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Surge Arrestor Installation


RichNSpect
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The panel I inspected yesterday was a 150 amp split-bus configuration. The panel had numerous deficiencies (more than six disconnects, double taps, double neutrals, etc.), but it also had a surge arrestor installed.

This surge arrestor was installed on the 40 amp disconnect for the electric range. Plus, it was connected directly to the terminals (double tap).

So, my question is this:

Why would the surge arrestor be installed on just the 40 amp breaker to the range? Wouldn't it be better for the arrestor to be installed on the main lighting disconnect breaker?

Since this is a split bus panel, installing the arrestor on just the 40 amp range disconnect would not provide protection for the rest of the panel, would it? I always thought that if you install a surge arrestor on a single bus panel that the entire panel is protected no matter where you install it on the bus, but what about a split bus panel?

Any help would be appreciated [^]

Kevin

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. . . Why would the surge arrestor be installed on just the 40 amp breaker to the range? Wouldn't it be better for the arrestor to be installed on the main lighting disconnect breaker?

Not necessarily. As long as it's connected to each pole, it'll work. It doesn't matter which breaker it is.

Since this is a split bus panel, installing the arrestor on just the 40 amp range disconnect would not provide protection for the rest of the panel, would it? I always thought that if you install a surge arrestor on a single bus panel that the entire panel is protected no matter where you install it on the bus, but what about a split bus panel?

It doesn't matter. It'll still work.

It's supposed to be installed on the outside of the box, though.

Personally, I prefer the kind that are built into circuit breakers. They're much neater.

- JIm Katen, Oregon

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Hey Kevin,

Doesn't matter which breaker you connect it to as that is just the way it makes it's ultimate connection to the main bus. The electrician likely chose that breaker as the terminal for it will handle the extra wire (double tap) just like it was another strand in the wire that was already attached to it. It's not a terminal screw on that 40 amp breaker, it's more like a lug, it's meant to handle multistrand wire. Even though it is a split bus, the two sides are connected to each other and if it is going to take a hit, it would likely be on the mains side anyway.

On installations I've done in the past where there was plenty of room in the new panel I would wire the surge arrestor to it's own breaker only to have the code inspector come and say "why'd you waste breaker space, you could have just double tapped it to another circuit" Basically, double tapping these, as well as low voltage transformers, is a very accepted practice. I've never wasted my time griping about them.

In short, the only thing I would even mention about that installation would be about the device sitting loose inside the panel, it should be installed through a knockout with the bulk of the device on the outside of the panel.

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. . . Why would the surge arrestor be installed on just the 40 amp breaker to the range? Wouldn't it be better for the arrestor to be installed on the main lighting disconnect breaker?

Not necessarily. As long as it's connected to each pole, it'll work. It doesn't matter which breaker it is.

Since this is a split bus panel, installing the arrestor on just the 40 amp range disconnect would not provide protection for the rest of the panel, would it? I always thought that if you install a surge arrestor on a single bus panel that the entire panel is protected no matter where you install it on the bus, but what about a split bus panel?

It doesn't matter. It'll still work.

It's supposed to be installed on the outside of the box, though.

Personally, I prefer the kind that are built into circuit breakers. They're much neater.

- JIm Katen, Oregon

Man o man, you weren't even logged on when I started typing... My wife distracted me. Thats my story and I'm sticking to it. [:-weepn]

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Hey Kevin,

Doesn't matter which breaker you connect it to as that is just the way it makes it's ultimate connection to the main bus. The electrician likely chose that breaker as the terminal for it will handle the extra wire (double tap) just like it was another strand in the wire that was already attached to it. It's not a terminal screw on that 40 amp breaker, it's more like a lug, it's meant to handle multistrand wire. Even though it is a split bus, the two sides are connected to each other and if it is going to take a hit, it would likely be on the mains side anyway.

On installations I've done in the past where there was plenty of room in the new panel I would wire the surge arrestor to it's own breaker only to have the code inspector come and say "why'd you waste breaker space, you could have just double tapped it to another circuit" Basically, double tapping these, as well as low voltage transformers, is a very accepted practice. I've never wasted my time griping about them.

In short, the only thing I would even mention about that installation would be about the device sitting loose inside the panel, it should be installed through a knockout with the bulk of the device on the outside of the panel.

Thanks, Kyle (and others)!

I appreciate the help :) I'm being told by another source that there is a difference in the installation between a lightning arrestor and a TVSS or SPD. The lightning arrestor should be installed on the line side and the SPD installed on the load side protected by an over-current protection device.

Lesson learned on my end :( I should have paid more attention to what the label said on the device. At any rate, I called it out as being improperly installed (loose inside panel) and called for a Licensed Electrician. I was also told that the wires are too long and that they should be as short as possible.

I love my job :)

Kevin

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