Lobster tank GFCI protection?

[mbrooke]

if what you are saying under a bolted fault 1/2 of the v appears across each conductor (if equal z), so???

The person is exposed to half this V for a few cycles- until the breaker opens.

under hi z, low leakage, the person is in the path, parallel
assume 120/0.05 = 2400 a fault

Add an EGC to the mix and watch how the current from frame to earth plummets.

High Z about a few volts tops until the fault continues.

Low Z about 60 volts max for a few cycles.

Under both conditions the person is not harmed, hence why an EGC alone is permitted in so many code scenarios. High or low Z fault EGC protects.

person sees 0.1/1000 x 2400 = 240 ma
kills in 0.16 sec for a 100 lb person
the gfci would trip much faster and limit it to x ma range

Yup- and IEC 479-1 is a good reference. (sorry for the junky picture, there are better ones out there but not finding them)


https://www.google.com/search?q=fig...UICygC&biw=1440&bih=725#imgrc=vbJ79wccZPekrM:

 

[mbrooke]

Better one:


https://no.wikipedia.org/wiki/Fil:IEC_TS_60479-1_electric_shock_graph.svg

 

[Ingenieur]

The person is exposed to half this V for a few cycles- until the breaker opens.




Add an EGC to the mix and watch how the current from frame to earth plummets.

High Z about a few volts tops until the fault continues.

Low Z about 60 volts max for a few cycles.

Under both conditions the person is not harmed, hence why an EGC alone is permitted in so many code scenarios. High or low Z fault EGC protects.


Yup- and IEC 479-1 is a good reference. (sorry for the junky picture, there are better ones out there but not finding them)


https://www.google.com/search?q=fig...UICygC&biw=1440&bih=725#imgrc=vbJ79wccZPekrM:

still may kill them, and does
less often now with gfci

 

[Ingenieur]

Better one:


https://no.wikipedia.org/wiki/Fil:IEC_TS_60479-1_electric_shock_graph.svg

????
I work this stuff every day

240 ma for 1.5 cyc will likely kill you

 

[mbrooke]

still may kill them, and does
less often now with gfci

Where? In the mines or residential/commercial/industrial? If you don't think EGCs are adequate, you need to let the CMPs know. Submit a proposal.

 

[mbrooke]

????
I work this stuff every day

240 ma for 1.5 cyc will likely kill you

You mean you have never seen that graph? Does IEC 61200-413 or IEC TS 60479-1 not ring a bell? Its important enough that even UL is no using it... thats like a cardiologist not knowing what an ECG is.

AC-1, AC-2 ect are decoded below- the effects of time and current on the human body.

 

[Ingenieur]

you do not grasp the concept

egc intact
hair dryer, etc. old, insul aged, cracks, etc
you just showered, soaking wet
grab device, moisture bond you to hot (but not egc)
you see 120 ma, 20 cb, you die
with gfci you live

wag
that is why the nec requires them in wet (or potentially) areas
hmmmm

 

[Ingenieur]

Where? In the mines or residential/commercial/industrial? If you don't think EGCs are adequate, you need to let the CMPs know. Submit a proposal.

homes, commercial, EVERYWHERE
electricity is the same


don't need to
nec requires them where most needed

 

[Ingenieur]

You mean you have never seen that graph? Does IEC 61200-413 or IEC TS 60479-1 not ring a bell? Its important enough that even UL is no using it... thats like a cardiologist not knowing what an ECG is.

AC-1, AC-2 ect are decoded below- the effects of time and current on the human body.


View attachment 20900

I have seen it 1000's of times, the ??? was it is moot
derived from ma = body wt/sqrt t, which is more accurate
it may even be called the 'Dalziel' curve
'Dalziel'

IEC has a 300 pg doc on shock with dozens of tables for body z based on various scenarios: hand-foot, hand-hand, wet, dry, gloves, etc

 

[kwired]

you do not grasp the concept

egc intact
hair dryer, etc. old, insul aged, cracks, etc
you just showered, soaking wet
grab device, moisture bond you to hot (but not egc)
you see 120 ma, 20 cb, you die
with gfci you live

wag
that is why the nec requires them in wet (or potentially) areas
hmmmm

If standing on insulating flooring very possible nothing happens, you must contact another potential.

Do I think a GFCI is a good idea near the lobster tank - definitely and especially if there is grounded working surfaces and if there is anything that may energize the tank/water.

Do I think NEC requires GFCI here? Not specifically. If it is in a commercial kitchen then yes, but not because it is a tank containing water. Otherwise one needs to see if any other conditions mentioned in 210.8 would apply, location of receptacles is more of a driving factor here then what is being supplied.

 

[mbrooke]

I have seen it 1000's of times
derived from ma = body wt/sqrt t
'Dalziel'

Ok, so we are now at least on the same page?

IEC has a 300 pg doc on shock with dozens of tables for body z based on various scenarios: hand-foot, hand-hand, wet, dry, gloves, etc

Yup- which can be used to calculate body current for a given voltage. That given voltage comes from knowing your fault circuit Z.

 

[Ingenieur]

• Dalziel, Charles F. The effects of electric shock on man / by Charles F. Dalziel. Washington, D.C. : U.S. Atomic Energy Commission, Office of Health and Safety, 1956. Series: Safety and fire protection technical bulletin; no. 7

Your name is Charles Dalziel and you have just begun. You will establish criteria on fibrillation currents using dogs, pigs, calves, and sheep. You become the authority on dangerous electric currents. Your experimentation will establish the principles for protecting persons from the hazards arising from the use of electricity, and your findings will be used for the notes to the Tables in Article 725 of the National Electrical Code.

 

[mbrooke]

homes, commercial, EVERYWHERE
electricity is the same

Write to the NFPA that EGC are allowing to high a voltage for much a time when a fault occurs. Personally I think source Z, phase and EGC Z along with the time current curves of circuit breaker do a fine job in preventing irreversible ventricular fibrillation and tissue damage.

don't need to
nec requires them where most needed

Yup- where an EGC is most likely to be missing and a low body Z present.

 

[Ingenieur]

Ok, so we are now at least on the same page?


Yup- which can be used to calculate body current for a given voltage. That given voltage comes from knowing your fault circuit Z.

no we are not

the given voltage does not come from knowing body z
it is the constant, the system v
the i comes from knowing z for a given v

 

[Ingenieur]

If standing on insulating flooring very possible nothing happens, you must contact another potential.

Do I think a GFCI is a good idea near the lobster tank - definitely and especially if there is grounded working surfaces and if there is anything that may energize the tank/water.

Do I think NEC requires GFCI here? Not specifically. If it is in a commercial kitchen then yes, but not because it is a tank containing water. Otherwise one needs to see if any other conditions mentioned in 210.8 would apply, location of receptacles is more of a driving factor here then what is being supplied.

not saying it is required
but big benefit for low cost although risk is only low/moderate, not high

 

[mbrooke]

• Dalziel, Charles F. The effects of electric shock on man / by Charles F. Dalziel. Washington, D.C. : U.S. Atomic Energy Commission, Office of Health and Safety, 1956. Series: Safety and fire protection technical bulletin; no. 7

Your name is Charles Dalziel and you have just begun. You will establish criteria on fibrillation currents using dogs, pigs, calves, and sheep. You become the authority on dangerous electric currents. Your experimentation will establish the principles for protecting persons from the hazards arising from the use of electricity, and your findings will be used for the notes to the Tables in Article 725 of the National Electrical Code.

I do not dispute that. Once the threshold (time vs magnitude) is known for organ damage, cardiac arrhythmia and respitory arrest you can then design a power system that subjects users to level below critical during adverse conditions.

The time current curves of breakers along with the sizing of branch circuits makes for faults which produce voltage and times which are below the level of physiologically harmful or lethal. The CMPs didn't make table 250.122 out of arbitrary.

 

[Ingenieur]

Write to the NFPA that EGC are allowing to high a voltage for much a time when a fault occurs. Personally I think source Z, phase and EGC Z along with the time current curves of circuit breaker do a fine job in preventing irreversible ventricular fibrillation and tissue damage.

Yup- where an EGC is most likely to be missing and a low body Z present.

they do not agree with you
they require gfci in many locations
homes first, then expanded to other occupancies

you miss the point
when wet you may bypass the egc, become the gf path
and even with an egc it may limit i < the threadhold, where as without it you may die

 

[mbrooke]

no we are not

the given voltage does not come from knowing body z

Never said that, it comes from the circuit Z. Once the circuit Z is known you get voltage from frame to remote earth. Once you know that voltage you can then calculate body current by knowing body Z.

it is the constant, the system v
the i comes from knowing z for a given v

Correct.

 

[Ingenieur]

I do not dispute that. Once the threshold (time vs magnitude) is known for organ damage, cardiac arrhythmia and respitory arrest you can then design a power system that subjects users to level below critical during adverse conditions.

The time current curves of breakers along with the sizing of branch circuits makes for faults which produce voltage and times which are below the level of physiologically harmful or lethal. The CMPs didn't make table 250.122 out of arbitrary.

it is good you accept facts

not in all, or even most scenarios where the person is/initiates the fault

 

[Ingenieur]

Never said that, it comes from the circuit Z. Once the circuit Z is known you get voltage from frame to remote earth. Once you know that voltage you can then calculate body current by knowing body Z.



Correct.

Yup- which can be used to calculate body current for a given voltage. That given voltage comes from knowing your fault circuit Z.