Power Factor Correction Equipment - UL

Power Factor Correction Equipment

With the high cost of energy, many individuals and companies are becoming
more conscientious of wasteful spending and are looking for ways to cut
expenses. One of the ways to cut expenses is by using less energy. A number
of manufacturers have been promoting the use of power factor correction
equipment as a way of reducing electricity use and saving money.

Claims of up to 50 percent savings can be how this relates to reducing energy con- note that most electrical equipment that has
found with a routine internet search. As is sumption and expenses. been Listed by UL has only been evaluated
generally true with such product claims, one to comply with the applicable UL Standard
should be cautious when considering UL does not verify a manufacturer’s with respect to the risks of fire, electric shock
products that claim to save money by claims of energy consumption and injury to persons. Performance claims
reducing electric consumption. The purpose UL Lists products that can be used in (efficacy) by the equipment manufacturers
of this article is to describe how power residential, commercial, and industrial are not normally part of the UL evaluation.
factor correction equipment functions, and applications that claim to reduce the
consumption of electricity. It is important to continued »

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Power Factor Correction Equipment (continued)

What is power factor? Reactive Power (kVAR) Electric utility-imposed penalties tion instructions furnished with the product.
Power factor is a term that expresses the Use of power factor correction equipment The Listing Mark for these products
relationship between true power (the power could result in significant cost savings for a includes the product name “Power Factor
actually consumed — also known as real mid- or large-size primary-metered service Correction Unit” or “Capacitor Bank,” or
power) and the apparent power (the power customer, depending on electric utility other appropriate product name as shown
that must be supplied by the electric utility penalties imposed due to lagging power in the individual Listings. This equipment is
to have this true power available). This ratio factor. Electric utilities contacted confirmed investigated in accordance with UL 810, the
is a number between 0 and 1, and is that they have rate structures that take low UL Standard for Safety for Capacitors.
expressed as a percentage (e.g. 0.75 = power factor into account. One utility
75% pf). indicated that if the customer’s power factor UL 810 includes requirements applicable to
is less than 90 percent, they are permitted general-use power factor correction units,
True power is expressed in kilowatts (kW), to substitute the kVA reading (apparent consisting of one or more capacitors either
and represents the ability of the circuit to power) for the kW reading (true power) for with or without protective fusing or other
perform useful work. Apparent power billing purposes. overload protection, with or without a switch or
required is expressed in kilovolt-amperes other disconnect device, all housed within a
(kVA). Electrical equipment, such as Another called for penalties ranging from 1 protective enclosure. These units are intended
generators and transformers, are usually to 3 percent when power factor drops for installation in circuits in accordance with the
rated in kVA. See the power triangle shown below 85 percent but not less than 70 National Electrical Code®) (NEC®), and intended
to the right for a graphical representation of percent. Power factors below 70 percent for installation in ordinary locations, where the
this relationship. are not permitted, and customers are ambient temperature does not exceed 40°C
required to invest in power factor correction (104°F) maximum.
Many types of machines, motors, transform- equipment to improve the power factor
ers, relays or contactor coils, and ballasted above this level. Until corrections are made, Industrial control equipment
a 25 percent penalty is applied after two Power factor correction equipment is also
Power Triangle consecutive months below 70 percent and Listed under the Power Circuit and Motor-
continues until corrections are completed. mounted Apparatus (NMTR) product
Apparent Power (kVA) category. UL Guide Information for this
UL Listed power factor product category is located in the UL White
True Power (kW) correction equipment Book and can also be found on UL’s Online
You can find UL Listings for power factor Certifications Directory at www.ul.com/
Power Factor = True Power (kW) correction equipment under 2 different UL database. While this category covers
Apparent Power (kVA) product categories. The details covering numerous product types, most unrelated to
UL’s certifications are as follows: this subject matter, certain types of power
lighting are examples of equipment that may factor correction equipment are included.
have lagging power factor, requiring reactive Capacitors
power due to magnetic fields and energy Capacitors are one of the options that can The requirements of UL 810 (Capacitors) do
storage in the loads. Non-linear loads may be used to improve power factor. UL Lists not apply to power factor correction units
also contribute to low power factor. For these devices under the product category containing automatic or other circuit
these types of loads, and in the absence of for Capacitors (CYWT). UL Guide Informa- monitoring/conditioning controls or auto-
power factor correction, reactive power is tion for this category is located in the UL matic systems of multiple connected power
required to be provided by the utility in White Book and can also be found on UL’s factor correction units. Power factor
addition to true power, resulting in the need Online Certifications Directory at www. correction units with these additional
for larger generators, transformers, and ul.com/database. This category covers features are evaluated in accordance with
other utility distribution components. general-use power factor correction units the requirements in UL 508, the Standard
rated 600 V maximum. These assemblies for Safety for Industrial Control Equipment.
employ integrally protected capacitors, and The Listing Mark for these products
are intended for indoor use, unless other- includes the product name “Industrial
wise indicated. Control Equipment” (or “Ind. Cont. Eq.”).

The guide information, together with other
restrictions of use, such as mounting
means and special electrical connections,
are detailed in the manufacturer’s installa-

02 Copyright © material from the 2009 April Issue of The Code Authority: Electrical Connections newsletter.
This material may not reflect changes that have occurred since its original publication.

Power Factor Correction Equipment (continued)

Power factor correction equipment

Summary of key points
• Low power factor is generally associated

with industrial machinery, but can also
result from ballasted lighting or the
current wave shape of non-linear loads.

• Some utilities impose low power factor
penalties for mid- and large-size primary-
metered service customers.

• UL does not evaluate or validate any
manufacturer’s claims of energy usage
reduction or energy cost reduction
due to the use of power factor
correction equipment.

• UL evaluates and Lists power factor
correction equipment only for the risks of
fire, electric shock, or injury to persons.

• UL Listed equipment that may be used in
power factor correction applications is
covered under the UL product categories
for Capacitors (CYWT) and Power Circuit
and Motor-Mounted Apparatus (NMTR).

03 Copyright © material from the 2009 April Issue of The Code Authority: Electrical Connections newsletter.
This material may not reflect changes that have occurred since its original publication.