what value of capacitor to use for surge protection 240V

[westom]

so how can they sell this with a logo on the front saying "surge protector"

If bread is wheat bread, then it can be white bread colored with molasses. No Federal law says what the expression "surge protector" means. Many even have completely different definitions of a surge. Some call a surge only a few volts increase or decrease. Is a surge a voltage increase or a current increase? Some say a surge is current going from 0 amps to 1 amp in light bulb. Even USB ports have surge protection that has nothing to do with voltage. USB surge protection is about too many milliamps.

Any name not defined (framed) by spec numbers is how scams get promoted. A company may sell "Old Fashion Whole Wheat Bread". By adding words, then it does not have to be whole wheat bread. Nothing is known without hard facts and numbers. The expression "surge protector" is a subjective expression. Since you did not have a tidal flood, then a "surge protector" did its job? As ridiculous as that sounds, it is also a very legal defense. The term "surge protector" is only subjective. So it can mean almost anything.

Multiple types of surges exist. A protector adjacent to appliances only claims to protect from a type of surge that should be made irrelevant by circuits already inside electronics. See its spec numbers. Protectors used in facilities that can never have damage are for all types of surges. Including the typically destructive type. Those relevant protectors have a low impedance connection to earth. No way around that requirement.

 

[KeepItSimpleStupid]

A protector adjacent to appliances only claims to protect from a type of surge that should be made irrelevant by circuits already inside electronics.

I agree, but I've proven that to be false with my analyzer conversation with the manufacturer.

The point is surge protection as offered by simple MOV's is expensive for the manufacturer. At a $1.00 each x 3 over 100,000 units, it can chew into profits.

The automobile is a very hostile environment yet computers survive. Why? They are designed too. Failure could mean death. If a personal computer gets hit by a slight surge and gets fried usually death of a person doesn't occur.

The surge protector "with a warranty" is your best assurance.

Note that iin your "surge suppressor" the devices are small. it's enough to earn the name, but the larger and more expensive the device the larger surge it will withstand.

Telco systems too are designed to withstand a lightning hit. Why? You could be killed if talking on the phone and the phone line was hit.

Now, personal safety and liability trumps over cost and an inconvenience.

A "whole house" surge suppressor is not a bad idea, but it could cost > $1000 to get one. You might buy one when you have lost a number of appliances and then you know "first-hand" about 20/20 hindsight.

At home, I had to install a power line filter at the furnace because there was no protection from the noise generated from the commutation of the variable speed drive and it was affecting some powerline automation controls (X-10). INHO, there should have been an RFI filter there. Installing a wired-in surge suppressor for the furnace makes sense. I just havn't done it. Whole house makes more sense.

 

[lecman]

thats very interesting and i have lost my faith in products that say view pictureView attachment 64195

I am so glad i joined this forum and really appreciate people who know what they are talking about many thanks for your comments west, KISS and Ron
This has left me in a bit of dilemma as i did plan on putting MOV's inside some of our mains sockets in the house because i was under the impression this would
1.protect my equipment
2. very cheap
3. easy to fit
As this is not the case, can you advise electrical circuit projects i could fit, i know i can go out and buy something its just that i like to learn and love electrical and electronics.

 

[KeepItSimpleStupid]

1, 2 and 3 is valid and it will offer some protection so it's an OK thing to do.

Inside actual wall sockets is a problem for various reasons.
Inside equipment is a better place, but it will void the equipment warranty.
Inside an existing outlet strip isn't a bad place either.

Select the highest energy rating you can afford. Use the fuse, breaker or thermal fuse as protection. Fuses don't work when their breakdown is exceeded. The good news is that the MOV's USUALLY fail shorted.

Just realize it won't protect against lightning and if it fails to work, it failed to work.

 

[westom]

This has left me in a bit of dilemma as i did plan on putting MOV's inside some of our mains sockets in the house because i was under the impression this would
1.protect my equipment
2. very cheap
3. easy to fit

Any facility that cannot have damage will not do that. As I said, protection inside appliances is superior. And it does not use MOVs or other expensive items to do so.

Second, MOVs without a necessary thermal fuse is a major fire hazard. Power strips and other grossly undersized protectors contain fuses. That disconnects an MOV from a surge as fast as possible. And leave the appliance connected to that surge. Then a surge, too tiny to overwhelm protection inside appliances, may blow the protector. That promotes a myth. "My protector sacrificed itself to save my computer." Bull. The computer protected itself. That tiny surge destroyed the protector. And got the naive to recommend that protector.

Sometimes the fuse does not blow fast enough. Then fires have resulted. MOVs must never fail shorted. Only acceptable failure for MOVs is to degraded. Read datasheets. MOVs that fail shorted are the reason for fires.

Protection means no surge currents inside. Once that current is inside, then it will hunt for earth destructively via appliances. Protection is always about earthing a surge before it can enter the building. That was how it was done even 100 years ago. That is how it is done in any facility that cannot have damage. Once that current is inside, then superior protection inside an appliance either protects that appliance or is overwhelmed.

Stop paying so much attention to MOVs. Those are only simple science. Worry about what actually does protection. Most of your questions should be about earthing. That is the art. And that is what must always exist in any facility that does not have damage.

Some venues have no protectors (need no MOVs). But always have the item that does protection. Single point earth ground.

In your case, best possible protection is also the least expensive. Earth a 'whole house' protector. About $1 per protected appliance. Read its numbers. Lightning is typically 20,000 amps. The superior and less expensive solution must be at least 50,000 amps - to even make lightning irrelevant.

How to make that even better? Upgrade the earthing. Once you have grasped surge protection, then most of your questions will be about the art. What actually does protection.

 

[KeepItSimpleStupid]

Some advanced facilities such as hospitals may actually have two different "grounds". One is indeed "Earth" and is for surges only. The other is a reference.

 

[westom]

One is indeed "Earth" and is for surges only. The other is a reference.

A building must have both a safety ground and earth ground. The concept of ground is often confused by subjective reasoning.

For example, a computer has a digital ground, may have an analog ground, and has a chassis ground. All three are connected. And all three are electrically different.

Appreciate what most never understand. For example, a 200 watt transmitter connects to a long wire antenna. Touch one part of that antenna wire to feel zero volts. Touch another part of the same wire to be shocked by over 100 volts. Why two completely different voltages on the same wire? These same concepts are why earthing is an art. And why protectors adjacent to appliances may even make surge damage easier.

Repeatedly stated was an example of that art. "Less than 10 feet". An electrically important concept summarized by the expression "low impedance". These electrical concepts are why facilities that cannot have damage locate protectors at the service entrance. And as close as possible to single point earth ground. But again, a protector (or MOV) is only as effective as its earth ground.

 

[tcmtech]

There is more to this than just the loose term of surges. There is also line noise that can come in a wide range of high frequencies.

At my place I run a lot of high power industrial equipment like my big welders and 105 amp inverter based plasma cutter along with a number of things that have electric motors up to 15 Hp running off of my 200 amp 120/240 VAC single phase service.

For me I used a two step protection system. I have several MOV's in my system that are the size of D batteries that I think are rated for around 300 VAC operation going from line to line and line to common/earth ground at my shop, main utility meter box, and my house service. I also have 1 uf 2000 VAC rated low ESR capacitors in parallel to the MOV's to shunt HF line noise to ground.
I also use two or more ground rods at the shop main service and house as well so that noise has some place to go to once it is shunted away from everything else.

The thing was my plasma cutter used to turn my touch lamps on in the house when I used it so I put the big MOV's in. It helped some but I still had the lights going on at times when I did heavy plate cutting for extended periods. Adding the Low ESR capacitors cured it!

To me proper protection does not come from just one single device but takes several different methods and approaches to work properly.

 

[westom]

In industrial settings, the solution is installed at each noise generator. Not on other appliances. To fix what was missing inside that machine.

Meanwhile, homeowners that want the OP's protection will upgrade earthing to meet and exceed code requirements. And earth a 'whole house' protector (that typically uses MOVs). Then transients are not inside the house hunting for earth destructively via appliances.

 

[KeepItSimpleStupid]

Adding a MOV to a device that has no ground connection will help. Stopping them is more effective if done at the source. e.g. plasma cutter.

If the utility looses power and it's reapplied, the best solution is whole house.

You can think of surge supression in terms of the surge getting out and/or getting in.

So suppose a toaster gets hit by lightning and the lightning jumps to a water pipe some distance away. The toaster might be trash and the low Z point was found. The sink.

Finally, I think we are on the same page.

I think at home we had this sort of scenero. The kitchen roof ventgot hit and the resulting surge found it's way to an inadequae ground and severed it.

The prevention that could have been used is lightning rods or a low Z path at the roof vent to earth. This perfectly illustrates the importance of a low Z earth.

 

[KeepItSimpleStupid]

Adding a MOV to a device that has no ground connection will help. Stopping them is more effective if done at the source. e.g. plasma cutter.

If the utility looses power and it's reapplied, the best solution is whole house.

You can think of surge supression in terms of the surge getting out and/or getting in.

So suppose a toaster gets hit by lightning and the lightning jumps to a water pipe some distance away. The toaster might be trash and the low Z point was found. The sink.

Finally, I think we are on the same page.

I think at home we had this sort of scenero. The kitchen roof ventgot hit and the resulting surge found it's way to an inadequae ground and severed it.

The prevention that could have been used is lightning rods or a low Z path at the roof vent to earth. This perfectly illustrates the importance of a low Z earth.

 

[tcmtech]

Adding a MOV to a device that has no ground connection will help. Stopping them is more effective if done at the source. e.g. plasma cutter.

Most equipment has all the necessary protection that the manufacturing codes required the day it was built but that does not mean it was ever designed properly or adequately.

After that its up to something else to prevent it from going any further.

 

[KeepItSimpleStupid]

Back in the day I bought some scanning ThermoCouple multiplexors. CMOS logic and wall wart Power Supply. Used it nnear some quartz halogen heaters. It did't survive long.

Took it apart and ther were pads for an entire 723 based regulator. It was missing in all of them. I added just two TVS diodes and all fixed.

This is wierd. Nearly all the industrial repairs were either surge or capacitor aging/temperature.

One or two wasn't:

1. The HV power supply transformer that was located under a drip. A liguid nitrogenreplacement system.
2. The RFID reader that fell behind the wall.
3. The mssing connection. A wire wrapped commercial system was WWed except for power and ground. They missed a socket.
4. A few designs were so bad they were returned or fixed by the manufactuer for free once brought to their attention. One was a tough sell, but it was suge too

 

[lecman]

I found this circuit regarding surge protection **broken link removed**

What i can't understand why the Earth has not being Incorporated,
I 100% understand about the art of earth many thanks, but i am not sure about the circuit, any comments about the link would be much appreciated, i did read some contradicting things on the other website regarding smoothing caps and MOV but do not want to start an argument, please advise on the link

 

[KeepItSimpleStupid]

Interesting. 1) It's not whole house. 2) It's slow to respond

That said, it may be of use say with a refrigerator which has a motor starting up.

 

[KeepItSimpleStupid]

Let's just add that there is something called Common mode and Normal mode.

A common mode signal is common to both inputs. So Neutral and ground could shift the same amount and the device would still see the line voltage.

A Normal mode signal is where one line shifts. This is where earth comes into play.

Let's take the above circuit and make another one from it. Suppose that when you turned on a device a resistor was inserted and then sometime later, it was removed. This is the principle of a soft-starter. The circuit that you found wants to incorporate a "soft-start" yechnique when it detects an overvoltage. That doesn't need earth.

 

[lecman]

so the circuit i found is common mode and i take it the the resistor for the soft-start should be inserted at one leg of the resistor where C1 and R1 are connected and the other leg of the resistor to the appliance, is this what you mean?

 

[WTP Pepper]

A perfect example of conclusions based in subjective reasoning and wild speculation.

View the numbers. A fuse is rated for maybe 250 volts. How does that blown fuse stop something rated at thousands of volts? It doesn't. The blown fuse remains conductive - as it specification numbers state.

More numbers. A fuse takes milliseconds or longer to blow. Surges are done in microseconds. *Easily* 300 consecutive surges could pass through a fuse before it even thinks about blowing. Where is the protection? I can only exist when subjective reasoning exists by ignoring numbers.

A fuse only disconnects power AFTER surge damage has occurred. So that fire does not kill humans. Known when one first learns specification numbers. And if one ignores subjective claims based only in speculation.

A perfect example of not having a clue....

It's current that blows a fuse. Not voltage. The MOV will respond much faster than a fuse. During this period of overload when the MOV is under stress, the fuse will blow cutting off the power. The fuse is there to prevent the MOV smoking.

 

[KeepItSimpleStupid]

R5 gets inserted in series with the power line to "drop the voltage" on a "slow detected surge".

 

[westom]

It's current that blows a fuse. Not voltage. .

Exactly what my post said. You are correct. A fuse exists so that a grossly undersized MOV does not smoke and cause a house fire. But all fuses have a voltage rating. Don't take my word for it. Read numbers on each fuse.

A classic line fuse (ie inside power plugs) is 250 volts. When ‘current’ is excessive, then a fuse blows. Does a fuse stop that current? Yes, if driven by less than 250 volt. No, if the open fuse results in a voltage well exceeding 250 volts (ie a surge). All fuses and circuit breakers have a critically important ‘voltage’ number. If voltage is excessive, a blown fuse remains conductive.

Every so often, we would find someone who foolishly installed an automobile (AGC) fuse for a line fuse. Therefore a 32 volt fuse was ineffective. Anyone who knows about fuses and circuit breakers knows the basics; each has a critically important voltage rating.

What does a fuse do during a surge? This introduces another concept critical to surge protection. Destructive surges are current sources - not voltage sources. Voltage will increase as necessary so that the current will still flow. Anything that tries to stop a surge will only see voltage increase high enough to blow through. Nothing stops a destructive surge.

A fuse will not stop or block a surge. Voltage increases to blow through a 250 volt fuse. A protector will not stop or block a surge. Voltage will easily increase as necessary to blow through that 2 cm part.

What does a surge protector (cited by lecman) do? First, it claims to block a surge. Nonsense. Second, one line of AC mains connects directly to the appliance. So no protection exists. A surge current is incoming on that topmost AC wire. And outgoing destructively through the adjacent appliance. That protector simply connected a surge current directly into the appliance. Relevant is “common mode”. And no, that protector circuit is normal mode; not common mode.

Third, will those tiny semiconductors stop what three miles of sky could not? Of course not. That protector does not protect from any typically destructive surge. It protects from what is already made irrelevant by circuits inside electronics (ie galvanic isolation).

Anything adjacent to an appliance can only stop, block, or absorb a surge. That is impossible. A surge will increase voltage as necessary to blow through any such protector. The protection is what absorbs hundreds of thousands of joules. Earth ground. A protector either connects tens of thousands of amps to earth ground. Or that protector does nothing (is a profit center).

MOV are used in the effective and ineffective solution. Protection is not about MOVs. Protection is always about earth ground.

And finally, well proven protection means an MOV does not blow. Grossly undersized protectors are often called 'one-shot' devices by the naive. Naive because they saw a grossly undersized (high profit) protector fail. And then assumed that is acceptable. MOVs must remain functional decades later after many surges. So that nobody even knew a surge existed. Otherwise the protection is ineffective.

A simple concept: a protector is only as effective as its earth ground. A concept demonstrated even by Ben Franklin in 1752. A concept well proven by over 100 years of science and experience.