Some key differences between Type 1 and Type 2 SPDs are:
- External Overcurrent Protection. Type 2 SPDs may require external overcurrent
protection or it may be included within the SPD. Type 1 SPDs generally include
overcurrent protection within the SPD or other means to satisfy the requirements
of the standard; thus, Type 1 SPDs and Type 2 SPDs that do not require external
overcurrent protection devices eliminate the potential for installing an incorrectly
rated (mismatched) overcurrent protection device with the SPD.
- Nominal Discharge Current Ratings. Available Nominal Discharge Current (In)
ratings of Type 1 SPDs are 10 kA or 20 kA; whereas, Type 2 SPDs may have 3
kA , 5 kA, 10 kA or 20 kA Nominal Discharge Current ratings.
- UL 1283 EMI/RFI Filtering. Some UL 1449 Listed SPDs include filter circuits
that have been evaluated as a UL 1283 (Standard for Electromagnetic Interference
Filters) filter. These are complimentary UL Listed as a UL 1283 filter and a UL
1449 SPD. By definition and the scope of UL 1283, UL 1283 Listed filters are
evaluated for load-side applications only, not line-side applications.
Consequently, UL will not complimentary list a Type 1 SPD as a UL 1283 Listed
filter. However, a Type 1 SPD might include a UL 1283 filter as a Recognized
Component within a Listed Type 1 SPD, which has been fully evaluated for lineside
usage. Manufacturers of such products generally offer the identical SPD as a
Type 2 UL 1449 Listed SPD with complimentary Listing as a UL 1283 Listed
- Capacitors. Capacitors utilized in Type 1 SPDs may be evaluated for safety
differently than in Type 2 SPDs. All capacitors in Type 1 SPD applications are
evaluated to UL 810 (Standard for Capacitors). This includes filtering capacitors
referenced above in UL 1283 (Standard for Electromagnetic Interference Filters)
applications. Capacitors in Type 2 SPDs are evaluated to UL 1414 (Standard for
Capacitors and Suppressors for Radio- and Television-Type Appliances) and/or
UL 1283 (Standard for Electromagnetic Interference Filters).