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#221894 09/06/22 12:12 PM
Joined: Jan 2005
Posts: 5,360
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Cat Servant
Member
Having just re-activated my license and got up to speed with a code seminar, I eagerly dove into a service change job. Panel(s) installed, wires run, it was time to go get some breakers.

At the parts house I was met by a little confusion when I asked for the newly mandated surge suppressor. Huh? Seems they’ve yet to sell one.
It gets worse. If you’re using a Square D Homeline (or similar) panel, it appears the only SPD’s available mount to the outside of the panel. If you want one that snaps into a breaker position, you need to use a QO panel.

This is a service location item. More important, SPD’s need pigtails as short as possible or they won’t work right. With services being located outdoors, the last thing I want to do is punch another hole in the box.

Outside disco with indoor panel? With interior panels set IN the wall, does code even allow me to bury the gizmo behind the Sheetrock?

Okay, I’m in one of the less trendy parts of the USA. That might explain the local trade. That’s still no excuse for Square D, whom I can only assume was heavily involved in writing this new requirement.

What about you? Have you installed SPD’s? Have you had trouble finding them? Are there alternatives I don’t know about?

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Joined: Jul 2004
Posts: 9,766
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G
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Does your PoCo offer the SPD in the meter can? That is an option if it is available. Just be sure you have as good a ground electrode system as possible.


Greg Fretwell
Joined: Jan 2005
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Cat Servant
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No, the POCO doesn’t offer an SPD. They ARE adamant that there be a lever bypass (no horns and jumpers).

The irony is that I’ve personally been sold on the idea of surge protection for a long time. I tried to have it for my home twenty years ago — where I encountered all manner of engineering techno-babble from suppliers. I recall seeing a picture of the “hang on the side of the box” version ten years ago.

I had thought, with the 2020 code nearly outdated, these things would be in the pipeline by now.

Joined: Jul 2004
Posts: 9,766
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G
Member
You might be stuck with a 3R SPD on the bottom of the box.


Greg Fretwell
Joined: Jan 2005
Posts: 5,360
Likes: 1
Cat Servant
Member
Might as well not even bother, if that’s the case.
Check the math with your local EE. Even a trivial 6” pigtail greatly reduces the effectiveness of an SPD. Make those leads 18” long and the device will never see any surges. That’s why it’s so important to mount them directly to the bussbars.

At this point I’m inclined to omit the SPD and let the inspector call me on it. Code has no business requiring things that aren’t available.

Joined: Jul 2004
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G
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That is not exactly true. We did a lot of surge protection here in SW Florida with about 300 customers who were not going to turn off their machines and unplug them every time we had a thunderstorm and that is just about every day. in the summer. The article in EC&M said we have a couple hundred strikes per square mile every year in Florida. The surge will still get to that SPD down 18" of wire and stop it before it can go the 20-30 feet to the first piece of equipment you want to protect. The reality is most damage is caused by multiple ground and signal paths anyway. We fixed as much with bonding as we did with SPDs but we did take what was 2 or 3 calls a week down to a couple a year, usually on unprotected stuff. One thing we found out is a lot of "engineers" are wrong. Things they think they know don't pan out when the lightning strikes.
You do want to keep your wires as straight as possible on the SPD and GEC and put chokes in the ones feeding the equipment. We actually did that with Ferrite Beads but some folks swore tying a knot in the power cord worked.


Greg Fretwell
Joined: Jan 2005
Posts: 5,360
Likes: 1
Cat Servant
Member
I decided to try something radical: shop around.
It’s hard to break the habit of trusting the local supply house. Yet, it appears the SPD’s -even a snap-in Homeline - are readily available over the internet.
Even so, there are two details that combine to chill demand: a week-long lead time and the $120 price. All that money and you lose two spaces — what’s not to like? 😀

Oddly enough, marketing materials for these things fail to mention lightning. Rather, the concern seems to be over surges / transients introduced by the appliances. They’re trying to protect the electronics from each other! LED’s, anyone? (Or, for that matter, I wonder about the AFCI contribution to the problem).

Joined: Jul 2004
Posts: 9,766
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G
Member
There are other sources of power line transients but lightning is our heavy hitter here. It is not usually a direct strike, just the spike induced by a near miss. That can also show up as a ground shift where different grounding electrode systems have different potentials. That is probably the most destructive. Manufacturers try to avoid using the word lightning since a true lightning protection system goes beyond surge protection. For that matter, surge protection goes beyond simply having point of entry protection too but it is the starting point. Be sure all of your inputs (power, phone TV and data) have protectors bonded to the same grounding point. The NEC addressed this several cycles ago when they required the inter system ground bus. True lightning protection also requires air terminals and fat braided ground wires for the most part. As counter intuitive as it sounds, that should be bonded to the GES. You should also have protection on any sensitive equipment you want to save tying all input protection together. That is more about locally produced transients.
The switcher power supplies are a good news bad news joke. They tend to insert high frequency noise on the power line but those supplies themselves are somewhat immune to that noise.
IBM had a big war on power line noise, all the time not admitting that it was our own power supplies doing it. Once all of our power supplies were switchers, the problem went away, at least for our stuff. These days that is the power supply most people are using so the scary term "sensitive electronic equipment" is somewhat obsolete. If your power supply says 100-250v 50 or 60 hz, it is not going to see most transients if they put in a 10 cent MOV but you still need to worry about transients from different inputs.


Greg Fretwell
Joined: Dec 2002
Posts: 326
S
Member
Greg has the right of it in both posts. I (an Engineer and also work in NFPA 780) have been a proponent of properly installed surge protection from the beginning of my career.

IBM wasn't the only one to not admit or be unaware of what they were doing. Data General sold lines of equipment that were only available in 3 phase , however inside the massive units, the power supply was made up of three single phase power supplies. And we were spending $10,000's each site to bring 3-phase power in. These we protected on site with silicon avalanche diode based surge arrestors to do any good (response time and under 300 V turn on) (short straight as possible leads). We also had to take multiple precautions to keep the voltage noise down.

In my previous life designing sensors, we found MOV's, though helpful protecting the sensors from failure, transmitted surges without fail through the instruments affecting the output. Or maybe they were Spree candies with wires coming out of them, hard to tell as the candies would have done just as good on spikes caused by nearby equipment.

But getting things back on topic. I found last year when trying to find a QO type surgebreaker that had been very common, it was not available any where except on line (about $70). Home Depot had the HOM surgebreaker, but 5 different parts houses did not even know what I was talking about. I had to be talking to the wrong people.

Shane

Joined: Jul 2004
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G
Member
Not sure about DG but 3 phase power was the norm in IBM computer rooms so we never saw it as a burden. There was no neutral brought to computer panels either. It was all L/L load. They really did it to reduce the ampacity required (1.73 more bang for the amp at 3P). Back in the days when I was working in that field we had enough 3P motors to make 3p the norm. I agree single phase 208 power supplies were common but not all of them. The big switchers in water cool stuff were still 3p. There was also a large array of different type supplies. Some were real noisy. The 3705 communications controller used SCRs to pick off the DC directly from the 208 3P line voltage. That was a spiky sommich. By the 90s our mid range stuff was starting to be single phase but we still needed 3p for the old technology tape disk drives.


Greg Fretwell
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