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Author Topic: brain storm an optimal human safety system for back line  (Read 97254 times)

Mike Sokol

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Re: brain storm an optimal human safety system for back line
« Reply #170 on: February 11, 2015, 12:52:18 pm »

In Australia we always have an active, neutral and earth at all receptacles (GPO’s) including light fittings. In the passed an earth was not required for all light fittings. 

The issues for us in OZ, other than the condition of the wiring includes; no RCD protection, a reversed active & earth, or a poor neutral connection at the switch board or infrastructure level.  While I have never seen a boot-leg earth I believe very occasionally it does happen.

In addition all electrical work must be done by a licensed electrician and they are required by law to issue a certificate of electrical compliance for the work they do.

The problem in the USA is that electrical wiring is "grandfathered" and doesn't require an upgrade to code unless you're doing major renovation. So my 1923 house still has a lot of K&T (Knob & Tube) wiring which I'm replacing as we renovate each room. And there's a ton of Big Box stores (Home Depot and Lowes, etc...) that will sell anything to anybody, electrician or not. So anyone here can walk into a Home Depot store and buy a service panel, breakers, entrance wire, receptacles, GFCI's and anything else they like. And while local codes may requre a licensed electrician if there's going to be an inspection, most of time it's some DIY guy working on things with no formal training. And certainly, even licensed electricians make mistakes as well, even though they're supposed to know better. The USA still has a lot the original electrical distro systems we developed in the early part of the 20th century, while many other countries started wiring much later. We just hate to throw away our mistakes.     
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Stephen Swaffer

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Re: brain storm an optimal human safety system for back line
« Reply #171 on: February 11, 2015, 04:57:10 pm »

If everything is from three phase and derived from the same generation source can you detect an inverted active neutral by phase?  Eg correctly wired will all be at 0deg, 120deg, 240deg while inverted wiring will be at another phase angle.

Doesn't help if they are all wired inverted.

If multiple phases are available, that is simply a voltage check-phase to phase V is always higher than phase to neutral.

Not only grandfathering is an issue, but up until about 10 years ago there were no licensing/inspection requirements in most of my service area.  I come across major code violations created by electricians that are of relatively recent install.  The inspection process is also a teaching process at times.

While we don't have "certificates of compliance", the permit (issued to the contractor responsible) along with an inspectors approval serves as the same legally.
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Steve Swaffer

Jonathan Johnson

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Re: brain storm an optimal human safety system for back line
« Reply #172 on: February 11, 2015, 07:04:19 pm »

The USA still has a lot the original electrical distro systems we developed in the early part of the 20th century, while many other countries started wiring much later. We just hate to throw away our mistakes.   

Hence, things like "stinger caps," non-polarized plugs, and the general reason for this thread. If everything that's not double-insulated was in fact grounded, and grounded according to modern electrical standards, there would be almost no need for this thread. But it's not. So we're left with finding a way to make something that's inherently unsafe, safe. Without modifying the tone.
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Peter Morris

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Re: brain storm an optimal human safety system for back line
« Reply #173 on: February 11, 2015, 10:14:30 pm »

The problem in the USA is that electrical wiring is "grandfathered" and doesn't require an upgrade to code unless you're doing major renovation. So my 1923 house still has a lot of K&T (Knob & Tube) wiring which I'm replacing as we renovate each room. And there's a ton of Big Box stores (Home Depot and Lowes, etc...) that will sell anything to anybody, electrician or not. So anyone here can walk into a Home Depot store and buy a service panel, breakers, entrance wire, receptacles, GFCI's and anything else they like. And while local codes may requre a licensed electrician if there's going to be an inspection, most of time it's some DIY guy working on things with no formal training. And certainly, even licensed electricians make mistakes as well, even though they're supposed to know better. The USA still has a lot the original electrical distro systems we developed in the early part of the 20th century, while many other countries started wiring much later. We just hate to throw away our mistakes.   

Its similar in Australia – existing wiring can remain but all new wiring and modifications need to be done to the new / current standards. There can often be a knock on effect and a small addition can cause a major switchboard upgrade.

It’s generally not possible to get a new or reconnected supply from the network unless an electrician has signed off that the installation is safe.
Wiring standards are also reasonably consistent across the whole country.

You can also buy DIY parts, but most people use electricians.  I suspect the additional dangers associated with 230V as opposed to 110V may have something to do with it; 230 volts tends not to be very forgiving.
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Peter Morris

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Re: brain storm an optimal human safety system for back line
« Reply #174 on: February 13, 2015, 02:09:25 am »

OK, here is my suggestion for what its worth. :-\

An RCD (GFCI) that is subject to two things-

1)   The logic of these simple neon power-point testers
2)   The RCD must be turned on to provide power.  This is done by a touch switch that also checks that the “hot” is connect correctly.

The only issue is - if the power drops off it will not reset when the power turns back on. Maybe you can build some smart logic involving time, or  make the touch test so its only needed to switch on again if it has been switched off or unplugged.

« Last Edit: February 13, 2015, 05:20:52 am by Peter Morris »
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Peter Morris

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Re: brain storm an optimal human safety system for back line
« Reply #175 on: February 13, 2015, 05:13:09 am »

OK, here is my suggestion for what its worth. :-\

An RCD (GFCI) that is subject to two things-

1)   The logic of these simple neon power-point testers
2)   The RCD must be turned on to provide power.  This is done by a touch switch that also checks that the “hot” is connect correctly.

The only issue is - if the power drops off it will not reset when the power turns back on. Maybe you can build some smart logic involving time, or  make the touch test so its only needed to switch on again if it has been switched off or unplugged.



Cheap version  $$$$ , but not complete protection - delete (2)
« Last Edit: February 13, 2015, 05:22:08 am by Peter Morris »
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #176 on: February 13, 2015, 09:50:30 am »

OK, here is my suggestion for what its worth. :-\

An RCD (GFCI) that is subject to two things-

1)   The logic of these simple neon power-point testers
2)   The RCD must be turned on to provide power.  This is done by a touch switch that also checks that the “hot” is connect correctly.

The only issue is - if the power drops off it will not reset when the power turns back on. Maybe you can build some smart logic involving time, or  make the touch test so its only needed to switch on again if it has been switched off or unplugged.

I like the concept...  8)  It might confuse some people if it doesn't turn on when they try while wearing gloves.

A charged up capacitor could keep it turned on during brief power outages, but not very long. I'd need to think about unintended consequences if an already on power drop gets unplugged and then plugged into a different outlet without properly vetting that second outlet. 

The safest way is to require manual resetting.  If you give users a way to cheat a safety system, they will...

 
JR
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frank kayser

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Re: brain storm an optimal human safety system for back line
« Reply #177 on: February 13, 2015, 11:16:46 am »


The safest way is to require manual resetting.  If you give users a way to cheat a safety system, they will...

JR
True that. :(
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #178 on: February 17, 2015, 01:23:10 pm »

Well my modified GFCI outlet drop is sitting in my friends shop, but he is slammed with NAMM orders and a recent ice storm so has been too busy to check it out yet.

I'm glad to see somebody in the MI business doing so well (go James). 

++++++++

I have given more thought to Peter's idea, and using the touch switch to turn on triacs sensing the difference between the (hot) line and environmental ground would in effect confirm that the line is actually hot, so neutral by definition can not be hot. This does not protect against ground being hot but it seems less likely.

The stinger cap in series with ground still seems like the ultimate solution and why complicate this with extra sense circuits? KISS just modify a standard GFCI if my friend's noise floor testing of the stinger cap approach proves satisfactory. 

JR
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John Roberts {JR}

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Re: brain storm an optimal human safety system for back line
« Reply #179 on: March 07, 2015, 10:16:32 am »

Got my parts in...  ;D

Since I still have my modified GFCI out on loan for testing, I need to build another GFCI + relay into a junction box. I have one GFCI outlet laying around I can use.

I need to experiment some with the ground current detector... I need to light up the LED input side of an opto-isolator with 1.2V or so... A few hundred ohm resistor in series with the ground lead should generate enough voltage to fire the opto (output imbalanced the GFCI) with only a few mA leakage in the ground lead.

I can use a few neon lamps to indicate 1- On power available/or off tripped 2- a neon lamp from input side neutral to output side neutral could light up is reverse polarity "and" GFCI tripped.

So the smart outlet will not automatically disconnect from RPBG drop, until it senses a few mA of current in the ground lead.

I guess I could add another opto-isolator between the input side neutral (that should be 0V) and output side neutral but I don't know if there is enough current there to trip the GFCI. 

JR
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