Surge Protection Installation

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Rich M

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Largo, Florida USA
Manufacturers of discreet components, such as MOV's, SAD's, GDT's, etc., all specify a reaction time to their components.
Based on that information, is there a recommended wire distance that should be allowed for between the protector and the equipment to be protected?

Where as if the protector is too close to the equipment it is protecting, wil there be enough "reaction time" for the protector to turn on and to shunt the fault away from the circuit to ground?

What should the wire distance be for SPD units on electrical panels?
What should the wire distance be for SPD units on low voltage communication lines?
What should the wire distance be for SPD units on telephone circuits?
What should the wire distcnae be for SPD units on signaling loop circuits on fire alarm panels?
Is there an IEEE or NEC section that refers to this?


Thanks for your help!
 
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GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
Rich M said:
Manufacturers of discreet components, such as MOV's, SAD's, GDT's, etc., all specify a reaction time to their components.
Based on that information, is there a recommended wire distance that should be allowed for between the protector and the equipment to be protected?

Where as if the protector is too close to the equipment it is protecting, wil there be enough "reaction time" for the protector to turn on and to shunt the fault away from the circuit to ground?

What should the wire distance be for SPD units on electrical panels?
What should the wire distance be for SPD units on low voltage communication lines?
What should the wire distance be for SPD units on telephone circuits?
What should the wire distcnae be for SPD units on signaling loop circuits on fire alarm panels?
Is there an IEEE or NEC section that refers to this?


Thanks for your help!
Click to expand...

The time that the surge takes to move down the wire is on the rough order of one nanosecond (10-9 seconds) per foot, so that does not make a big difference based on how far the SPD is from the load on the upstream side. :)
But there will be a difference in the way the surge voltage is reduced by the voltage divider effect of the wiring between the source and the SPD. So the closer to the load the better for that specific case. For SPDs like whole house units at the breaker box, since they are off to the side rather than inline the wires must be as short as possible, following the manufacturer's install instructions.
 
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