Transformers & Capacitors

The following requirements apply to all transformers except the following:

Current transformers
Dry-type transformers installed as a component part of other apparatus
Transformers that are an integral part of an X-ray, high frequency, or electrostatic-coating apparatus
Transformers used with Class 2 and Class 3 circuits, sign and outline lighting, electric discharge lighting, and power-limited, fire-protective signaling circuits

Signs or visible markings on the equipment or structure must indicate the operating voltage of exposed live parts of transformer installations.

All capacitors, except surge capacitors or capacitors included as a component part of other apparatus, must have an automatic means of draining the stored charge after the capacitor is disconnected from its source of supply. Certain specific requirements, which are provided in 29 CFR 1926.405, apply to capacitors installed on circuits operating at more than 600 volts, nominal.

Certain types of transformers must be kept in a vault, as follows:

Dry-type, high-fire-point, liquid-insulated and Askarel-insulated transformers installed indoors and rated over 35 kilovolts
Oil-insulated transformers installed indoors, if they present a fire hazard to employees

Transformer vaults must meet certain requirements, as follows:

Contain fire
Contain combustible liquids
Prevent unauthorized access
Have locks and latches arranged in a way that allows the door to open from the inside of the vault

Materials cannot be stored inside a transformer vault, and pipes or ducts foreign to the vault installation cannot pass through the vault.

Oil-insulated transformers adjacent to a building or combustible material require safeguards from fire for specific areas, such as the following: