Is SPD for a separately derived system mandatory or voluntary (NEC-2020)

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victor.cherkashi

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Location
NYC, NY
In NEC 2020, section 280 285 moved into section 242. Wording was changed.

Wording in 2017: “285.21 Connection. Where an SPD device is installed, it shall comply with 285.23 through 285.28.”. Based on this wording SPD is not mandatory for Separately Derived System.

Reading the 2020 code, section 242, I'm not sure if the SPD for a separately derived system is mandatory or voluntary 242.14(C).

Thank you for responses in advance
 
Dennis Alwon

Dennis Alwon

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Location
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Looks like it is required to me. It says shall be installed in A thru C


242.14 Type 2 SPDs.



Type 2 SPDs shall be installed in accordance with 242.14(A) through (C).


(A) Service-Supplied Building or Structure.



Type 2 SPDs shall be connected anywhere on the load side of a service disconnect overcurrent device required in 230.91 unless installed in accordance with 230.82(8).



(B) Feeder-Supplied Building or Structure.



Type 2 SPDs shall be connected at the building or structure anywhere on the load side of the first overcurrent device at the building or structure.



(C) Separately Derived System.



The SPD shall be connected on the load side of the first overcurrent device in a separately derived system.
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jaggedben

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victor.cherkashi said:
In NEC 2020, section 280 285 moved into section 242. Wording was changed.

Wording in 2017: “285.21 Connection. Where an SPD device is installed, it shall comply with 285.23 through 285.28.”. Based on this wording SPD is not mandatory for Separately Derived System.

Reading the 2020 code, section 242, I'm not sure if the SPD for a separately derived system is mandatory or voluntary 242.14(C).

Thank you for responses in advance
Click to expand...
The new requirement for an SPD on services with dwelling units is in 230.67 in the 2020 NEC.

There is no requirement to install an SPD on an SDS as far as I can see. You only have to follow 242 if you decide to install one, but it's your decision.
 
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victor.cherkashi

Senior Member
Location
NYC, NY
NEC-2020 has paragraph and table - 242.3 Other Articles. Equipment shall be protected against
overvoltage in accordance with the article in this Code that covers the type of equipment or location specified in Table 242.3.

I am thinking:
1. if S.D.S. is associated with one of the location/equipment/system listed in table 242.3 then SPD is mandatory for S.D.S.
2. If S.D.S. is privately owned and installed in office building for example then SPD installation for S.D.S. is voluntary.

What do you think about the above statements.
 
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victor.cherkashi

Senior Member
Location
NYC, NY
I don't understand why Article 406 is the table #242.3.
Article 406 does not contain any requirements for SPD. (All others on that list contain the requirement for SPD)
Any idea?
 
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