John Curl's Blowtorch preamplifier part II

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In the US, code allows the installation of a GFCI outlet in place of a 2-wire non-safety-grounded outlet in homes, bonding neutral wire to both neutral and safety on the outlet. Nuisance tripping is common and it's otherwise a pain, but might be a safer option than leaving the original.

I think the most important part of the Whitlock paper mentioned earlier is to connect all AC plugs into the same power distribution strip. Not mentioned but important for most modern home use is to connect the TV cable/satellite drop/antenna cable shield to the same strip. This is done automagically in the "lightning protection" strips incorporating F connectors, but if not included is easily added with a "grounding block". a short wire and a banana plug into safety ground of a spare outlet. Keeps all the ground loops right there and personal.

All good fortune,
Chris
 
Oh! I could not imagine that, sorry. Is-it because you run only 110V that your country take less precautions than us ? In France, all the power plugs are equipped with an earth plug, and there is GFCI ('differential') in the central board for each room plus one main for the house/apartment.

It's because our state and local governments don't force every homeowner to re-wire their homes. It's only if you do new construction or remodeling that you have to upgrade the electrical.

se
 
I still try to understand the negative consequences of such an inversion, while it it just the primary of the transformer's device, supposed to be isolated from the equipment ground. If the leakage is reduced, the danger too.

If it's the transformer's primary windings being swapped, there's no added danger, but that's not what was being discussed.

Thanks,
Chris
 
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Steve, don’t get upset :)

In many European countries the AC domestic receptacle/plug is by code of the Schuko type.
Schuko - Wikipedia, the free encyclopedia

With these, live and neutral can be on either pin at the consuming device. (Earth prong also is the first to engage and the last to disengage)

Distribution transformers on the utility network are not of the balance type with a center tap. They are 3 phase, either delta or star, so any phase is symmetrical to the single common neutral (return) line. Phase to neutral=230V/50Hz

Differential GFCI is mandatory (at least one on each distribution panel).

But as I said previously, not everyone reading these forums lives in Europe.

se
 
The current US National Electrical Code (NEC) requires GFI's in bathrooms, kitchens, laundry rooms (near water sources) and outdoors. It requires arc interrupting circuit breakers for just about all the others.

However the NEC is not law. It is a standard develop by the National Fire Protection Agency (Also not a law making body) and is used as a model to be adopted by the local municipalities.

Now what good practice and following code have to do with what is often found is quite different. You only have to comply with code in the areas where it applies on new construction or a substantial remodel. I have seen buildings where they tear everything down except one wall so they are only doing a remodel and do not have to comply with all the new codes! (Mostly building codes, the electrical code would require adherence.)
 
If it's the transformer's primary windings being swapped, there's no added danger, but that's not what was being discussed.
What was discussed ? Swapping the two AC wires of an equipment connected to the primary of the transformer (inside or outside of it) is not the same thing ?
I don't understand, really ! (Am-i suddenly crazy ?)
I proposed to dedicate a power distribution for this purpose, reserved for your audio system, with each plug referenced for one precise device, nothing else. If you prefer to do -it inside your device, it would more elegant, but what about guaranty ?
Notice that, if each of your audio parts is correctly manufactured, you will have nothing to invert, and, if not, you increase your security.
And if this is a DIY device, i wanted to warn people about the good AC sens of the primary transformer for less leakage when you wire-it.

Well, i suppose everything had been said on the subject now ?
 
What was discussed ? Swapping the two AC wires of an equipment connected to the primary of the transformer (inside or outside of it) is not the same thing ?
I don't understand, really ! (Am-i suddenly crazy ?)
I proposed to dedicate a power distribution for this purpose, reserved for your audio system, with each plug referenced for one precise device, nothing else. If you prefer to do -it inside your device, it would more elegant, but what about guaranty ?
Notice that, if each of your audio parts is correctly manufactured, you will have nothing to invert, and, if not, you increase your security.
And if this is a DIY device, i wanted to warn people about the good AC sens of the primary transformer for less leakage when you wire-it.

Well, i suppose everything had been said on the subject now ?

No it is not the same thing. The hot wire goes through the fuse, through the single pole power switch and into the transformer. If there is a short to ground the fuse will blow. If you swap the neutral outside the unit and you have the same short no fuse will blow.

Now if you have the correct wiring and there is a short from the neutral to ground, the power will only trip if there is a GFI, as some current that should be on the wrong wire. However if you put the hot lead in on the same wire then you are only protected by the main circuit breaker.
 
No it is not the same thing. The hot wire goes through the fuse, through the single pole power switch and into the transformer. If there is a short to ground the fuse will blow. If you swap the neutral outside the unit and you have the same short no fuse will blow.
Ok , i understand now. You are talking about a short circuit of the wire between the fuse and the primary of the transformer with the metallic enclosure of your device. Hum. Never seen that.
By habit, all AC wires inside an audio device have double isolation (sleeves), and connection protected by heat shrink sleeves, to minimize the service's risk, not ?
 
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When I teach firearms handling I begin and often repeat Colonel Jeff Cooper's four rules of firearm safety. They're chosen in such a way that if you violate only one and are lucky, nobody gets hurt. If you violate two at the same time, you're a serious risk and need some time for reflection. It's done this way because *everybody* will, at some time, violate one of the rules. We're all human. Electrical safety needs to be treated similarly - if one thing breaks still nobody gets hurt.

Thanks,
Chris
 
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US practice is different from EU practice for AC power. In some countried the power is not connected to ground on either terminal. Others, one end or even a center tap. This can lead to a lot of confusion. I had to deal with these issues with Surge suppressors for EU countries. Each EC country has its own rules, despite harmonization. Similar issues exist around the world. The only countries that duplicate US practice are Canada and Taiwan. The rest of the world is different in significant ways. And with power you can never assume anything.

The actual connection reality needs to be understood or there will be a lot of confusion in understanding the issues and context.
 
I'd bet the laws are more brought on by wire sales lobbys
than true safety concerns.
Each time i was powered off by my GFI (washing machine, toaster or coffee machine), means 1 time a year, i thank the ground wire.
Writing this, i realize it is mostly due to liquids inside electric devices. Or singers tuning their electric lamps from their baths (Claude Francois) :)

Oh, by the way, US is known as one of the country witch use the most electrical power by citizen: How can they manage such power with 110V only ?
 
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Another thing to consider- many products, especially newer ones, will have an AC line filter that will swamp and leakage from the transformer to the chassis. On those products the chassis will be at 1/2 the line voltage is the ground is disconnected (depending on the "match" of the caps). There are UL rules on leakage that limit the size of the caps.

GFCI's can be a good idea but using one for a whole house runs the risk of shutting the house down (darkness) in the middle of the night. I think local GFCI's make more sense.

Grounding is a safety issue, not a noise thing. Depending on a ground from the power network will not help reduce noise. Its not unusual to see 2-3V of noise between ground and neutral in the US and the two wires are large gauge and tied together not too far away (100') from the outlet.

Most of the rules exist because someone wound up dead or a large fire happened. They are not means for greedy companies to sell stuff (we Americans are just too cynical).
 
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Each time i was powered off by my GFI (washing machine, toaster or coffee machine), means 1 time a year, i thank the ground wire.
Writing this, i realize it is mostly due to liquids inside electric devices. Or singers tuning their electric lamps from their baths (Claude Francois) :)

Oh, by the way, US is known as one of the country witch use the most electrical power by citizen: How can they manage such power with 110V only ?

GFCI's work by sensing imbalance in the current going into the load. No ground connection is necessary for them to work.

The US has a huge power infrastructure to support our growing (excessive?) need for power. We pay for it. Some times excessively, remember Enron? California is still paying for that adventure.
 
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I still try to understand the negative consequences of such an inversion, while it it just the primary of the transformer's device, supposed to be isolated from the equipment ground. If the leakage is reduced, the danger too ?

There is no harm if just swapping at the transformer's primary attachment/leads. The leakage comes from EI windings' C to its own core and grounded/mounted directly to chassis... and from transformers field coupling into chassis. Swapping wires causes the C to transformer core to change (often lowered)... depends on winding construction and symmetry. Toroids limit both leakage means as they are easily insulated from the chassis they are mounted to and have low radiated fields. -RNM
 
Each time i was powered off by my GFI (washing machine, toaster or coffee machine), means 1 time a year, i thank the ground wire.
Writing this, i realize it is mostly due to liquids inside electric devices. Or singers tuning their electric lamps from their baths (Claude Francois) :)

Oh, by the way, US is known as one of the country witch use the most electrical power by citizen: How can they manage such power with 110V only ?

We have an 11kV step down about 30' from the main box. Virtually all homes get 220 in two phases and all very large appliances run directly on it.
 
GFCI's work by sensing imbalance in the current going into the load. No ground connection is necessary for them to work.
When there is a liquid, by example, making contact between one AC wire and the metallic enclosure of an electric device, connected to a ground wire, the current will flow immediately to the earth and the differential will see the > 30mA imbalance and cut the two ACs. And with a very good efficiency, because the ground wire is low impedance. no need for you to touch anything.

If no ground wire, it is your body that will create the imbalance, while the current flows across the metallic enclosure then your body then the earth of your floor. And you do not like-it.

Thanks Scott and Demian for your explanations.
 
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C core are better, because there is no (or very little) capacitance between primary and secondary, so no HF injection from the AC, if the core is not conductive (ceramic), and the HF will be send to the ground of the core are conductive and screwed to the enclosure.
I wonder why they are so rare and expensive.
Toroidal could be very good against HF injection if a shield is between primary and secondary, and primary wound first, but it is not often the case. They present a big contact surface between primary and secondary coils,
 
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