For decades now, we all have gotten used to the idea that of course our computer or any other small consumer electronic device should not be plugged directly into an electrical outlet but should be instead be plugged into a surge protection power strip which is in turn plugged into the electrical outlet. We do this because for decades now we have had hammered into our brains that all sorts of bad things like lightning can somehow enter our electrical wires and if we fail to use a surge protection power strip, the bad things will travel through the electrical wires into our computers and other consumer electronic devices and damage them.
This blog article tells you that now “whole-house” surge protection is a thing. Yes if you don’t mind throwing money at the problem, you can add an extra layer of protection from electrical surges at the place where your electrical power enters your house, and it protects the whole house. Not only is this a thing, but the 2020 national electrical code actually requires this kind of protection in newly constructed homes. I’ll talk about this kind of protection in this blog article.
Let’s start with the familiar — the ordinary surge-protection outlet strip that everybody has several of in their house. Every outlet strip that provides surge protection has a three-wire plug because it cannot do its “surge protection” job unless it has a ground connection available to it. The main ways that most surge-protection outlet strips accomplish surge protection are:
- the line carrying electrical power passes through an inductor, and
- an MOV (metal oxide varistor) is connected between that line and the ground line.
As we all recall from the electricity and magnetism chapter of our physics class, the inductor tends to pass lower frequencies and tends to block higher frequencies. This is exactly the right thing to do if you want to keep a surge away from some sensitive piece of consumer electronics, since surges are high-frequency in nature, while the ordinary 60-Hertz or 50-Hertz electrical power being consumed by the consumer electronic device is low-frequency in nature.
The MOV (Wikipedia article) is a device that sits and does nothing all day, until some spike in electrical voltage arrives, at which point it starts conducting. The goal is that most of the energy in an electrical surge will pass harmlessly through the MOV to ground, and thus will not propagate further to the sensitive consumer electronic device.
MOVs are quite interesting in many ways. One interesting thing about an MOV is that its behavior today may be different from what its behavior was a week ago. This can happen because the MOV absorbed a big lightning strike which caused permanent changes in the internal structure of the MOV.
Each of us will recall having stood in front of a store display trying to figure out whether to purchase one surge protector outlet strip or another. Today on Amazon I saw for example:
- an outlet strip costing $13 rated at 800 Joules
- an outlet strip costing $25 rated at 1700 Joules
- an outlet strip costing $40 rated at 4320 Joules
You can guess where I am going with this. The companies that make MOVs make bigger ones and smaller ones and of course the bigger ones are more expensive. If you want to be able to protect against a bigger power surge (maybe a lightning strike that is closer to your location) then of course what you do is throw more money at it. You buy a more expensive power strip that has a bigger MOV in it (and probably it also has a bigger inductor).
Everything about this — the sources of the surges, the types of harm visited upon the consumer electronic devices, and the devices used to try to block the surges — is extremely analog and extremely nonlinear. And much of what goes on here is time-cumulative — little harms can accumulate over time. This means that many things that a person might assume about surge protection are probably wrong or at least unhelpful to assume.
For example, you might think that if your computer got plugged into some (appropriately rated) surge protection power strip twenty years ago, and has been plugged into that power strip continuously since then, then this must mean that everything is okay for the computer. What this overlooks is that the MOV inside that power strip may have absorbed a lightning strike during those twenty years and may have undergone permanent internal changes so that it is no longer providing meaningful surge protection. Or it may have absorbed fifty smaller surges that led to a similar degradation in protection. How can you know? Most of the surge protection power strips that I have purchased over the years have no way for the user to find out whether the MOV inside is still good as new or has been fried and no longer does what MOVs usually do.
You might also think that if some appliance of yours is functioning (which is a “yes or no” question), then this must mean that it has not been harmed by surges such as lightning strikes. Which might mean that there have not been any lightning strikes, or might mean that your surge protector outlet strip did its job successfully. Nope. Sometimes the damage to an appliance is bit by bit. Cumulative. A number of medium sized surges over a period of time could cause bits of harm that add up.
It also turns out that the electrical surges that might cause harm to one’s consumer electronic devices do not solely come from lightning. Lots of other things can cause electrical surges, including things like a big electric motor turning off or a big relay de-energizing. Any high current being turned on or off can lead to transient voltages that might count as “surges” for purposes of this discussion. So some of the sources of such surges are indoors and have nothing to do with stormy weather outdoors.
Lots of the really big surges that really cause a lot of harm are indeed caused by lightning, and it really is true that some places get more lightning than other places (see map). One company that makes whole-house surge protectors has a product line of three different protectors each with a different size of MOVs inside, and the company suggests you look at a map depicting lightning risk so that you can decide which protector is right for you depending on where you are located.
Which now brings us to whole-house surge protection. The idea is that you find a place where the big fat electrical wires enter your house from the power company, and that is where to try to provide the protection.
When I first encountered this notion of whole-house surge protection, my reaction was that any inductor that was big enough to meaningfully block lightning-type surges, and that was able to pass ordinary electrical flows the rest of the time, would have to be enormous. A typical new home these days has service in a range of 100 Amperes to 200 Amperes and thus the electrical wires providing the power to the house are as big around as your thumb. The inductor would have to have several hundred turns of wire of such a diameter. The inductor would be the size of a clothes washer. I assumed that for this reason, whole-house surge protection would be an unrealistic goal for any but the most cost-insensitive homeowner.
But it turns out that MOVs alone, if sized right and if placed appropriately in the house, can provide meaningful surge protection. Here’s how it works.
You find your “load panel”. Years ago this would have been called a “fuse box” or “circuit breaker box”. But anyway nowadays most people call it a “load panel”. It has some big fat cables coming in either at the top or the bottom, providing electrical power. And it has dozens of circuit breakers that make the electrical power available to electrical receptacles and lights and appliances around the house.
If you are super lucky, there will be two vacant adjacent positions in the load panel right next to where the fat cables come in. (These positions will be labeled either “1 and 3” or “2 and 4”.) This never happens, because when electricians wire up a house they always start plugging in circuit breakers starting at that end of the load panel to be closest to the big fat cables. But maybe if you are lucky, the breakers at positions 1 and 3 or at positions 2 and 4 will be breakers that can be moved to some more distant position. Then what you do is make plans to put a 2-pole 20-amp breaker into the two newly vacant positions.
Having figured out that you have these two available positions in your load panel right next to where the big fat cables come in, you pull out your checkbook and purchase a whole-house surge protection device (WHSPD). This is a fairly big device, at least as big as your fist and maybe the size of a large brick, and it has four wires coming out (green, white, black, and black). We will talk about hooking up the wires in a moment, but first of course is the pesky business of deciding which WHSPD to purchase. You can immediately guess where I am going with this. Of course you want big MOVs instead of little MOVs. You can purchase a small WHSPD that just barely complies with the new requirements of the national electrical code for new-house construction. It has little MOVs in it. That WHSPD is the size of your fist. Or you can purchase a physically large WHSPD that is the kind that people choose if they live in Florida where lightning is always striking everywhere. Of course it has big MOVs inside.
The just-barely-code-compliant device costs $80. The biggest-MOV device that money can buy costs $180. The money that you would have to pay to an electrician to install either one (several hundred dollars, probably) is exactly the same no matter which one you pick. For goodness sake spring for the extra $100 so that you have the biggest MOVs.
Oh and then the next thing. Remember how I mentioned that the power strip that has been in use for ten or twenty years might not be protecting you any more? Remember how I mentioned that the MOVs are sacrificial devices? They degrade over time as they absorb surge after surge.
As it turns out, the electrical code and the UL ratings for these things require that the WHSPD have one or more indicator lights that tell you whether the MOV is able to do its job or whether it has degraded. The typical WHSPD has either one or two green LEDs to indicate this. The idea is that the homeowner will remember to go around to the load panel maybe once a month to check to see if the green LEDs are still lit. And if one or both LEDs have extinguished, this means it is time to replace the device. The reason of course is that one or more of the MOVs inside the device are shot. So you have to replace the device to get a fresh start with new MOVs.
One WHSPD product puts the MOVs into little cartridges and the idea is that the homeowner could replace a cartridge when an LED goes out. This would save having to replace the entire device which requires opening up the load panel.
But what are the chances that the average homeowner is going to be diligent about going around and checking the LEDs once a month? Forget about it. Not to mention, sometimes the installer will put the WHSPD inside the load panel. Meaning that the only way you could check the LED is to remove the front cover of the load panel.
The WHSPD that you see in the photo at the top of the article is the only one that I know about that provides an audible alarm (beeping) if any of the MOVs inside are shot. It’s the one that I think would be a good choice for lots of people. This particular WHSPD is available in three sizes, the largest of which is the “Florida” model called the FS140 (Amazon link).
Back to the four wires that come out from one of these devices. It turns out that you want to keep the wires as short as possible, because of course you want the lightning to find the path through the WHSPD to be a more attractive path than the path through any of the other circuit breakers. And you want the wires to not have any sharp corners in them, because sharp corners are sort of like inductors. You want the wires to be straight or to have gentle rounded large-radius bends.
The green wire goes to the ground bus in the load panel. The white wire goes to the neutral bus in the load panel. The two black wires go to terminals on a two-pole 20-amp breaker that you will install in positions 1 and 3 or 2 and 4 of your load panel. Why? Because the lightning that just entered your load panel on the big fat wires will reach these positions sooner than it reaches most of the other circuit breakers in the load panel.
If you know your way around load panels and know how to avoid getting shocked when you work on stuff like this, and if you know how to comply with electrical codes, you could probably install a WHSPD yourself. Otherwise you would want to hire a qualified electrician to do it. If you hire an electrician, what will it cost? Surely it will be at least a couple of hundred dollars, assuming everything about it turns out to be easy. But if it is difficult to find a good place to put the WHSPD, for example not very much extra space nearby to the load panel, and if all of the positions in the load panel are already occupied, then it could be really a lot of work.
If you install a WHSPD does this mean you don’t need surge protection power strips any more? I’d say it does not mean that. People who do this stuff for a living say that there’s no harm in having both kinds of protection in place, and indeed it improves the chances of successfully protecting your sensitive electronic devices.
Circling back around to the main question — do you really need whole-house surge protection? What if you really do diligently use surge protection power strips, and replace them from time to time as their MOVs get old? One thing to realize is that nowadays more and more things have sensitive electronics inside and can’t be plugged into power strips. Think of the fancy oven with a touch screen, or the fancy clothes dryer that has a delayed start timer so that it starts the drying cycle in the evening when the time-of-day electrical rates get cheaper.
Do you already have whole-house surge protection in your house? Has this article made you consider installing such protection? Please post a comment below.