Ground question

Hi, There is an older part of my house that has steel or galvanised pipe for the electricals. I test the positive against the housing and get a reading,
is this an acceptable ground; or should I run a wire from the house ground to put a three prong plug outlet? thanks req
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If the reading was the same as the line to a direct ground (water pipe or whatever), probably 110 or 120 vac in your case its legal in most places to use the conduit as the recepticle *ground.... the green terminal, not the neutral although some people use the conduit as the neutral because it 'works'... it is also a severe fire hazard.
Grounding is a significant issue. Especially if electronics are involved ....how well the driven ground is attached to the grounded electrical panel and its connected conduit is a significant issue.
Usually its legal to use the conduit as a ground though you should ask you local building depts electrical inspector. The quality of the existing conduit is an issue..if thats sloppy, corroded or not fully connected etc then its a poor ground even if it reads as a ground when you check it.
One of the problems is the current carrying capacity of the conduit ground...it might check ok with a regular ohm meter, but not with a load applied (meg ohm testing). Most systems these days run a separate green or bare copper ground wire. Retrofits can have different rules as long as the local building authorities agree.
Phil Scott .

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Phil thanks for understanding me; a layman. req
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 2/19/06 5:47 PM, in article snipped-for-privacy@corp.supernews.com, "reqluq"

Please rephrase the question in a way I can understand.
Bill -- Ferme le Bush
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Hmm what don't you understand about: 1) There is an older part of my house that has steel or galvanised pipe for the electricals. 2)I test the positive against the housing and get a reading,is this an acceptable ground 3)or should I run a wire from the house ground to put a three prong plug outlet? You are an electrician of sorts no? who has to deal with the general public? Read them one by one and then draw a picture in your mind of a house with galvanised pipes with electrical wires running through them and someone wanting to insall a three pronged plug receptacle where one wasn't before, and wanting to use the housing that is connected to the galvanised pipe showing that it is grounded by testing the positive cable against it with a meter as the ground. req
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So what you're asking is if it's OK to use the conduit as an equipment ground for the 3 wire outlet? Checking voltage as you did only proves the connections in the conduit were good enough to make the meter work. It won't guarantee that it's a good enough conductor if there is an actual fault condition.
Dean
-
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

This statement is decidedly 'non-conforming'. Just what do you mean by 'test the positive'?? Do you have a DC installation? Or are you trying to say you tested with a voltmeter between the 'hot' conductor and the housing and got something other than zero volts?

Again, there is no 'postive cable'. There is a 'hot' wire and a 'neutral'. Also referred to as a 'non-grounded current-carrying conductor' and the 'grounded current-carrying conductor'.
From your description, it *sounds* like you tested between the 'hot' and the housing and got a reading. What kind of reading did you get? If you read 60VAC, then no, you shouldn't try to use the housing as the ground. Even if you read the same voltage as between hot and neutral, you still might not want to use the housing as the 'grounding conductor' (note the difference between 'grounded current-carrying conductor' and 'grounding conductor').
If the various conduit connections and joints between the new receptacle and the service panel have a variety of resistances that add up to something like 240 ohms, then your voltmeter reading would still show the same, but it would be very poor grounding connection. (a direct hot-ground fault would only draw 0.5 amp, not enough to trip the breaker (unless it's GFCI), but would raise the frame of any appliance to ~120V)
This is why some areas require separate grounding conductors, regardless of metal conduit ('pipes'). Or if the conduit *is* used for grounding, special precautions are taken at the joints to be sure of clean, tight connections (one of the reasons for those 'funny' locking nuts on threaded fittings is to maintain good electrical contact).
daestrom
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

In my house?no postive means live, the hot .
Or are you trying to

exactly I got 120 volts

semantics where a layman like me is concerned. To me a positive or hot or live will shock.
anyway reading the posts I see to be safer I should run new wires thanks all req
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

for
reading,
ground
no you can not use the water pipe as a ground conductor. Best way is to run a new cable to the service. Next is to run a ground wire, BUT the ground wire must take the same path as the conductors.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 19 Feb 2006 20:47:29 -0500, reqluq wrote:

Even though using the pipe as your ground connection MAY meet the regulations you are required to follow, and it MAY even be safe to do so assuming that all the pipe joints make a good enough connection, I would recomend running your wiring for any new outlets using wire that meets the current wiring codes as if it were a new installation...... ie:- run new wires for all 3, active, neutral and earth.
Running new 3 core cable is going to make sure your installation is a safe as possible, rather than taking a risk.
Pip
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

thanks pip will do req
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
reqluq wrote:

If you used a solenoid tester rather than a high impedance multimeter to test for voltage between the hot and the conduit then that is a good start. To be more certain you will have to power a load between the ungrounded current carrying conductor (hot) and the conduit long enough to obtain a stable voltage reading under load. The difference between the no load voltage and the voltage across a known load would allow you to compare the voltage drop in the Equipment Grounding Conductor with the drop in the neutral. If the difference is marked then the Equipment Grounding Conductor pathway has a high resistance connection somewhere along its run.
--
Tom Horne

Well we aren't no thin blue heroes and yet we aren't no blackguards to.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.