R1+R2 in metal conduit

[jay_t]

For a ring circuit, what is the correct way of testing R1+R2, or R2 alone, in metal conduit if the conduit is being used as cpc? ?:|

 

[green-hornet]

This is sometimes difficult if not impossible to do because of cross bonding etc that imports an earth to other services and metal structures within the building.

If you do the end to end continuity you should end up with a reasonable figure dependant on the integrety of any joints.

I normally do end to end on all cables and end to end on the conduit, Ze, and Zs these readings combined will give a reasonable result.

Just fill in each end to end reading on the cert and leave the r1+r2 as n/a or calculate it.

 

[jay_t]

Thanks m8, that's helpful

 

[electrizion]

Personally I would pull a cpc through it and not rely on the conduit

 

[Apache]

Personally I would pull a cpc through it and not rely on the conduit

's ok if you wired it and not just testing it

 

[green-hornet]

Very good point actually Apache, there has been many articles written on the reliability of conduit as a cpc and all accounts are very poor.

Main reasons are the connection of joints lowering the continuity, and corrosion making breaks in the effective cpc.

Personally I would not rely on conduit as a cpc for any circuit.

 

[electrizion]

Exactly and if I was testing it would fail

 

[batty]

All depends on installation. Schools wired in conduit where a problem to fact with heating up in day and cooling down at night corrosion can be a problem. I had a factory years ago all joints where gone. In a town near me they have maisonettes the downstairs is conduit the readings you get are better than tw/e and they are 40 odd years old. You cannot condemn any installation, test and see this is what my part p provider has told me.

Batty

 

[steptoe]

Exactly and if I was testing it would fail

WHY?

 

[Andy™]

Exactly and if I was testing it would fail

you need to stop doing PIR's. you obviously dont know what your doing. just because its in steel conduit doesnt mean its dangerous

 

[steptoe]

you need to stop doing PIR's. you obviously dont know what your doing. just because its in steel conduit doesnt mean its dangerous

AGREED.

 

[batty]

Thats what I said.

 

[steptoe]

Im sorry if I keep banging on,

but it makes you wonder sometimes if someone like that has actually ever seen a galv conduit job.

I do some factory work for a large multi national company that works 24/7/365 and the conduit is as new(bit dirty/dusty perhaps but mechanically sound),

so it is never an issue as to the continuity.

its all down to having a little piece of paper thats says you are qualified to fry someone,

or having the experience to know how NOT to.

 

[batty]

And a lot of factories are wired in trunking with galv conduit coming of it did one last year and there was no problems with it although the extra points I put in where wired in swa. Only problem I can see with it is singles need to be well marked up especially if it is 3 phase not easy in a large install.

Batty

 

[green-hornet]

Im sorry if I keep banging on,but it makes you wonder sometimes if someone like that has actually ever seen a galv conduit job.

I do some factory work for a large multi national company that works 24/7/365 and the conduit is as new(bit dirty/dusty perhaps but mechanically sound),

so it is never an issue as to the continuity.

its all down to having a little piece of paper thats says you are qualified to fry someone,

or having the experience to know how NOT to.

I like that:^OApplaud SmileyApplaud SmileyApplaud Smiley

 

[electrizion]

you need to stop doing PIR's. you obviously dont know what your doing. just because its in steel conduit doesnt mean its dangerous

Where in my post do i say its dangerous ?

Every conduit installation that I have done as a seperate cpc installed and in many case such has hospitals it is specified.Conduits are often installed in areas where they are not accessable and therefore not open to inspection.

I have come across conduit installations where the impedance changes with the weather. So when carrying a PIR and the conduit is embedded or I am not able to inspect it throughout its run I always recommend a cpc is installed.

Oh and incidently I do know what I am doing andyc

 

[SPECIAL LOCATION]

Where in my post do i say its dangerous ?

I guess probably assumed because you said you would fail it..

Normally a fail (unsatisfactory) is because of some danger to people property or livestock?

maybe wrong assumptions?

:| ?:| :coat

 

[green-hornet]

The problem is that years ago it was totally acceptable to use the conduit as a cpc.

Since then there has been some serious implications on the suitability.

However this is only shown on testing, you can not fail an installation unless there is shown in the tests that the circuit protective core is now at risk.

 

[SPECIAL LOCATION]

The problem is that years ago it was totally acceptable to use the conduit as a cpc.Since then there has been some serious implications on the suitability.

However this is only shown on testing, you can not fail an installation unless there is shown in the tests that the circuit protective core is now at risk.

AND...

whilst testing the earth loop impedance some nasty voltages could appear across the conduit! :|

 

[Andy™]

Where in my post do i say its dangerous ? Every conduit installation that I have done as a seperate cpc installed and in many case such has hospitals it is specified.Conduits are often installed in areas where they are not accessable and therefore not open to inspection.

I have come across conduit installations where the impedance changes with the weather. So when carrying a PIR and the conduit is embedded or I am not able to inspect it throughout its run I always recommend a cpc is installed.

Oh and incidently I do know what I am doing andyc

you said it was dangerous when you said you would fail it.