Bulk Workwear - Clothing Suppliers for the Whole Forum Network
This official sponsor may provide discounts for members
Advertisement - Content continues below
Advertisement - Content continues below

Discuss Excessive earth fault loop impedance in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

I work for a hotel chain and recently we’ve had our 5 yearly test they have 8 circuits from our LV panel with excessive loop impedance readings !! So apart from either introducing an rcd or dropping mcb ratings or type is there any other way of achieving satisfactory readings ??
Also if I have a fuseboard fed from another fuseboard ie a distribution circuit when doing a certificate is the (ze) on the furthest board recorded as a zs I think it’s called a zdb I’m just trying to understand there report as it doesn’t state anything just high loops
Can someone advice me please

395BCEB0-7110-44BC-B0DD-69A0583B574E.png
 
Aico Carbon Monoxide Detectors
This official sponsor may provide discounts for members
Advertisement - Content continues below

telectrix

-
Mentor
Arms
Esteemed
it sounds like maybe the Ze is excessive or a fault with main earthing. need far more info to make an accurate diagnosis.
 
  • Thread Starter Thread Starter
  • #5
it sounds like maybe the Ze is excessive or a fault with main earthing. need far more info to make an accurate diagnosis.
I’m going to the hotel tomorrow to have a look will provide more info then but if it is the ze wouldn’t all the circuits have a high reading ?
Also regarding zdb is the ze from another dB recorded as a zs reading ?
Many thanks for your reply
 

telectrix

-
Mentor
Arms
Esteemed
I’m going to the hotel tomorrow to have a look will provide more info then but if it is the ze wouldn’t all the circuits have a high reading ?
Also regarding zdb is the ze from another dB recorded as a zs reading ?
Many thanks for your reply
yes. your Ze is the EFLI at source of installation.all readings downstream ( after main earth) are Zs. ( sometimes referee to as Zdb at dis. boards. ) these Zs readings are taken with bonding connected, as opposed to the Ze where bonding is not.
 

Ian1981

-
Mentor
Arms
Esteemed
Presuming that the LV panel contains mccb’s then It could be that either the maximum zs that the inspector has allowed for the device is incorrect and it actually complies(manufacturer’s data is required) or that the original install , incorrect maximum zs values for the ocpd was incorrectly assumed to comply when in fact it never did.

Or as others have said the Ze is on the high side.
Some results/values of the excessive zs values might help
 
Last edited:

telectrix

-
Mentor
Arms
Esteemed
another thing springs to mind. maybe testing at no-trip and the MCBs are corrupting the readings due to internal components.
 

Andy-1960

-
Arms
Esteemed
Another thought, how close is the main DB to the supply transformer and has the tester used a MF meter that is suitable with a high current test facility?
Standard domestic type MF meters can give incorrect Zs readings if close to the supply transformer.
 
T

Toneyz

Do you have a previous or better still initial report/certificate? as for your question other than what you posted to overcome this would be the increase of conductor size/additional earth.
 
  • Thread Starter Thread Starter
  • #11
Hi sorry for delay I’ve been to the job and they are protected by Berlin gerun BS100N Mccb I have 3 phase 100a and single phase 63a and 32a they are saying max zs is 0.10 for these can anyone confirm or tell me what the max zs is for these many thanks

7076F013-1A75-46BF-9B32-FF3DB454EC56.jpeg

6F225430-8407-404D-8D8B-4BC206C4AF23.jpeg

2F200605-9FA2-4B4B-9A42-BE5AC05E8A39.jpeg

E0B12D01-F8F6-468E-8F50-A3E81EBF2580.jpeg

51A99293-C3AA-4CD2-90DA-1B59E1DD7DDC.jpeg
 
  • Thread Starter Thread Starter
  • #13
Many thanks o did s bit of digging and worked out 0-24 so I knew they all comply but thanks for your help
 
Aico 3000 Range
This official sponsor may provide discounts for members
Advertisement - Content continues below

Reply to Excessive earth fault loop impedance in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

Electrical2Go - Online Electrical Supplier
This official sponsor may provide discounts for members
Advertisement - Content continues below
Top Bottom