The electrical ratings required on a UL label include:
Voltage/Configuration
Frequency
Maximum Continuous Operating Voltage (MCOV)
Voltage Protection Ratings (VPR)
Nominal Discharge Current Rating (In)
The electrical ratings are critical for ensuring the proper application of a surge protective device.
Let's take them one-by-one:
REQUIRED ELECTRICAL RATING SOURCE (WHERE DO THEY COME FROM?)
Voltage Configuration
This is a function of the suppressor design
itself. For example, 3-phase Wye,
120/208 or Split-phase 120/240 are
common voltage configurations. The
components utilized in the specific
suppressor dictate the voltage and
configuration.
Frequency
Again, this is a function of the design and
UL's listing function - the scope of UL 1449
is limited to 50/60 hz.
Maximum Continuous
Operating Voltage (MCOV)
This is a manufacturer declared value
based on the design of the device and the
installation location. This declared value
is utilized during the UL testing process
itself.
Voltage Protection Ratings
(VPR)
These ratings are applied to each mode,
L-N, L-L, L-G, and N-G. They are based on
the VPR tests from UL 1449. The
waveform utilized is the 6 kV/ 3 kA
Combination Wave from C62.41.2. A
series of measured limiting voltages are
taken before and after the Nominal
Discharge Current test. The VPRs are
determined before the Nominal Discharge
Current tests and confirmed after the
Nominal Discharge Current tests.
Nominal Discharge Current
(In)
A completely new test under UL 1449, this
test is conducted using an 8/20 µs
current driven waveform. A series of 15
impulses are conducted in three groups of
5. The current selected for each test is
based on the SPD Type 1 or 2 for
permanently connected devices. Type 1
devices require testing at 10 or 20 kA to
meet the requirements of NFPA 780 for
lightning arresters. The Type 2 devices
can be tested using a 3, 5, 10 or 20 kA
current value. The actual impulses are
conducted with no power applied.
Immediately following the current
impulse, the MCOV is applied for 1
minute. A rest period is allowed between
the three groups of 5 surges. Then, the
MCOV is applied for 30 minutes following
the completed tests.
As a reminder, an SPD Type 1 Device indicates that it is a permanently connected device that can be installed on the line-side OR the load-side of the main overcurrent disconnect and meets the requirements of NFPA 780 and NEC 2008 Article 285 as a secondary surge arrester.
A Type 2 Device on the other hand, is a permanently connected device that can be installed ONLY on the load side of the main overcurrent protective device.
Type 3 devices are cord connected or direct plug in type devices while Type 4 are considered component or partial assemblies requiring an enclosure. Type 4 devices are typically recognized components rather than complete listed devices.
