ground

[restez]

Hi
Can someone explain in lamens terms how ground works. i get it is a safety for us but just want to understand how it works .
example take a furnace that has a black grd wire connected to the cabnet what does it mean if it was unhooked , what would happen
and why? just a curious person with probably a dumb ?

 

[trev]

Not sure I understand the question mate. Do you want to know how earthing works?

 

[telectrix]

sounds like you are in U.S.A . maybe. the ground or earth wire is there so that id a fault ( short circuit ) from the live shorts down the the mtal casing of an appliance, then because the casing is connected to earth , which is at zero potential, a large current will flow, thus causing the fuse/MCB to trip.

 

[i=p/u]

at the speed of light, so correct measure and calcs your flying..

 

[Deleted member 26818]

The ground/earth is there to provide a pathway for the current, if there's a fault.
Otherwise, we might become the pathway.

 

[restez]

Thanks guys the pathway for the current, if there's a fault.
Otherwise, we might become the pathway this is what i mean if i am touching the cabnet and a short happens seems i will be shocked
also because the ground wire is connected to the cabinet then goes through me or do i just have this backwards
i appreciate the help yes i am in USA Modesto,ca

 

[danzor]

Soccer balls kill people. Beware!

 

[MarkieSparkie]

The grounding cable from the furnace provides a low impedance (low AC resistance) path to ground. The fault current will always seek the lowest impedance path to ground. If your hand is in contact with the heat insulated, metal structure of the furnace and the furnace develops an electrical fault from one of it's elements to it's metal case, the fault current will travel through the low impedance grounding cable rather than the much greater impedance of your body. If the grounding cable was disconnected in above scenario, the fault current would try flow through your body, hand to foot, you would probably experience an electric shock, the severity of the shock would depend on the quality of the electrical insulation from ground provided by the soles of your shoes, if this insulation was poor (e.g. thin soles) or non-existent (bare feet, very unlikely in a foundry) the shock might prove fatal.

 

[i=p/u]

spelled out perfectly sparkie,, what resistance would are body need to be to not complete a circuit,?? like an it earthing system high high resistance

 

[Knobhead]

The grounding cable from the furnace provides a low impedance (low AC resistance) path to ground. The fault current will always seek the lowest impedance path to ground. If your hand is in contact with the heat insulated, metal structure of the furnace and the furnace develops an electrical fault from one of it's elements to it's metal case, the fault current will travel through the low impedance grounding cable rather than the much greater impedance of your body. If the grounding cable was disconnected in above scenario, the fault current would try flow through your body, hand to foot, you would probably experience an electric shock, the severity of the shock would depend on the quality of the electrical insulation from ground provided by the soles of your shoes, if this insulation was poor (e.g. thin soles) or non-existent (bare feet, very unlikely in a foundry) the shock might prove fatal.

Furnace has a different meaning in the US, AKA central heating boiler. Being an ex foundry man I kept falling foul of that one talking to friends in the US.

 

[MarkieSparkie]

Furnace has a different meaning in the US, AKA central heating boiler. Being an ex foundry man I kept falling foul of that one talking to friends in the US.

Cheers Tony, I must file that away in case it comes up again.
I thought that when the OP referred to touching the furnace it was rather brave of him, but assumed he must mean a thermal insulated craft type furnace.

 

[restez]

markiesparkie Bingo !! i dont have much experience with electrical but your reply of - low impedance (low AC resistance) path to ground. The fault current will always seek the lowest impedance path to ground. ] was a perfect explanation i fully get it. i really appreciate your time in explaining that one last mystery thoough if something was not grounded proprly why does this effet it from operating proprtly i was told this once about my ac condensing unit not wanting to run they said it was not grounded properly or it was a ground issue why
thanks

 

[restez]

thanks for your feedback i totally understand this i appreciate it
Tony