Section 10C. No person shall alter, repair or install any oil burning equipment or any of the appurtenances thereto, except for electrical wiring and connections, as defined by rules and regulations promulgated under the provisions of section ten governing the construction, installation and operation of oil burning equipment and the keeping, storage and use of fuel oil or other inflammable products used in connection therewith, unless he holds a certificate granted by an examiner for the certification of oil burner technicians. Notwithstanding the provisions of the preceding sentence, the cleaning of an oil burner strainer or nozzle or the cleaning or replacement of a photo cell, in any building or structure by the owner or manager thereof or by any regular employee of such owner or manager in a building or structure owned or managed by his employer, may be done without the holding by such owner, manager or employee of a certificate as an oil burner technician.