What does a ZS test prove?
A Zs test is not to prove an earth connection exists, although it would do so, but to prove that the CPD would operate within the time required by BS7671. Smpling should be of circuits, not equipment of a circuit that is being tested.
What is the source to check values of Zs?
For overcurrent devices not covered by those tables, another reliable source of information on the limiting values of Zs must be consulted, such as the manufacturer’s data. Where the protective device is a nondelayed RCD, the maximum value of Zs can be found from Table 41.5 of BS 7671.
How do you measure Zs at DB?
Zs is your total impedence of the circuit including your sub main. There is only one Ze which is at the origin of the supply. The board fed by the sub main will have a Zs value at the board which will roughly equal Ze = R1 +R2. You measure the Zs at the incomming terminals of the sub board.
What is the 80% ZS rule?
The 80% rule of thumb is only intended to be applied to a test result taken from an impedance test. You have to ensure that the tested value does not exceed 80% of the tabulated value.
What is difference between Ze and Zs?
Zs is the total impedance of the complete circuit and it is made up of: The impedance of the supply cables and transformer windings, Ze. The resistance of our circuit line conductor, R1. The resistance of our circuit cpc, R2.
What happens if Zs is too high?
If a Zs value is high, then you need to establish whether it is due to circuit conditions, supply conditions, or a fault. You can then descide the appropriate course of action. Just installing an RCD or RCBO may not be the solution in a deteriorating installation. It would appear that PME is psychic.
What is maximum Zs?
The 1.37 ohms value is the 100% max Zs value which should be recorded on the test certificate.
How do you calculate ZS PFC?
Divide the voltage by your Ze added to your Zs for the board. So for a three phase board you would have: 400 / (0.08 + Zs for your board).
Is ZS a live test?
The presenter does live Zs testing at sockets with a plug top lead switching on the socket switch before taking the test. So this in the words of the Regulation would be “reasonable”.
What if Zs is too high?
If a Zs value is high, then you need to establish whether it is due to circuit conditions, supply conditions, or a fault. You can then descide the appropriate course of action. Just installing an RCD or RCBO may not be the solution in a deteriorating installation.
How do you calculate ZS using R1 R2?
To measure Zs do just that go to the highest point of R1+R2 on that circuit and carry out a live test. Record your result. 2. Calculate Zs by Zs=Ze+(R1+R2).
Should ZS be higher than R1 R2?
Zs=Ze+(R1+R2) well not in this case. Just not come across such a difference before that Zs has been so much lower than Ze+(R1+R2)….See Also:
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