Is this charger safe?

[Zero999]

"High voltage test (also called hipot or HV test worldwide) has by far the highest priority among all of the electrical safety tests. This test of the dielectric strength is mandatory as it is part of the requirements of all national standards (e.g. VDE and UL) and international standards (e.g. EN and IEC). The often used term insulation test or insulation measurement is wrong in this context as a real, ohmic resistance is measured with the direct voltage in this case. In contrast, the high voltage test is carried out with both direct and alternating current. The result of this test is a leakage current, flowing between live parts and the metallic casing. Devices of protection class I always come with a metal casing, whereas the casing of the devices of protection class II must be replaced by a metallic contour during the test. In reality, the high voltage test is a geometric distance measurement in the DUT (Device Under Test): If the DUT withstands a certain voltage without flashover, an appropriate minimum distance between the metal casing and electrical components in the device is ensured. Thus, the term withstand voltage is also plausible again."

https://www.spselectronic.com/en/products/high-voltage/

I've done more research and I stand corrected. The regulations mandate some high voltage testing. I had confused the withstand voltage and breakdown voltage.

Yes, you can. By design, I mean the whole process, not just the components and laying out the PCB, but the materials and how they're physically put together. The video you've linked to demonstrates this perfectly. Proper design could have avoided this fault. Testing could have made this worse by weakening some marginal components, causing them to fail in the Yes. I've seen hi-pot stickers and have never seen the point.

The point is to indicate that test was passed. Therefore no untested device may accidentally slip further.

It won't stop marginal devices from slipping through or show up poor manufacturing. Only disassembly and visual inspection can do that. Yes, you're right, it shouldn't damage the insulation, as long as the test voltage isn't too high (much lower than the withstand voltage) and hasn't been applied for too long.

Visual inspection will happily pass most of the faults  , it's only good for finding the most obvious defects. It's really obvious you never dealt with actual production. And you cannot inspect inside the parts (where most of the faults happen), and you won't be able to see imperfections in insulation anyway. Exactly Hi-POT test is what weeds out marginal devices.

I meant spot checks, involving destructive visual inspection.

Withstand voltage means withstand don't confuse that with breakdown voltage.

Yes, I confused withstand with breakdown voltage. 

I disagree with you about the construction of the transformer. There isn't enough insulation, where the windings pass near one another and it appears too much force has been used when it was wound. Very shoddy.

Wire used in secondary winding had reinforced insulation by itself. Basically you could wind primary winding directly on top of it, and it would be just fine. The issue was that a big piece of that insulation was missing because of mechanical damage.
EDIT: Something like this http://www.totoku.com/products/cables/tiw/post-2.php, additional insulation between windings is not required at all.

Mechanical damaged, caused by poor manufacturing process. If the winding machine was incorrectly set, there will be other devices with a similar fault and the high voltage withstand test might not have revealed it.

[oldway]

I think you were influenced by the multimeters, which is why you wrote that you felt that a device undergoing a high voltage test could no longer be sold to the customer.

For electrical appliances and power electronics, the standards are different and this has nothing to do with multimeters.

There are several classes of isolation, I refer you to Wikipedia for more explanations.
https://en.wikipedia.org/wiki/Appliance_classes

Chargers and power supplies belong to Class II double insulation.

Since the secondary is not grounded, the safety of the user depends only on the quality of the insulation between primary and secondary.

This safety is guaranteed by an Hi-Pot test.

The test conditions are difficult to find on the Internet because the standards are protected by Copyright and are not free available on the Internet .... Moreover, these standards are complicated and difficult to interpret correctly.

As far as I can remember, the test voltage applied for Class I equipment is 1500Vrms in 50 or 60Hz or 2121Vdc and 3000Veff 50 or 60Hz or 4240Vdc for Class II.

The test time is normally 1 min. But can be reduced to minimum 1s. (It should not be possible to make a test of 1 min. duration in mass producted appliances.)
It is intended that the voltage should be applied gradually. (ramp).

This test is fundamental and it is the only guarantee of safety for the user against the risks of electrocution.

It should be remembered that in Europe, many distribution networks have a 230V ground-phase voltage and the risks are high.

Is this test actually done at the factory?

There is no guarantee and no way to verify it.

So you can only trust in the well known brands.

Any no-brand or unknown brand, or fake gear is therefore not safe.

To answer Charkel, no, this charger is not safe

[madires]

I'd like to suggest that you take three randomly choosen wall warts apart. As the family's repair shop I see what's under the cover with all the fancy certification labels. Paper doesn't blush. And I'm talking about typical consumer electronics from more or less known vendors, and not about cheap crap bought directly from China.

[wraper]

Mechanical damaged, caused by poor manufacturing process. If the winding machine was incorrectly set, there will be other devices with a similar fault and the high voltage withstand test might not have revealed it.

Such fault may happen to one in 100 000 transformers and destructive inspection of sampled devices won't reveal anything wrong. The good thing with Hi-pot test is that 100% of devices are tested and may reveal rare issue with production process.

[Zero999]

Mechanical damaged, caused by poor manufacturing process. If the winding machine was incorrectly set, there will be other devices with a similar fault and the high voltage withstand test might not have revealed it.

Such fault may happen to one in 100 000 transformers and destructive inspection of sampled devices won't reveal anything wrong. The good thing with Hi-pot test is that 100% of devices are tested and may reveal rare issue with production process.

Or you might have 100 000 transformers, with shoddy winding like that, but only a few of them are bad enough to fail the high voltage test. Many of the others will fail in the field. The test shouldn't be relied up on to catch all faults.

[oldway]

This test of the dielectric strengh is part of the requirements of all national standards (e.g. VDE and UL) and international standards (e.g. EN and IEC), it is mandatory and there is nothing to discuss about utility of these standarts.
It is like a law .....You must obey or you will have serious troubles....
This is the way a quality control works....you must comply with the standarts....nothing more.

Do you think you are more clever than the people how make these standarts ? 

.

[Zero999]

This test of the dielectric strengh is part of the requirements of all national standards (e.g. VDE and UL) and international standards (e.g. EN and IEC), it is mandatory and there is nothing to discuss about utility of these standarts.
It is like a law .....You must obey or you will have serious troubles....

I've already told you I've changed my position on that. Yes I agree, it's law but that doesn't mean it's perfect.

This is the way a quality control works....you must comply with the standarts....nothing more.

No! Standards are just the bare minimum. Electrical tests will not catch all faults and relying on them alone, will only lull one into a false sense of security. There are plenty of faults which will not cause the device to fail the test, yet still cause catastrophic failure later on. We might have seen an example of this here. It's possible that the transformer passed the high voltage test with flying colours, then after some rough handling the insulation chafed, causing a short from the primary to secondary. No electrical tests will pick up on this kind of thing. I still blame poor manufacturing, test or no test.

Do you think you are more clever than the people how make these standarts ? 

I'm smarter than some of them, but not as smart as others. 

[Audioguru]

Many electrical "standard tests" are done then a passing design is certified to be safe.

My electrical utility gave away compact fluorescent light bulbs for free for people to try then replace all the power-robbing incandescent light bulbs so that the utility will not need to build additional very expensive generating stations. But many of the new bulbs dripped burning plastic. The Chinese no-name-brand manufacturer never had the bulbs certified to be safe, instead they stole a certification number from a competitor and put that number on all their faulty bulbs. They were all recalled and replaced with name-brand certified and safe bulbs.

[Mr. Scram]

This test of the dielectric strengh is part of the requirements of all national standards (e.g. VDE and UL) and international standards (e.g. EN and IEC), it is mandatory and there is nothing to discuss about utility of these standarts.
It is like a law .....You must obey or you will have serious troubles....
This is the way a quality control works....you must comply with the standarts....nothing more.

Do you think you are more clever than the people how make these standarts ? 

I used to think that standards and certifications meant thorough inspections and qualification. Boy, was I wrong. Thinking quality control is the same as complying with standards is setting yourself up for failure. You just make life easier on yourself by being compliant, but generally much more is needed to do it right.

[oldway]

It seems that you did not understand what I meant.

When I say "you must comply with the standarts .... nothing more.  ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,

[Mr. Scram]

It seems that you did not understand what I meant.

When I say "you must comply with the standarts .... nothing more.  ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,

I understood, but I don't agree. Understanding why you do something is a huge boon.

[oldway]

It seems that you did not understand what I meant.

When I say "you must comply with the standarts .... nothing more.  ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,

I understood, but I don't agree. Understanding why you do something is a huge boon.

This kind of discussion has nothing to do with the topic.
The question is simple,"Is this charger safe ?" the answer is also simple...NO...
The high pot test is mandatory and it is the fundamental test to ensure safety.

Has the charger passed the higt pot test?
Probably not.
Is it safe? NO .... final point.

[Zero999]

It seems that you did not understand what I meant.

When I say "you must comply with the standarts .... nothing more.  ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,

I understood, but I don't agree. Understanding why you do something is a huge boon.

This kind of discussion has nothing to do with the topic.
The question is simple,"Is this charger safe ?" the answer is also simple...NO...
The high pot test is mandatory and it is the fundamental test to ensure safety.

Has the charger passed the higt pot test?
Probably not.
Is it safe? NO .... final point.

We don't know whether it has been high voltage tested or not and even if it hasn't, it still might be safe.

It seems that you did not understand what I meant.

When I say "you must comply with the standarts .... nothing more.  ", I mean that we do not have to discuss these standarts, nor seek to know whether they should be applied or not, whether they are valid or not, just apply them,

I understood, but I don't agree. Understanding why you do something is a huge boon.

It's also vital to understand the limitations of the test, in order to design a safe product, otherwise one is just designing something to pass a test, not be safe. The same is true with car emissions tests.

[oldway]

We don't know whether it has been high voltage tested or not and even if it hasn't, it still might be safe.

Safety is not a lottery...

Your security conception is completely false ... and you continue in your mistakes.

Not long ago, you said that the Hi Pot tests were not mandatory and now you claim that a device can be considered as safe even if it has not passed the hi pot test ....

No at all, if a device has not passed the mandatory tests, it is not safe even if nobody has been electrocuted .... We must not confuse safety with Russian roulette.

It's also vital to understand the limitations of the test, in order to design a safe product, otherwise one is just designing something to pass a test, not be safe. The same is true with car emissions tests.

Absolutely non sense 

If insulation passed a High Pot test of 4240Vdc, we can be sure that it is safe and that there is no risk of insulation failure between primary and secondary with only 230Vac (325Vpeak).

[Zero999]

We don't know whether it has been high voltage tested or not and even if it hasn't, it still might be safe.

Safety is not a lottery...

Your security conception is completely false ... and you continue in your mistakes.

Not long ago, you said that the Hi Pot tests were not mandatory and now you claim that a device can be considered as safe even if it has not passed the hi pot test ....

I didn't say it's safe, just that you can't be certain it isn't safe. Was a learner driver unsafe the morning before they passed their driving test? Passing the test is just a legal requirement. I agree, there's a sound reason for the test, but it doesn't make it perfect.

No at all, if a device has not passed the mandatory tests, it is not safe even if nobody has been electrocuted .... We must not confuse safety with Russian roulette.

I see your point. I don't blame you for erring on the side of caution and believing something is not safe, until tested, but I'm certain I take bigger risks in every day life, than using a switched mode power supply, which might not have been tested, so it wouldn't bother me personally. Everyone has a different idea of what level of risk they're prepared to take. At least now the original poster, if they're still here, has some idea of the level of risk they might be taking.

It's also vital to understand the limitations of the test, in order to design a safe product, otherwise one is just designing something to pass a test, not be safe. The same is true with car emissions tests.

Absolutely non sense 

If insulation passed a High Pot test of 4240Vdc, we can be sure that it is safe and that there is no risk of insulation failure between primary and secondary with only 230Vac (325Vpeak).

No. Passing the test, just means it can withstand that voltage at that point in time. It doesn't mean it's of mechanically sound construction and will continue to do so, in the future, or under all operating conditions. Suppose the insulation isn't adequately rated to withstand the nominal operating temperature, due to a bad design, or a faulty batch of tape? The power supply may pass the high potential test, when cold, but when it heats up, the insulation would melt, potentially shorting the primary winding to the secondary.

You still fail to understand the limits of the high potential test and that it's not perfect. There are plenty of other possible reasons why the device may pass a certain test in the laboratory, then fail it later. This is why it took a lot to convince me, that the high potential test, is a legal requirement in the first place. It may be a legal requirement but that doesn't mean it will prove the device is safe.

[madires]

Just a simple question: how many consumers got a Hi Pot tester, know how to use it and test every device? Based on the arguments stated several times we would have to assume that any device is unsafe until proven by a Hi Pot test. The reality is that consumers have to trust fancy certification labels and laws. And we've all seen wall warts with nasty surprises despite several certification labels printed on the enclosure. In theory every wall wart should be Hi Pot tested, in reality they aren't. And it's also reality that we have far more fatal traffic accidents than fatalities caused by poor wall warts.

[Zero999]

Just a simple question: how many consumers got a Hi Pot tester, know how to use it and test every device? Based on the arguments stated several times we would have to assume that any device is unsafe until proven by a Hi Pot test. The reality is that consumers have to trust fancy certification labels and laws. And we've all seen wall warts with nasty surprises despite several certification labels printed on the enclosure. In theory every wall wart should be Hi Pot tested, in reality they aren't. And it's also reality that we have far more fatal traffic accidents than fatalities caused by poor wall warts.

I agree. In this case, it would certainly pass non-destructive visual inspection. It seems to be of sound mechanical construction, with adequate creepage and clearances on the PCB. It has a common mode choke, a Y-capacitor and a ferrite bead. All indicative of a fair effort at both safety and EMC compliance.

No special equipment is necessary to test that it's safe. All that's needed is a multimeter and a 10k resistor. Plug the PSU in to the mains, connect a 10k resistor between one of the  the output conductors (either + or -) and mains earth and measure the voltage across the resistor. The maximum allowable current is 0.25mA, which means the voltage across the resistor should be below 2.5V. Check both + and - conductors, on AC and DC ranges. If the resistor gets hot or the voltage is higher than 2.5V, then you have a dangerous power supply, which shouldn't be used.

[oldway]

How can you compare a technical problem (a hi pot test) and an human problem (an unsafe driver learner) .... nothing to do ... comparing apples and pears is wrong and a proof of lack of rigor of reasoning.

Is a test perfect? no, but it is considered sufficient ...

Is it really?
It is not up to us to decide ...... but standarts have scope of law for the quality control and it is mandatory to respect them.

Anyone who does not respect them becomes criminally responsible in the event of an accident, at least in Europe.

Something is not safe until it is prooven that it is safe and not the opposite!

You play with the lives of other people, comparison with car accidents is not acceptable ....

In Europe, the principle of accepting a victim on 5000 or 10,000 chargers sold is not acceptable (it seems that in China, yes) .... There can not be victims, not one!

All European countries have a penal code that punishes with jail assaults and killings, even through negligence (not carrying out the imposed tests is a negligence)

The hypotheses of melted insulation and others are absurd ..... The hig pot test is not the only test imposed by the standarts ..... if there was a fault such as transformer would heat to the point of melting the insulation, the first fault would be the short circuit between coils and layers, which would cause to blow up the Mosfet and the input fuse.

No special equipment is necessary to test that it's safe. All that's needed is a multimeter and a 10k resistor. Plug the PSU in to the mains, connect a 10k resistor between one of the  the output conductors (either + or -) and mains earth and measure the voltage across the resistor. The maximum allowable current is 0.25mA, which means the voltage across the resistor should be below 2.5V. Check both + and - conductors, on AC and DC ranges. If the resistor gets hot or the voltage is higher than 2.5V, then you have a dangerous power supply, which shouldn't be used.

No sense .... how can you ensure that the insulation resists transient network overvoltages without doing a Hi-Pot test?

[Zero999]

Is a test perfect? no, but it is considered sufficient ...

No, the test alone is not sufficient. It's just something which must be done because the law says so.

Is it really?
It is not up to us to decide ...... but standarts have scope of law for the quality control and it is mandatory to respect them.

Anyone who does not respect them becomes criminally responsible in the event of an accident, at least in Europe.

Something is not safe until it is prooven that it is safe and not the opposite!

You play with the lives of other people, comparison with car accidents is not acceptable ....

In Europe, the principle of accepting a victim on 5000 or 10,000 chargers sold is not acceptable (it seems that in China, yes) .... There can not be victims, not one!

All European countries have a penal code that punishes with jail assaults and killings, even through negligence (not carrying out the imposed tests is a negligence)

I agree, which is why one shouldn't rely on these tests as the only way to ensure the product is safe.

The hypotheses of melted insulation and others are absurd ..... The hig pot test is not the only test imposed by the standarts ..... if there was a fault such as transformer would heat to the point of melting the insulation, the first fault would be the short circuit between coils and layers, which would cause to blow up the Mosfet and the input fuse.

Melted insulation is a possibility and the fuse could be on the neutral line, if it has a crappy non-polarised EU plug. The PSU would go dead and possibly the user too. Melted insulation was just an example. There are other possibilities: a weak coil former, crappy soldering, poor PCB mechanical support and an unearthed metal enclosure. The tests can't catch everything and will certainly not detect poor/unsafe design/manufacturing. The tests should supplement existing quality assurance measures. They're not a replacement and cannot guarantee the design is safe.

No special equipment is necessary to test that it's safe. All that's needed is a multimeter and a 10k resistor. Plug the PSU in to the mains, connect a 10k resistor between one of the  the output conductors (either + or -) and mains earth and measure the voltage across the resistor. The maximum allowable current is 0.25mA, which means the voltage across the resistor should be below 2.5V. Check both + and - conductors, on AC and DC ranges. If the resistor gets hot or the voltage is higher than 2.5V, then you have a dangerous power supply, which shouldn't be used.

No sense .... how can you ensure that the insulation resists transient network overvoltages without doing a Hi-Pot test?

Yes, it won't test for a transient over voltage but it's "good enough" in a domestic situation and it passes all the basic visual inspection criteria: creapage, clearances, build quality etc. It certainly reduces the level of risk further. I think we forget the scope of this thread is, assisting someone to determine whether their switched mode power supply is safe, not compliance testing in a factory.

[oldway]

I agree, which is why one shouldn't rely on these tests as the only way to ensure the product is safe.

Hi Pot is not the only test to check if the product is safe, I have said this several times...but it has by far the highest priority among all of the electrical safety tests.

...Melted insulation is a possibility and the fuse could be on the neutral line, if it has a crappy non-polarised EU plug. The PSU would go dead and possibly the user too.

If the power supply stop to work, temperature stop increasing and will not be high enough to melt thicker and reforced insulation between primary and secondary.

There are other possibilities: a weak coil former (Not possible, would not pass the Hi Pot test), crappy soldering (nothing to do with insulation prmary/secondary), poor PCB mechanical support (nothing to do with insulation primary/secondary) and an unearthed metal enclosure ( this only apply to class I devices...continuity of hearting must also be tested, it is also mandatory. The present charger is a class II device, not a class I ). The tests can't catch everything and will certainly not detect poor/unsafe design/manufacturing. (poor design and unsafe design are totally different things...Standarts have a lot of details about good design, but a bad design is not necessary an unsafe design... The electric test as hi_Pot are basic and mandatory to ensure safety of the user.)The tests should supplement existing quality assurance measures. They're not a replacement and cannot guarantee the design is safe (did you even worked in an industry ? A new product is developped by engineering, a prototype is done, tested, modified, a pre-production is made, eventually some minor modifications are done, the design is then approved, and the production start...the quality control only test the units manufactured to verify if they comply with standarts and with the internal procedure of controls and tests)

......
Yes, it won't test for a transient over voltage but it's "good enough" in a domestic situation ( good enough is to pass the HI-Pot test, nothing other is legally allowed...Standarts are mandatory, if it has not passed through the hig Pot test, it can't be declared beeing safe...) and it passes all the basic visual inspection: creapage clearances (impossible to verify the ferrite transformer only by visual inspection) . It certainly reduces the level of risk further. I think we forget the scope of this thread is, assisting someone to determine whether their switched mode power supply is safe, not compliance testing in a factory.

Every switched mode supply must pass the High Pot test.
Class I power supplies (with earthed secondary) must pass the High Pot test at 2120Vdc between primary and (earthed ) secondary, class II (dubbel insulation) power supplies must pass the test with 4240Vdc....for power supplies with secondary not earthed, this test is absolutely essential for the safety of the user !!!
This test must be executed at the factory.
The problem is that, with no name or unknown name products,  there is no way to be sure that this test  has really been made or not....
For this reason, all brands fake or no name must be considered as not safe, you buy and use it at your own risks.
Don't risk your life, buy good quality products from a well known brand, not crap devices as this charger.

[oldway]

It's common to only do HiPot testing during design and certification phase on the entire power supply.
Then, only safety critical parts need to be tested in production, not the power supply itself.
That's to say, if a PSU with UL certified design uses safety rated PCB (with UL number on it), safety rated optocoupler, safety rated X/Y caps, safety rated fuse and safety rated transformer, then it should be allowed to bear NRTL which is has been certified for.
Also, to bear an NRTL logo, the actual OEM factory must be routinely inspected by an NRTL agency, such as UL. ISO9001 doesn't exempt a factory from NRTL factory inspection.
Since usually transformers are made in house by PSU manufacturers, you will usually see a HiPot pass label on it, but that's usually HiPot for transformer itself, not the entire PSU.
I believe some specialty PSUs, such as medical ones, require 100% individual HiPot test, but I don't think consumer PSUs must be tested individually.

If , as you said, all parts and pcb are safety rated, the transformer is High Pot tested, there is no necessity to High Pot test the entire PSU....but you speak about OEM factory , not really the kind of factory who manufactured this piece of crap you see on the pictures of this topic....
You can be sure nothing is certified, the components are of lowest quality and cost possible, the transformer has never been High Pot tested.....It can't be safe.....It only don't kill many people because not every electric chock kill you and because we have a 30mA earth fault current circuit breaker.

[Zero999]

I agree, which is why one shouldn't rely on these tests as the only way to ensure the product is safe.

Hi Pot is not the only test to check if the product is safe, I have said this several times...but it has by far the highest priority among all of the electrical safety tests.

...Melted insulation is a possibility and the fuse could be on the neutral line, if it has a crappy non-polarised EU plug. The PSU would go dead and possibly the user too.

If the power supply stop to work, temperature stop increasing and will not be high enough to melt thicker and reforced insulation between primary and secondary.

There are other possibilities: a weak coil former (Not possible, would not pass the Hi Pot test), crappy soldering (nothing to do with insulation prmary/secondary), poor PCB mechanical support (nothing to do with insulation primary/secondary) and an unearthed metal enclosure ( this only apply to class I devices...continuity of hearting must also be tested, it is also mandatory. The present charger is a class II device, not a class I ). The tests can't catch everything and will certainly not detect poor/unsafe design/manufacturing. (poor design and unsafe design are totally different things...Standarts have a lot of details about good design, but a bad design is not necessary an unsafe design... The electric test as hi_Pot are basic and mandatory to ensure safety of the user.)The tests should supplement existing quality assurance measures. They're not a replacement and cannot guarantee the design is safe (did you even worked in an industry ? A new product is developped by engineering, a prototype is done, tested, modified, a pre-production is made, eventually some minor modifications are done, the design is then approved, and the production start...the quality control only test the units manufactured to verify if they comply with standarts and with the internal procedure of controls and tests)

......
Yes, it won't test for a transient over voltage but it's "good enough" in a domestic situation ( good enough is to pass the HI-Pot test, nothing other is legally allowed...Standarts are mandatory, if it has not passed through the hig Pot test, it can't be declared beeing safe...) and it passes all the basic visual inspection: creapage clearances (impossible to verify the ferrite transformer only by visual inspection) . It certainly reduces the level of risk further. I think we forget the scope of this thread is, assisting someone to determine whether their switched mode power supply is safe, not compliance testing in a factory.

Every switched mode supply must pass the High Pot test.
Class I power supplies (with earthed secondary) must pass the High Pot test at 2120Vdc between primary and (earthed ) secondary, class II (dubbel insulation) power supplies must pass the test with 4240Vdc....for power supplies with secondary not earthed, this test is absolutely essential for the safety of the user !!!
This test must be executed at the factory.
The problem is that, with no name or unknown name products,  there is no way to be sure that this test  has really been made or not....
For this reason, all brands fake or no name must be considered as not safe, you buy and use it at your own risks.
Don't risk your life, buy good quality products from a well known brand, not crap devices as this charger.

Class II appliances can have a metal case you know!

Appliances should still remain safe, even if they're no longer functional, so a failure of the insulation due to overheating, will still leave the device in an unsafe state. Whether it's functional or not, is immaterial.

Insulating materials can be mechanically weak and brittle, yet still hold off the required voltage, until subject to vibration or heat. Weak solder joints can break, allowing loose wires/components to come into contact with things they shouldn't. If the enclosure isn't adequately fastened together, it can come apart, leaving the user exposed to live parts.

Electrical tests will not catch any of the above! Please don't imply they can.

It's common to only do HiPot testing during design and certification phase on the entire power supply.
Then, only safety critical parts need to be tested in production, not the power supply itself.
That's to say, if a PSU with UL certified design uses safety rated PCB (with UL number on it), safety rated optocoupler, safety rated X/Y caps, safety rated fuse and safety rated transformer, then it should be allowed to bear NRTL which is has been certified for.
Also, to bear an NRTL logo, the actual OEM factory must be routinely inspected by an NRTL agency, such as UL. ISO9001 doesn't exempt a factory from NRTL factory inspection.
Since usually transformers are made in house by PSU manufacturers, you will usually see a HiPot pass label on it, but that's usually HiPot for transformer itself, not the entire PSU.
I believe some specialty PSUs, such as medical ones, require 100% individual HiPot test, but I don't think consumer PSUs must be tested individually.

Thanks, that makes much more sense.

If , as you said, all parts and pcb are safety rated, the transformer is High Pot tested, there is no necessity to High Pot test the entire PSU....but you speak about OEM factory , not really the kind of factory who manufactured this piece of crap you see on the pictures of this topic....
You can be sure nothing is certified, the components are of lowest quality and cost possible, the transformer has never been High Pot tested.....It can't be safe.....It only don't kill many people because not every electric chock kill you and because we have a 30mA earth fault current circuit breaker.

How do you know this is the case with the original poster's SMPS? All they posted was a picture of a PCB. It might have gone through all the necessary tests or it might not have. Just because something has a marking to say it's been tested, it doesn't mean it has. Brand isn't always a reliable indicator these days.

There are different levels of risk. Forget the law for a second. The original poster is not getting this power supply mas produced. They just want to be 99% sure it won't kill them. By looking at the inside and doing a visual inspection, they've already lowered the risk somewhat. A basic electrical test, such as the one I mentioned above, would lower the risk further, even though it may not be stringent enough to satisfy the legal requirements.

[oldway]

Class II appliances can have a metal case you know!

Yes indeed, class II (double insulation) does not require a safety connection to electrical earth (ground) of metal case, if any. Safety is usually achieved by having at least two layers of insulating material between live parts and the user, or by using reinforced insulation.
With reinforced insulation is choosed, no need of earth connection of the metal case.

Hi Pot is a test made on NEW or REPAIRED devices, it is a punctual test, not a safety warranty against abuses as transformers used in humid and salty atmosphere, transformers that have fallen,....
In normal use that meets the manufacturer's technical specifications, there can be no degradation of the insulation, except normal ones due to aging.
You are inventing something stupid that borders on ridicule.

Weak solder joints can break, allowing loose wires/components to come into contact with things they shouldn't.

Not possible, there is a physical separation (distance) between the primary and the secondary circuits...If it would come in contact with "things they shouldn't", it could only be "things" of the same circuit, not a safety concern.

If the enclosure isn't adequately fastened together, it can come apart, leaving the user exposed to live parts.

And the user will turn on the open device because he has not noticed that the device falls apart...you are kidding ?

How do you know this is the case with the original poster's SMPS?

Lowest tecnology possible, low quality components and PCB, no marking on transformer, no brand on PCB (RXZ does not seems to be any brand)....

There are different levels of risk. Forget the law for a second. The original poster is not getting this power supply mas produced. They just want to be 99% sure it won't kill them. By looking at the inside and doing a visual inspection, they've already lowered the risk somewhat. A basic electrical test, such as the one I mentioned above, would lower the risk further, even though it may not be stringent enough to satisfy the legal requirements.

We will never agree because your point of view is that of an amateur who knows nothing about quality control and who treats safety with lightness and unconsciousness, whereas I has been quality control manager (actually retired).
Sorry, but in a quality control department, a person like you has no place. More or less does not exist in quality control...It pass or it fails.....

[Zero999]

Class II appliances can have a metal case you know!

Yes indeed, class II (double insulation) does not require a safety connection to electrical earth (ground) of metal case, if any. Safety is usually achieved by having at least two layers of insulating material between live parts and the user, or by using reinforced insulation.
With reinforced insulation is choosed, no need of earth connection of the metal case.

Hi Pot is a test made on NEW or REPAIRED devices, it is a punctual test, not a safety warranty against abuses as transformers used in humid and salty atmosphere, transformers that have fallen,....
In normal use that meets the manufacturer's technical specifications, there can be no degradation of the insulation, except normal ones due to aging.
You are inventing something stupid that borders on ridicule.

Weak solder joints can break, allowing loose wires/components to come into contact with things they shouldn't.

Not possible, there is a physical separation (distance) between the primary and the secondary circuits...If it would come in contact with "things they shouldn't", it could only be "things" of the same circuit, not a safety concern.

It happens, I've seen it before and have had to repair a device, because the PCB support wasn't strong enough to stop live parts from touching the case, just because you've not seen it, it doesn't mean it never happens.

If the enclosure isn't adequately fastened together, it can come apart, leaving the user exposed to live parts.

And the user will turn on the open device because he has not noticed that the device falls apart...you are kidding ?

Yes, it happens. This is why we have portable appliance testing in the UK.

How do you know this is the case with the original poster's SMPS?

Lowest tecnology possible, low quality components and PCB, no marking on transformer, no brand on PCB (RXZ does not seems to be any brand)....

Then by that logic 99% of consumer grade power supplies aren't safe. Throw away your phone charger now!

There are different levels of risk. Forget the law for a second. The original poster is not getting this power supply mas produced. They just want to be 99% sure it won't kill them. By looking at the inside and doing a visual inspection, they've already lowered the risk somewhat. A basic electrical test, such as the one I mentioned above, would lower the risk further, even though it may not be stringent enough to satisfy the legal requirements.

We will never agree because your point of view is that of an amateur who knows nothing about quality control and who treats safety with lightness and unconsciousness, whereas I has been quality control manager (actually retired).
Sorry, but in a quality control department, a person like you has no place. More or less does not exist in quality control...It pass or it fails.....

Oh dear, you're one of those people who's so indoctrinated with procedure, they blindly follow it, without actually understanding its limitations or applying any critical thinking whatsoever: monkey see, monkey do. Clearly there's no point in attempting to have a rational discussion.

[wraper]

How do you know this is the case with the original poster's SMPS?

Lowest tecnology possible, low quality components and PCB, no marking on transformer, no brand on PCB (RXZ does not seems to be any brand)....

It's not even remotely lowest technology possible. Not that many PSUs have 2 layer PCBs to start with, and FR4 as such is not that common in PSUs. Secondly this PCB have SMT components with soldering of decent quality, which already puts it above most of the cheap PSUs.
For example, monitor PSU/inverter made by Delta, which is no way to be called a dodgy company. 1 layer, phenolic PCB. Technology used is on around the same level.