surge suppressor voltage limit

In a previous thread a reference was made to an expert recommendation that surge suppressors have their clamping voltage doubled from 330V to 660V for
120VAC suppressors.
Originally, I thought that was a bad idea. But now I think maybe that will be useful. How I came to that conclusion was finding that suppressors were not readily available for 240VAC power systems. With such a change in the clamping voltage, I could use these more common suppressors as part of the changeover from 120V to 240V for my computers.
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You mean use a TVSS built for 120V and apply it at 240V? I worry it would be bleeding catastrophic amounts of current with double nominal voltage applied. Plus, a terminal intended for neutral (0V) would not be insulated for the 120V applied if the 240V is +-120 V. If the 240V is 240V and neutral, the 240 V terminal may only be good for 120 V nominal. Also I doubt it is 'acceptable' to apply a device intended for 120 V at 240 V.
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| |> In a previous thread a reference was made to an expert |> recommendation that |> surge suppressors have their clamping voltage doubled from 330V to |> 660V for |> 120VAC suppressors. |> |> Originally, I thought that was a bad idea. But now I think maybe |> that will |> be useful. How I came to that conclusion was finding that |> suppressors were |> not readily available for 240VAC power systems. With such a change |> in the |> clamping voltage, I could use these more common suppressors as part |> of the |> changeover from 120V to 240V for my computers. |> |> -- |> |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to |> ignorance | |> | by the abuse department, bellsouth.net is blocked. If you |> post to | |> | Usenet from these places, find another Usenet provider |> ASAP. | |> | Phil Howard KA9WGN (email for humans: first name in lower case at |> ipal.net) | | | You mean use a TVSS built for 120V and apply it at 240V? I worry it | would be bleeding catastrophic amounts of current with double nominal | voltage applied. Plus, a terminal intended for neutral (0V) would not | be insulated for the 120V applied if the 240V is +-120 V. If the 240V | is 240V and neutral, the 240 V terminal may only be good for 120 V
If 330V clamping level works on 120VAC, then 660V clamping level should work on 240VAC. The disadvantage would be that the L1-G and L2-G paths would be 660V as well, and those potentials are 120VAC each on a North American 240V system.
I have disassembled power strips, including a nice TrippLite one that became unusable due to water damage. These things are wired symmetrically.
| nominal. Also I doubt it is 'acceptable' to apply a device intended | for 120 V at 240 V.
I find it not 'acceptable' that the manufacturers don't make decent 240V ones in the first place. If they did, I'd buy one.
I did find one on the TrippLite web site for 240V. But it has NEMA 5-15 plug and outlets. There's something wrong with that concept. And it has a poor level of protection.
The fact that there is not a genuine decent one on the market means I have no choice but to "construct" one in some way. Feel free to advise HOW to do that. But any suggestion to not do that will be ignored since it is not a valid path to the goal.
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The clamping voltage statement doesn't sound right. I'd go back and reread the information and pay particular attention to the knee voltage and the current rank just prior to it. I'm not saying it's a bad idea; just that it might have a lot of leakage on 240 that surpasses the component's temp ratings.
You don't give enough info on how you plan to use these, but I do know that the UK style 230Vac 50Hz does have accomodating surge suppressors. Their grid is configured differently than here in the US where I am of course.
HTH
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MOVs used in surge suppression circuit for 240VAC are normally selected based on 240 +10% and then + 10% again. This allow for a 10% increase in the nominal supply voltage to 264 VAC and for the 10% manufacturing tolerance on the AC rating of the MOV. Therefore for 240VAC you would normally select a MOV with a nominal AC rating of at least 290 VAC. The standard rating for an MOV is either 300 VAC or 320 VAC depending on the manufacturer. These normally clamp the surge at about 800V.
In your posting you talk about 660 V, I would guess that this is the clamping voltage, not the AC rating. If you use a surge suppressor rated at 120VAC these normally use a MOV rated at 150 VAC. These will fail very quickly if are used at 240VAC, due the high leakage current.
Best regards
BillB
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On Tue, 16 Sep 2008 19:03:19 GMT snipped-for-privacy@nospam.tesco.net wrote: | MOVs used in surge suppression circuit for 240VAC are normally selected | based on 240 +10% and then + 10% again. This allow for a 10% increase in the | nominal supply voltage to 264 VAC and for the 10% manufacturing tolerance on | the AC rating of the MOV. Therefore for 240VAC you would normally select a | MOV with a nominal AC rating of at least 290 VAC. The standard rating for an | MOV is either 300 VAC or 320 VAC depending on the manufacturer. These | normally clamp the surge at about 800V. | | In your posting you talk about 660 V, I would guess that this is the | clamping voltage, not the AC rating. If you use a surge suppressor rated at | 120VAC these normally use a MOV rated at 150 VAC. These will fail very | quickly if are used at 240VAC, due the high leakage current. | | Best regards | | BillB
Don't forget, Bill, that I am talking about 120VAC protectors based on DOUBLING their clamping level ... NOT the current crop of 120VAC protectors that perhaps still have the low clamping level.
I've read in multiple places that the common clamping voltage for 120VAC is 330V and for 240VAC is 660V. Fewer of the readings mentioned the 240VAC and 660V clamping level. But the ratio makes sense.
The PEAK voltage on 120VAC is 170V. The PEAK voltage on 240VAC is 340V. So the 330V level for protecting 120VAC, and the 660V level for protecting 240VAC, is well above the peak operating voltage.
If you DOUBLE the clamping level AND double the AC voltage, what do you think happens?
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Please explain what you mean by doubling their clamping voltage?
All the surge suppression devices we have tested are suitable for use at 240VAC and use 300V MOVs with rated clamping voltages of around 770V. These have all had clamping voltages of around 800V when subjected to 8/20us pulses. I am talking of testing surge suppression devices not just an MOV by its self.
Similar sized MOV rated at 150VAC have rated clamping voltages of between 360 and 400V.
See Little Fuse website for details http://www.littelfuse.com/searchresults.html?NN=0%3aTechnology%3a156
BillB
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On Thu, 18 Sep 2008 18:40:50 GMT snipped-for-privacy@nospam.tesco.net wrote:
| Please explain what you mean by doubling their clamping voltage?
Using a 660V level instead of ao 330V level.
| All the surge suppression devices we have tested are suitable for use at | 240VAC and use 300V MOVs with rated clamping voltages of around 770V. These | have all had clamping voltages of around 800V when subjected to 8/20us | pulses.
I've not tested these in labs. I'm just going on things I have read in the past. In particular someone did post here that an "expert" recommended that the levels be double.
| I am talking of testing surge suppression devices not just an MOV by its | self. | | Similar sized MOV rated at 150VAC have rated clamping voltages of between | 360 and 400V. | | See Little Fuse website for details | http://www.littelfuse.com/searchresults.html?NN=0%3aTechnology%3a156
I'll bookmark that to check it out.
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I now know what you are speaking of regarding the situation in the USA. Your 240 V supply is two hot wires with 120 V to ground and 240 V live to live. In Europe we have one live, a neutral and ground. The live has 230 V to Neutral and to Ground, Neutral has 0 V to ground.
For the US system I would use 3 MOVs 2 with 150V AC ratings connected live to ground and one with a 300 VAC rating, connected live to live. In Europe I would use 3 MOVs all rated 300 VAC, one connected live to ground, one live to neutral and one neutral to ground. With the US system the MOVs will provide a clamping voltage of about 400 V live to ground and 800 V live to live. While the European version will give 800V live to ground, live to neutral and neutral to ground.
The situation is even more complex in Europe as we have to limit the leakage to ground, normally by the use of a Gas Discharge Tube, GDT. The GDT is installed between live , the live to ground MOV and ground and neutral, its MOV and ground. The GDT has negotiable leakage at line voltage, but during a surge it will conduct, but it responds slowly increasing the peak clamping voltage due to its slow response.
So if you use a European surge suppression unit in the US it will work fine, but will not give the same protection live to ground that a unit designed for your supply would, but should be electrically safe.
BillB
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On Fri, 19 Sep 2008 23:18:47 GMT snipped-for-privacy@nospam.tesco.net wrote: | I now know what you are speaking of regarding the situation in the USA. Your | 240 V supply is two hot wires with 120 V to ground and 240 V live to live. | In Europe we have one live, a neutral and ground. The live has 230 V to | Neutral and to Ground, Neutral has 0 V to ground. | | For the US system I would use 3 MOVs 2 with 150V AC ratings connected live | to ground and one with a 300 VAC rating, connected live to live. In Europe I | would use 3 MOVs all rated 300 VAC, one connected live to ground, one live | to neutral and one neutral to ground. | With the US system the MOVs will provide a clamping voltage of about 400 V | live to ground and 800 V live to live. While the European version will give | 800V live to ground, live to neutral and neutral to ground. | | The situation is even more complex in Europe as we have to limit the leakage | to ground, normally by the use of a Gas Discharge Tube, GDT. The GDT is | installed between live , the live to ground MOV and ground and neutral, its | MOV and ground. The GDT has negotiable leakage at line voltage, but during a | surge it will conduct, but it responds slowly increasing the peak clamping | voltage due to its slow response. | | So if you use a European surge suppression unit in the US it will work fine, | but will not give the same protection live to ground that a unit designed | for your supply would, but should be electrically safe.
However, I believe it would get at least as good a protection level as the proposed doubling of the clamp voltage. The proposed 120V protection design would have 800 V on all pairs, L-G, L-N, and N-G. But maybe the European devices would be better with regard to leakage.
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Hi Phil
The so called European devices are the same as the ones as the US version, made in the same plant in China, tested to the same standard as a component.
Yes I agree you would get less leakage to ground using a higher voltage MOV, but you would also get 800V live to ground clamping voltage instead of 400V live to ground when using the 150V MOV. The reason you fit a surge suppression device is to limit the value of any surges on the line to the lowest value economically possible to get the best protection for your money. If reducing the leakage is the prime requirement you should investigate other solutions to the problem eg GDTs.
What we have been discussing above is only half of the requirement, in addition you need to consider thermal protection for the MOVs, plus short circuit protection. An MOV without the protection can produce quite a good explosion when it fails, which all will do eventually if subjected to repeat surges. If a MOV fails you also need to know it has failed, in other words you need some form of indication. The simplest is that when you plug the device in all the circuits are dead, but this is not always possible the achieve easily. Otherwise you will continue using it, but not have the protection you think you have.
Look inside any well know surge strip and you will find all these feature. Also have at look at http://www.littelfuse.com/data/en/Application_Notes/Littelfuse_app-note_an9767.pdf and http://www.littelfuse.com/data/en/Application_Notes/EC638.pdf and http://www.littelfuse.com/data/en/Application_Notes/EC640.pdf
BillB
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On Sat, 20 Sep 2008 07:55:42 GMT snipped-for-privacy@nospam.tesco.net wrote: | Hi Phil | | The so called European devices are the same as the ones as the US version, | made in the same plant in China, tested to the same standard as a component. | | Yes I agree you would get less leakage to ground using a higher voltage MOV, | but you would also get 800V live to ground clamping voltage instead of 400V | live to ground when using the 150V MOV. The reason you fit a surge | suppression device is to limit the value of any surges on the line to the | lowest value economically possible to get the best protection for your | money. If reducing the leakage is the prime requirement you should | investigate other solutions to the problem eg GDTs.
Is there any reason the 800V level of clamping would be bad? This is for a 240VAC circuit.
If course there is the argument I _can_ use a lower clamping voltage between either of the two live wires, and the grounding wire (there being no neutral in this case). My counter to that argument is that there is a suggestion being made to double the clamping level for 120VAC devices. If that is valid science then how would it apply to the North American 240V configuration?
| What we have been discussing above is only half of the requirement, in | addition you need to consider thermal protection for the MOVs, plus short | circuit protection. An MOV without the protection can produce quite a good | explosion when it fails, which all will do eventually if subjected to repeat | surges. If a MOV fails you also need to know it has failed, in other words | you need some form of indication. The simplest is that when you plug the | device in all the circuits are dead, but this is not always possible the | achieve easily. Otherwise you will continue using it, but not have the | protection you think you have.
Presumably some circuit within the device will test if the MOV is completely open, or sufficiently open to not offer the protection. Some implication in an earlier post is that the leakage itself might be a means to do this aspect of the test.
For cases of the MOV being fused closed, being behind a fuse or circuit breaker would be expected to achieve that test.
| Look inside any well know surge strip and you will find all these feature. | Also have at look at | http://www.littelfuse.com/data/en/Application_Notes/Littelfuse_app-note_an9767.pdf | and http://www.littelfuse.com/data/en/Application_Notes/EC638.pdf | and http://www.littelfuse.com/data/en/Application_Notes/EC640.pdf
In what percentage of power strip type point of use protectors do you see these features?
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Hi again Phil
All the surge protected power strip from the major suppliers use circuits similar to those I described, most use more MOVs. The cheaper no name ones have only one MOV and no working protection circuits.
I cannot see any valid reason for doubling the live to ground clamping voltage, it the same as saying why bother to fit surge suppression in the first place. The lower the clamping voltage the less likely it is to damage the connected equipment. One perceived advantage of using higher voltage MOVs is the transient energy rating, for example a 20mm 150 VAC MOV typically has a rating of 120J, while a 20mm, 300V MOV has a rating of 250J. Therefore the higher voltage device can withstand a larger surge energy level before failure, but against this you will have the higher clamping voltage that is more likely to damage the connected equipment. Energy ratings are used as a marketing tool by some manufactures. Finally it is the connected equipment that we are trying to protect not the MOVs from failure. The simple answer is use a large diameter MOV, which gives the best of the both, a similar clamping voltage and a higher energy rating. Some manufactures attempt to increase this by the use of MOVs in parallel, unfortunately this does not normally work. For it to work it requires matched MOVs, without this the lowest rated MOV takes all the surge energy, while the other does very little.
The basic circuits we have been discussing, do provide reasonable levels of protection, but do have limitation, in relation to the energy they can absorb.
BillB
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On Sat, 20 Sep 2008 21:12:19 GMT snipped-for-privacy@nospam.tesco.net wrote:
| I cannot see any valid reason for doubling the live to ground clamping | voltage, it the same as saying why bother to fit surge suppression in the | first place. The lower the clamping voltage the less likely it is to damage | the connected equipment.
I do agree with this concept. But my point is something else.
If *they* go ahead and change the surge protector designs so that the clamping voltage is doubled for the 120V protectors, then maybe that creates a device that could be used on twice the voltage.
If the clamping voltage in the USA is doubled, but this does not happen in Europe, then the devices in both would end up being about the same, right?
I'm looking for devices to protect against surges at point of use for 240V as wired in the USA. I could use a protective device from Europe, but it would not be optimal. But my big point is, if they double the clamping voltage of protective devices from USA, they would basically be the same and this gives me another choice to find a device that should work be will be less than optimal.
The optimal design would be one that considers the voltage to be 240V L1-L2, 120V L1-G, and 120V L2-G. The less that optimal designs have one advantage over the optimal designs: they are available.
So the remaining question is, if they do double the clamping voltage on the the models for the 120V market, are they usable on 240V? Would there be any difference between these "doubled for 120V" compared to the "normal for 240V" models in UK (not considering the NEMA vs. BS outlets and plugs, fusing requirements, etc).
| One perceived advantage of using higher voltage MOVs is the transient energy | rating, for example a 20mm 150 VAC MOV typically has a rating of 120J, while | a 20mm, 300V MOV has a rating of 250J. Therefore the higher voltage device | can withstand a larger surge energy level before failure, but against this | you will have the higher clamping voltage that is more likely to damage the | connected equipment. Energy ratings are used as a marketing tool by some | manufactures. Finally it is the connected equipment that we are trying to | protect not the MOVs from failure. The simple answer is use a large diameter | MOV, which gives the best of the both, a similar clamping voltage and a | higher energy rating. Some manufactures attempt to increase this by the use | of MOVs in parallel, unfortunately this does not normally work. For it to | work it requires matched MOVs, without this the lowest rated MOV takes all | the surge energy, while the other does very little.
Apparently some "experts" think that today's home appliances can withstand some higher surge levels, and that the MOVs are being destroyed more often than desireable in the protectors.
When I look at my computer SMPSUs and see "100-240V 50/60Hz" on them, should I assume these units can withstand the surge levels that would not be clamped by a 240V protector device in UK, when used in the USA whether on 120V or 240V?
Surges that originate upstream on the power utility distribution lines might well have twice the voltage on a 240V connection compared to a 120V connection. But surges that originate after the utility transformer steps the voltage down to the utilization voltage, are going to be the same.
The only reason I see to have any more protection in the USA compared to the UK is that we have areas of the country with more frequent lightning.
| The basic circuits we have been discussing, do provide reasonable levels of | protection, but do have limitation, in relation to the energy they can | absorb.
1. So maybe we don't need a lower clamping voltage in the USA, given that more and more appliances (especially computers) handle all of 100-240V.
2. So maybe there is an advantage in the ability to handle more energy with the clamping voltage doubled. That and being destroyed less often.
1+2 = maybe the "experts" are right.
3. I want to use 240V, even though that means a different system configuration in the USA (compared to UK).
1+2+3 = more devices available (but I have to be very careful to choose units that have this doubled clamping voltage else the MOVs will give up their magic smoke as soon as I plug them in).
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Hi Phil
Lets try and answer your questions.
On 21-Sep-2008, snipped-for-privacy@ipal.net wrote:

The answer is no, you could not use it at twice the voltage. Only the ratings of the MOVs between Live and Ground have been increased in voltage rating. The MOV between live and live is still the same (300VAC). If you tried to use the unit on a higher rated supply the MOV between live and live would fail, as it is only rated for a 240 VAC supply.

Yes the MOVs would be the same.

If the device is a power strip the would it could have the same protection circuit, but it would not meet US or Canadian requirements due to the sockets been European and not meeting US or Canadian standards.

The answer should be yes if you ignore the differences in the standard requirements. Most counties other than the US base their standard on IEC 60884-1 for the electrical safety of the basic power strip and on IEC 61643-1 for surge suppression. So what is designed for Germany can also be sold in Holland, Spain etc. and what is designed for the UK can be sold in Hong Kong, Cyprus, Malta etc. Although Japan use the same socket as Japan it must be tested to Japanese standard and have a PSE approval before it can be sold there.

They can, but they will last longer with the lower clampng voltage, It is the marketing department like to use the higher energy rating as a marketing tool, the engineer still prefer the lower clamping voltage.

Yes, but they will last longer with the lower clamping voltage level between live and ground.

No it depends on the source of the surge.

Not true some area of the UK have similar lighting strikes frequency as the US.

As I have already said the lower the clamping voltage the longer the life of the protected device will be.

No a lower clamping voltage should always be the prime objective, the life of the MOVs can always be improved by using a larger more expensive device if cost is not the limiting factor.

The choice is yours.

NO any device rated for 240 VAC should give acceptable life both for your equipment and the protection device itself, if purchased from one of the major manufacturers. Do not be tempted to buy a cheap no name unit, irrespective of the manufacturers claims.
BillB
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On Sun, 21 Sep 2008 20:50:05 GMT snipped-for-privacy@nospam.tesco.net wrote: | Hi Phil | | Lets try and answer your questions. | | On 21-Sep-2008, snipped-for-privacy@ipal.net wrote: | |> If *they* go ahead and change the surge protector designs so that the |> clamping |> voltage is doubled for the 120V protectors, then maybe that creates a |> device |> that could be used on twice the voltage. | | The answer is no, you could not use it at twice the voltage. Only the | ratings of the MOVs between Live and Ground have been increased in voltage | rating. The MOV between live and live is still the same (300VAC). If you | tried to use the unit on a higher rated supply the MOV between live and live | would fail, as it is only rated for a 240 VAC supply.
Your reference to "The MOV between live and live is still the same (300VAC)" isn't making any sense here. If you are talking about a device intended for 120V as in USA, then there is no "live and live". There is only one live, and a neutral, and a ground.
Unless you are referring to balanced power as in NEC 647. And that is quite a different beast.
If the voltage of ALL the MOVs on a 120V power strip are doubled, then that means the L-N are doubled, the L-G are doubled, and the N-G are doubled. So then if I use that device on 240V (USA style) then we change L to L1, and N to L2. So are yoy trying to say that when the voltage of a surge suppressor is doubled, it's not really doubled on the L-N pairing (which becomes L1-L2 when used for 240V)?
|> If the clamping voltage in the USA is doubled, but this does not happen in |> Europe, then the devices in both would end up being about the same, right? | | Yes the MOVs would be the same.
So why could the be used on 240V in Europe but not in USA?
|> I'm looking for devices to protect against surges at point of use for 240V |> as wired in the USA. I could use a protective device from Europe, but it |> would not be optimal. But my big point is, if they double the clamping |> voltage of protective devices from USA, they would basically be the same |> and this gives me another choice to find a device that should work be will |> be less than optimal. | | If the device is a power strip the would it could have the same protection | circuit, but it would not meet US or Canadian requirements due to the | sockets been European and not meeting US or Canadian standards.
That's a different issue. I might swap out the receptacle parts, plus other components that can only handle 120V.
|> So the remaining question is, if they do double the clamping voltage on |> the |> the models for the 120V market, are they usable on 240V? Would there be |> any |> difference between these "doubled for 120V" compared to the "normal for |> 240V" models in UK (not considering the NEMA vs. BS outlets and plugs, |> fusing requirements, etc). | | The answer should be yes if you ignore the differences in the standard | requirements. | Most counties other than the US base their standard on IEC 60884-1 for the | electrical safety of the basic power strip and on IEC 61643-1 for surge | suppression. So what is designed for Germany can also be sold in Holland, | Spain etc. and what is designed for the UK can be sold in Hong Kong, Cyprus, | Malta etc. Although Japan use the same socket as Japan it must be tested to | Japanese standard and have a PSE approval before it can be sold there.
I have some "wall warts" that are rated for 100-240V 50/60Hz, but the plugs are NEMA 1-15 (e.g. standard for 120V w/o ground pin).
|> Apparently some "experts" think that today's home appliances can withstand |> some higher surge levels, and that the MOVs are being destroyed more often |> than desirable in the protectors. | | They can, but they will last longer with the lower clampng voltage, It is | the marketing department like to use the higher energy rating as a marketing | tool, the engineer still prefer the lower clamping voltage.
But on 240V, the clamping voltage would be "just right" (doubled from 120V).
|> The only reason I see to have any more protection in the USA compared to |> the UK |> is that we have areas of the country with more frequent lightning. | | Not true some area of the UK have similar lighting strikes frequency as the | US.
Some areas of the US have substantially more than most of the US. How does the UK compare to say, Florida?
|> 1. So maybe we don't need a lower clamping voltage in the USA, given that |> more and more appliances (especially computers) handle all of |> 100-240V. | | As I have already said the lower the clamping voltage the longer the life of | the protected device will be.
Of course. But I want to run the device at 240V for power efficiency.
|> 1+2+3 = more devices available (but I have to be very careful to choose |> units |> that have this doubled clamping voltage else the MOVs will give up their |> magic |> smoke as soon as I plug them in). | | NO any device rated for 240 VAC should give acceptable life both for your | equipment and the protection device itself, if purchased from one of the | major manufacturers. Do not be tempted to buy a cheap no name unit, | irrespective of the manufacturers claims.
I never do that. I always want to know who to sue (even if that would be a very unrealistic thing) :-)
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Hi Again Phil
My reference to L to L is based on an earlier comment that the 240V domestic supply was 120VAC-Ground-120VAC ie 240V Live to Live. If this is not the case please advise what a 240VAC domestic supply is as all my comments have been based on this assumption.
On 23-Sep-2008, snipped-for-privacy@ipal.net wrote:

If you change the AC rated voltage of all the MOVs to 300VAC the device can work at either 120VAC live to ground or at 240VAC live to ground. In both cases the clamping voltage will be approximately 800V live to live (or neutral), live to ground and neutral to ground. Where as if the live to ground voltage is 120VAC and the neutral to ground AC voltage is either 0 or 120V and you use a 150VAC MOV, the clamping voltage to ground for both MOVs will be approximately 400V.

The answer is yes they can, but a European device will not meet US/Canadian standards and likewise the US version would not meet European standards, as the standards set different requirements.

Do these have surge protection?

What is "just right" ?

Its the same in the UK.

I have not implied that you should not use 240V, I have only tried to state that the lower the clamping voltage is the better the equipment will be protected.

In the UK I am not as concerned over who you will sue, but about trying to make sure you do not need to sue anyone.
Best regards
BillB
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On Tue, 23 Sep 2008 20:09:09 GMT snipped-for-privacy@nospam.tesco.net wrote:
| My reference to L to L is based on an earlier comment that the 240V domestic | supply was 120VAC-Ground-120VAC ie 240V Live to Live. If this is not the | case please advise what a 240VAC domestic supply is as all my comments have | been based on this assumption.
That is the correct assumption for 240V in the USA.
| If you change the AC rated voltage of all the MOVs to 300VAC the device can | work at either 120VAC live to ground or at 240VAC live to ground. In both | cases the clamping voltage will be approximately 800V live to live (or | neutral), live to ground and neutral to ground. | Where as if the live to ground voltage is 120VAC and the neutral to ground | AC voltage is either 0 or 120V and you use a 150VAC MOV, the clamping | voltage to ground for both MOVs will be approximately 400V.
I don't see any ratings for the suppressors with regard to the MOVs other than the clamping voltage. And the value I see is 330V. Not 400V. So I assume if they are doubled, it would be 660V.
|> > If the clamping voltage in the USA is doubled, but this does not happen |> > in |> |> Europe, then the devices in both would end up being about the same, |> right? |> | |> | Yes the MOVs would be the same. |> |> So why could the be used on 240V in Europe but not in USA? | | The answer is yes they can, but a European device will not meet US/Canadian | standards and likewise the US version would not meet European standards, as | the standards set different requirements.
Right. And that can be an issue. OTOH, the 120VAC device would only meet US standards in the 120VAC context, even if the MOV clamping voltage is doubled. So either way, I'm forced to use the device inappropriately since 240V only devices for the USA either don't exist, or do not have adequate level of protection.
|> I have some "wall warts" that are rated for 100-240V 50/60Hz, but the |> plugs |> are NEMA 1-15 (e.g. standard for 120V w/o ground pin). | | Do these have surge protection?
I don't know if they have surge protection built in. Presumably since they are rated 100-240VAC 50/60Hz, the manufacturer is saying they are good to go around the world. Could I take them to Brazil where they use the same outlet as in USA, but run 240V on it, and plug them in there? Could I plug them in using an adaptor (not a step-down transformer) in Europe? My guess is yes. That is a guess based on the printed rating. If it turns out one of these has surge protection that would trigger on the peaks of 240VAC because it is assuming 120V, despite being marked for use 100-240V, I'd be talking to my lawyer about a fraudulent advertising lawsuit.
|> |> Apparently some "experts" think that today's home appliances can |> withstand |> |> some higher surge levels, and that the MOVs are being destroyed more |> often |> |> than desirable in the protectors. |> | |> | They can, but they will last longer with the lower clamping voltage, It |> is |> | the marketing department like to use the higher energy rating as a |> marketing |> | tool, the engineer still prefer the lower clamping voltage. |> |> But on 240V, the clamping voltage would be "just right" (doubled from |> 120V). | | What is "just right" ?
If 330V or 400V clamping is right for 120V, then 660V or 800V clamping should be right for 240V. Do you see any reason otherwise?
|> Some areas of the US have substantially more than most of the US. How |> does |> the UK compare to say, Florida? | | Its the same in the UK.
There's a part of UK with as much lightning as Florida?
|> |> 1. So maybe we don't need a lower clamping voltage in the USA, given |> that |> |> more and more appliances (especially computers) handle all of |> |> 100-240V. |> | |> | As I have already said the lower the clamping voltage the longer the |> life of |> | the protected device will be. |> |> Of course. But I want to run the device at 240V for power efficiency. | | I have not implied that you should not use 240V, I have only tried to state | that the lower the clamping voltage is the better the equipment will be | protected.
I would agree. That makes me wonder why the "experts" recommend a higher clamping level. But in one case the implication was that the extra level of protection wasn't needed, and it was better to make the surge protector last longer over needless clamping of small surges, so it can handle the rare "big one" at least once.
|> I never do that. I always want to know who to sue (even if that would be |> a |> very unrealistic thing) :-) | | In the UK I am not as concerned over who you will sue, but about trying to | make sure you do not need to sue anyone.
And life would be easier if they just switch the USA over to 240V for all.
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Phil
I give up you don't seem to understand any of the comments I make I hope someone else has more patience then me. We could go on for ever and you will not understand the topic. Like said I give up on the topic.
BillB
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On Wed, 24 Sep 2008 20:22:27 GMT snipped-for-privacy@nospam.tesco.net wrote:
| I give up you don't seem to understand any of the comments I make I hope | someone else has more patience then me. We could go on for ever and you will | not understand the topic. | Like said I give up on the topic.
Maybe this is because you were never really trying to answer the exact question I asked, and instead were trying to answer something else. Maybe that something else is something you thought was more important. And maybe it is. But you did not connect it to the topic. I am only focusing on the issue I raised and am intentionally ignoring other issues, unless it can be shown they have specific bearing on the issue of interest.
Maybe if you narrow down the points you think I misunderstand instead of trying to clump a bunch all together (that always makes things more confusing to follow through with).
I've dealt with a few people here who seem to have a lack of understanding (especially those guys that just quote other people's stuff in circumstances where it doesn't apply, hoping to win points with facts). But you do seem to be someone that understands stuff. I think the problem might be you are not expressing yourself well enough in terms of relating it to the context at issue.
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