amps kill!

[Shaun B]

it is said that amps is what kill when a person is electricuted. So in higher voltages such as 277v and 480v with amps usually being lower when powering equipment than if it was 120v, why is the higher voltage more dangerous? Is the voltage the dangerous part or is it the amps?

 

[480sparky]

Amperage. You can have a million volts running through you with no ill effect, so long as the amperage is low enough. Google the words "Electrocution" and "Defibrillation".

 

[mdshunk]

The amps that you can turn up to "11" are the worst.

 

[ronaldrc]

Ohms Laws.

 

[quogueelectric]

it is said that amps is what kill when a person is electricuted. So in higher voltages such as 277v and 480v with amps usually being lower when powering equipment than if it was 120v, why is the higher voltage more dangerous? Is the voltage the dangerous part or is it the amps?

Higher voltage will push more amps over the same resistance plus there is a higher chance of an arcflash at higher voltage which can fatally burn you.

 

[jim dungar]

Amps is what will eventually kill you.

Voltage is what overpowers the insulation (skin) allowing the current to flow through the body. Voltage also cause muscles to contract and freeze in place preventing you from letting go of the circuit.

 

[K8MHZ]

The amps that you can turn up to "11" are the worst.

That looks like a picture of an amp owned by my friend Nigel Tufnel.

 

[zog]

it is said that amps is what kill when a person is electricuted. So in higher voltages such as 277v and 480v with amps usually being lower when powering equipment than if it was 120v, why is the higher voltage more dangerous? Is the voltage the dangerous part or is it the amps?

Dont get confused with load current, that has nothing to do with it. The current that flows through a persons body is the voltage across the body divided vy the total body resistance.

 

[zog]

Higher voltage will push more amps over the same resistance plus there is a higher chance of an arcflash at higher voltage which can fatally burn you.

LV systems typically have larger arc flash hazards than MV or HV systems.

 

[celtic]

It is not one single item that kills, it is a combination of four items:
- Amount of current
- Time current passes through body
- Path current passes through body
- Frequency (hz) of circuit

....so says Mr. Soares :

 

[TOOL_5150]

The amps that you can turn up to "11" are the worst.

I owned one of them. They are marshall guitar amps.

~Matt

 

[LarryFine]

So in higher voltages such as 277v and 480v with amps usually being lower when powering equipment than if it was 120v, why is the higher voltage more dangerous?

The whole higher-voltage-means-lower-current idea is easy to misunderstand.

That only applies in the manufacturing of electrical equipment. For a given amount of power, as in watts, a higher voltage allows a lesser current to do the same work. mathematically, volts x amps = watts.

A heater manufacturer can design a heater to deliver 1000 watts of heat while running on 120v, and another one to deliver 1000 watts while running on 240v. They do this by making the heater for 240v element four times the resistance of the 120v element.

To maintain a given power level, when you apply twice the voltage, you must halve the current. For a given resistance, when you double the applied voltage, the resultant current also doubles, which would result in quadruple the current.

If you merely doubled the resistance, applying twice the voltage would result in the same current, doubling the power. Therefore, in order to produce the same power with twice the voltage, it takes four times the resistance to cut the current in half.

That's why electrical equipment has to be constructed to operate on a specified voltage (or voltage range). The resistance has to be made to allow just the right amount of current to flow in order to produce the power, which electrical equipment converts into work.

In the real world, however, you have to remember which factors are the constants and which are the variables. For a given piece of equipment, or a human body, the resistance is what it is, depending on everything that affects resistance. The resultant current will depend on the applied voltage.

When you expose yourself to a higher voltage, nothing is being done to incerase your resistance, so the current risis proportionately with the voltage. The resulting power that is produced, absorbed, used to cook food or flesh, etc. will increase with the applied voltage.

 

[quogueelectric]

LV systems typically have larger arc flash hazards than MV or HV systems.

This is due to ground fault protection at the main however many older systems do not have this luxury. And newer sytems have fuse proyection to keep arc flash to a minimum. I am talking about what is out there in the field.

 

[zog]

This is due to ground fault protection at the main however many older systems do not have this luxury. And newer sytems have fuse proyection to keep arc flash to a minimum. I am talking about what is out there in the field.

So am I, on nearly every arc flash study I have done the LV systems have much higher Ei's than the MV or HV systems.

 

[jim dungar]

This is due to ground fault protection at the main however many older systems do not have this luxury. And newer sytems have fuse proyection to keep arc flash to a minimum. I am talking about what is out there in the field.

I do not consider any GF when I calculate arc flash incident energy AFIE. MV almost always has lower AFIE than does 480V. I also find many large branch circuits do not have a high enough bolted fault current to cause fuses to enter their current limiting range so they offer no advantage over circuit breakers.

 

[sparky723]

Nice!!

Nice!!

Sweet explanation, Larry.
It's nice to find someone who will take the time to help educate those of us who may or may not know the whole answer to some questions. I think the OP was a legite question that I am sure may people have thought about. There are a few guys on here that I like to read their posts to someones questions and well, you are one of them. Keep up the good work. sparky 723:smile:

 

[ATSman]

GFCI trip current

GFCI trip current

Another point to mention is that a Ground Fault Circuit Interrupter whether
built into the 120v outlet or the panel circuit breaker is a people protector. It is designed to trip (open the circuit) at 5 milliamps in a fraction of a second. This has been determined as the body's threshold limit before electrocution.

 

[don_resqcapt19]

Another point to mention is that a Ground Fault Circuit Interrupter whether
built into the 120v outlet or the panel circuit breaker is a people protector. It is designed to trip (open the circuit) at 5 milliamps in a fraction of a second. This has been determined as the body's threshold limit before electrocution.

Actually at 5mA the UL standard does not require it to open in a fraction of a second...it can be up to ~6 seconds before it is required to open at that fault level.

 

[ATSman]

Thanks

Thanks

I stand corrected. Can you name the UL article# ?
Although if it was me on the end of the wire I would
prefer a fraction of a sec.:grin:

 

[Buck Parrish]

How many volts are taser guns? And how come they don't kill you?