Connecting grounded, mains supplied scope to the output of the audio system changes operating conditions of the system and usually shows false results. Battery operated scope should be used or at least isolating transformer with lowest possible coupling capacitance.
I have been informed that I was not clear enough as to what/who triggered me to make reference to Rule 3, note 2. My apologies for that.
The reason I mentioned the Rule was for warning against not posting potentially dangerous practices (intentionally shorting audio equipment fuses in this case) and the offending posts were:
John Curl's Blowtorch preamplifier part III
John Curl's Blowtorch preamplifier part III
Mention of practices deviating from local electric codes and safety standards is not to be posted without consideration of the responsibility each one of us bears toward every potential reader with unknown technical background.
As of now, another potentially dangerous practice has appeared here.
John Curl's Blowtorch preamplifier part III
George
George, the MEN arrangement is intact and as per code except that the MEN wire link is replaced by a seriously heavy duty inductor.
I see no hazards during normal operation, perhaps you might like to explain any such hazard as you see it ?.
Dan.
I see no hazards during normal operation, perhaps you might like to explain any such hazard as you see it ?.
Dan.
So, are the main breaker fuses a potential power loss too...?
They are upgrading the 11kV overhead cables here to a thicker gauge, so I should hear that difference...
They are upgrading the 11kV overhead cables here to a thicker gauge, so I should hear that difference...
I found measurement of resistance of my START1 circuit (2 fuses there) used in this scope measurements posted here
John Curl's Blowtorch preamplifier part III
and it was 0.105 ohm. I think all these current considerations on fuse or home breaker resistance make not much sense. Do not forget to consider home mains wiring impedance as well 😉. Usual audiophile incompetent blabla.
John Curl's Blowtorch preamplifier part III
and it was 0.105 ohm. I think all these current considerations on fuse or home breaker resistance make not much sense. Do not forget to consider home mains wiring impedance as well 😉. Usual audiophile incompetent blabla.
I know that if you connect 1kW amplifier to a single phase US/Japanese 100-110V mains you get reduced maximum power because of impedance losses. However, an instrument like this should not be designed for a single-phase 100V input, use 3phase then, or make it single-phase only for a rational European standard, 230V. 100V system is crazy.
To all:
Placing a reactive element in series with the house bonding or grounding system is absolutely against code.
There are two very specific safety reasons reasons to NOT do that.
If you have to ask why it is dangerous, then you do not have the experience or knowledge to be performing that type of modification.
The relevant articles within NEC are bonding, and grounding. They are two different things.
Dan, I must apologize for the next request. Mods, please have his drawings either removed, or somehow flagged as dangerous and to not be done.
jn
John, this kind of request is of low impact. You have to go to the post and send this post to moderator's team with your explanation why you ask the post to be removed or moderated. There is an exclamation mark bottom left of every post (report post) that would let you to announce it to the mods.
😉
My concern is that the subtlety of the reasons not to do it may escape those who have never studied code. Even people one earth diameter away should not try to re-interpret code on a whim. Code is an evolving animal because some things are indeed quite subtle and have been developed as a result of tragedy.
jn
I just tried but I am not sure if the report was sent. So please try as well, John. I sent it with explanation that any impedance inserted into neutral or protective wire is a safety hazard and may lead to lethal injury.
Agreed. I waffle between having it completely removed and censured, or brought into the light as a very bad thing to do and avoid by anybody thinking of something like it.
As an aside, I have been slowly doing electrical work on a house built in the 60's give or take.
The owner (passed) did a lot of plumbing and electrical work in the basement.
He was a very good plumber..sigh..
A rats nest of romex, cable, telephone, doorbell, burglar alarm wires, mainly unsupported tie wrapped together, and in many cases tie wrapped to the hot water or heating pipes. Romex is 60C insulation, tied to a hot water pipe far exceeds that temp, leaving no headroom for actually running current. Two conductor cloth wrapped exiting the service panel, then going into a splice box where 3 conductor exits and runs to things that should be grounded such as appliances, duplex sockets... any metal appliance where a hot short to chassis could energize the chassis, and no bonding path to open the circuit breaker..
Oh, and quite a few 20 amp breakers with a 14 AWG connected directly at the breaker.
The worst so far, the #10-3 feeding the electric dryer, the white jacket at the clamp insertion is black for an inch outside the box...major overheat that needs looking into. I assume the wire is not aluminum, but haven't popped the cover yet.
If the breakers could be LOTO'd, I'd do so. meanwhile, I am using duct tape to cover breakers that really should not be energized, and putting labels on the panel to remind me which ones to leave off.
Edit: Oh and the water feed to the house is on the opposite side of the basement, there is a #4 AWG single from the panel to the water main feeding in. Good for bonding, but not so much for lightning protection. It is almost an upside down scheme Ala Martzloff.
One good thing I found there was a plastic bodied whole house filter inserted in the main feed, but a copper bypass with three valves was used so that the filter could be entirely bypassed to replace the filter. While convenient for the plumber, the copper continues the bonding of the house plumbing. I've seen these filters put in by homeowners without a bonding jumper to protect the occupants.
jn
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Hi Dan
Better consult a Safety Inspector first to make sure the scheme as well as the implementation doesn’t violate your local electric installation code.
I wouldn’t try to post alternative untested Earthing scheme for reasons of introducing potentially unsafe scenarios.
The way I see it ( don’t count on it, I am not qualified/certified for this), is that
-The impedance imposed by the choke will be high when a pulse of current will have to pass through it.
-Per your third attachment, John Curl's Blowtorch preamplifier part III
- the inductor is btn the incoming utility Neutral and the neutral connecting bar at the distribution box. It is not at the functional position of the MEN link as is shown in your first attachment. Am I wrong on this?
-as you show you have a two-conductor connection with the utility (Neutral and live). Wherever you place the inductor (either btn the incoming utility Neutral and the neutral connecting bar at the distribution box, or btn the neutral connecting bar at the distribution box and your local ground) you insert a component that impedes the pass of a current impulse, thus undermining the safety redundancy that the electrical system tries to ensure through the use of multiple low impedance earthing of the neutral conductor at the utility distribution poles and also through your local ground bar.
-In case the inductor is placed at the position of the MEN link the impedance btn the neutral connecting bar and the local earth rod is increased. Is there a code-specified upper impedance limit for this neutral-earth link? What waveform is used to measure it?
George
PS. jneutron and PMA have posted while I was writing the post, confirming my suspicion of an unsafe suggested scenario.
Timed out...
I have also noted that all the old single gang metal boxes used for splicing have not been bonded. If something happens such that hot accidentally contacts the box, the entire box can be energized. A simple example is where the homeowner over tightens the clamp such that the clamp metal cuts through the jacket and into the hot conductor. Clamps typically have two dimpled surfaces that push harder directly over hot and neutral, meaning 50/50 should someone over tighten Ala the hulk..
Now the boxes I purchase at the Depot have a dimped raised back area tapped #8, for use as a bonding connection. They also sell bonding pigtails, makes it easy to bond when using a blank cover. (if putting a duplex in... the grounding connection on the duplex frame, remove the paper screw holders so the the duplex frame is in direct contact so you are not relying on the screw to carry current.)
Edit: If one examines the breakers in a panel, modern breakers will have the noted fault current listed directly on the front. The breakers in my house for example, are rated 10 kilo amps bolted fault, meaning they are required to survive without a hull breach, fault currents of that level.
The main breaker panel will be rated significantly higher. 100 kilo amps is typical. (IIRC, the utility is not allowed to have residential feeds capable of bolted fault currents exceeding this, but commercial/industrial feeds do not have this restriction. As they replace transformers with higher efficiency ones, they could easily exceed the bolted fault ratings for equipment inside the building. Arc flash calculations always have to be recalculated after such changes.)
Inserting any element into the bonding circuit between the street and the house means that element could see fault currents far far higher than the continuous rating of the panel. Assuming that any inductor could survive that level of fault current is playing Russian roulette. Code requires the bonding system be good enough that any energized surface cannot exceed 50 volts during a fault prior to the interrupting element opening the circuit. Placing elements in series with the bonds does not guarantee that. The IIT rating of breakers in the magnetic regime allows significant currents for one or two cycles, even 15 amp breakers.
I also am wondering about soldering of any bonding element. Within code, it is illegal to rely on solder for any bonding connection for any equipment that could become energized by a hot fault to ground.. So what is solder doing there?
ps..in any case, always refer such work to a qualified electrician, as the subtleties can kill. Never trust online sources (such as myself) for advice on how to properly follow code..
jn
I have also noted that all the old single gang metal boxes used for splicing have not been bonded. If something happens such that hot accidentally contacts the box, the entire box can be energized. A simple example is where the homeowner over tightens the clamp such that the clamp metal cuts through the jacket and into the hot conductor. Clamps typically have two dimpled surfaces that push harder directly over hot and neutral, meaning 50/50 should someone over tighten Ala the hulk..
Now the boxes I purchase at the Depot have a dimped raised back area tapped #8, for use as a bonding connection. They also sell bonding pigtails, makes it easy to bond when using a blank cover. (if putting a duplex in... the grounding connection on the duplex frame, remove the paper screw holders so the the duplex frame is in direct contact so you are not relying on the screw to carry current.)
Edit: If one examines the breakers in a panel, modern breakers will have the noted fault current listed directly on the front. The breakers in my house for example, are rated 10 kilo amps bolted fault, meaning they are required to survive without a hull breach, fault currents of that level.
The main breaker panel will be rated significantly higher. 100 kilo amps is typical. (IIRC, the utility is not allowed to have residential feeds capable of bolted fault currents exceeding this, but commercial/industrial feeds do not have this restriction. As they replace transformers with higher efficiency ones, they could easily exceed the bolted fault ratings for equipment inside the building. Arc flash calculations always have to be recalculated after such changes.)
Inserting any element into the bonding circuit between the street and the house means that element could see fault currents far far higher than the continuous rating of the panel. Assuming that any inductor could survive that level of fault current is playing Russian roulette. Code requires the bonding system be good enough that any energized surface cannot exceed 50 volts during a fault prior to the interrupting element opening the circuit. Placing elements in series with the bonds does not guarantee that. The IIT rating of breakers in the magnetic regime allows significant currents for one or two cycles, even 15 amp breakers.
I also am wondering about soldering of any bonding element. Within code, it is illegal to rely on solder for any bonding connection for any equipment that could become energized by a hot fault to ground.. So what is solder doing there?
ps..in any case, always refer such work to a qualified electrician, as the subtleties can kill. Never trust online sources (such as myself) for advice on how to properly follow code..
jn
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JN,
60C is of course 140F so the insulation on the romex should be fine as long as you don't draw any current!
The first house I saw totally rewired had the original knife switch as a main breaker and fuse wire to each branch. Of course knob and tube for the lights. All original from when electricity was introduced.
My current house was completely stripped of all systems, heating, plumbing, electrical and insulation. Went from hot air to hot water heat, with allowance for a concealed duct system for air conditioning. 1/2" plumbing replaced with 3/4" and even installed a main shut off valve that never was there! Local utility nicely shut off the curb service for the day of change over. There is a ground jumper across the meter even though one of the AC ground connection is right at the building entrance. Other two grounds are to an old service entrance and ground rods.
All new electric wiring with conduit in the basement, cable tray in the basement to protect cables until they rise in the walls. Of course metal protection plates on all the studs. I also have a 24 VDC distribution for specialty LED lighting.
Breakers are GFCI or Arc interrupting depending on location. Biggest issue is that lack of proper size circuit breakers for the normal lighting circuits. 5 or even 3 amp units would be a better size! I use two circuits for house lighting so that if one circuit fails I will still have enough lights to get to the breaker panel.
BTY it was faster to just replace it all rather that clean it up.
60C is of course 140F so the insulation on the romex should be fine as long as you don't draw any current!
The first house I saw totally rewired had the original knife switch as a main breaker and fuse wire to each branch. Of course knob and tube for the lights. All original from when electricity was introduced.
My current house was completely stripped of all systems, heating, plumbing, electrical and insulation. Went from hot air to hot water heat, with allowance for a concealed duct system for air conditioning. 1/2" plumbing replaced with 3/4" and even installed a main shut off valve that never was there! Local utility nicely shut off the curb service for the day of change over. There is a ground jumper across the meter even though one of the AC ground connection is right at the building entrance. Other two grounds are to an old service entrance and ground rods.
All new electric wiring with conduit in the basement, cable tray in the basement to protect cables until they rise in the walls. Of course metal protection plates on all the studs. I also have a 24 VDC distribution for specialty LED lighting.
Breakers are GFCI or Arc interrupting depending on location. Biggest issue is that lack of proper size circuit breakers for the normal lighting circuits. 5 or even 3 amp units would be a better size! I use two circuits for house lighting so that if one circuit fails I will still have enough lights to get to the breaker panel.
BTY it was faster to just replace it all rather that clean it up.
There is a significant difference between an earthing system and a bonding system.
The earthing system is NOT designed to protect you in the event a hot to ground short occurs. It is only there for protection against lightning strikes.
The bonding system is designed to protect you in the event there is a fault between hot and ground, for example an electric stove or electric dryer.
If you are relying on an inductor in place of the "men link" thingy, you are relying on the inductor to support current faults on the order of up to 10 kilo amps (in the USA) before a breaker can trip magnetically. The dryer I am currently working on uses #10 wire, perhaps 15 feet long. If it failed internally, hot to frame, the fault current would go through your inductor back to feed neutral, and if that inductor opens, the circuit would not clear....the dryer frame would remain at hot potential. Since it is within 4 inches of the washer, a wife or love one may not survive touching both simultaneously.
I have a double oven at home, it has a 50 amp run...it's fault currents would be even higher.
As to how your code violating modifications sound, I do NOT care. I care about your well being, I care about the well being of any who would be unwise enough to duplicate what you propose.
NEC does not consider how something sounds when it comes to safety.
And the soldered ground thing you provided a picture of... I would not hesitate to issue a stop work order if I found that, and force a complete LOTO on your butt..😀 (Lock Out/Tag Out). It is a really bad violation of code.
Remember, this is not a simple disagreement between us over minuscule things. I am arguing about your safety.
jn
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I believe I said that...😉
Boy, you like living on the edge. I could just see myself breaking out the code book to explain to a residential inspector article 392. I would prefer to just do it such that he is comfortable with what he sees and expects to see. I assume you used aluminum. Did you use the #14 jumpers tray to tray? At work, we ran a #2 stranded bare copper along every tray, used clamps for all the bonds..
I hear you there. But I have a few years to do the house I'm working on now.
My personal home, I took every room to stud, insulated, wired, new windows, proper plumbing, rocked (hired a spackler as I don't do that well). Took seven years, but we were not in a hurry, preferred to live life.
jn
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