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What do LV and HV designate on low voltage dry type transformer drawings?

LV stands for "low voltage". HV stands for "high voltage".

Square D does not label low voltage dry type distribution transformers as "primary" and "secondary". Per the NEC, the side of the transformer connected to the source is the primary, and the side connected to the load is the secondary. The winding that has the higher maximum line-to-line voltage receives the HV, and the lower maximum line-to-line voltage the LV. For example, an EE25S3H transformer (240 x 480 to 120/240) has the HV on the 240 x 480 volt winding (maximum voltage is 480) and the LV on the 120/240 volt winding (maximum voltage is 240).

It's a little more interesting with an EE25S60H (208 to 120/240) where the LV goes on the 208 volt winding and the HV goes on the 120/240 volt winding because 240 is higher than 208.
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