I don’t have any issue with your statement. If you operate with planning and the proper knowledge it can be done safely. My point is that in a thread asking about how to safely protect electronic devices I wanted to address a casual bit of advice that could be potentially dangerous if followed without such knowledge or care.
How often do these “surges” occur?
Isn’t that what breakers are for?
Also, while probably safe day-to-day, there is still the issue that if a surge occurs, the two surge protectors can potentially interrupt each other’s attempt to shut themselves off, thus providing no protection from the surge (this is most likely to occur if they’re both the same model and are using the same method of surge protection). For an analogy think of having two anti-malware programs running on a computer; rather than giving double protection they just get in each others’ way. If you had, say, a plain power strip plugged into a surge protector you wouldn’t have that particular risk.
Breakers aren’t foolproof, especially in a building with older wiring.
A circuit breaker protects the wiring in the walls inside your house against over-current.
A surge protector protects against voltage transients (“voltage spikes”) that sometimes occur between the hot and neutral wires on a circuit. (Some protectors also provide protection between hot and ground, and between neutral and ground.) A voltage transient won’t cause a sustained over-current situation, hence the circuit breaker won’t trip. But a voltage transient can certainty fry some of the loads that contain electronics.
Fairlt frequently, but mostly go unnoticed. (They won’t noticeably affect incandescent light bulbs, and most CFL & LED bulb are also built to withstand them.)
They can come from natural causes (like lightning strikes), power co causes (like when they turn generators on or off or switch lines around), and from other users (the big coolers in the corner grocery store switch on, or a nearby car repair garage starts up machinery, or a neighbor uses his welder in his workshop, etc.) – they might even be caused by your own refrigerator or AC motor switching on. Most are small & transient, and don’t bother electronic equipment – manufacturers have learned to build in a certain amount of protection The surge protectors or UPS’s we’re talking about are for bigger or more frequent surges.
No, circuit breakers only protect against overloads, that can cause your wiring to heat up and possibly cause a fire. Well, direct shorts, too.
A breaker protects you from having too much current, which causes the wires to overheat and then your house catches fire and burns down. If you plug too much stuff into a circuit or you have a short circuit somewhere, a breaker will protect you from that.
A breaker does not protect you from a ground fault, and a breaker often does not protect you from something like a frayed extension cord, unless the frayed cord actually shorts the wires together well enough to draw enough current to trip the breaker.
Current is supposed to go out through one wire and back through the other (hence, a “circuit”). Technically, with alternating current, the current switches direction 60 times per second (50 in some parts of the world), but the basic point is that all of the current going out through one wire is supposed to come back through the other wire. However, you can have a situation where the current finds some other path back, and unfortunately, it often finds that path back through a person. This is called a ground fault. A ground fault circuit interrupter (GFCI, aka a GFI, or ground fault interrupter, and for those on the other side of the pond it’s called an RCD, for residual current device) measures the current in both wires and makes sure that they are equal. If they aren’t equal, then the GFCI shuts the circuit off. GFCIs are required in bathrooms and other “wet” locations as defined by the NEC, like garages. GFCIs can be built into breakers, and are also commonly found built into the outlets themselves. If your bathroom electrical outlet has a reset switch on it, it’s a GFCI.
GFCIs have been required in certain locations (bathrooms, garages, etc) since the 1970s. Where a breaker is designed to protect your house from fire, a GFCI is designed to protect a human being from a low current ground fault.
Years of experience have taught us that something like a frayed extension cord can generate enough heat to start a fire, yet often won’t trip a breaker. So, starting about 20 years ago or so, arc-fault circuit interrupters (AFCI) have been required in bedrooms and other living areas. These will detect an arcing current, like what you get with a frayed extension cord, and will shut off the circuit. AFCIs can be built into circuit breakers, and can also be built into outlets.
How often surges occur depends on your location. Some areas are more prone to lightning strikes than others. If you are close to a substation, you may get voltage spikes on your power lines just from nearby equipment being switched on and off of the line. Sometimes they switch transformer leads around to bring the voltage up or down towards the end of long distribution lines, to compensate for loads. For example, in the summer, when everyone turns on their air conditioners, all of that electrical load tends to bring down the voltage, so they may choose to boost the voltage a bit on longer lines so that the folks near the end of the line don’t get undervoltages and brownouts. Residential power loads also tend to be slightly inductive (due to motors in washing machines, clothes dryers, vacuum cleaners, etc), so the power company switches large capacitor banks on and off of the line to balance those loads out. Whenever something gets switched on and off of the line, it can potentially cause a voltage spike.
Spikes from substations tend to get snubbed fairly quickly due to the natural inductance and capacitance of the wire in the power lines. Spikes from a lightning strike though can travel for many miles down power lines. The power company does a lot of different things to try to prevent these spikes, or to at least minimize them, but voltage spikes from lightning can still be very damaging.
Think of it this way. A lightning bolt is a few hundred million volts, and your electrical stuff is designed to run on a bit over a hundred volts. A voltage spike around a thousand volts or so is only a tiny fraction of what came from that lightning bolt, but it’s still about ten times what your devices are designed to use, and that can cause a lot of damage.
How good are the “whole house” surge protectors that install in the breaker panel? I’m looking at this one in particular, as it’s made for my panel. The specs are at the far end of that brochure…is this thing worth $90?
I’m interested in this question. I’ve got two 200A panels that this device will fit, and it would be nice to protect the entire house.
They don’t give too many specs on the thing. I was able to find some of the specs by poking around on google though.
It’s not the worst whole-house surge protector I’ve seen, but it’s definitely not the best.
Pros: The fault current is decent (50,000 amps). Cheapies are around 20,000 amps, better ones are in the 80,000 to 100,000 range. The unit has both line to neutral and line to line protection. Clamping voltage is good (150 volts line to neutral and 300 volts line to line).
Cons: Joule rating (720) is low. A high energy spike will blast right through the MOVs. There is no protection on the ground (no line to ground or neutral to ground MOVs). A surge/spike from a lightning strike hitting a nearby tree or hitting the ground could come up through the ground wire and not get clamped.
Personally, I expect more than that from a whole-house surge protector. On the other hand, a decent one will probably cost you more than $90.
Can you recommend a better one?
I installed:
- Five MOVs and five TVSs between Hot 1 and Neutral.
- Five MOVs and five TVSs between Hot 2 and Neutral.
- Four MOVs and four TVSs between Hot 1 and Hot 2.
The unit also:
- Measures RMS voltage between Hot 1 and Neutral.
- Measures RMS voltage between Hot 2 and Neutral.
- Measures RMS voltage between Hot 1 and Hot 2.
- Measures whole-house generator voltage & current on Hot 1 (when generator is used).
- Measures whole-house generator voltage & current on Hot 2 (when generator is used).
- Has a buzzer and switch connected to the output side of the utility meter mounted outside the house. (This lets me know when the grid power is back on while the main CB is off and I am using the whole-house generator.)
Do I need more than 50 kA? Where I live, as a rule, we just don’t get lightning. We barely get rain as it is.
There are more robust units like Siemens’ FS140, which is rated for 140,000 amps. With the fairly recent adoption of UL 1449, joules are no longer considered for these devices. Like watts for a stereo system, it was too easy to get fast and loose with advertising how many joules a protector is good for.
Only issues I’d have with the FS140 are that it costs $230, and it normally mounts outside of the panel. It’s in a NEMA 4X enclosure, so it can be mounted in a breaker panel, (if it fits) but then you lose the ability to see its status lights, unless you buy one of the Siemens load centers that have this thing built in. Mounting it outside a panel is not a problem if you have a surface-mounted panel, but mine is flush, or in-wall. That alone makes the truly plug-and-play Square D very appealing for me.
No line-ground protection shouldn’t be an issue in a normal main panel as the neutral and ground are bonded in the panel. It could be a problem in a scenario like a sub-panel as the ground and neutral remain independent in the sub.