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PowerCET Corporation
3350 Scott Blvd., Bldg. 55. Unit 1
Santa Clara, CA 95054 USA
Voice: 408/988-1346 | Fax: 408/988-4869
URL: http://www.powercet.com
E-mail: [email protected]
UL Laboratory Power Quality Testing Report
Cables-R-Us
Silicon Valley, CA
Introduction / Background
Underwriters Laboratories (UL) has implemented an annual Laboratory—Power Quality
testing/certification requirement for their clients with UL certified testing facilities.
The purpose of the specification is to ensure that the electrical distribution for the client laboratories can
support reliable (and repeatable) testing for UL Standards. The thrust of the requirement is to create an
electrical environment with dedicated branch circuits serving the equipment use in testing and certifying
of various products to UL Standards and Specifications.
PowerCET Corporation was retained by Cables-R-Us to perform the initial UL Laboratory—Power Quality
testing UL Lab located in the Cables-R-Us production facility located in Silicon Valley, California.
Methodology / Technical Approach
The testing required by the UL Laboratory—Power Quality document is straight forward and can be
completed with a minimum of equipment consisting of a modern power monitor and resistive load banks.
The following equipment was selected to perform the required testing:
•
•
•
Dranetz-BMI PowerVisa 440 Power Monitor capable of supporting 4 differential voltage channels
and 4 independent current channels. The PowerVisa 440 meets all the current IEC standards
with respect to measurement capabilities and has software that supports the post processing of
the data.
Avtron Model K490 is a 10kW load bank that supports 120Vac and 120/240Vac applications in
0.25kW steps.
Avtron Liberty model load bank has a capacity of up to 75kW and supports both single-phase and
poly-phase applications from 120Vac through 480Vac
Photo 1 - Dranetz-BMI
PowerVisa 440.
Photo 2 - Avtron K490 load
bank.
Date: 05/13/2009
Filename: Sample_UL_PQ_Report_081001.doc
Photo 3 -- Avtron Liberty
load bank
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The UL testing requirements include the following measurements:
1) Independence of Test Circuits
2) L, N, G Voltage Measurement Test
3) Electrical Regulation / Circuit Capacity Test
a) Voltage Regulation / Circuit Capacity Test
b) Frequency Stability – Loaded Supply Test
c) Total Harmonic Distortion Test
Initial testing was conducted during the week of September 8, 2008. The following report documents the
results of the initial testing and recommendations for corrective action as required.
Key Findings
The good news is that the initial testing indicates that the Cables-R-Us UL Lab should not encounter
significant issues in meeting both the letter of the UL Laboratory—Power Quality requirement or the spirit
of the program. Some, not insignificant, work will be required to bring the UL Lab’s electrical energy
supply and distribution to both UL and National Electrical Code (NEC) standards and requirements.
The main Cables-R-Us UL Lab is located in a raised mezzanine area inside the Silicon Valley production
facility. The Lab is currently served by the plants 460Vac electrical distribution via three feeders
supplying 460-220/110Vac step-down transformers. The 220/110Vac is then distributed through normal
low-voltage electrical distribution—see Drawing 1 below. The “cold chamber” is located in a separate
building (Annex) just outside the main production facility and is fed by the third 460Vac feeder
The plants main electrical supply is from a bank of transformers with 13.8kV secondary winding which
feeds a series of substations throughout the plant where the voltage is transformed down to 460Vac.
Drawing 1 (below) shows the single-line distribution for the Lab and Annex.
Drawing 1 – Existing single line of Cables-R-Us UL Lab distribution.
The distribution in the main lab area which is fed by the 37.5kVA 460/220-110Vac transformer is under
sized for the application with a rated current rating of 170 Amps at 220Vac which should be de-rated to
80% which nets 136 Amps available per supply conductor—see Drawing 2.
Date: 5/13/2009
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Silicon Valley, CA
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Silicon Valley, CA
Drawing 2 -- Cables-R-Us UL Lab floor plan.
The second step-down transformer is rated at 15kVA 460/220-110Vac and supplies ovens #9 and #10 in
the oven room.
There are four main areas of concern that were identified as a result of the UL Laboratory—Power Quality
inspection and testing. Briefly these areas are:
1. Oven Room Electrical Distribution
There are a total of 10 ovens, 2 of which—#9 and #10—are being supplied from the separate
15kVA transformer and the remaining 8 are supplied from the Lab’s 54kVA transformer
distribution. The 110Vac ovens—#3, #4, #7 and #8—are supplied via a plug/cord connection to a
single 110Vac circuit (P3-19) which has, at least, 12 different receptacle terminations in the UL
Lab area. Also 2 of the ovens—#1 and #2—share a common circuit (P3-16/18) which trips
occasionally with both ovens operating
2. Water Bath Electrical Supply
All 4 of the baths—A, B, C and D—are supplied from a single 220Vac circuit breaker (P2-22/24)
rated at 40-Amps. When all 4 of the baths are heading the combined current draw reaches
approximately 36-Amps. The NEC limits the continuous connected load to 80% of the circuit
breaker rating, or in this case 32-Amps. There are 2 unused 220Vac 30-Amp circuits (P2-14/16
and P2-18/20) terminated on the north wall of the water bath area which could be rearranged
along with finding a third supply to provide each bath with a dedicated circuit.
Date: 5/13/2009
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Gate Controlled Loads (Water Bath): The circuit feeding the 110Vac quad receptacles—
locations 29 and 30 on the floor plan—are actually wired to one of the supply conductors for the
circuit supplying the water bath’s (P2-22/24). This configuration is NOT compliant with the NEC
nor will the electrical circuits associate with the water bath’s, in their present configuration, meet
the UL-PQ testing requirements.
3. Rheometer / Tensometer Electrical Supply
The Rheometer and Tensometer equipment is supplied from the 110Vac (P3-19) which is
common with at least 12 other receptacles. There is no question that the test equipment can be
impacted by other equipment being powered from the P3-19 circuit.
4. Electrical Room
The NEC is very specific about electrical rooms being used for storage or other purposes. A
review of the NEC with respect to sink installations in electrical rooms was made, but nothing was
found that would specifically prohibit the installation…it is just not a good practice.
The electrical room where the 37.5kVA transformer and panelboards 1 through 4 are located
needs to be cleaned up. There should be 30-inches clear space in front of the electrical
equipment and the NEC specifically prohibits electrical room from being used as storage spaces.
As long as you can maintain the 30-inch clearance you can probably get by with other things in
the room.
Also the NEC requires overhead lighting in electrical rooms.
Recommendations
Oven Room Electrical Distribution
The best way to correct the present situation would be to increase the capacity of the circuitry associated
with the 15kVA transformer and Panelboard 5. The transformer is fed from a 100-Amp 460Vac feeder
which, with a larger transformer 46kVA to 50kVA could supply around 153A which could still be marginal
with all 10 ovens operating.
By moving all of the ovens to Panelboard 5 (and upgrading the capacity of the supply) it will free pole
positions and capacity associated with the 37.5kVA transformer and panelboards 1, 2, 3 and 4.
Each of the ovens needs a dedicated circuit to meet the UL requirements. There are 6 large ovens that
operate at 220Vac and 4 smaller ovens operating at 110Vac. A total of 16-circuit breaker pole positions
would be required just for the ovens and there should be several 110Vac convenience receptacles
installed for portable test equipment in the oven room. It will be necessary to increase the size of
Panelboard 5 from the current 12-pole positions to a minimum of 20-pole positions as well as increasing
the 460Vac feeder and associated transformer.
The actual operating current draw for each oven type needs to be verified to determine the capacity
required to support the ovens. I would recommend only loading the new transformer to a maximum of
80% of its rated capacity which should include any plans for additional equipment or lab expansion...
There may be a benefit to sizing the service for the oven room to accommodate the water bath test area
as well. This would free up capacity associated with the existing 37.5kVA transformer and circuit breaker
pole positions in panelboards 1, 2, 3 and 4 providing sufficient capacity of the additional circuits required
by the UL Laboratory—Power Quality specification. Increasing the feeder circuit to 125-Amps at 460Vac
would yield 57.5kVA and a usable 209-Amps at the 220Vac step-down output voltage.
Date: 5/13/2009
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Cables-R-Us UL Lab
Silicon Valley, CA
There is sufficient space in the existing oven room to locate the new supply transformer along the wall at
the right side of Photo 2 (below). The associated 30-position panelboard could be mounted next to the
transformer keeping branch circuit wiring lengths to the ovens and water baths to a minimum.
Also the wiring in the oven room needs to be cleaned-up which should be part of the upgrade activity.
Photo 4 – Cables-R-Us UL Lab oven room.
Photo 5 -- Junction box associated with
Ovens #1 and #2 (P3-16/18).
Water Bath Electrical Supply
The water baths—A, B, C and D—are all powered from a single 220Vac 40-Amp circuit breaker (P222/24). In addition the gate controlled loads and associated test equipment are wired as single-phase
loads off of the same circuits. The baths draw approximately 9-Amps during heading with the total load
exceeding the allowable level of 32-Amps (80% of the circuit breaker rating).
Individual 220Vac 20-Amp circuits need to be provided for each of the baths. There are two 220Vac
circuits terminated on the north wall of the water bath area which can be reused, if necessary, for two of
the baths. A fourth circuit would need to be installed to complete the rearrangement to bring the
installation into both NEC and UL compliance.
A better solution would be to power the water baths from an upgraded distribution for the oven room. The
advantage of this is that is would significantly decrease the loading on the 37.5kVA transformer currently
supplying the majority of the Cables-R-Us UL Lab—see the section above discussing oven room
electrical distribution. This solution would also free up a total of 6 single-phase circuit breaker positions in
panelboards 1-4 which would aid in meeting new dedicated circuit requirements for the general lab area.
Gate Controlled Loads (Water Bath): The circuit feeding the 110Vac quad receptacles—locations 29
and 30 on the floor plan—is actually wired to one of the supply conductors for the circuit supplying the
water bath’s (P2-22/24). This configuration is NOT compliant with the NEC nor will the electrical circuits
associate with the water bath’s, in their present configuration, meet the UL-PQ testing requirements.
Separate dedicated circuits need to be installed for the gate controlled loads (location 29) and a 5-15R
quad receptacle box (location #30) for non-gate controlled loads.
Date: 5/13/2009
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Silicon Valley, CA
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Photo 6 – Gate controlled loads (location #29) and existing convenience receptacle (location #30).
The 5-15R duplex receptacle (location #31) should be removed and covered…this appears to have been
a conversion of a light-switch and is not a good location for a duplex receptacle.
Drawing 4 below is a one-line drawing of a configuration for the UL Lab that would move all of the
heading loads to a new 75kVA transformer which would free up necessary capacity and circuit breaker
pole-positions in the existing distribution served by the 37.5kVA transformer.
Drawing 3 – Proposed addition to accommodate energy needs for Oven Room and Water Bath
area.
Date: 5/13/2009
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Rheometer / Tensometer Electrical Supply
The Rheometer / Tensometer work area (currently powered from circuit breaker P3-19) will require a total
of 5 dedicated 20-Amp circuits terminated with quad (2 each 5-15R duplex) receptacles. The 3 existing
duplex receptacles located on the wall above the Rheometer work surface need to be converted to a
quad configuration and served from individual 20-Amp circuit breakers.
Photo 7 -- Rheometer / Tensometer area showing existing work bench receptacles and new quadreceptacle for Tensometer.
Two new quad duplex receptacles need to be added to the wall area behind the Tensometers. Each
circuit must be served from individual 20-Amp breaker. The use of quad receptacle boxes will eliminate
the need for plug strips and provide the required dedicated circuit for the Tensometers used for UL
testing.
Drawing 3 (below) summarizes the electrical distribution needed along the north wall and water bath area
of the Cables-R-Us UL Lab.
Date: 5/13/2009
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Silicon Valley, CA
Sample Report
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Drawing 4 – Cables-R-Us UL Lab north wall and water bath electrical distribution changes.
Electrical Room
Electrical Room Issues
There are two areas that need to be addressed with respect to the UL Lab electrical room.
1. The electrical room for the Cables-R-Us UL Lab is being used as a miscellaneous storage room
and janitorial closet—sees Photo 9. The NEC requires that 30-inches of clear space be provided
in front of all electrical equipment. Photo 9 shows that the area in front of the four panelboards is
blocked by various material and cleaning supplies. At minimum the area in front of the electrical
panelboards needs to be kept clear. Many installations employee yellow stripes indicating the
minimum clear space in front of electrical equipment.
2. The NEC also requires that electrical rooms be equipped with lighting…the present electrical
room configuration does not have an overhead light installed. An overhead light must be
installed in the electrical room.
A review of the 2008 NEC could not locate any specific prohibition concerning the location of wet sinks—
see Photo 10—in electrical rooms, but given the size of the room and the sinks proximity to the 37.5kVA
transformer this arrangement this configuration. Relocating the sink and janitorial supplies to either the
storeroom (which shares a common wall with the electrical room) or to the bathroom area should be
evaluated.
Date: 5/13/2009
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Photo 8 – UL Lab electrical room showing
storage of miscellaneous items and cleaning
supplies.
Sample Report
Consulting Report
Cables-R-Us UL Lab
Silicon Valley, CA
Photo 9 – UL Lab electrical room wet sink.
Tandem Circuit Breaker Use
Panelboards P2 and P3 have a total of 10 tandem circuit breakers (overcurrent devices) installed.
Tandem (aka “piggyback”) circuit breakers allow for two separate breakered circuits to be installed in a
single pole position. Photo 10 shows the tandem circuit breakers installed in P3. Obviously, the
advantage is that additional circuit breaker protected branch circuits can be supplied from an existing
panelboard. The restriction on the total number of circuit breakers allowed in a panelboard has been
limited to a total of 42-pole positions. Also the tandem circuit breaker MUST be listed for use in the
panelboard in which it is installed.
Photo 10 – Panelboard P3 showing various type of circuit breakers installed.
Date: 5/13/2009
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The 2008 NEC has changed the overcurrent device limitation to the number specified in the panelboards
design and certification listing. In other words, unless the panelboard’s listing specified additional
overcurrent devices beyond the number of physical pole positions the use of tandem circuit breakers
would be prohibited. The following is the excerpt from the 2008 NEC Handbook.
408.54 Maximum Number of Overcurrent Devices.
A panelboard shall be provided with physical means to prevent the installation of more
overcurrent devices than that number for which the panelboard was designed, rated, and
listed. For the purposes of this section, a 2-pole circuit breaker or fusible switch shall be
considered two overcurrent devices; a 3-pole circuit breaker or fusible switch shall be
considered three overcurrent devices. Aside from the second exception to 408.36, the
maximum of 42 overcurrent devices was deleted for the 2008 Code. Now the quantity of
overcurrent devices is limited to design and listing of the panelboard.
With respect to electrical code (NEC) compliance, some jurisdictions require that anytime construction
activity involves existing equipment the installation is brought into compliance with the, then in effect,
electrical code(s). It is unlikely that the P2 (20-pole position) or P3 (24-pole position) panelboards were
ever listed for use with more than their designed number of pole positions.
Relocating the oven and water bath heating loads off of the 37.5kVA transformer (discussed in the
previous section), and its associated distribution, will significant decrease the overall loading. If the
loading and use of tandem breakers is a concern then panelboards P2 and P3 could be upgraded to 30pole position equipment.
The following four photos document the current circuit breaker configuration of the existing panelboards
P1 through P4.
Photo 11 -- Panelboard 1 (P1) 6-pole design
with 6-poles installed.
Date: 5/13/2009
Photo 12 -- Panelboard 2 (P2) 20-pole design
with 26-poles installed…i.e., 12-tandem
circuit breakers.
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Silicon Valley, CA
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Photo 13 -- Panelboard 3 (P3) 24-pole design
with 28-poles installed…i.e. 8 tandem circuit
breakers.
Photo 14 -- Panelboard 4 (P-4) 16-pole design
with 4-poles installed.
Oven Energy Measurements
Periodic measurement of oven power consumption is necessary as part of the overall product testing and
certification. Currently it is necessary for the individual making the measurements to unscrew the rear
panel of the larger ovens, while operating, to access the input electrical wiring for both voltage and
current readings. A Dranetz-808 Energy Analyzer (obsolete meter) is used for the measurements.
During the rewiring of the oven room it would be simple matter to install a small RHC NEMA enclosure
with hinge cover. The input power conductors could easily be looped for easy installation of a small
current clamp and 4mm safety sockets could be installed for voltage connections. Photo 15 shows the
enclosure which be ordered in a 6”x6”x4” size.
Photo 15 – Small RHC NEMA 3R hinge-cover wall mount.
In addition to installing a safe way to access the circuit conductors a new energy meter should be
considered. There are a number of new single and 3-phase power meters which will do the simple job of
energy measurements.
Things to consider in making a selection…
Date: 5/13/2009
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•
Measurement standards…EN 50160, IEC 61000-4-30…describe how the measurements are to
be made. Meters supporting these standards are probably going to required in the future. Not all
of the units conform to the standard so some research will be required.
•
Basic accuracy…the truth is that unless metering current transformers are installed using most
any portable equipment will end up with a basic accuracy of something between +/- 2%.
Positioning of clamp-on current probes can impact the measurements. Most hand-held portable
equipment quotes between 2% and 4% accuracy on their power/energy measurements.
Possible meters to consider…
•
Fluke 43B (43B/003 $2695 Kit): Single-phase hand-held unit with a basic power accuracy of
around 4%. Single phase only. Software somewhat difficult, but is probably adequate for most
users.
•
AEMC 8230 ($1995 w/200A CT) and 8220 ($1299 w/200A CT): Does not specify method of
measurement (probably does not conform to all international standards). Basic accuracy not
specified. Single-phase only. Software adequate.
•
Hioki 3197 ($2995 Kit): Does not specify method of measurement (probably does not conform to
all international standards). Basic accuracy specified plus the associated current
clamp/probe…+/-2% is probably the best that can be expected. Unit has 3-phase capability.
Software adequate.
•
Fluke 434 (434/003 $5212 Kit): Accuracy typically +/- 1% (or less) before adding current
probe…realistically probably +/- 2% for field use. Has 3-phsae capability. Does perform
measurements according to international EC and IEC standards. Software leaves a lot to be
desired…multiple programs required to realize the full capability of the meter.
•
Dranetz-BMI PowerVisa 440 ($4495 Kit): Does measurements according to IEC and EC
standards. Voltage readings are specified at 0.05% FS, current readings are specified at 1% of
reading plus current probe. Best accuracy for field use is probably +/- 2%. Unit has 3-phase
capability. (Note: The PowerVisa 440 can be used for UL Lab—Power Quality certification as
well as other energy/power related activities.) Software is fully featured and has the ability to post
process data.
Identification of UL Lab Certified Circuits
It is probably prudent to have a method of identifying circuits that are to be used for UL testing and
certification as well as to document the date of certification.
Common duplex receptacles may be ordered in a variety of colors as well as the associated cover plates.
In cases where colored cover plates are not available spray paint or colored tape could provide and
adequate method of identification.
Labels should be affixed to each circuit termination indicating the circuit’s source and date of last
certification in the case of UL testing circuits. The following is an example of what the label might contain.
Loc 35
U
Certified
9/8/2008
L
P2-21
Date: 5/13/2009
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Silicon Valley, CA
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Silicon Valley, CA
For non-UL circuits the following labeling would suffice.
Loc 35
P2-21
Summary
It appears that the UL Labs electrical distribution has experienced “load creep” over its history and is
probably at the point where some clean-up; rearrangement and expansion are called for.
The UL requirement for annual certification of electrical facilities associated with UL testing has served to
raise the level of awareness of some problem areas.
The good news is that the Lab should be able to achieve certification of its electrical environment, but it
will require some investment, but should not significantly disrupt the normal lab activities.
At present the 37.5kVA transformer located in the electrical closet is probably marginally over loaded
during peak activity. The large UL loads are the 10 ovens and 4 water baths. This report proposes to
install a new 460Vac 150-Amp feeder to a 75kVA step-down transformer located in the oven room. The
new transformer and associated output distribution panel could feed the 10 ovens, 4 water baths and
necessary convenience circuits for those areas. By moving the heater loads off of the 37.5kVA
transformer there should have sufficient capacity to supply the general lab needs as well as the expanded
dedicated branch circuits required by the UL Laboratory—Power Quality program.
With the exception of circuit P3-19 there is little other work required in the general lab area. Circuit P3-19
has approximately 12 appearances and currently supplies UL testing and certification equipment.
The primary objective of the UL program is to insure that the electrical distribution supplying equipment
used in testing and certification is not adversely impacted by other loads cycling on the same facility
which is why the dedicated circuits for most UL equipment will be required.
Following completion of the corrective activities outlined in the Recommendations section of this report it
will be necessary to test all of the newly configured branch circuits.
Report prepared by:
Bruce Lonie
President, PowerCET Corporation
Disclaimer
The information contained in this document is provided for educational purposes only as an example
on how to incorporate power monitoring data and other observations into a report format. It is not
intended to provide consulting advice for any specific problem or situation. This is a copyrighted
document and intended for individual use and should not be reproduced or distributed in any form
without specific written permission from PowerCET Corporation.
Date: 5/13/2009
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