091205-0851 EST
SPARKYNSJ:
Additional information is needed.
We really need to know if source is single or three phase. Measure each line to neutral voltage with a DVM that resolves 0.1 V. Then measure the line to line voltage with the same meter. If the sum of the two voltages from line to neutral are close to equal to the line to line voltage, then it is a single phase center tapped transformer supply. If the sum of the two line to neutral voltages is closer to the line to line voltage divided by 0.866, then it is a 3 phase Y source.
Next remove all loads from the main panel. Measure the current from the ground bus of the main panel to all grounding paths. Most particularly the water pipe. If there is negligible current, then the neutral current is a result of loads on the main panel.
If the supply is three phase, both line to neutral voltages are very close in value (like within 1 V), and all loads are resistive, then assuming 120 deg phase difference the neutral current is about 38 - 0.5*21 = 38 - 10.5 = 27.5 A. Not too far from the 26 A measured.
Separately assume it is really single phase, then an adequate reactive load can cause the same result.
.