This Standard specifies requirements and methods of test for tunnel type terminal neutral bars for low voltage switchboards for termination of copper conductors up to 50 mm2. It applies to bars of the tunnel terminal type for connection to copper conductors—(a) of the rigid, stranded or flexible type; and(b) with a cross-sectional area of 1.0 mm2 up to and including 50 mm2.NOTES:1 Preferred current ratings are 63 A, 80 A, 100 A and 125 A.2 This Standard is for tunnel terminal type neutral bars for use as components in switchboards,panel boards, load centres, meter boxes and the like.3 The current ratings in this Standard apply to bars with a maximum temperature rise of 45 Kwhen tested at ambient temperature in open air.The ratings obtained in this Standard are applicable to switchboards with an internal airtemperature rise of up to 25 K.NOTE: Refer to Appendix A of this document for further details.