6.4.4.4 Test points

A test joint must be provided at every connection of a down conductor to the earthing system (above the earth entry point, if practicable).
Test joints are required to facilitate the inspection of the following characteristics of the lightning protection system:

• Connections of the down conductors via the air-termination systems to the next down conductor
• Interconnections of the terminal lugs via the earth-termination system, e.g. in case of ring or foundation earth electrodes (type B earth electrodes)
• Earth resistances of single earth electrodes (type A earth electrodes)

Test joints are not required if the structural design (e.g. reinforced concrete or steel frame structure) allows no electrical isolation of the natural down conductor from the earth-termination system (e.g. foundation earth electrode). The test joint may only be opened with the help of a tool for measurement purposes, otherwise it must be closed. Each test joint must be clearly identifiable in the plan of the lightning protection system. Typically, all test joints are marked with numbers (Figure 6.4.4.4.1).