Since the release of that report, Code proposals have been developed within Code Panel 2 based on this mathematical relationship. These proposals have been hampered by uncertainty in an appropriate value

for Ipssc, the available current at the panelboard. In some applications of the formula, Ipssc is assumed to be arbitrarily large and therefore is neglected.

However, the effect of Ipssc can be significant until the available

current at the panelboard rises very high, to 5kA or higher. Though obtaining solid data on realistic values for Ipssc has been difficult, proposals within Code Panel 2 have put forth a minimum available current of

500A at the panelboard.

A UL investigation into the available current at receptacles conducted in 1993

tends to substantiate this value.6 Using 500A for Ipssc will tend to significantly shorten the allowable run

length if the magnetic trip level (Imag) is held at 300A. However, there is a desire to hold the maximum run length to 50 feet while assuming 500A available at the panelboard.

This forces either the wire gauge or the maximum allowable magnetic trip level to be adjusted to balance the equation: since it is preferable to

assume that 14 AWG will be used, the magnetic trip level of the circuit breaker must be lowered.

This work focuses on experimentally verifying the mathematical relationship when available panelboard current is adjusted while maintaining a 50-foot run length.