Use of auto-transformers
20.—(1)  When installing an auto-transformer in an electrical installation, a licensed electrical worker shall take suitable measures to ensure that —
(a)the lower voltage system in such auto-transformer will not be accidentally charged above its designated voltage during the use of such auto-transformer by leakage from or contact with the higher voltage system of the electrical installation; and
(b)the voltage between any part of the lower voltage winding of such auto-transformer and Earth shall not, at any time during the use of such auto-transformer, exceed the voltage between the terminals of the lower voltage winding of such auto-transformer.
(2)  No person shall use an auto-transformer to supply electricity to —
(a)a socket-outlet;
(b)a portable appliance, unless the auto-transformer is contained therein;
(c)an electric toy; or
(d)any extra-low voltage circuit.