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Now that we know SPDs will be required for electrical services, it may be time to add some information about them. We've all been seeing more installations of these, and of course, for emergency systems, their installation has been required. Here we go.
What is the difference between the terms “Surge Arrester”, “Transient Voltage Surge Suppressor (TVSS)” and now “Surge Protective Devices (SPD)”?
Up until the third edition of the ANSI/UL 1449 standard was introduced and put into effect in 2009 there were various terms used when referencing devices intended to limit the effects of transient surge events. Surge arresters less than 1000 volts, commonly referred to as secondary surge arresters, were originally developed for and applied to the line side of the power distribution system to protect utility supplied equipment and building wiring. Surge arresters were intended to protect the system structure and not necessarily the connected equipment and loads.
A TVSS as it was defined must be applied to the load side of the main service overcurrent disconnect device. Unlike a surge arrester, a TVSS was intended to protect the sensitive electronics and microprocessor based loads by having a tighter ‘clamp’ or limiting effect on transient voltages.
With the adoption of ANSI/UL 1449 – Third Edition, both the terms “Secondary Surge Arrester” and “TVSS” were done away with and replaced with a more general term of “Surge Protective Devices (SPD)”. With this new term there was a need to identify the proper SPD for its intended application so UL also introduced the different Types of SPDs. For those applications similar to where a surge arrester would have been used on the line side of the system, it would now require a Type 1 SPD. In those applications where you once placed TVSS devices on the load side of the system, these same installations require a minimum of a Type 2 SPD. Bringing these devices under one ‘SPD umbrella’ and one test standard of ANSI/UL 1449 insures a consistent product.
The electrical industry has followed these changes. The NEC 2008 Sec 285 has updated their terminology eliminating the term TVSS and describes the proper application of Type1 and Type2 SPDs.
What do the various product markings on a surge protective device (SPD) really mean, and which are important?
Underwriters Laboratories (UL) requires certain markings be on any UL listed or recognized SPD. Some parameters which are important and should be considered when selecting an SPD include:
What is the difference between the terms “Surge Arrester”, “Transient Voltage Surge Suppressor (TVSS)” and now “Surge Protective Devices (SPD)”?
Up until the third edition of the ANSI/UL 1449 standard was introduced and put into effect in 2009 there were various terms used when referencing devices intended to limit the effects of transient surge events. Surge arresters less than 1000 volts, commonly referred to as secondary surge arresters, were originally developed for and applied to the line side of the power distribution system to protect utility supplied equipment and building wiring. Surge arresters were intended to protect the system structure and not necessarily the connected equipment and loads.
A TVSS as it was defined must be applied to the load side of the main service overcurrent disconnect device. Unlike a surge arrester, a TVSS was intended to protect the sensitive electronics and microprocessor based loads by having a tighter ‘clamp’ or limiting effect on transient voltages.
With the adoption of ANSI/UL 1449 – Third Edition, both the terms “Secondary Surge Arrester” and “TVSS” were done away with and replaced with a more general term of “Surge Protective Devices (SPD)”. With this new term there was a need to identify the proper SPD for its intended application so UL also introduced the different Types of SPDs. For those applications similar to where a surge arrester would have been used on the line side of the system, it would now require a Type 1 SPD. In those applications where you once placed TVSS devices on the load side of the system, these same installations require a minimum of a Type 2 SPD. Bringing these devices under one ‘SPD umbrella’ and one test standard of ANSI/UL 1449 insures a consistent product.
The electrical industry has followed these changes. The NEC 2008 Sec 285 has updated their terminology eliminating the term TVSS and describes the proper application of Type1 and Type2 SPDs.
What do the various product markings on a surge protective device (SPD) really mean, and which are important?
Underwriters Laboratories (UL) requires certain markings be on any UL listed or recognized SPD. Some parameters which are important and should be considered when selecting an SPD include:
- SPD Type – used to describe the intended application location of the SPD, either upstream or downstream of the main overcurrent protective device of the facility. SPD Types include:
- Type 1– A permanently connected SPD intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures and Molded Case SPDs intended to be installed without an external overcurrent protective device.
- Type 2– A permanently connected SPD intended for installation on the load side of the service equipment overcurrent device, including SPDs located at the branch panel and Molded Case SPDs.
- Type 3– Point of utilization SPDs, installed at a minimum conductor length of 10 meters (30 feet) from the electrical service panel to the point of utilization, for example cord connected, direct plug-in, receptacle type SPDs installed at the utilization equipment being protected. The distance (10 meters) is exclusive of the conductors provided with or used to attach SPDs.
- Type 4– Component Assemblies -,Component assembly consisting of one or more Type 5 components together with a disconnect (internal or external) or a means of complying with the limited current tests.
- Type 1, 2, 3 Component Assemblies – Consist of a Type 4 component assembly with internal or external short circuit protection.
- Type 5 – Discrete component surge suppressors, such as MOVs that may be mounted on a PWB, connected by its leads or provided within an enclosure with mounting means and wring terminations.