exam question...surge arresters

[97catintenn]

How many surge arresters are need for a four wire 3 phase system?

I looked at ART 280.3 Number Required....surge arrester shall be connected to each ungrounded conductor

and I answered 3. Is that correct?

 

[Sgriffiths]

surge arrestors

surge arrestors

Article 280 surge arrestors, 280.3 in NEC states surge arrestor shall be connected to each ungrounded conductor

 

[Dennis Alwon]

I believe there is a surge arrestor that will do 3 phase. I would say one

 

[don_resqcapt19]

Surge arresters are used on systems over 1kV and I don't think there are 3 phase versions. I think you need one for each phase.

 

[Dennis Alwon]

Surge arresters are used on systems over 1kV and I don't think there are 3 phase versions. I think you need one for each phase.

Well then they are not calling this the proper term.. http://www.grainger.com/Grainger/SQUARE-D-Surge-Arrestor-3-Phase-600vac-3XB87

 

[don_resqcapt19]

Dennis,
In the real world, that may be a surge arrestor, but in the NEC world that would be a "surge protective device" or "transient voltage surge suppressor" as covered by Article 285.
Surge arrestors are covered by Article 280.

 

[guschash]

I say 3. 285.4 ( the SPD (surge arrestor or TVSS ) shall be connected to each ungrounded conductor. This would be for systems under 1kV.


Article 280.3 surge arrestor shall be connect to each ungrounded conductor,also for systems over 1kV

gus

 

[guschash]

I think I am changing my mind. After reading 285.21 Part 3 again, I'm saying one.

 

[don_resqcapt19]

If it is a code question and the question uses the term "surge arrestor" it is my opinion you have to look to Article 280 and not 285 for the answer.

 

[Sixonebubble]

As mentioned, Article 280 addresses 1kV and above, Article 285 addresses "Low Voltage devices" <1000V, also known as UL 1449 Type 1 SPDs.

 

[don_resqcapt19]

As mentioned, Article 280 addresses 1kV and above, Article 285 addresses "Low Voltage devices" <1000V, also known as UL 1449 Type 1 SPDs.
View attachment 6914

The only device that the NEC calls a "surge arrester" is the device covered by Article 280. The NEC does not call the devices covered by Article 285 "surge arresters".