The BS 7671 tables state that the highest measured Zs should not be more than 0.8.
Contents
- What if the ZS is too high?
- What is a good fault loop impedance reading?
- What is the maximum ZS permitted by BS 7671?
- What is a high Ze reading?
- What does a ZS test prove?
- What is a good earth loop impedance?
- What is Zs and Ze?
- Who is responsible for earthing a property?
- Why is ZS important?
- Can ZS be calculated?
- What is RCD uplift?
What if the ZS is too high?
If a Zs value is high, you need to know if it’s due to a fault or a circuit condition. The appropriate course of action can be decided by you. Installation of an RCD or RCBO may not be enough to fix an installation that is in bad shape.
What is a good fault loop impedance reading?
The value of external earth loop impedance may be different from the average maximum value declared by the electricity distributor. The system is called a TN-C-S system.
What is the maximum ZS permitted by BS 7671?
The maximum ZS allowed by BS 7661 is on the IET forum. Is the correct value to be entered for the RCBO type B.
What is a high Ze reading?
There are earthing arrangements on the property. There is a wiring fault on the earth cable.
What does a ZS test prove?
The Zs test is not to prove an earth connection, but to prove that the CPD will operate within the time required by BS 7661. It is notmpling equipment that is being tested.
What is a good earth loop impedance?
The value of external earth loop impedance may be different from the average maximum value declared by the electricity distributor. The system is called a TN-C-S system.
What is Zs and Ze?
Zs is the earth fault loop impedance, and ze is the external impedance.
Who is responsible for earthing a property?
It is up to the electrical installer, acting on behalf of the consumer, to make sure that the earthing connection is suitable for the requirements of the electrical installation and that it is connected to the earthing conductor of the installation.
Why is ZS important?
The Zs value is important because if the wrong type of RCD is used, it will not operate effectively under certain types of equipment fault, and we will not be able to connect.
Can ZS be calculated?
You can get the Zs by using either the Earth Fault loop impedance meter or a calculation. The measured value is used by the company.
What is RCD uplift?
RCD uplift is one of the most common problems. Because of the measurement technique used, the result will include the internal impedance of RCD and RCBO in the displayed value, which can be far higher than the actual loop measurement alone.