© 2006
GE ECM
by Regal-Beloit
- 12 -
Indoor Blower Motors
v0.2
ECM Myths and the Air Distribution System
ECM motors can overcome poor duct construction and sizing.
This is true
within reason. However, severe duct blockages, improper installation practices and
under sizing can cause airflow problems and noise issues.
ECM motors can overcome dirty filters and coils
. This is also true within reason.
In fact this problem may even be worsened if the filter being used has a high
pressure drop.
Here are some air distribution system guidelines:
-
Low static, high quality ducted applications will run slowly, quietly and
efficiently while delivering the correct airflow.
-
High static applications will run fast, be noisy and power hungry. The ECM
may still provide the correct airflow, but at a price.
Use good duct design practices and hold static pressure to less than 1”, ideally
around .5”, or the pressure recommended by the manufacturer.
Use deep pleated, low pressure drop, high efficiency filters, sized to the proper CFM.
Because of the ECM motor’s reputation for “constant airflow” over a wide range of
static pressure too often contractors install ECM’s to overcome poor ductwork
practices.
ECM’s will run quiet and with high efficiency at the manufactures
recommended external static pressure.
Even ECM Motors do have their limits:
If we didn’t put limits on the motor, it would just keep increasing power and speed,
beyond the reliable design of its components. The motor program has a built in limit,
again specific to each OEM. In extreme high static applications the motor may reach
that limit and basically “max out”. This can lead to oscillation and high power
consumption.
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ECM motors are not thermally protected
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Open returns in high ambient areas may cause permanent damage to the
motor.
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Zoning and humidifier bypass connections should be as far upstream in the
return as possible from the unit.
-
ECM motors are designed to handle the maximum (or higher) return air
temperature specified by the manufacturer for their unit.
