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Posted By: Joe Tedesco Where did this advice come from? - 06/30/04 12:30 AM
I would like to get some feedback on the following advice that is given to a Home Inspector:

Quote
When you first touch the main electrical panel, do it by tapping the panel with the back of your hand. If it is hot, the shock will then knock you away rather than freezing you onto it.

I was never taught to use this method!
Posted By: Dave55 Re: Where did this advice come from? - 06/30/04 01:24 AM
I heard this advice from the Frugal Gourmet on checking a hot frying pan!

Dave
Posted By: DougW Re: Where did this advice come from? - 06/30/04 03:56 AM
I heard that one as a youngster from a plumber who was rodding the drain in my parent's basement - circa 1986 or so.

He used to connect all his plugs, and operate all his switches "backhanded", under the belief that, if your arm muscles involuntarily contract with your palm towards you, they would pull back towards the center of the body, rather than pressing the hand against the energized surface, as would supposedly happen with the palm away from you.

In the fire service, we check doors for heat using the back of our hands for three reasons - first, because the back of the hand is more sensitve to heat/cold (less callouses, scars, etc; secondly because the pain generated by a really hot door will cause you to flinch, and your arm seems to pull away faster palm-in; and third, because you can still use your hand to write / drive / grasp stuff if the back of it is burned checking a "too hot" door for heat! [Linked Image]
Posted By: pauluk Re: Where did this advice come from? - 06/30/04 09:45 AM
I think if I had reason to suspect that the panel might be hot I'd rather check with a meter than just brushing it with the back of my hand.

But that said, this is a "technique" I've heard mentioned in the past from various sources.
Posted By: cs409 Re: Where did this advice come from? - 06/30/04 11:37 AM
After grabing to open a couple of times and being bit hard, once causing me to rip my finger open, I will stick with my brushing with the back of my hand across a panel etc verses grabing to open right away any day....it only takes one time with the right conditions for someone to get hurt...not saying this is a great way to check something out, but even a good looking system can bite u...do any of yall ever get calls for repair where the lady or guy says, every time i go to flip a breaker or change a fuse, the door bites them???? i get many of these a year.
Posted By: jhumphrey Re: Where did this advice come from? - 07/03/04 07:24 PM
First heard this one in the mid 60's

Better one was anactual electrical work practices book from the early 1900's had a step by step procedure for checking voltage with your fingers.

A friend has the book and I'm looking for a copy
Posted By: Lostazhell Re: Where did this advice come from? - 07/05/04 05:24 PM
I can't say I've ever heard of this before??? If I had any inkling that something might be energized like this,(signs of arcing around conduit entries/fittings etc..) first thing I'd do is a hotstick test for EMF... then wiggy the metal to ground to see if stray voltage is present... Although if you were wearing proper gloves, you couldn't do the "back of the hand" trick.... You wouldn't have to [Linked Image]

-Randy
Posted By: George Corron Re: Where did this advice come from? - 07/05/04 11:35 PM
Joe,
I've always taught my apprentices to energize with their legs facing AWAY from the switch. When an 'event' happens, your first instinct is to run. If you are pointed into your work, your tendency is to run INTO it, not away. I've seen several guys not go home because of this, seems like a fair practice.
Posted By: sparky Re: Where did this advice come from? - 07/06/04 01:39 AM
the 'backhand' method, was one of the first things the old timers taught me

it shouldn't surprise anyone here that some electrical installations are in such deacy as to utilize such precautions should it?

~S~
Posted By: JCooper Re: Where did this advice come from? - 07/08/04 11:25 PM
One other reason I see to check with the back of your hand rather than a finger or two is if it is hot you take away the risk of the muscles in your hand contracting and not being able to let go of whatever is hot.
Posted By: sparky Re: Where did this advice come from? - 07/09/04 02:44 AM
bingo JC

and hey, look at the added benifit of having the involunmtary musculary contractility to be able to give yourself a black eye for such an obvious breech of safety standards too.....

~S~
Posted By: PEdoubleNIZZLE Re: Where did this advice come from? - 07/09/04 08:49 AM
What?!?! Use your hand? I was always told to use your tongue to see if it's hot. You know, that same test you do on a 9V battery to see if it's dead or not. Everyone knows that the toungue test is the only way! [Linked Image]

[Disclaimer][Directed towards = DIY] I am just joking! The tongue test should not be used on anything higher than a 9V batery. If you decide to do the tongue test out of your own ignorance or stupidity, you're gonna get what's comin to ya. Besides, does Copper (or aluminum) really taste that good anyways? [/Disclaimer]
Posted By: pauluk Re: Where did this advice come from? - 07/09/04 01:14 PM
Quote
The tongue test should not be used on anything higher than a 9V batery
I can vouch for that! Back somewhere around the age of 10 or 11 I got a little daring and tried it on a 12V supply (which off-load was probably nearer 14 or 15V anyway).

Yeee-OUCH! [Linked Image]
Posted By: Trumpy Re: Where did this advice come from? - 07/10/04 09:58 AM
Joe,
As a HUGE assumption, I am assuming that all of the fronts on Panels in the US are metallic?.
Here the Dead Front is either PVC or PE plastics.
But, while the backhand method applies to Fire-fighter search techniques, it equally should apply to any area where bare live wires could be present.
Other side of the coin, I reckon that a "test before touch" approach should be used, get a lead to a known Ground and get your Voltage Indicator of your choice out!. [Linked Image]
Posted By: RobbieD Re: Where did this advice come from? - 07/25/04 05:23 PM
When I was a marine electrician we were instructed on the back hand method. When we went around and checked our motors we would touch the frames to make sure they were not too hot. "Too Hot" I'm still not sure what this means my hand wasn't a percise thermometor. The ship was three phase delta and the ground was the hull of the ship. There was a bonding jumper from the frame of the motor to the hull because of rubber mounts to lessen vibration. They told us to use the back of our hand just incase the bond went crappy and our muscles would contract and hopefully we would survive. Nice Thought! Maybe this is where the guy picked it up. That is where I heard of it before. Anyway For what it matters I think this is a good habit to have, but if you noticable saw something wrong I would use a meter instead of my hand.

[This message has been edited by RobbieD (edited 07-25-2004).]
Posted By: PCBelarge Re: Where did this advice come from? - 07/29/04 01:41 AM
Years ago, before the meters and other devices were available, these practices were common. You were not a 'real' electrician if you did not test this way. I was taught the 'thumb - forefinger' method when I started. Meters are now not only available, but not too costly - especially when it is your life we are discussing. With the advent of the volt tic, the non contact devices, and the handheld thermometer, I do not see the need to use one's hand anymore.

Pierre
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