The HVAC industry currently uses a variety of motor technologies
in its equipment. The type specified in any product design
depends upon several criteria, including the product’s
performance goals, positioning, cost, and potential application.
Historically, the two predominant motor types have been
permanent split capacitor (PSC) single-speed motors and 2.3
electronically commutated motors (ECMs) with variable-speed
capability. Most HVAC professionals understand the key
differences between these two motor types and are comfortable
discussing the benefits of one technology over another.
In 2006, Regal-Beloit (formerly known as General Electric, now
known as Genteq) introduced a third motor technology to the
industry. Referred to as its X13 motor, this new technology has
significantly gained in popularity among all heating and air
conditioning equipment manufacturers. What is this newer motor,
and how does it compare to PSC single-speed and ECM
variable-speed motor technologies? Why is it popular?
The Genteq X13 motor is a high-efficiency motor that helped
manufacturers meet the 13 SEER mandate implemented by the
federal government in 2006 (hence, the branding name of X13).
The motors are based on ECM technology and can contribute to the
increased overall cooling efficiency of a complete HVAC system
when used as the circulating air blower motor in a furnace, air
handler or packaged unit. In fact, manufacturers of these types
of motors may refer to them as a standard ECM motor, or as a
constant torque motor.
For clarification, X13 is the
Genteq brand name. Several other manufacturers offer similar
motors. However, for the purpose of this article, the term
constant torque motor will be used to describe all such motors.
In order to understand the benefits of constant torque motor
technology, it is important to look at, understand, and compare
the two other motor technologies prevalent in the industry - PSC
single-speed and ECM 2.3 variable-speed. Constant torque motor
technology offers several benefits with respect to efficiency,
operation, comfort, and cost when compared to these two other
PSC single-speed motor technology
has been the standard in the industry for many years and
represents the highest installed base. PSC motors are typically
positioned by most manufacturers as a standard product offering
and are used in furnaces, air handlers, condensing units, and
packaged products. The popularity of the PSC motor can be
attributed to its simplicity, reliability, low cost, and
PSC motors, often referred to as induction
motors, typically use alternating current (AC) and include two
key components in their design - a stator (the stationary
section of the motor) and a rotor (the rotating section of the
motor). A magnetic field is induced in the rotor opposite in
polarity of the magnetic field in the stator. Therefore, as the
magnetic field rotates in the stator, the rotor also rotates to
maintain its alignment with the stator's magnetic field. In this
operation, the rotor constantly lags behind the magnetic field
in the stator, resulting in what is known as asynchronous (i.e.,
not synchronized) operation. This operational characteristic,
which also generates excessive heat, greatly contributes to the
degraded operational efficiency of PSC motors (which are at best
only 60 percent efficient). However, since there are few
mechanical components, this design has proven to be very simple
and reliable, and can be manufactured at a relatively low cost.
PSC motors are considered single-speed (speed refers to
the rate of rotational motion) because they do not have any
internal controls that can be programmed to automatically vary
the rotation of the motor over an operating range. For example,
an equipment manufacturer may utilize a ½-hp motor in a 3-ton
drive furnace in order to deliver an average airflow of 1,200
cfm within a range of external static pressures (ESP) often
found in assorted applications.
But what if the duct
system layout in a specific application has an increased static
pressure because the mechanical contractor added a very
restrictive media filter?
In order to make PSC motors
more flexible for a variety of applications, they include speed
taps that allow the mechanical contractor (or manufacturer) to
manipulate the motor’s speed to ensure that the correct amount
of airflow is delivered for both optimal performance and safety
within a range of external static pressures. It should be
understood that there is a limit to the amount of static
pressure the motor can handle. As static pressure increases, a
PSC motor’s performance drops off, because it cannot adjust
speed or torque. As a result, higher static pressures equate to
lower airflows. Although the lack of programmability may appear
to be a disadvantage, it actually makes PSC motors more flexible
or universal because they can be used for most retrofit and
original equipment manufacturer (OEM) applications.
Because of the motor’s design, there are some disadvantages
inherent in PSC motors. For example, PSC motors are
significantly less efficient than constant torque or ECM 2.3
motors because they consume more watts, making them more
difficult for a manufacturer to apply to a high-SEER system
design. On average, PSC motors will use approximately 552 watts
in cooling mode and 515 watts in continuous fan mode. Therefore,
they are not ideal for continuous fan operation because they run
close to full speed when applied in this manner, using more
energy than this function really requires. (As a comparison,
imagine the power consumed by five 100-watt light bulbs lit all
day long). This also makes them less attractive for continuous
filtration applications. Additionally, since PSC motors are not
programmable and their motor speed cannot be easily varied, it
is more difficult to apply the motors to two-stage or advanced
PSC motors are also the least quiet of the
three motor technologies. In addition, PSC motors do not offer
customized airflow patterns, which are often critical in designs
intended to manage humidity. Consistent air stratification and
temperatures are also harder to obtain.
products that utilize PSC motors typically do not qualify for
the federal tax credit program based on the motor itself.
However, if the rest of the system components meet performance
requirements (specific SEER, EER and HSPF combinations or a
minimum 95 percent AFUE) as outlined under the program, then the
installation may be eligible for a federal tax credit.
PREMIUM ECM 2.3 VARIABLE-SPEED MOTOR TECHNOLOGY
ECM 2.3 variable-speed motor technology can be compared to using
a dimmer switch in lighting applications, meaning it is highly
variable, making its precise performance ideal for a variety of
advanced applications. Most manufacturers typically position an
ECM 2.3 motor as a premium product offering and use the motors
in furnaces, air handlers, condensing units, and packaged
products. The popularity of the ECM 2.3 motor can be attributed
to its performance, flexibility, and reliability.
There are several other ECM motor designs on the market. Some of
these models are identified as ECM 2.5 or ECM 3.0 and include
additional features that allow for more sophisticated
programming options specifically intended for equipment that
utilizes communicating control systems (also known as four-wire
systems). In any case, the information that follows generally
applies to all three ECM motor types.)
ECM technology is
based on a direct current (DC) design that is inherently more
efficient and runs cooler than alternating current PSC motor
designs. In fact, ECM 2.3 motors are approximately 80 percent
efficient compared to the 60 percent efficiency rating typical
of PSC designs.
In a traditional DC motor, permanent
magnets replace the stator, and a series of windings wrap around
the rotor. When electricity is applied to the motor, a magnetic
field is created in the windings, causing it to turn toward the
magnetic field created by the stator. From there, brushes in
contact with a commutator (i.e., an electrical switch that
periodically reverses electrical current) allow the current and
magnetic field to shift from winding to winding, forcing the
rotor to continuously rotate. Unfortunately, the brushes and the
commutator eventually wear out, resulting in motor failure.
So what makes ECM 2.3 motor designs better than their
traditional DC counterparts? First, in the ECM 2.3 motor, the
magnets and windings switch positions - the permanent magnet is
on the rotor and the series of windings are placed around the
rotor. This makes the ECM 2.3 a brushless motor, eliminating
failures caused by worn brushes and commutators.
the ECM 2.3 design combines a microprocessor and an electronic
control directly with the motor. These electronics precisely
manage the commutation of the stator so that it is always
synchronous (i.e., in tune) with the rotor. They also make the
motor programmable. Additionally, in the case of a failure,
either the control or the motor can be replaced without
necessarily replacing the entire unit.
conventional PSC motors, which are designed to operate at one
speed, ECM 2.3 variable-speed motors can run over a wide range
of speeds. This is critical because blowers need to be flexible
in order to deliver the airflow required by a multitude of
system designs. ECM 2.3 motor technology provides the ability to
program and deliver constant airflow over a wide range of ESP,
typically up to 1.0 inches water column.
automatically compensates for any added pressure drop introduced
to the system. For example, if a duct system layout has an
increased static pressure due to a dirty filter, the presence of
a media filter, or simply because of poor design, the motor will
automatically ramp up to ensure that the programmed amount of
airflow is delivered. This is accomplished without the use of
any additional components.
Equipment manufacturers don’t
condone poor duct design, but ECM 2.3 motor technology can
compensate for some applications if sized incorrectly. However,
it is important to be cautious, because increased noise levels,
which are uncharacteristic of these motors, may result if the
design is overly restrictive.
Overall, ECM 2.3 motors
draw the least amount of watts, which makes them the most
efficient. On average, they will use approximately 413 watts in
cooling mode and only 83 watts (less than a 100-watt light bulb)
in continuous fan mode. This combination of performance,
reliability, and programmable flexibility makes ECM 2.3 motors
an ideal solution for high-SEER or multi-stage system designs.
It also has the potential to increase overall cooling system
performance by as much as one or more SEER points.
Beyond programmability and efficiency, ECM 2.3 motors offer many
other advantages that enhance consumer comfort. These motors are
the quietest of the three motor types because they have the
ability to ramp up and down slowly, making them ideal for
applications where noise is a concern.
motors are also the best choice for constant fan or constant
filtering applications because the motor will only run at about
one-third of its designed speed, using less power than a
100-watt light bulb and resulting in both noise reduction and
energy savings that the consumer will appreciate. The indoor
environment will also benefit from better air stratification,
ensuring more consistent and precise temperatures.
addition, ECM 2.3 motors have the ability to deliver customized
airflow based on the consumer’s geographic region, making them
versatile in humid, arid, or temperate climates. If
dehumidification is required, variable-speed motors offer the
best solution because of the wide range of speeds, and they are
particularly effective when combined with two-stage compressors
and a dehumidification control.
Lastly, due to their
efficiency, most products that utilize ECM 2.3 motors may
qualify for up to $1,500 under the federal tax credit program.
ECM 2.3 variable-speed motors do have a few
disadvantages, including a cost premium. On average, a
mechanical contractor can anticipate a 40-60 percent cost
premium for products that utilize ECM 2.3 motors.
STANDARD ECM CONSTANT TORQUE MOTOR TECHNOLOGY
Constant torque motor technology is quickly becoming a popular
motor technology. As a matter of fact, it may totally replace
PSC motors in the near future as government actions and
regulations continue to mandate increased efficiencies. Most
manufacturers typically position constant torque motors as a
mid-tier product offering and use the motors in furnaces, air
handlers, and packaged products. The popularity of the constant
torque motor can be attributed to its performance and cost.
Constant torque motors are high-efficiency, brushless DC
motors that are based on the same ECM technology described in
ECM 2.3 variable-speed motors. They are controlled by 24-volt
signals and were designed so that OEMs can program them, using a
programming tool at the factory, for use in a variety of
high-efficiency applications without modifying or increasing the
size of existing product designs. The programming is not as
flexible as a premium ECM 2.3 motor (for example, it does not
allow for wider speed ranges, climate-based airflow performance
profiles, or constant airflow algorithms). Although constant
torque motors utilize ECM technology, they are not
variable-speed motors, as many people have considered or defined
them. This is probably one of the biggest misconceptions
regarding constant torque technology.
sake, constant torque motors are basically upgraded,
next-generation PSC motors. What differentiates constant torque
motors from PSC motors is their ability to deliver constant
torque (i.e., rotational force or power output down a shaft). In
other words, if the ESP changes, then the motor program will
maintain the amount of torque for which it was programmed (this
the same as constant airflow). Even though
constant torque motors can maintain torque, if the external
static pressure increases, airflow will decrease similar to a
PSC motor. However, the decrease is not as drastic, since the
torque is being maintained. At the other extreme, an ECM 2.3
motor has the ability, via programming, to increase torque in
order to maintain constant airflow in response to changes in
When compared to similarly sized PSC motors,
constant torque motors reduce power consumption, using
approximately 413 watts in cooling mode and only 200 watts in
continuous fan mode - compared to 552 watts and 515 watts,
respectively, for PSC models. These savings make the overall
efficiency of a constant torque motor similar to that of an ECM
2.3 variable-speed motor, which is approximately 80 percent.
Constant torque motors are programmed by the OEM at the
factory. But what do they actually program? Constant torque
motors are designed to deliver constant torque (not speed). But
the same amount of torque may not be required for all functions
or all applications. So, equipment manufacturers determine the
level of torque needed for each product application. Once
determined, they program each of the motor’s speed taps
(typically up to five taps) to produce the desired airflow for
heating, cooling, or continuous fan operation, depending upon
which tap is used.
The manufacturer has the flexibility
to specify either a percentage of the maximum torque or the
actual torque value in their motor programs. For example, tap 1
= 100 percent torque, tap 2 = 85 percent torque, tap 3 = 65
percent torque, tap 4 = 50 percent torque, and tap 5 = 25
Many manufacturers will only program the
taps needed for the specific equipment design, meaning some taps
may not be active. The manufacturer also programs any off-delays
needed at each tap. On-delays cannot be programmed. However, the
manufacturer can accomplish on-delays with external control
boards (i.e., an integrated furnace control board or a fan
So how does the mechanical contractor
use these taps? Let’s assume that we have applied a 4-ton drive
(1,600 cfm nominal) gas furnace to a duct system. In order to
make certain that the furnace is operating at the correct ATR,
which ensures proper and safe heating operation as well as heat
exchanger longevity, the motor speed typically must be adjusted.
The technician will usually do this by re-assigning the heating
speed tap from one designated speed to another (often labeled as
low, medium low, medium, medium high, or high).
let’s assume that the consumer has a fairly restrictive media
filter installed at a later date. The technician most likely had
to manipulate the motor speed once again in order to ensure
correct operation. This manipulation interface is familiar to
all mechanical contractors, which is important because the
reality is that changing tap connections on constant torque
motors does not actually change the speed of the motor. Instead,
it changes the programmed torque levels of the motor (most
technicians understand adjusting speed and not torque). The
manufacturer will most often not provide the actual torque
values, but instead will indicate, via a chart, which of the
five taps are to be selected for proper heating, cooling, or
continuous fan airflow.
Constant torque motors offer
several consumer benefits. With increased SEER ratings in
cooling mode, homeowners will appreciate lower utility bills.
Since these motors utilize ECM technology, they are also
slightly quieter than a traditional PSC motor and will
contribute to the emotional comfort factor.
Additionally, products that use constant torque motors can
contribute to a slight improvement in dehumidification. Lastly,
because of their efficiency, some products that utilize constant
torque motor technology may
qualify for up to $1,500
under the federal tax credit program. (Check with the equipment
manufacturer for confirmation.)
KEY HIGHLIGHTS OF THE CONSTANT TORQUE MOTOR
Now that there is an understanding of the three main motor
technologies used in the industry, contractors should realize
the importance and benefit of including equipment in their
product offering that features constant torque motor technology
and be prepared to discuss them with their customers.
confirms that consumers prefer choices and often migrate to the
middle option when presented with a “good, better, best”
scenario. Products with constant torque motor technology are
typically positioned as mid-tier product offerings - they are
the “better” in a good, better, best proposal. It is doubtful
that the price point to upgrade to a product with constant
torque motor technology will be hard to defend.
Reduced Utility Bills.
Many consumers are interested in
lowering their energy costs, especially in the current economic
climate. When applied as a complete system, constant torque
motors can increase the overall cooling efficiency by as much as
one or more SEER points. Depending on the consumer’s lifestyle,
the size of their home, and the region where they live, this can
equate to several hundred dollars in energy savings per year.
Federal Tax Credits.
that utilize constant torque motor technology may qualify for up
to $1,500 in tax credits under the current federal program due
to the motor’s contribution to efficiency. (Check with the
furnace equipment manufacturer to determine eligibility.) If
eligible, the constant torque motor would be defined as an
advanced air circulating fan, meaning that the motor itself has
an annual electricity usage of no more than 2 percent of the
total annual energy used by the furnace, as determined by U.S.
Department of Energy (DOE) test procedures.
It should be
noted that this criteria, including the tax credit itself, does
not apply to air handlers with constant torque motors because
the benefit of the advanced main air circulating fan has already
been accounted for in the overall energy efficiency ratings of
the outdoor products. Sustainability.
One of the hottest buzzwords today is sustainability. All
contractors and service technicians should be aware of what the
term means and how sustainability relates to the equipment they
sell and service. The U.S. Environmental Protection Agency (EPA)
Website defines sustainability as “meeting the needs of the
present without compromising the ability of future generations
to meet their own needs.”
applies to the HVACR industry. In the case of products with
constant torque motor technology, sustainability can be
associated with reduced energy use and less environmental
pollution. And, depending on the equipment manufacturer, the
sustainability conversation may include green or recycled
packaging and reduced noise levels.
technology is rapidly gaining popularity among OEMs in the
industry and among consumers interested in improving the
efficiency of their home comfort systems. By understanding the
advantages this new motor technology offers, contractors can
create a unique, professional selling proposition that will set
them apart from their competition, contribute to higher profit
margins, and address consumer demands for efficiency,
reliability, and comfort.