Surge Protection

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xformer

Senior Member
Location
Dallas, Tx
Occupation
Master Electrician
Hello,
I am dealing with an electrical issue in which I need some assistance. I have 2 surge protectors protecting two separate DP panels that feed various equipment and RTUS. It seems that some occasional surges are still rendering the RTU controls in need of repair despite the fact of the Square D FC4IMA16 160Ka surge protectors on the DP panels for the equipment. Any suggestions?
 
Mike Holt once said for SPDs
"You get what you pay for
More is better"
What is a DP?
Do you have SPD at the service entrance?
 
A surge protector is a shunt (parallel) device. The farther the protected device is from the surge protector, the less protected. The voltage as seen by the protected device consists of Vls+Vs+Vsg where Vs is the surge protector voltage. For a 120V circuit 150 V or 270 V is common. Then we have Vls which is the voltage from the line terminal of the protected device to the surge arrester line terminal. This depends on the surge impedance of the line and the surge current. Both can be quite large leading to kilovolts even with only a few meters away. Vsg is the same but on the neutral/ground side. This value plus the line side dwarfs the surge arrester rating unless it is only a few feet away at most. Do the surge arrester at the distribution panel is effectively useless at protecting anything but the distribution panel itself. At best it knocks down the surge voltage a little bit making the job of other parallel surge arresters easier.
 
A SPD at the service entrance is a must, it reduces the surge and then the impedance of the building wiring reduces it to each panel
I suggest reviewing NEC Article 280.
The SPDs I use come with 18" leads all zip tied together, when installing keep the leads as short as possible, install directly opposite the branch breaker, no loops or similar
I would use a Leviton 42,000 series at the service entrance and 32,000 series at panels. it if was a large service, say over 400 A I would use a Leviton 52,000 series (it has replaceable modules). The Advantage line in the above post seems like a good line, price out the Leviton and Advantage.
My electronic equipment failures were substantially reduced when I started using SPDs,
 
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