Hope you don't have to go in front of the judge with all that paper work down the road. He'll have plenty to throw the book at you
Earth Loop Impedance Testing
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Speaking as somebody who grew up in Britain and spent years working with "straight" 240V, I really don't see as much of a problem here in the U.S. with 120V as seems to be commonly believed back in the U.K. Obviously voltage-drop concerns (and safe current-carrying capacity) necessitate larger conductors for a given load, but it's just a matter of scale. The biggest problem seems to be with things like people trying to run power tools with heavy start-up surges on very long, undersized extension cords. Plug your Skilsaw into a 100 ft. 18-gauge extension cord and you're bound to have trouble, just as can happen with people trying to use long 0.75 sq. mm extension leads for heavy loads in Britain or Ireland.
Remember that the heaviest loads in homes generally run on 240V anyway - The electric range, clothes dryer, large fixed heating and air conditioning units, etc. Admittedly the standard 120V general-use outlets do limit the power of portable heaters and similar appliances, but that's probably the most restrictive aspect of the system.
There was a time when the neutral was not considered to be a live conductor though. I think it changed with the 15th edition, or possibly a later revision.
"Hot" is something of a colloquialism. The NEC terminology refers to it as an ungrounded conductor, as opposed to a grounded conductor (which may or may not be a neutral in the true sense, which the NEC retained long after the IEE defined it as any earthed circuit conductor, regardless of whether it was carrying only imbalance current or not). Perhaps somewhat confusingly upon first reading, the NEC then uses the term grounding conductor to refer to a protective earth/ground wire.
Were main ELCB's (voltage or current types) ever used extensively in Ireland in the past? I know that these days ESB requires all new services to be wired as TN-C-S ("neutralizing" the earth system of the installation as they put it), but I don't know how far back that rule goes.
Yes, the specific resistance of copper is a little over 10 ohms per cmil-ft., but that does equate to 2.57 ohms/M ft. for #14 at 25 deg. C. (as per NEC tables).
120V x 3% = 3.6V
3.6V / 15A = 0.24 ohm maximum permissible resistance
0.24 / 2.57 x 1000 = 93 ft. approx.
But that's for both conductors. So half of that for the maximum cable length.
At 80 ft. you'd have over 5% voltage drop.
Try this ... The resistance is by per foot of length Ed=KIL/CSA
So to get L alone
Cross sectional area in cir mils x VD/KI
Table 8 NEC # 14 =4110 cir mils
4110x3/10.4x15=79.038 feet
Max VD@ 3%
You're using 3 in the formula instead of 3% of 120V which is 3.6V.
L = (CSA x Ed) / (K x I) = (4110 x 3.6) / (10.4 x 15) = 94.8 ft. approx.
That's close enough to my 93 ft. figure allowing for rounding and a very slightly different starting figure for resistivity. But that's the maximum length of the circuit as a whole, both conductors.
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Thanks for pointing that out the 3 versus the 3%
Not much bang for you buck running about 47' when you consider the Vd of a 14/2 circuit with 15amps at 120volts
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Where there has been a death the authorities clearly look at the paperwork. The Emma Shaw case details what was found and when reading such reports at least I consider my past work and wonder if my trust in colleges could every come back and bite me.
I did my apprenticeship at a time when we did as we were told. Attitude was if it goes wrong not my fault boss told me to do it which was clearly wrong. The taking of the IEE (now IET) regulation book and making it a British Standard also started a process of re-training where us old electricians had to go to college and get out "16 Edition" which for many was an eye opener. Until then ask the boss to see regulation book and you got "Why do you want that" and regulations were learn by rummer control often giving incorrect information as to what should be done.
There was also that them and us between boss and worker and we considered it was our job to take readings but their job to interpret those readings. Again wrong but it was the way we were taught, no way would you annoy the union if you got thrown out you lost your job. It was the Union who policed standards at that time.
In 1980 I went to work in Algeria and for first time saw the USA system of 110 volt. Only for around a month as most sites I worked on used generators and we worked to Dutch standards in the main. But what I quickly realised there was not a universal standard for USA system but many different systems and one really needed a volt meter. Algiers at the time used three phase 110 volt and often people would use 220 or 240 volt gear using two phases but that's only 190 volt not 220 volt as three phase. I am told USA today uses 120 volt which would give 207.5 volt phase to phase and also often they use split phase which would then give 240 phase to phase.
We in the UK also use split phase but we don't use anything phase to phase with a split phase supply so it's not a problem. Only with three phase do we connect phase to phase so we know all supplies 230 volt phase to neutral and 400 volt phase to phase and except for mines and quarries where 550 volt is still used we have one system for whole of Europe only the domestic plugs and sockets change country to country. Well maybe not quite true France does seem to use more split phase and cookers can use the split phase but each element is only 230 volt they don't use 460 volt elements.
Working on a Robins TBM I also came across the USA system. I really hated it. This was in Hong Kong supply was 11kV transformed down to 10kV for TBM and then to 660 volt for main motors and further down to 220 volt delta supply for the control circuits and lighting. Believe me working in a iron ore laden wet environment with 220 volt delta was shocking. Really good money but it needed to be it was a really dangerous job. Made worse as TBM was for a dry tunnel and it simply was not dry needed 3 x 10 inch pumps to keep water level down.
I would guess if brought up with the USA system you would develop methods to keep your self safe. I was glad when contract ended and I could return to UK and true British standards not the stretched standards used in HK.
As to Algeria that was not a problem. The ground was normally so dry you could touch live wires without getting a shock. Not that I did but we have to accept in the UK it is rare to need anything more than a single earth rod to get a RCD to trip when required. USA is a massive country and they get extremes we never see. Our 230 volt system works well for us but with a different climate you will likely need a different system. The great Serbian designed the USA system with the war of the currents and had to adjust his ideas to battle with getting AC accepted. History has meant USA is stuck with 120 volt 60 Hz just like we have 230 volt 50 Hz I am sure a 100 Hz system would be better with smaller transformers given long distance is DC anyway. But unlikely there will be any change. Aircraft use I think 600 Hz but that's the odd one out. Earthing aircraft is a problem specially with German built aircraft landing in USA.
I did my apprenticeship at a time when we did as we were told. Attitude was if it goes wrong not my fault boss told me to do it which was clearly wrong. The taking of the IEE (now IET) regulation book and making it a British Standard also started a process of re-training where us old electricians had to go to college and get out "16 Edition" which for many was an eye opener. Until then ask the boss to see regulation book and you got "Why do you want that" and regulations were learn by rummer control often giving incorrect information as to what should be done.
There was also that them and us between boss and worker and we considered it was our job to take readings but their job to interpret those readings. Again wrong but it was the way we were taught, no way would you annoy the union if you got thrown out you lost your job. It was the Union who policed standards at that time.
In 1980 I went to work in Algeria and for first time saw the USA system of 110 volt. Only for around a month as most sites I worked on used generators and we worked to Dutch standards in the main. But what I quickly realised there was not a universal standard for USA system but many different systems and one really needed a volt meter. Algiers at the time used three phase 110 volt and often people would use 220 or 240 volt gear using two phases but that's only 190 volt not 220 volt as three phase. I am told USA today uses 120 volt which would give 207.5 volt phase to phase and also often they use split phase which would then give 240 phase to phase.
We in the UK also use split phase but we don't use anything phase to phase with a split phase supply so it's not a problem. Only with three phase do we connect phase to phase so we know all supplies 230 volt phase to neutral and 400 volt phase to phase and except for mines and quarries where 550 volt is still used we have one system for whole of Europe only the domestic plugs and sockets change country to country. Well maybe not quite true France does seem to use more split phase and cookers can use the split phase but each element is only 230 volt they don't use 460 volt elements.
Working on a Robins TBM I also came across the USA system. I really hated it. This was in Hong Kong supply was 11kV transformed down to 10kV for TBM and then to 660 volt for main motors and further down to 220 volt delta supply for the control circuits and lighting. Believe me working in a iron ore laden wet environment with 220 volt delta was shocking. Really good money but it needed to be it was a really dangerous job. Made worse as TBM was for a dry tunnel and it simply was not dry needed 3 x 10 inch pumps to keep water level down.
I would guess if brought up with the USA system you would develop methods to keep your self safe. I was glad when contract ended and I could return to UK and true British standards not the stretched standards used in HK.
As to Algeria that was not a problem. The ground was normally so dry you could touch live wires without getting a shock. Not that I did but we have to accept in the UK it is rare to need anything more than a single earth rod to get a RCD to trip when required. USA is a massive country and they get extremes we never see. Our 230 volt system works well for us but with a different climate you will likely need a different system. The great Serbian designed the USA system with the war of the currents and had to adjust his ideas to battle with getting AC accepted. History has meant USA is stuck with 120 volt 60 Hz just like we have 230 volt 50 Hz I am sure a 100 Hz system would be better with smaller transformers given long distance is DC anyway. But unlikely there will be any change. Aircraft use I think 600 Hz but that's the odd one out. Earthing aircraft is a problem specially with German built aircraft landing in USA.
we are not really to stuck. It'sa split phase 120/240 coming in for residential mains with the neutral(grounded conductor)The electrical panel has a two pole mcb that feeds a two bus bars. We come off to feed 120v and 240v circuits
Our general lighting and all appliance run on 120v And our cookers, oven, electric water heaters, space heaters , air conditioning are all mostly 240v circuits.Works well a lot safer working with 120v circuits never a problem with both voltage available
Our commercial end has several different voltages starting with the most common 3 phase 120/208 ;277/ 480v; and there are several other not as common
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I had problems in the Falklands with split phase. Some farmer thought it would be safer, however unlike you he uses a UK consumer unit so not double MCB and also most items he used did not have double pole switching. Had to rewire to 0-240 as a result.
Your system is 60 Hz and to swap 50 to 60 Hz is expensive. Some guy working for a contractor supplying lighting towers to T5 Heathrow airport thought he had made a killing. He bought a whole load of lighting towers from the USA they had 240 volt lights and 110 volt sockets so seemed great. Until it was found it was 120 - 0 not 55 - 0 - 55 so all sockets had to be removed and blanked off. They also found the lamps were not available in UK and had to be imported.
There are still areas in USA using the Delta system 240 volt three phase with centre of one winding earthed so two phases are 110 volt to earth but third is around 220 volt to earth can't remember exact voltage not inclined to work it out. It was 14 Nov 2007 that the last of the DC supplies were turned off in New York.
I seem to remember it was some village near Bala in Mid Wales last to have private generator in UK I think around 1990 it finally go connected to the grid and even then it was AC at 230 volt.
We are a very densely populated island and as such standardising the supply was far easier for us then for you in the USA. Some day you will catch up but it will take time. After all your gun laws means Dick Turpin could still exist in USA.
Your system is 60 Hz and to swap 50 to 60 Hz is expensive. Some guy working for a contractor supplying lighting towers to T5 Heathrow airport thought he had made a killing. He bought a whole load of lighting towers from the USA they had 240 volt lights and 110 volt sockets so seemed great. Until it was found it was 120 - 0 not 55 - 0 - 55 so all sockets had to be removed and blanked off. They also found the lamps were not available in UK and had to be imported.
There are still areas in USA using the Delta system 240 volt three phase with centre of one winding earthed so two phases are 110 volt to earth but third is around 220 volt to earth can't remember exact voltage not inclined to work it out. It was 14 Nov 2007 that the last of the DC supplies were turned off in New York.
I seem to remember it was some village near Bala in Mid Wales last to have private generator in UK I think around 1990 it finally go connected to the grid and even then it was AC at 230 volt.
We are a very densely populated island and as such standardising the supply was far easier for us then for you in the USA. Some day you will catch up but it will take time. After all your gun laws means Dick Turpin could still exist in USA.
When there is no game to shoot the hill billies use the insulators on power lines as targets.
Some old farm and similar properties with split-phase service had 400-500V single-phase motors, at least at one time. No doubt they're becoming rare now, but there might still be some around in service in rural areas (the area of Norfolk in which I used to live had quite a few 240/480V distribution systems).
Most often 400Hz, and used on some ships as well.
That's the 4-wire delta, also known variously as high-leg delta, wild-leg delta, bastard-leg delta, and red-leg delta (the latter from the common practice at one time of using red to identify the phase with the higher voltage to ground, although orange has been the recommended color since the early 1970's). With 120V to the neutral on each of two phases the third phase ends up at 208V to neutral/ground.
The arrangement grew out of the plain 240V delta which had come into use for many motor applications in order to allow a relatively small 120V load to be run from the same service without the need for extra transformers. As such, it was quite effective: You can connect single-phase 120V A-N or C-N, single-phase 240V loads A-B, A-C or B-C, and, of course, 3-phase delta 240V loads A-B-C. You could get 208V B-N, although that's rarely done.
The 4-wire delta, along with regular 240V and 480V delta systems are often regarded as "legacy" systems now though, and many utilities will maintain such supplies but won't provide them for new installations anymore. A 4-wire wye system at 120/208V or 277/480V is typically now all that's on offer, along with the standard 120/240V single-phase service for residential and light commercial.
Well, that's a whole different subject, but the laws also mean that his potential victims are more likely to be armed as well and able to fight back!
What's the electrical inspection process in the UK? Do you having inspectors that come on site and go over the job and your regs for violations or is it up to electrician? Here everything is about the code and so much confusion between
Inspector interpretation of the rules from town to town and state to state. Certain states adopting current code cycles
Some several cycles behind And the biggest problem is almost nothing gets tested like in the UK . No paper work recording any impedance values to insure volt drop in particular is with in safe guidelines
I think part of the overall problem is with our training. It is seriously lacking these skills and to much focus on the code. If you asked most apprentices how to do an impedance test they would not know how and maybe a few well qualified electrician
Are even aware that such testing exists . We are one of very few nations on earth that don't test .almost every other country in the world performs loop impedance testing
Inspector interpretation of the rules from town to town and state to state. Certain states adopting current code cycles
Some several cycles behind And the biggest problem is almost nothing gets tested like in the UK . No paper work recording any impedance values to insure volt drop in particular is with in safe guidelines
I think part of the overall problem is with our training. It is seriously lacking these skills and to much focus on the code. If you asked most apprentices how to do an impedance test they would not know how and maybe a few well qualified electrician
Are even aware that such testing exists . We are one of very few nations on earth that don't test .almost every other country in the world performs loop impedance testing
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That is a surprise I thought all now test loop impedance. The inspection of other peoples work is not that regimented. For domestic theory with scheme member electricians the scheme operators should do spot tests. However at a resent meeting between government and scheme operators and other parties the question was asked about how many electricians had been kicked off the scheme due to bad workmanship the number was extremely low comment was raised that they did not believe all scheme member electricians were that good dementia alone should result in a higher figure. So although there is a system in place it seems it does not work and all the schemes do is make money.
In theroy again domestic should be inspected on change of occupant or every 10 years which ever is sooner, it seems in Scotland for rental properties this is to be mandatory every 3 years but don't think it's in yet.
Commercial it's the electricity at work act, The HSE is responsible for policing and hospitals inform HSE of any people who have been injured at work plus need to inform is off work for more than 3 days I think! So they tend to visit premises where there have been accidents but leave alone those with clean records. Once caught out with faults they will visit regularly and firms are often given time to comply.
In the main it is the thought in the back of ones mind when you read reports, there by the grace of god go I. You see how the foreman in the Emma Shaw case was singled out as guilty party even though he had never visited the site. I know I have worked with good electricians mates who were very capable of taking readings. You will note he was not asked to inspect only take readings which after all is only a case of plug in and press the button. Reading between the lines he had not been able to get a reading and fudged the results rather than simply tell the foreman something was wrong.
It is the reading of these reports which motivates many to ensure their test results are A1. However even when the inspection and testing is done well often there is a problem with record taking. I had it myself we used Robin software and recorded all PAT testing results on the computer. However two flaws. One we were not making back-ups and even if we did only one computer had software to read them. And second they could be altered after. We had a problem where one guy forgot to enter his code and as a results all his test results when down as being done by some one else. I was asked to correct it and quickly wrote a VB program to correct errors. But of course same VB program could be used to change records and the foreman was caught re-entering last years results with this years date. From that point we had to print and sign paperwork. The paperwork did not have all results but did show who had done the test.
We I am sure all get when we ask when we can turn off X the answer you can't turn off that. To reply since you will not give me a time or date then I will turn off on X often seems to fail to come from electricians lips, and they simply accept it can't be turned off. I can hear myself saying I need to turn off X how much of a window do I have before the UPS goes flat only to be told no UPS installed so my reply is then clearly not problem losing power.
This recording of electrical condition clearly cost money and where one is pushed fixing break downs there is a temptation to leave testing to tomorrow which of course never comes.
In theroy again domestic should be inspected on change of occupant or every 10 years which ever is sooner, it seems in Scotland for rental properties this is to be mandatory every 3 years but don't think it's in yet.
Commercial it's the electricity at work act, The HSE is responsible for policing and hospitals inform HSE of any people who have been injured at work plus need to inform is off work for more than 3 days I think! So they tend to visit premises where there have been accidents but leave alone those with clean records. Once caught out with faults they will visit regularly and firms are often given time to comply.
In the main it is the thought in the back of ones mind when you read reports, there by the grace of god go I. You see how the foreman in the Emma Shaw case was singled out as guilty party even though he had never visited the site. I know I have worked with good electricians mates who were very capable of taking readings. You will note he was not asked to inspect only take readings which after all is only a case of plug in and press the button. Reading between the lines he had not been able to get a reading and fudged the results rather than simply tell the foreman something was wrong.
It is the reading of these reports which motivates many to ensure their test results are A1. However even when the inspection and testing is done well often there is a problem with record taking. I had it myself we used Robin software and recorded all PAT testing results on the computer. However two flaws. One we were not making back-ups and even if we did only one computer had software to read them. And second they could be altered after. We had a problem where one guy forgot to enter his code and as a results all his test results when down as being done by some one else. I was asked to correct it and quickly wrote a VB program to correct errors. But of course same VB program could be used to change records and the foreman was caught re-entering last years results with this years date. From that point we had to print and sign paperwork. The paperwork did not have all results but did show who had done the test.
We I am sure all get when we ask when we can turn off X the answer you can't turn off that. To reply since you will not give me a time or date then I will turn off on X often seems to fail to come from electricians lips, and they simply accept it can't be turned off. I can hear myself saying I need to turn off X how much of a window do I have before the UPS goes flat only to be told no UPS installed so my reply is then clearly not problem losing power.
This recording of electrical condition clearly cost money and where one is pushed fixing break downs there is a temptation to leave testing to tomorrow which of course never comes.
I read the Emma Shaw case and thought,It not until something's tragic happens that the enforcing athurothies step up to the place. There are way too many untrained and unlicensed people here doing electrical work everyday. The inspector alone can' t catch the violators . The state agencies does not have the man power to police the industry that there answer. They leave it to us electricians to report this type of illegal activity
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