Sec.16-11-120. Accuracy of watthour meters

(a) A watthour meter that has an incorrect register constant, test constant, gear ratio to dial train, or which creeps (that is, registers on no load), shall not be placed in service or allowed to remain in service without adjustment and correction after knowledge of the defect.

(b) The average meter error for a watthour meter shall not be in excess of one per cent at unity power factor and, in the case of polyphase meters, the elements shall be in balance within two per cent at one hundred per cent load and unity power factor. When tested in the shop, the error of polyphase meters shall not be in excess of two per cent at one hundred per cent load and fifty per cent lagging power factor.

(c) Whenever a test of a watthour meter shows the average error to be in excess of one per cent, or, in the case of polyphase meter, the elements are not balanced within two per cent at one hundred per cent load and unity power factor, the meter shall be removed from service or adjusted.

(d) For the purpose of pre-installation, installation, complaint, periodic or evaluation tests, the average error shall be determined as follows: (1) The error at light load, at approximately ten per cent of the rated current (test amperes) specified for the meter; (2) the error at heavy load, at approximately one hundred per cent of the rated current (test amperes) specified for the meter; (3) the average error of the meter shall then be computed by taking one-fifth of the algebraic sum of the error at light load and four times the error at heavy load.