Section 57.21. Demand meter testing

(a) A demand meter of the block interval type, which fails to properly reset completely to zero at the end of each time interval, or a demand meter which has an incorrect register constant, test constant gear ratio or dial train may not be placed in service or allowed to remain in service without adjustment and correction.

(b) Tests of graphic and indicating types of demand meters shall be made at points about 1/3 to 2/3 scale in terms of full scale indication. The deviation shall be recorded in terms of full scale deflection.

(c) A demand meter of the block interval type which has an error in demand indication of more than ±2% in terms of full scale indication on graphic and indicating meters may not be placed in service or allowed to remain in service without adjustment. If a timing element also serves to keep a record of the time of day at which the demand occurs, it shall be adjusted if its rate is more than ±.25% in error.

(d) A thermal type demand meter which has an error in demand indication or registration of more than ±3% in terms of full scale indication on graphic and indicating meters may not be placed in service or allowed to remain in service without adjustment. If a timing element also serves to keep a record of the time of day at which the demand occurs, it shall be adjusted if its rate is more than -.25% in error.

(e) A demand meter with solid state digital display for measured quantities shall be tested for accuracy of the register using its internal input pulse initiator and a watthour meter or using an auxiliary pulse device as the input source. The applied test current or pulse rate may not exceed the class of the meter. The accuracy of the displayed demand shall be within ±2.0% of the input.

(f) A utility shall make periodic test of its demand meters in service, as follows:

(1) Self-contained thermal demand meters, up to and including 50 amperes rated test current, shall be tested on the same schedule as the watthour meters with which they are associated.

(2) Self-contained thermal demand meters, of over 50 amperes rated test current, shall be tested at least once every 96 months.

(3) Thermal demand meters connected through current transformers or current and potential transformers shall be tested at least once every 48 months.

(4) Curve drawing watt meters used for determining demands shall be tested at least once every 24 months.

(5) Demand meters of the block interval type shall be tested on the same schedule as the watthour meters with which they are associated.

(g) A demand meter shall be tested for accuracy by the public utility prior to its installation, or be so tested within 90 days after its installation. It shall also be inspected by the public utility for proper connection, mechanical condition and suitability of location within 90 days after installation.

The provisions of this § 57.21 adopted February 25, 1946; amended through May 29, 1973; amended January 7, 1983, effective January 8, 1983, 13 Pa.B. 131; amended August 7, 1987, effective August 8, 1987, 17 Pa.B. 3324; amended March 8, 1991, effective March 9, 1991, 21 Pa.B. 947. Immediately preceding text appears at serial pages (125377) to (125378).

Notation

Authority

The provisions of this § 57.21 issued under: the Public Utility Code, 66 Pa.C.S. § § 331, 501, 504 and 1501; amended under: Public Utility Code,66 Pa.C.S. § § 501, 1501 and 1504.

Cross References

This section cited in 52 Pa. Code § 57.22 (relating to request tests and fees); 52 Pa. Code § 57.23 (relating to general testing conditions); and 52 Pa. Code § 57.254 (relating to advanced meter standards).