# Square D electrical panel question

Show me some evidence as to why you think I don't. I have a degree in electronics and I can assure you I know everything there is to know about resistance.
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wrote:

Something to do with the physiological responce to the shock. Some voltages make you hang on, others throw you off - making it virtually impossible to hold on.. I can't remember what my Dad used to say (he was an electrician) but some of the higher voltages could be safer than the lower voltages because the lower voltage made you grab the wire hard and not let go.
The let-go phenomenon for low (<600 V) contact
A factor that makes a large difference in the injury sustained in low-voltage shocks is the inability to let go. The amount of current in the arm that will cause the hand to involuntarily grip strongly is referred to as the let-go current.7 If a person's fingers are wrapped around a large cable or energized vacuum cleaner handle, for example, most adults will be able to let go with a current of less than 6 mA. At 22 mA, more than 99% of adults will not be able to let go. The pain associated with the let-go current is so severe that young, motivated volunteers could tolerate it for only a few seconds.7 With current flow in the forearm, the muscles of flexion and extension are both stimulated. However, the muscles of flexion are stronger, making the person unable to voluntarily let go. Nearly all cases of inability to let go involve alternating current. Alternating current repetitively stimulates nerves and muscles, resulting in a tetanic (sustained) contraction that lasts as long as the contact is continued. If this leads to the subject tightening his or her grip on a conductor, the result is continued electric current flow through the person and lowered contact resistance.8
With alternating current, there is a feeling of electric shock as long as contact is made. In contrast, with direct current, there is only a feeling of shock when the circuit is made or broken. While the contact is maintained, there is no sensation of shock. Below 300 mA DC rms, there is no let-go phenomenon because the hand is not involuntarily clamped. There is a feeling of warmth while the current travels through the arm. Making or breaking the circuit leads to painful unpleasant shocks. Above 300 mA, letting go may be impossible.4 The threshold for ventricular fibrillation for direct current shocks longer than 2 seconds is 150 mA as compared with 50 mA for 60-Hz shocks; for shocks shorter than 0.2 seconds, the threshold is the same as that for 60-HZ shocks, that is, approximately 500 mA.4
Heating power is also increased when a person cannot let go. This is because a firm grip increases the area of skin effectively in contact with the conductors. Additionally, highly conductive sweat accumulates between the skin and conductors over time. Both of these factors lower the contact resistance, which increases the amount of current flow. In addition, the heating is greater because the duration of the contact is often several minutes in comparison with the fraction of a second that it takes to withdraw from a painful stimulus.
Being unable to let go results in more current for a longer period of time. This will increase damage due to heating of muscle and nerves. There will also be an increase in pain and the incidence of respiratory and cardiac arrest. There can also be shoulder dislocation with associated tendon and ligament injury, as well as bony fractures in the area of the shoulders.
Go to:
The let-go phenomenon for high (>600 V) contact
Several different outcomes may occur when a person grasps a conductor giving 10 kV AC hand-to-hand voltage. It takes over 0.5 seconds of such contact before most of the distal forearm cells are heat damaged. However, within 10 to 100 milliseconds, muscles in the current path will strongly contract. The person may be stimulated to grasp the conductor more tightly, making a stronger mechanical contact. Or, the person may be propelled away from the contact. Which of these events occurs depends on the position of the hand relative to the conductor. Most eyewitnesses report the victims being propelled from the conductor, possibly because of generalized muscle contractions. The time of contact is estimated to be about 100 milliseconds or less in such cases.9(p57
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I thought all AC allowed you to let go? DC cramps your muscles up.

I call "bollocks". I once picked up a wall socket which I'd used as a trailing socket, and it was wired backwards (earlier on, not by me), so when I'd switched it off, I'd disconnected the neutral and not the live. Hence I got 240V through my hand from live to earth. All it did was warm up my hand. I let go very easily.

Incorrect again. Place a PP3 9V battery on your tongue. That will sting continuously until you remove it.
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On Sunday, March 6, 2016 at 6:01:32 PM UTC-5, Mr Macaw wrote:

ailing socket, and it was wired backwards (earlier on, not by me), so when I'd switched it off, I'd disconnected the neutral and not the live. Hence I got 240V through my hand from live to earth. All it did was warm up my h and. I let go very easily.

It also doesn't make sense as written. Volunteers could only tolerate it f or a few seconds? How long does it take to let go?

continuously until you remove it.

Agree, been there, done that too.
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Back to the main panel disconnect question.
My house always had the meter outside and the main panel inside, with the main disconnect on the panel.
When an upgrade was done to the main panel, an extra breaker was added outside just below the meter. The electrician said this was a code requirement, because wire between the meter and the panel needed to be protected because of the location.
Did this new breaker now become the service disconnect? And if so, is the main panel now noncompliant for having ground and neutral bonded?
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Yes they should have pulled in a 4 wire feeder and separated the neutral and ground. The issue of how far the SE is running inside the house before it needs protection is really undefined. Inspectors in the same jurisdictions may even disagree. On one extreme some say a few feet, as directly it can be run, using SE cable, is just fine. Others say they want a back to back installation with the wire simply passing through the wall in a short pipe nipple. The most extreme interpretation pretty much wants an outside disconnect no matter what.
This is the code 230.70(A)(1) Readily Accessible Location. The service disconnecting means shall be installed at a readily accessible location either outside of a building or structure or inside nearest the point of entrance of the service conductors.
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What is this fuss about ground and neutral? They are one and the same here. Neutral is strapped to ground at the transformer.
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You have superconductors there? Cool. Here we have voltage drop on our conductors and the farther you get from the place where the neutral is bonded, the higher the voltage is on the neutral.
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Yeah, it could be something dangerous like 2 volts :-) The wire coming to my house is 300 amps. That thing won't drop much voltage.
Think about it, say it dropped enough to give you a shock (I believe you need 30 volts to even make you feel it) that would mean I'd have 30 volts on neutral with reference to ground. So the voltage drop on the live would be the same. That would mean I'd have 200 volts and 30 volts, a PD of 170 volts. Now they're required by law to provide me with 230 volts +10%/-8%, so anything under 211.6 volts is no good (some equipment wouldn't work, bulbs would be dim etc). 170 is a lot less than 211.6.
I have actually tested the voltage under high load conditions, and it never drops more than about 5 volts (it'll be an equal drop on both conductors) - so I could get a 2.5V shock off neutral - that's less than a lithium torch battery, which I can touch the ends off with wet hands and not even feel it.
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"Mr Macaw" wrote in message wrote:

Yeah, it could be something dangerous like 2 volts :-) The wire coming to my house is 300 amps. That thing won't drop much voltage.
Think about it, say it dropped enough to give you a shock (I believe you need 30 volts to even make you feel it) that would mean I'd have 30 volts on neutral with reference to ground. So the voltage drop on the live would be the same. That would mean I'd have 200 volts and 30 volts, a PD of 170 volts. Now they're required by law to provide me with 230 volts +10%/-8%, so anything under 211.6 volts is no good (some equipment wouldn't work, bulbs would be dim etc). 170 is a lot less than 211.6.
I have actually tested the voltage under high load conditions, and it never drops more than about 5 volts (it'll be an equal drop on both conductors) - so I could get a 2.5V shock off neutral - that's less than a lithium torch battery, which I can touch the ends off with wet hands and not even feel it.
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wrote:

Don't know what code the electrician was going by, so I can't say for sure - but IF the neutral and ground were not bonded together at the outside breaker, the bonded panel definitely meets code and the outside breaker is not considered to be a "service disconnect"
How much cable is there between the outside breaker and the panel???
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To disconnect the wire between the meter and fusebox here, I simply pull out the master fuse next to the meter.
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Why not?

I held on for a few seconds until I realised why my hand was getting very warm inside. It wasn't painful, just weird.

It was the classic dare at primary school. All little handheld games ran on those at that time.
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On Sunday, March 6, 2016 at 5:52:15 PM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

Based on my "inability to let go" experience while in the USCG, I don't think I agree with this statement:
"...with direct current, there is only a feeling of shock when the circuit is made or broken. While the contact is maintained, there is no sensation of shock."
I was learning how to work on power supplies using a "training device" while attending the USCG electronics school. The training device was a microwave sized 300VDC power supply which was set up to easily accept failed components that the students had to find via systematic trouble shooting steps. It was basically an open box so that all the components were in full view. It weighed in at about 35 lbs.
One of the troubleshooting steps was to remove the built in load from the power supply to see if the symptoms changed. The proper way to remove the load was to shut down the power supply, remove a jumper - a short cable with banana plugs on both ends - and then turn the power supply back on.
I was a cocky kid and to save time I figured I would just grab the jumper in the middle of the loop and just yank it out. Unfortunately, the load side of the jumper came out, but the supply side stayed in. I had my left forearm resting on the case and the open end of the jumper came in contact with my hand. (4 decades later and the scars are still very visible). At that point my arm became the load for the 300VDC supply and my brain did not like it. I couldn't move my left arm so my brain told my right arm to push the case away. As soon as my right arm touched the case, I was stuck. I grabbed the 35 lb unit and lifted it right off the table screaming "Turn it off! Turn it off!" I absolutely could not let go and I absolutely felt the electricity flowing through my arms and chest. It was no "feeling of warmth", it was in every way the "sensation of shock".
The lab was set up like a classroom and when I started yelling the guy in front of me turned around and grabbed the power cord to pull it out of the power strip on my table. Unfortunately, the power strip just came up with the cord. The guy next to him slammed the power strip back down to the table and the cord came out. Once the current stopped flowing through my chest, I literally threw the power supply down onto the table. Man, was I pissed.
They took me to the infirmary and did the whole EKG thing. It turned out that I was OK, other than being pretty shook up and having some bad burns on both hands. When I went back to class the next day, a couple of things had changed:
1 - 2 guys quit electronics school after seeing what happened to me. 2 - All the power strips had been screwed down to the tables. :-)
Anyway, bottom line is that I do not agree that with DC there is "no sensation of shock" while contact is maintained.
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On Sun, 6 Mar 2016 16:17:21 -0800 (PST), DerbyDad03

But totally different than an AC shock. You had the muscle clench but it's totally different from AC.

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On Sunday, March 6, 2016 at 8:13:13 PM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

The lines I object to are not related to the muscle clench. I specifically quoted the lines related to no sensation of shock while contact is maintained. The article says that no shock will be felt and I sure as hell felt the shock during the entire time I maintained contact. Up one arm, across my chest and back down the other arm.

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On Sun, 6 Mar 2016 18:28:47 -0800 (PST), DerbyDad03

I've had ac and dc shocks - and I will say for the same voltage/current capacity, AC hurts one hell of a lot more than DC. DC hurts like hell when you get hit, and again when you get off of it. In between there is pain - but mostly due to constant muscle contraction - and there is heat.
With AC it just plain hurts like hell - period.. Along with the pain is the continuous pulsing of the muscle contractions - with 50 or 60 hz AC - a bit different with 400 or higher frequency - and even worse with something like 25 hz. Lets just say it "hertz"
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On Sunday, March 6, 2016 at 9:45:09 PM UTC-5, snipped-for-privacy@snyder.on.ca wrote:

Clare probably knows more about getting shocked from personal experience than anyone else here, given how he's wrong on electrical questions half the time.
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Then your body isn't the same as everyone else's.
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What a wimp!

You had two unshocked legs, why didn't you use them?

Now you see myself, and most people I studied with at uni would have laughed or filmed the incident before helping you.

Oh what a surprise.

I';m sure you'll live. Oh, you did.

Even more wimpier than you.

Glad to hear they didn't go all health and softy and change the jumpers. It was you that did something daft, no changes were necessary.

I'd say from personal experience of both, that both feel the same, but AC allows you to let go, as your muscles are "shivering" at 50Hz, not cramped up.
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