40 AMP Surge Protector

[jonny1982]

What's the proper way to size a surge protector? Let's just say it there is a 40 amp, 3 phase, 480 volt control panel with no neutral that needs surge protecton. Looking at the specs, it doesn't seem like it is clear cut if it's good for 40 amps. Would that be nominal Discharge current rating?

 

[retirede]

Surge protectors are sized by voltage and energy dissipation. I don’t recall seeing any with an ampere rating.

 

[tom baker]

Most SPDs are connected in parallel. The difference is in the protection provided and how much it offers, you basically get what you pay for.

 

[jonny1982]

Thanks! What about the KA rating? Is there a recomended size based on certain factors? Using the 40 amp 480 volt 3 phase UV control panel as an example, would there be a recommended size KA rating of surge protector for this?

 

[kwired]

Any kA rating would basically be how many available kA from the normal supply is available that it can be applied on.

Otherwise the transients it is there to "absorb" are high voltages typically with pretty low current capability behind them.

It can not sustain long time overvoltages like you would have in fairly direct lightning strike or in situation where higher voltage distribution line falls on lower voltage distribution line.

 

[jonny1982]

so basically you can use the AIC rating of the panel as a guide for the KA rating of the SPD?

 

[jim dungar]

so basically you can use the AIC rating of the panel as a guide for the KA rating of the SPD?

No.

They are not related.
The AIC of the panel is based on current from a short circuit.
The kA of the SPD us based on current from a lightning strike.

 

[jonny1982]

Thanks, here is another (probably dumb) question. If the surge protector only has #10 wire comming out of the whip, can I still connect that in parallel with a 40 amp circuit? Are they typically UL listed to be able to that? Or would I have to somehow have to protect those wires with overcurrent protection properly rated for the #10 wires?

 

[tom baker]

Protection is based on the SPDs mfg instructions, most require a BC breaker. Since this is for a control panel is more of a UL508A listing question. I would suggest you take a look at Leviton products, they have some that may be suitable, they have DIN rail mount. AB has some nice control panel SPDs

 

[Little Bill]

Some surge breakers are also OCPD. In other words, a surge protector requires a breaker, or breaker space, to connect to. There are some that are current rated such as a 40A, 50A, 20A, etc. You can use these for OCP for a circuit as well as surge protection for the whole panel. These just allow you to have surge protection without losing space in the panel. Then of course, you would have to use the appropriate sized conductors for the OCP.