Section 460.3607. Watt-hour meter requirements.

(1) Watthour meters that are used for measuring electrical quantities supplied shall conform to ANSI specifications and meet all of the following requirements:

(a)   Be of proper design for the circuit on which the meters are used; be in good mechanical and electrical condition; and have adequate insulation, correct internal connections, and correct register.

(b)   Not creep at no load with all load wires disconnected at a rate of one complete revolution of the moving element in ten minutes  when  potential  is impressed.

(c)   Be accurate to within plus or minus 1.0%, referred to the portable standard watthour meter as a base, at two unity power factor loads: light load (l.l.) and heavy load (h.l.).

Meter  Must   be  Accurate   within  ±  1.0%   to Portable Standard
Meter Class	Light Load Test Amperes	Heav y      Load Test Amperes	Inductiv e           Load 50% Lagging Power Factor Test Amperes
Self- Contained	10% Rated Test Amperes of Meter	75- 100% Rated Test Amperes of Meter	75- 100% Rated Test Amperes  of Meter
Transfor mer Rated	5-10% Rated Test Amperes of Meter	75- 100% Rated Test Amperes of Meter	75- 100% Rated Test Amperes  of Meter

(d)   Be accurate to within plus or minus 2.0%,  referred  to  the   portable standard watthour meter as a base, at inductive load (i.l.).

(2)   Polyphase meters shall have their elements in balance within  2.0%  at rated test amperes at unity power factor and  at approximately 50%  lagging power factor.

(3)   Meters that are used with instrument transformers shall be adjusted so that the overall accuracy of the metering installation meets the requirements of this rule.

(4)    Meters and associated devices shall be adjusted as close as   practical to zero error and within the accuracy limits specified in subrule (1)(c) of this rule.

History: 1983 AACS; 2008 AACS.