Getting Shocked

[zarobhr]

i seem to be getting shocked when i touch any 1 of my machines plugged into 1 outlet and any machine plugged into another outlet. but not if i touch any 2 machines on the same outlet

i took my volt meter and checked the voltage from cabinet to cabinet (supposedly ground and i am getting 49volts

i also checked the outlets and they are

left prong to right prong 123v
left prong to ground 0v
right prong to ground 123v

which i believe may be correct but is it possible polarity is reversed

[poppo]

i also checked the outlets and they are

left prong to right prong 123v
left prong to ground 0v
right prong to ground 123v

which i believe may be correct but is it possible polarity is reversed

That is correct if you are looking at the oputlet and the left prong is the longer one.

What happens if you measure resistance from the ground lug on the cord to the chassis of each machine?

Can you measure the voltage between the two grounds of the actual outlets?

Is this an old house that originally has just 2 wires? If so they may be tying ground to neutral at the outlet making giving a difference of potential between the two outlets, especially if they are on different legs of the 240V input.

[zarobhr]

strange, it went away after unp[lugging everyhting and plugging it back in i will keep testing over next few days

[poppo]

Might just have a power cord with a bad ground.

[poppo]

Oh, also be sure to test it both when the house A/C is on and off. Strange things can happen when the full 240VAC is being used vice when it's not if you have problems between the two 120V legs. .

[Foster]

Neutral is at ground potential by design.
It is the return path to ground that is to be used for wiring 120V circuits
The Ground is there for safety only should not be used as an alternative to the neutral wire.

Now some 240V wiring has the neutral and ground which results in a 4 wire circuit with a 4 hole 240V socket.

Power company grounds the center output tap of the 240V at the Transformer.


   

[poppo]

Normally neutral and ground are tied together at the panel. But on some older houses that did not have a seperate ground, they are incorrectly tied together at the outlet. This can cause the neutral/ground to 'float' in respect to true ground. It can also cause there to be a difference of potential between the ground lugs on two separate outlets if they are an the different legs of the 240V input or if one is grounded to lets say a water pipe and the other isn't. Sometimes this difference of potential will appear or disappear when a 240V appliance is in use. Like an air conditioner or an electric clothes dryer.

In any case whether it has gone away for now or not, it really should be investigated. There should not have been 49V between the two cabinets. Either the problem is with the machines/cords or the house wiring. Either way the cause should be found and fixed.

[knagl]

 

I had the same problem years ago between an old EM pinball machine with a two prong plug and a newer pinball machine with a 3-prong plug.  If I touched both machines at the same time, ZZZZZAP!

I never did resolve the issue other than to unplug the EM -- it's been sitting down in my parent's basement for years now.