatively low-maintenance; the use of true ball bearings reduces the need for oiling, and varied start-up speeds reduce stress on mounting hardware. The operating range is significant enough to enable one ECM to replace two induction-style models, which simplifies the replacement, maintenance, and installation processes, and minimizes product choices. However, not all ECM motors run at variable speeds and selection depends heavily upon application specifications. The initial cost of an ECM can be high, but is typically balanced by overall energy savings in the long run. There is a draw back to the ECM motor though, There was once a time, The last thing that would burn out on a A/C was the Blower motor, ECMs are not lasting as long, We are seeing failure rates of 5 years, and were as a PSC motor may cost $300 to $400 to replace, ECM motors could cost as much as $800 depending on the make of equipment.
ECM in HVAC Systems
When considering an ECM for application in an HVAC system, there are several factors to keep in mind. Although ECMs are often selected because many models run at variable speeds, in certain condenser applications it is preferable to select and ECM that runs at a fixed speed—an ECM running at a fixed speed s in a condenser unit still uses less energy than a typical PSC motor running at a fixed speed in a similar unit. As a result of increased energy savings, a condenser operating with an ECM will have a higher SEER (seasonal energy efficiency ratio) rating. In other HVAC units, an ECM can run at variable speeds but depends on a controller that pre-programs speed, including the rate at which the motor ramps up. Whereas typical PSC motors start and almost immediately run at full capacity, an ECM can start slowly and stop slowly, which can help reduce humidity. Additionally, the control can be set to alter the amount of air an ECM motor drives through the system, which enables a greater range of possible air-flow rates.
It is possible to convert a ECM unit to a standard PSC application however it is not advisable, But in cases were the unit is out of warranty, It maybe a option. It is not necessary to stick with the OEM motor anymore if the unit id out of warranty, Many manufactures are now producing ECM motors for generic applications
