100. TESTING IN PLACE All tests on watt-hour meters and demand meters in service made upon complaint or request of the customer as provided for these rules shall, if practicable, be made in the place of permanent location on the customer's premises, with approved testing apparatus and under the local conditions of operation, unless otherwise stated in any rules or allowed by special order of the Commission.105. INSTRUMENT TRANSFORMER AND SHUNT Watt-hour meters installed with instrument transformers or shunts shall be tested jointly with such transformers or shunts, unless the ratio and phase angle of the transformers and the resistance of the shunts have been previously determined within ten (10) years and are on file at the office of the utility for use in calculating results of test. All such calibration tests must have been made by a laboratory of recognized standing or by the utility, using apparatus and methods satisfactory to the Commission. Unless the accuracy of the transformer ratios is questioned, manufacturer's rating will be acceptable.110. ROUTINE METER TESTS Meters may be removed from customer's premises and tested in the meter shop of the utility for routine tests.