testing tt systems

[Manator]

Ze can be taken without disconnection of earth, and should be noted. I often work in environments where it is impossible to remove any earthing to do the classic, text book tests. However, providing you make notes, there is nothing wrong in taking the results shown with all earthing in place.

 

[batty]

Well i can't see what the problem is i test all systems be it TT TNCS and TNS your ZS is going to be made up of the external ZE and R1 + R2. A TT system ZS is going to be different to a TNCS or TNS system it has to be because of the route the fault current is taking back to transformer.

 

[paul copeman]

sorry i didnt explain myself properly

yes it is PIRs and i can isolate to get ZE or resistance of rod but then they not happy when you keep switching things off

IR is LIM by the way

thanks to everyone that helped and please accept my appolagies for not being very detailed in my posts

im not used to posting stuff on the net

and i agree with you robin spark the tests dont prove much but thats what the firm want and whats been agreed with the owners of the pubs

 

[Robin Spark]

Ze can be taken without disconnection of earth, and should be noted. I often work in environments where it is impossible to remove any earthing to do the classic, text book tests. However, providing you make notes, there is nothing wrong in taking the results shown with all earthing in place.

This is the difference though Manator, as you will be stating on your paperwork that Ze was tested with earthing conductor and main bonds still in place as you werent able to isolate the installation. Also I dont think you would take your overall Zs away from your Ze test to come up with a hypothetical R1 + R2 for each circuit.

 

[Revved Up Sparky]

the thing is the pubs we are testing wont let us turn off curcuits to do testing as we are in there when they are open sothats how we do it im afraid

I've done a lot of work in pubs, many of which don't open until about 11.00am. If they want a proper job doing then they need to allow you access before they open, eg at 8.00am. For example, you cannot get an accurate reading for the Ra without isolating the supply and disconnecting the earthing conductor from all bonding to services and cpc's etc (to eliminate parallel paths). R1 + R2 tests are vital for ensuring that final circuits are earthed through a cpc rather than extraneous metalwork and RCD's must be checked to ensure they are tripping correctly under fault conditions thus providing supplementary shock protection. In a nutshell a persons life is more precious than a few hours takings (if out of hours work is refused).

 

[johninlondon1]

Deducting value of Ze from Zs will not give you true actual (R1 + R2) values due to parallel paths (ie fault current using extranuous conductive parts - Water main/Gas main/structual steelwork etc). Measured Zs should be lower than the calculated value of (R1 + R2) +Ze if it was found to be a higher value then further investigation is required.

 

[S60TEM]

if your not allowed to turn off the supply then what exactly do your reports look like? LIM LIM LIM? Worthless!

R1+R2 = Dead test

Ze/ Ra = Dead test

R2 (method2) = Dead test

IR = Dead test

only live tests you can do are

1) Zs of socket circuits as your not allowed on lighting circuits to open an accessory to expose live conductors.

2) I would say RCD testing but as your not allowed by your "firm" to knock the power off, they aren't gonna like you testing the RCD's either!

I think your wasting your time even "testing" anything as imo the report is worthless to anyone as it proves nothing safety wise and I'd think that any insurance company would just laugh at any claim that arose from any electrical issued claim!

 

[SLIPSHOD & SLAPDASH]

But thats how they can produce 'Satisfactory' reports :_| and get paid for it handsomely

 

[S60TEM]

But thats how they can produce 'Satisfactory' reports :_| and get paid for it handsomely

mmmm, I hate the word Satisfactory........it should be PASS or FAIL imo