Really depends a lot on the class of insulation used in the transformer design.
I generally specify class B for my designs which is more than adequate for anything my transformers will encounter in normal use.
Ok, as far as I understand it thus far:
This all seems very wrong.
And it's completely impractical for the production of single units of custom-made gear.
Ok, here are two hypothetical examples to illustrate my situation:
From my personal perspective (i.e., not considering legal aspects), the two examples are very much the same: someone wants me to build his hifi gear, I do it, enjoy it, and get a little bit of money for it.
However, when it comes to safety compliance and the associated legal points, I believe these two examples describe two totally different situations. I am pretty sure I will be liable if either the DAC or the tube amp blow up and causes fire/damage or injury to someone. But I guess in case of the DAC I can argue that all units/parts were acquired new (and thus can be assumed safe) and that there were no dangerous voltages involved. With the tube amp, the old tubes/transformers/caps/etc. were (probably) not safety approved in any way, the hot and fragile tubes are exposed, and there are dangerous voltages involved.
In both cases, I didn't test or certify the gear for safety (because my customers won't pay for that), and there was no sticker or label on the boxes.
Going from such hypothetical examples to the real world, what are the options if I don't want to break the law and risk to loose my personal money / property if something goes wrong?
- There is no straight forward check list that I can tick off and be sure I checked everything required by law. I have to find out on my own which points to consider, and I have no way of being sure that I got everything covered.
- The specifics of the legal safety requirements for a product are written down in "standards". These standards are not freely accessible and cost a lot of money. So I have to pay money to "read the law". This seems very wrong to me, and I find it hard to believe. Just as an example, I didn't have to pay money to learn that we have right-hand traffic in the country I live.
- I have to go through (and buy!) all kinds standards (and other documents?), just to find out if there's anything of relevance for my situation. Most of the (expensive!) standards will be irrelevant.
This all seems very wrong.
And it's completely impractical for the production of single units of custom-made gear.
Ok, here are two hypothetical examples to illustrate my situation:
- Someone asks me to build a digital/analog converter with USB input and line-level output. I buy a completely finished USB-DAC board (running from +/-12VDC), put it in a box, hook it up to some USB and cinch connectors, and use an external wall wart for power supply. All units and parts are bought new, so I assume everything is "in agreement with the applicable laws". Once the DAC works smoothly I sell it to my customer.
- Someone asks me to build a beautiful tube amplifier using NOS parts (tubes, transformers, capacitors) that I have either in my own stash, are provided by the customer, or sourced from elsewhere (ebay, etc.). The amplifier chassis will have 'open' tubes (no cover or grille), and voltages in the chassis and at the tube sockets will be up to 450 VDC. The power supply is built into the chassis, which is hooked up to the mains outlet. Once the amplifier works without producing smoke or flashes, I sell it to my customer.
From my personal perspective (i.e., not considering legal aspects), the two examples are very much the same: someone wants me to build his hifi gear, I do it, enjoy it, and get a little bit of money for it.
However, when it comes to safety compliance and the associated legal points, I believe these two examples describe two totally different situations. I am pretty sure I will be liable if either the DAC or the tube amp blow up and causes fire/damage or injury to someone. But I guess in case of the DAC I can argue that all units/parts were acquired new (and thus can be assumed safe) and that there were no dangerous voltages involved. With the tube amp, the old tubes/transformers/caps/etc. were (probably) not safety approved in any way, the hot and fragile tubes are exposed, and there are dangerous voltages involved.
In both cases, I didn't test or certify the gear for safety (because my customers won't pay for that), and there was no sticker or label on the boxes.
Going from such hypothetical examples to the real world, what are the options if I don't want to break the law and risk to loose my personal money / property if something goes wrong?
Well you are wrong!
The two are not the same.
The PSU in the first example should be to the required spec for the country your client lives in and therefore only the dac would be an issue. If the supply is isolated then you only have the low voltage to consider + the possible grounding and any components or solder types.
The second example is a mares nest. The chances of contact from heat, voltage stored charge fire electric shock, fault clearance are different.
The product type is different and the hazards are different.
What you are saying is electrical equipment is electrical equipment and that's wrong! IT is based upon hazard type, contact hazard and equipment usage.
Its like saying a 12 Vdc computer has the same hazards as national grid they are both electrical systems.
Or that a CRT TV has the same hazards as laptop..one contains 25Kv + the other has a 19V DC supply which is double insulated.
I find it hard to believe you can't differentiate the hazard?
If the tubes are not caged and a child falls onto them they break and come into direct contact with 400V DC you seem to think this is the same as a broken case on a dac with a 24V supply?
The IP rating is also different, if a child can put their finger into valve equipment or a TV connected to the mans supply or a difference in potential that can cause death there is a very serious issue. The same is true of an inverter supply that creates high voltage..this is dependant on the current available under shock situation which is why you can have an electric fence in a field but other systems must be protected with barriers.
There is also an issue with stored charge and every chance of stored charge must be taken into account with discharge systems or warning labels explaining the hazard.
This is why the regulations exist, not to stop DIYers from making equipment. But to stop DIYers that could make dangerous equipment selling them to unwary untrained people.
Ie someone knocking together CRT Tvs in the back of a shed with no case and selling them...to be honest there would even be an issue with them giving them away!
NB I'm not saying this is in reference to yourself, just that its the answer to what you are asking. Ie why can't I just knock out some equipment and sell it.
Now here is another example..what about if you build a kit for someone? In theory if the kit is approved you should be OK right..wrong not if you earth it incorrectly or do a mod that could circumvent the safety of the equipment. If you build it exactly as stated then yes its OK. As long as it meets the regs in that country.
Regards
M. Gregg
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I think one should do a risk assessment.
What are the risks?
How likely are the risks?
What are the consequences to each of the risks?
As a designer/manufacturer one assesses all of these and applies a weighting based on knowledge on which risks are acceptable, which are reduced and which are eliminated.
eg, a risk that is very unlikely to happen AND has low value consequences could be ignored.
whereas a risk that has potentially fatal consequences AND is unlikely to happen cannot be ignored.
Simple things like mains fuses are there to prevent the house catching fire in event that there is a serious fault. Omitting that fuse or specifying the wrong fuse value is incompetent. One would be liable if there was an accident that became worse as a result of the fuse specification, or non-fitting, incompetence. That's why you see a fuse rating on commercial equipment.
BTW. that high risk, low likelyhood is one situation where I find that double insulated (ClassII) equipment with interconnects and exposed conductive parts could be fatal to a child putting one end in their mouth. It is very unlikely that the equipment could send a fatal voltage out to the end of the interconnect AND it is very unlikely that the child will suck on it while the equipment is faulty. BUT the consequence is dire. In my mind the risk is unacceptable, it cannot be ignored.
The double insulated prevents the fuse from blowing in the event of a catastrophic mains fault. The double insulated prevents an RCD detecting an Earth return current. But the equipment is still LIVE !
Yet manufacturers build and sell equipment like this NOW !
What are the risks?
How likely are the risks?
What are the consequences to each of the risks?
As a designer/manufacturer one assesses all of these and applies a weighting based on knowledge on which risks are acceptable, which are reduced and which are eliminated.
eg, a risk that is very unlikely to happen AND has low value consequences could be ignored.
whereas a risk that has potentially fatal consequences AND is unlikely to happen cannot be ignored.
Simple things like mains fuses are there to prevent the house catching fire in event that there is a serious fault. Omitting that fuse or specifying the wrong fuse value is incompetent. One would be liable if there was an accident that became worse as a result of the fuse specification, or non-fitting, incompetence. That's why you see a fuse rating on commercial equipment.
BTW. that high risk, low likelyhood is one situation where I find that double insulated (ClassII) equipment with interconnects and exposed conductive parts could be fatal to a child putting one end in their mouth. It is very unlikely that the equipment could send a fatal voltage out to the end of the interconnect AND it is very unlikely that the child will suck on it while the equipment is faulty. BUT the consequence is dire. In my mind the risk is unacceptable, it cannot be ignored.
The double insulated prevents the fuse from blowing in the event of a catastrophic mains fault. The double insulated prevents an RCD detecting an Earth return current. But the equipment is still LIVE !
Yet manufacturers build and sell equipment like this NOW !
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Doubled insulated does not mean something cant go wrong... it just means at least two things have to go wrong...
The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation.
The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having two layers of insulating material surrounding live parts or by using reinforced insulation.
M Gregg has answered quite eloquently... and I agree with a lot of his assessment...
The DAC is low voltage so no creepage and clearance worries or mains protection just EMC.
The valve amp, high voltage so creepage and clearance comes into play, mains protection and good earthing practice, thermal protection of exposed valves possibly and possibly EMC....
The regulations are complex and a nightmare go work through, but they do work and force companies to be responsible for their designs... and it is very rarely these days that we get major problems with electronics and safety. But when things do go wrong then the sh*t will hit the fan.
There is such a list and it's embedded in the relevant IEC (or equivalent depending on Country) spec, by the way that's what the certifying Lab uses.
Fully agree, it's absolutely ridiculous.
The flawed "logic" appears to be that since certification will cost way more than that, you shouldn't worry about paying a couple hundred $$ for "the book".
Absolutely stupid and in bad faith.
They should be freely available, at least as design/build guides for people to follow, even if they eventually don't certificate stuff, even if they build for themselves.
Crazy.
Basically yes.
Fully agree, and by the way it's not "practical" for single units or even small series production.
Don't ask why I say so 🙁
Forget it, it's low voltage/power/temperature stuff, the power brick is the part needing certification.
I already mentioned that, and the reason why stuff perfectly capable of having internal mains powered supplies, use a power brick instead.
By the way, once you certify a power supply, all units must use same parts and be built the same way.
Even if you "improve" it, you'll need to re-certify.
Ouch !!!!!!
You are on your own, period.
You are right in the emotional/economic sense ... what does it have to do with Electrical Security and Legal exposure is way beyond my understanding.
IF the DAC catches fire and burns a house or worse, you are in very hot water, no matter it's low voltage, you bought averything new, *even if it's certified* , because it's not a James Bond type "007" licence .
As an example, here in Argentina there was a famous (and Jurisprudence setting case) when a driver killed a guy and claimed "he had the green light and the dead guy had crossed the street against his red light" .
The Judhe famously answered: "the green light is not a licence to kill" , phrase which since entered the popular vocabulary .
I guess it may be worse in USA where it's more common to get sued for various reasons.
Just personal opinion, in the first case, you are liable only if the DAC catches fire, in the second, even if it does not, simply because you broke so many "Laws".
Compare it to driving "under the influence" , you will be charged even if you hit nobody ... yet.
The point is that the Law recognizes a big danger *potential* and acts accordingly.
Personally, as a small builder, as I think you are, I'm obsessive about making stuff safe, period, and am aware that I *can* be sued and in big trouble if anything really bad happens.
The liability protection is indirect, not through expensive certification which is out of reach for single/small production , but by making certain that no problems will develop.
I haven't read it, but this looks like a good investment for anyone thinking about selling stuff:
https://www.tindie.com/products/emc...-and-hardware-startups-2/?pt=full_prod_search
/U.
https://www.tindie.com/products/emc...-and-hardware-startups-2/?pt=full_prod_search
/U.
haha great story
unlike the game of Monopoly there is no 'get out of jail free card' even if you supply a cheap wall wart you must show due diligence to make sure it is a safe one, if something happens the lawyers WILL go after anyone and everyone full stop, and at the end of it all the Judge or Jury may decide to award damages / punishment as a percentage basis. If the wall wart is sourced from a noname mom and pop shop in HangDow PRC you can probably guess who will be left holding the bag> please check the safety markings if any and ask the same questions to any of those importers of famously cheap devices shipped out from Hong Kong. if you click buy and provide it or install it in yours or somebodys else's home it's all on you!
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That's why some transformers have a thermal fuse..😀
Its a great get out..another reason to use inrush suppression so you can fuse closer to running current..🙂
In theory even a valve cage should be Earthed and removable with a tool.
The idea that the equipment is then run without a cage is up to the user<<they have circumvented your safety.
People forget that if a manufacturer can get away with not paying for a cage they would and make more money.
Of course if you provide a power brick which is under spec for the equipment its another excuse to be blamed for the failure.
Its a shame because the ever increasing regs often put small companies out of business.
Regards
M. Gregg
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on small stuff it's just primary windings tiny gauge and the hot core just helps it get there faster. more concerning is the insulation and case materials flammability and such. besides most of these bricks are not simple linears anymore, they just blow up or go into some weird current limit routine AFIAK the worst case is often a bad (E.g. not very good) short circuit at the end of a cheap jack. Most of the safety testing is geared towards old school transformers and doesn't stress SMPS as best as they could.
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I remember,
many years ago seeing a kettle lead burn like the fuse on dynamite and never take out the plug fuse. Everyone laughed and said is that a 3/16 whit fuse?
But it was a 10A fuse and rubber cable. A bright blue flare that moved along the cable..really strange. We split the cable and had a look the insulation was burnt along the length but there was no short between the cores just carbon deposit. We took the cable off stock in the stores. It was just like something out of a cartoon I would never have believed it if I hadn't been standing there and seen it happen. Just like some weird firework..
Regards
M. Gregg
many years ago seeing a kettle lead burn like the fuse on dynamite and never take out the plug fuse. Everyone laughed and said is that a 3/16 whit fuse?
But it was a 10A fuse and rubber cable. A bright blue flare that moved along the cable..really strange. We split the cable and had a look the insulation was burnt along the length but there was no short between the cores just carbon deposit. We took the cable off stock in the stores. It was just like something out of a cartoon I would never have believed it if I hadn't been standing there and seen it happen. Just like some weird firework..
Regards
M. Gregg
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flame observed > I know UL rule or 1st criteria the safety testing is now over = FAIL
Of course I do see the difference, that's how I made up these two examples. It seems the irony in my words didn't get through.
(sidenote: the incompatibility of children with "open" tube amps made me switch from tubes to solid state amps when my first kid was born.)
The point I was trying to make: I just want to find a workable solution that allows me to build customized gear for others without breaking the law.
There is a scene in "The Money Pit" when the electrical wiring in the house self destructs that your comment reminds me of..
https://en.wikipedia.org/wiki/The_Money_Pit
Here is an article from Rane that would generally confirm your contentions:
www.rane.com/pdf/bewilder.pdf
I'm not a lawyer so consider all of this stuff anecdotal, and just the tip of the iceberg.
The audio amplifier standard is specifically IEC 60628-3:2013 which is the current version of the standard. (I have not seen the recent ones) This does not cover electrical safety - just performance. If you google you will find that withdrawn revisions of the standard are available for download, these have been superseded but may nonetheless be useful.
I believe the relevant safety standard is IEC 60065:2014, again if you search withdrawn revisions are available for download which should give you a good idea of the safety requirements a safe design should be able to meet.
Note that there are UL/CSA/BSA equivalent documents which you may also be able to find.
www.rane.com/pdf/bewilder.pdf
I'm not a lawyer so consider all of this stuff anecdotal, and just the tip of the iceberg.
The audio amplifier standard is specifically IEC 60628-3:2013 which is the current version of the standard. (I have not seen the recent ones) This does not cover electrical safety - just performance. If you google you will find that withdrawn revisions of the standard are available for download, these have been superseded but may nonetheless be useful.
I believe the relevant safety standard is IEC 60065:2014, again if you search withdrawn revisions are available for download which should give you a good idea of the safety requirements a safe design should be able to meet.
Note that there are UL/CSA/BSA equivalent documents which you may also be able to find.
Yes,
https://www.youtube.com/watch?v=VhrSzUm3zhU
But the appliance kept working after the burn up..
It was an American company a Hubbell plug with rubber cable..it burnt from the plug to the appliance. Never seen anything like it since and the appliance just kept running after the burn up. The fuse never blew it burnt about 3 feet.
NB note the use of water to put out the fire..in the video.
Regards
M. Gregg
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Remember those wire nuts we talked about?
https://www.youtube.com/watch?v=_2HyTRxzwXs
Regards
M. Gregg
https://www.youtube.com/watch?v=_2HyTRxzwXs
Regards
M. Gregg
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