Fri, October 21, 2005 - 12:18 PM

Hi Phil

A  low impedance ground from the neutral AT THE SERVICE ENTRANCE (main
breaker) to physical ground. is not required in an old house

Don said that his house was old and had no Ground.

This was acceptable at one time and there are still houses that still do
not have ground wires in them. 

If you put in a peice of wire in such a house you have to re-wire (new
wires, new panels and all) to the whole house. If you do anything to the
wires  of such a house you have to re-wire the whole house  

You suggestion of a peice of new wire means that the WHOLE house is now out
of code and YOU would be resposible for any damage or misfortune that
occurs (fire for one)

To make an extension that goes to ground seperate of the house wire system
is acceptable.

Wate pipes if metal are a good grounding source. That was once acceptable
thing to do at one time. 

Regards Al



In , on 10/21/2005 
   at 10:37 AM, "Phil Kane"  said:



>On Thu, 20 Oct 2005 22:20:26 -0700, altownsend{at}dccnet.com wrote:

>>I am a "portable deisel eclectric plant operator
>>
>>This is my experince with electrical codes in Canada:
>>
>>If you conect a ground wire it the fashion as you say you will have a
>>LIVE ground and is not allowed by electrical codes

>  Current codes here provide the same restriction, but there are
>  local loopholes which permit that in old construction if it met code
>  requirements at the time of construction.

>>Older houses do not have to be grounded and it is not required
untill you touch the electric sevice anywhere then you have to upgrade the
whole house to modern standards

>  At one time the codes permitted the protective ground to be carried by
>  the metal conduits and boxes, but with the proliferation of PVC
>  conduit and "Romex" type plastic cable, a separate uninsulated wire
>  in the cable or green wire in the conduit was required.

>>Colours and number of wires:
>>1 White-  Neutral conected to power pole
>>2 Black-  Power   conected to power pole
>>1 Green- Ground conected to metal power panel
>>                               and to a ground stake in the
>>                               ground outside of a house

>  Our codes permit a ground rod (stake), a water-pipe ground on the
>  street-side of the meter and any insualting joints, or a "re-bar"
>  ("Heinemann") ground if enough metal re-bar is embedded in the
>  concrete slab in direct contact with the ground.  The latter is
>  quite rare, though.

>  For both signal and lightning ground purposes, though, I prefer a
>  series of ground rods around the building, interconnected with 4/0
>  cable, with the protective ground connection to one of the ground
>  rods.

>>Voltages
>>white to black  110 - 120 volts
>>Black to black 220 - 240 volts

>  In practice in the US, the second "hot" wire is usually red.

>>Green should have no voltage when checked to a white wire
>>Green WILL show voltage when check to a black wire
>>Green connected to white creates a short circuit and is not alllowed

>  You are correct that curent codes do not allow this, but from a
>  purely electrical standpoint they should be at the same static
>  potential, assuming no differential ground potential.

>>You suggestion will put the spike into your computer and poof you
>>have Don's problem

>  Actually my suggestion was to use a separate "green" protective
>  ground wire and run it over to the computer installation, there to
>  tie  it oto the "ground" screw of the UPS or the computer case.
>  The only question was where to tie the "far" end to a
"real" ground.

>  If the service entrance is installed correctly, there should be a
>  low impedance ground from the neutral AT THE SERVICE ENTRANCE (main
>  breaker) to physical ground.  The only question is where to tie the
>  separate protective ground wire that I suggested be installed.  I
>  agree that a direct connection to the ground point which may also
>  provides the ground that is fed to the neutral bus is the best.

>  For radio transmission equipment, though, the question of whether
>  the protective ground wire length approaches a fraction of the
>  wavelength of the radio signal is significant and has to be taken
>  into account when designing both the antenna system and its
>  supporting ground system -  odd half-wavelengths appear as an open
>  circuit to radiofrequency energy.

>  "Switch to safety"

>--
>   Phil Kane
>   Registered Professional
>   Engineer (Electrical)




> 
>Yahoo! Groups Links



> 




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*****************************************
* Alan Townsend      Sechelt, BC Canada
*
*  E-Mail:                  altownsend{at}dccnet.com
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*  
*  Mr2 Ice:                 Reg #582
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