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(iii) In situ bond testing
In situ bond testing is the ability to measure the earth integrity of a class I asset that is “hard wired” to the
electrical supply. Normally there would be no convenient method to connect the asset to the PAT400
without disconnecting the equipment from the supply.
The PAT400 can be connected to an adjacent electrical outlet and a bond test conducted to the case of
the asset. The measured resistance will be:
The resistance of the asset to the earth circuit (wall plate or fused spur)
The resistance of the fixed wiring through the building to the earth point into which the PAT400 is
connected. This could be a few metres or 10’s of meters.
Allowance should be made for the additional building (fixed) wiring resistance when deciding if the asset
is safe to use.
(iv) Parallel earth paths
Parallel earth paths warnings apply to a range of measurements. See Appendix A.8 for further
information.
(v) 25 A Bond limit exceeded
Testing a very low resistance circuit using the 25A Bond test can generate the message:
25 A Bond limit exceeded,
10 A Bond enabled.
To prevent the high current bond test from exceeding the 25 A limit, testing of very low resistance
(typically <0.03 !) will automatically drop the test current to 10 A.
(vi) Excessive lead resistance
The bond test may fail due to the excessive length of the equipment supply cord. Extension leads may
also fail due to increased resistance induced by long cable lengths. When a bond test fails the PAT400
will display a lead compensation table, allowing the pass limit to be modified. See section 3.11 and
Appendix A.6 for further details on lead compensation.
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