The Requirement for SPDs

In an effort to reduce the risk of injury and potential damage to electrical systems and buildings, the newest version of the National Electrical Code, the NEC 2020, will require the installation of a Type 1 or Type 2 SPD, Surge Suppression Device, on all new dwelling unit services. This requirement will also apply to upgraded services on dwelling units.

On September 11, 2019 the NFPA 70, National Electrical Code for 2020, was released. This new edition of the National Electrical code has brought a significant amount of changes and updates from the previous 2017 edition. The provisions for the addition of Article 230.67 which mandates the use of SPD devices made it through the committee’s and public comments without any amendments or motions being submitted, so it was adopted and added to the 2020 Code requirements.

What are SPDs?

These devices have been installed in commercial services for some time and have been referred to as TVSS’s or Transient Voltage Surge Suppressors. The 2009 edition of UL 1449 changed the name from TVSS to SPD or Surge Protection Devices. These devices limit voltage spikes or surges on the electrical system which are caused by lightning strikes, or from large inductive loads, such as motors, being turned on an off. When magnetic fields are generated, they expand and collapse when a motor is turned on and off. It is this expanding and collapsing magnetic field that creates voltage spikes. SPDs are basically filters that protect the electrical equipment and people from these sudden voltage spikes.

What is the difference between Type 1 and Type 2 SPDs?

A Type 1 SPD is a hardwired, permanently connected SPD which may be installed on the utility side of the main service overcurrent protective device (i.e. before the main breaker at the service), or it may be installed after the main breaker. The Type 1 SPD can be installed on the line side or load side of the main breaker.

A Type 2 SPD is also a hardwired, permanently connected SPD which must be installed after the main service overcurrent protective device. This means it must be installed on the load side of the main breaker.

Type 3 SPDs are point-of-use devices and are still recommended for the protection of computers, TV’s and other electronic devices, but are outside the scope of the Article 230.67 requirements and cannot be used to comply with the provisions of this section.

Additionally, Article 242 has been added and replaces articles 280 and 285 in the 2017 Code. Here the requirements for how the SPD is to be connected inside the panelboard and the short circuit current ratings requirements will be listed.

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