Surges and electronics

[Chamuit]

Educate me, please.

My only experience with surges in homes has been ones that cause multiple devices (computers, game consoles, microwaves, TVs) to fry at the same time. They have all been caused by a lost or faulty neutral. Easily identifiable and fixed. Catastrophic failures.

Where I currently live, people have "surge" damage all the time but usually only on one device in the house. I find it hard to believe with the number of electronic devices in most homes.

1. Why would that be true?

2. Wouldn't the power supply fail in addition the PCBs or other internal components?

3. Don't some of these devices have internal overload protection incorporated?

Yes, I have an SPD in my panel.

 

[LarryFine]

That's why the best protection is cascaded units; your panel unit and point-of-use devices.

I also suspect many device failures are improperly blamed on electrical surges.

 

[paulengr]

1. Surge arrester effectiveness goes down dramatically with ground impedance (length of wire).
2. Surge arresters are consumables. They don’t last forever.
3. Poor grounds reduce effectiveness. Remember when NEC says less than 25 ohms or add a rod? Better recheck and stop just putting two rods down because it meets a poorly written Code requirement. In most areas under 1 ohm is easily achieved.
4. Surge arresters are not 100% protection. And multiples matter.

http://www.arresterworks.com/arresterfacts/pdf_files/ArresterFacts_003_Understanding_Arrester_Voltage-Current_Characteristic_Curves.pdf

5. They are point of use. Panel arresters protect the panel but as you get further from the panel the surge reforms. Since there are no major electronics in a panel these things are basically useless. Cheap “power strips” are more effective.

http://www.arresterworks.com/arresterfacts/pdf_files/arrester_lead_length.pdf

http://www.arresterworks.com/arresterfacts/pdf_files/lead_length_effect_calculator.xls

6. Most surges contrary to popular belief happen locally, not lightning and transmission lines. It’s things like a well pump starter that has been neglected for 30 years.

http://www.arresterworks.com/arresterfacts/pdf_files/switching_surge_and_arresters.pdf

 

[Coppersmith]

Electronic devices don't require a huge surge to be destroyed. Tiny surges eat away at the tiny traces on the circuit boards and also cause cumulative damage to components. Over time, a number of tiny surges will cause an electronic device to fail. Surge suppressors "absorb" surges before they can hit plugged in devices.

 

[Chamuit]

Thanks, @paulengr for the info on the external causes.

Regarding #3. Interestingly, guys only put one rod in the ground here and call it good. Never heard of an inspector checking or requiring any readings. In Phoenix, we would drop 2 rods every time so we didn't have to hang out and show the inspector our readings.

@Coppersmith that would explain why a single device would fail and not others. Also explains why the power supply wouldn't be fried, necessarily, at the same time as the other component(s).

 

[synchro]

I also suspect many device failures are improperly blamed on electrical surges.

Agree. And I believe many early device failures are due to poor design and/or substandard components, especially with the proliferation of cheap consumer products in the market today. I'm sure that very few of these the have undergone any rigorous qualification and accelerated life testing. Such devices are considered throwaways now, and it's easier to blame surges for the failures than do any failure analysis to determine what really happened.

 

[retirede]

I wouldn’t call the over/under voltage situation caused by a faulty neutral a surge. Surge suppressors won’t help in that case.

Surges are usually caused by lightning strikes or some event on the utility lines.

I recently had a small audio amp get fried during a thunderstorm. The main panel has a suppressor. My receiver sitting right next to that amp was not affected. I realized after the fact that I had plugged the receiver into a power strip that contained surge suppression, but the amp was plugged directly into the wall receptacle. Needless to say, It’s all plugged into a local suppressor now!

 

[junkhound]

In most areas under 1 ohm is easily achieved.

http://www.arresterworks.com/arresterfacts/pdf_files/switching_surge_and_arresters.pdf

I believe that to be a fallacy.
1 ohm is difficult with ground rods, even concrete encased electrodes often do not achieve 1 ohm.

Own house is 0.6 ohms, 210 ft of concrete encased electrode with the rebar spot welded together and the bottom of the footing below the water table.

 

[paulengr]

Agree. And I believe many early device failures are due to poor design and/or substandard components, especially with the proliferation of cheap consumer products in the market today. I'm sure that very few of these the have undergone any rigorous qualification and accelerated life testing. Such devices are considered throwaways now, and it's easier to blame surges for the failures than do any failure analysis to determine what really happened.

The latest thing is to add a ferrite bead to everything. If you notice a “fat” plastic cylinder molded into the cord, that’s a ferrite filter. It is nonlinear and helps flatten and spread out surges by resisting rapid changes which is what inductors do.

 

[junkhound]

It is nonlinear
A non-linear ferrite inductor is an inductor going into saturation, means it aint workin' too good anymore......

 

[paulengr]

I believe that to be a fallacy.
1 ohm is difficult with ground rods, even concrete encased electrodes often do not achieve 1 ohm.

Own house is 0.6 ohms, 210 ft of concrete encased electrode with the rebar spot welded together and the bottom of the footing below the water table.

It depends on the soil in the area. In the Southwest for instance only a Ufala ground like you described is going to work. Same in mountainous terrain. In say Florida once you hit the water table it’s under 1 ohm. If you are in poor soil conditions the reality is that the soil specific resistance almost makes any good grounding nearly impossible. A few hundred ohms is common in granite/gneiss and sandy soil.

I’ve lived in areas with “good” soil in mist areas. I would feel differently in Arizona or most of Utah.

 

[petersonra]

Educate me, please.

My only experience with surges in homes has been ones that cause multiple devices (computers, game consoles, microwaves, TVs) to fry at the same time. They have all been caused by a lost or faulty neutral. Easily identifiable and fixed. Catastrophic failures.

Where I currently live, people have "surge" damage all the time but usually only on one device in the house. I find it hard to believe with the number of electronic devices in most homes.

1. Why would that be true?

2. Wouldn't the power supply fail in addition the PCBs or other internal components?

3. Don't some of these devices have internal overload protection incorporated?

Yes, I have an SPD in my panel.

people often blame surges or lightning (or "bad" grounding) when a component fails. Could have just been a component that failed.

most modern power supplies are fairly resistant to surges.

overload protection is not fast enough to protect against surges, and is not intended to. surges are overvoltages. overloads are excess current. they require completely different protection schemes.

I would put an SPD in every panel. I personally do not think that grounding of whatever quality makes any real difference in protecting devices from power surges.

 

[hbiss]

The latest thing is to add a ferrite bead to everything. If you notice a “fat” plastic cylinder molded into the cord, that’s a ferrite filter. It is nonlinear and helps flatten and spread out surges by resisting rapid changes which is what inductors do.

They do that on cables entering and exiting a device to suppress RF leakage so it complies with FCC rules on interference and emitted RFI. Usually an afterthought after the device was tested rather than redesign the PC board.

-Hal

 

[Coppersmith]

In say Florida once you hit the water table it’s under 1 ohm.

I've had jobs here in Florida where I could push the entire ground rod into the ground with my hand. I don't know what the ground resistance is and I don't bother to find out. It's easier to just put in two rods.

 

[LarryFine]

I've had jobs here in Florida where I could push the entire ground rod into the ground with my hand. I don't know what the ground resistance is and I don't bother to find out. It's easier to just put in two rods.

Literally, in those cases.

 

[ActionDave]

3. Poor grounds reduce effectiveness. Remember when NEC says less than 25 ohms or add a rod? Better recheck and stop just putting two rods down because it meets a poorly written Code requirement. In most areas under 1 ohm is easily achieved.

It depends on the soil in the area. In the Southwest for instance only a Ufala ground like you described is going to work. Same in mountainous terrain. In say Florida once you hit the water table it’s under 1 ohm. If you are in poor soil conditions the reality is that the soil specific resistance almost makes any good grounding nearly impossible. A few hundred ohms is common in granite/gneiss and sandy soil.

I’ve lived in areas with “good” soil in mist areas. I would feel differently in Arizona or most of Utah.

So what about people that live outside of "most areas"? Are they doomed to a destiny of poor working surge suppressors?

I don't think ohms to earth has anything to do with protection from surges. Quality surge protection devices and good bonding of all conductive parts is what matters most.

 

[kwired]

paulengr said:
3. Poor grounds reduce effectiveness. Remember when NEC says less than 25 ohms or add a rod? Better recheck and stop just putting two rods down because it meets a poorly written Code requirement. In most areas under 1 ohm is easily achieved.

paulengr said:
It depends on the soil in the area. In the Southwest for instance only a Ufala ground like you described is going to work. Same in mountainous terrain. In say Florida once you hit the water table it’s under 1 ohm. If you are in poor soil conditions the reality is that the soil specific resistance almost makes any good grounding nearly impossible. A few hundred ohms is common in granite/gneiss and sandy soil.

I’ve lived in areas with “good” soil in mist areas. I would feel differently in Arizona or most of Utah.

So what about people that live outside of "most areas"? Are they doomed to a destiny of poor working surge suppressors?

I don't think ohms to earth has anything to do with protection from surges. Quality surge protection devices and good bonding of all conductive parts is what matters most.

Doesn't good ground have most effectiveness for a lightning surge?

Transients from switching aren't necessarily seeking ground as much as another system conductor I would think, though one system conductor is usually also at/near ground potential.

 

[ActionDave]

Doesn't good ground have most effectiveness for a lightning surge?

Transients from switching aren't necessarily seeking ground as much as another system conductor I would think, though one system conductor is usually also at/near ground potential.

A surge suppressor is a blob of semiconductors that doesn't do anything till voltage gets high enough to make it conduct, I don't see where a connection to earth helps it do it's job in any way.

 

[GoldDigger]

A surge suppressor is a blob of semiconductors that doesn't do anything till voltage gets high enough to make it conduct, I don't see where a connection to earth helps it do it's job in any way.

It would make a real difference if the electronics needing protection is in something like a CNC machine which was installed with its own isolated ground rod!

 

[robertd]

5. They are point of use. Panel arresters protect the panel but as you get further from the panel the surge reforms. Since there are no major electronics in a panel these things are basically useless. Cheap “power strips” are more effective.

Surge protectors work by turning electrical energy into heat. The surge protectors in the panel reduce the energy in the surge, leaving a much smaller surge for the point of use protectors to deal with. Surge protectors installed in the panel are NOT useless. To provide good protection both panel and point of use protectors should be used.