Paragraph 1 Pre-heatingI1

he following tests shall not be carried out until the voltage circuits of meters under test and the voltage circuit of the working standard integrating meters have been energised for a period of one hour or half an hour if a current of not less than either 10% of basic current or 5% of marked current is applied to the current circuit of the meters, save that the non-registration test may be carried out during the pre-heating period.

Sub-paragraph (1) shall not apply to a meter which the examiner is satisfied is capable of full operation as soon as it is energised.