Surge protection value

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Barbqranch

Barbqranch

Senior Member
Location
Arcata, CA
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Plant maintenance electrician Semi-retired
I had a customer ask if installing a whole house surge protector on his home panel would be worth the expense. We have a half dozen or so outages a year, as well as a dozen flickers while a recloser does its job. I really don't have an opinion on that, nor do I have one on my house.
 
I think on a net basis it is a very dubious proposition. However, if the customer has money to spend, I see no reason not to let him spend it on a whole house SPD. It won't hurt anything and there is at least some chance it will be helpful.

A SPD does not protect against either flickers or outages. It protects (at least to some extent) against over voltage that could be caused by nearby lightning strikes or other network disturbances. It will NOT protect against a direct strike.

My personal opinion is that you probably get more bang for your buck by plugging the stuff you want to protect into a power strip that has surge protection built in. But, I don't know there is any way to prove this one way or the other.
 
petersonra said:
I think on a net basis it is a very dubious proposition. However, if the customer has money to spend, I see no reason not to let him spend it on a whole house SPD. It won't hurt anything and there is at least some chance it will be helpful.

A SPD does not protect against either flickers or outages. It protects (at least to some extent) against over voltage that could be caused by nearby lightning strikes or other network disturbances. It will NOT protect against a direct strike.

My personal opinion is that you probably get more bang for your buck by plugging the stuff you want to protect into a power strip that has surge protection built in. But, I don't know there is any way to prove this one way or the other.
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I had a panel-mount unit installed in my last home. It was under $100, I'm pretty sure. Frankly, cheap at twice the price. The idea is to do defense in depth. Have the panel mount unit and the local power strip with surge protection. Shoot, add the meter-style device while you're at it.
 
gadfly56 said:
I had a panel-mount unit installed in my last home. It was under $100, I'm pretty sure. Frankly, cheap at twice the price. The idea is to do defense in depth. Have the panel mount unit and the local power strip with surge protection. Shoot, add the meter-style device while you're at it.
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I doubt you could get a whole house SPD for $100, much less get an actual electrician to come out and install it. You might be able to get a unit that has a fairly low energy absorption rating for that, but what electrician can you even get to come out for $100?
 
Whole house SPDs are only the first line of defense.

#1. You need a good grounding electrode system, and there are literally books written on that subject alone.

#2. You need a whole house TVSS at the main panel.

#3 You need whole house TVSS at remotely located sub panels, especially a detached garage. The impedance is too high to facilitate the main TVSS at long distances.

#4. If you really want to go gung ho you can add additional grounding electrodes at each sub panel (required in detached building)

#5. Even with all this, you still want point of use surge protection for your valuable electronics. Get one that comes with a guarantee like up to $50,000 or so. Then you know they stand behind their product.

#6. For point of use SPDs to work properly, you need an intact, low impedance equipment ground at the receptacle.

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gadfly56 said:
The idea is to do defense in depth. Have the panel mount unit and the local power strip with surge protection.
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Agreed. Cascaded protection. Whole-house for external surges, point-of-use for internal.

That's the theory. Read the connected-equipment warranty fine print.
 
how does the GES change anything? the SPD will clamp the voltage L-L, L-N, and L-G. It is not even connected to the GES except through the EGC.
 
Need point of use TVSS combined with SPD’s.

My standard residential install includes panel-mount SPD, and TVSS at every TV or electronic equipment location.

Grounding certainly helps. This is only anecdotal evidence, but my parents built a new house when I was a teenager, and every year they’d lose a TV or something after a lightning storm. I remember seeing arcing coming out of receps in my room at one point. About 15 years ago, I ringed their house with a dozen ground rods and added an SPD, and they haven’t lost anything since then.

Had a lightning strike between myself and neighbor at one of my previous houses that I built, and I had all the surge protective devices i mentioned above. At least half a dozen houses on my street lost their garage door operators, TV’s, etc, and I lost nothing.

It’s been awhile since I wired a house with copper phone lines, but I always used those On-Q phone line surge suppressors, as well as the coax in-line suppressors.

Another tale; a house I wired about 4/yrs ago had their primary come in contact with another utility primary that crossed it during a storm. It knocked out all the panel mount SPD’s, probably 40+ AFCI, DF, and GFCI breakers, and a few of the TVSS receptacles, but they didn’t lose any electronic devices. Their insurance covered the $5k or so it cost to replace the surge devices and breakers.


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LarryFine said:
Agreed. Cascaded protection. Whole-house for external surges, point-of-use for internal.

That's the theory. Read the connected-equipment warranty fine print.
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Definitely. Because if you do have a surge event and you make a claim, they'll try to find a way out of it if you didn't RTFM.

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brantmacga said:
Need point of use TVSS combined with SPD’s.

My standard residential install includes panel-mount SPD, and TVSS at every TV or electronic equipment location.

Grounding certainly helps. This is only anecdotal evidence, but my parents built a new house when I was a teenager, and every year they’d lose a TV or something after a lightning storm. I remember seeing arcing coming out of receps in my room at one point. About 15 years ago, I ringed their house with a dozen ground rods and added an SPD, and they haven’t lost anything since then.

Had a lightning strike between myself and neighbor at one of my previous houses that I built, and I had all the surge protective devices i mentioned above. At least half a dozen houses on my street lost their garage door operators, TV’s, etc, and I lost nothing.

It’s been awhile since I wired a house with copper phone lines, but I always used those On-Q phone line surge suppressors, as well as the coax in-line suppressors.

Another tale; a house I wired about 4/yrs ago had their primary come in contact with another utility primary that crossed it during a storm. It knocked out all the panel mount SPD’s, probably 40+ AFCI, DF, and GFCI breakers, and a few of the TVSS receptacles, but they didn’t lose any electronic devices. Their insurance covered the $5k or so it cost to replace the surge devices and breakers.


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Nice anecdote. So hard to find data on efficacy. So hard to study though, of course.

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petersonra said:
how does the GES change anything? the SPD will clamp the voltage L-L, L-N, and L-G. It is not even connected to the GES except through the EGC.
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Where do you think the transient current goes?

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petersonra said:
It is dissipated as heat inside the spd. The spd effectively becomes a shirt circuit between two of the wires. No current of any significance flows to earth.
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That's a crowbar SPD. A clamp SPD directs the current to a ground reference. Why do you think the SPD comes with a ground wire?

Many TVSSs use both a clamp and crowbar circuit. So it's a good idea, for optimal protection to have low impedance path to earth ground at the point of installation. Additional electrodes is a good way to accomplish this.

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DrSparks said:
That's a crowbar SPD. A clamp SPD directs the current to a ground reference. Why do you think the SPD comes with a ground wire?

Many TVSSs use both a clamp and crowbar circuit. So it's a good idea, for optimal protection to have low impedance path to earth ground at the point of installation. Additional electrodes is a good way to accomplish this.

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Click to expand...
Exactly what do you think the current path would be that would go through the SPD and back to Earth???

Basically the SPD element is a variable resistor that goes to a very low resistance value when it sees a high voltage between any two terminals. One of those terminals is not earth ground. One of those terminals is equipment ground but there is no path into the earth through the SPD.
 
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