As most
people in our industry are well aware – a newer fan motor technology can
provide huge energy savings and extended service life. There are many existing buildings
full of older permanent split capacitor (PSC) motors that typically last for
10-12 years in a series fan-powered unit. These motors are 20-60% efficient and
service life may suffer if operating at lower speeds. As soon as these motors
start showing an increasing pattern of failures, building owners who are aware
of electronically-commuted motors (ECMs) may express an interest in upgrading
to this newer technology. ECMs have a minimum efficiency of 80% and a service
life of 25-30 years. It is possible to attempt this type of retrofit, but there
are a few things to be aware of.
Were the unit models in question ever
available with ECM?
If a
particular unit model has been available with an ECM option, all the parts and
pieces should be readily available. Of course the most important part is the
motor itself and it must be programmed for a given blower cabinet. Although it
may be possible to assemble parts and pieces that will fit into an existing
unit, motor programming could be an issue if the unit was never developed for
an ECM option. Depending on the number of units involved, it may be cost
prohibitive to develop custom ECM programming for each cabinet size. One
possible solution would be to factory program the ECMs for constant torque
rather than pressure independent control. This could limit or eliminate the
need for any development work.
Will the existing electrical service
handle the ECM?
The ECM
replacement will likely be rated for a different horsepower and full load
current. Although the resulting operating current draw should be less than the
PSC motor it replaced, motor nameplate ratings may require upsizing the supply
circuit in order to provide the necessary electrical safety. Obviously, this
could greatly complicate the retrofit process and add a lot of cost.
Did you know that the UL/ETL listing will
be voided?
Any field
modifications to a UL/ETL-listed product that results in a change of electrical
characteristics such as current draw or motor horsepower will void the listing.
This is true even if factory parts are field installed by factory personnel.
Once a UL/ETL-labeled product leaves the factory, any changes that do not match
the data found on the unit label will void the listing. The only way to
reinstate the label would involve having a UL/ETL inspector visit the jobsite
and field label the units. This could be very costly but may be unnecessary if local
inspectors will not be involved in the retrofit process.
Have you considered the total amount
of parts that will be required?
ECM retrofit
doesn’t just mean replacing the motor. It generally means replacing the motor,
the speed control, and blower assembly. It will likely also require additional
components like power cables, communication cables, and a power filter. It
could even require changing internal options like line and/or motor fuses.
Have you considered the cost of field
labor required?
All of these
modifications will have a field labor cost. It could easily take an hour to
access each unit and swap out the various parts. It may take longer depending
on the accessibility of a given unit. In an occupied building this work may
need to be carried out at night or on weekends. Additional hours of electrician
time would be required for any modifications to the supply circuit.
In summary
Although the temptation to upgrade from PSC
motors to ECM is strong, remember that the process is not as simple as just changing
motors. It involves many more parts and could require electrical work too. That
doesn’t necessarily rule out the possibility on an ECM retrofit. Many building
owners have contacted their local Titus representative to investigate the
possibilities. ECM technology is quickly taking over this industry and it’s
important to understand exactly what a retrofit may entail so that you can
provide the right answers to your customers.
For information on this topic, please contact Randy Zimmerman at rzimmerman@titus-hvac.com or Titus Communications at communications
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