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Transformer enclosures shall be constructed of heavy gauge sheet steel and coated with a
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gray powder paint finish (ANSI 61). Ventilated transformer enclosures shall be UL/NEMA
Type 1 rated and UL/NEMA Type 3R rated for outdoor use with the addition of a weather
shield. This information must be listed on the transformer nameplate.
Maximum transformer enclosure temperature must not exceed 650°C rise above a 400°C
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ambient under full load.
Transformers must have vibration isolators located between the core and coil assembly and
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the transformer enclosure to reduce audible sound levels caused from magnetostriction of
the transformer core. No externally located vibration dampening pads shall be used as they
tend to increase audible noise. Ventilated transformers are to be floor mounted to a concrete
pad.
The transformer enclosure must be grounded by the installer in accordance with the latest
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edition of the National Electric Code and any local codes or ordinances.
Performance
Audible sound levels will not exceed limits established in NEMA ST 20:
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10 to 50 KVA 45 db
51 to 150 KVA 50 db
151 to 300 KVA 55 db
301 to 500 KVA 60 db
Transformers, 15 KVA to 500 KVA, shall incorporate a UL recognized 2200C insulation
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system and exhibit a maximum 1500C temperature rise above a maximum ambient of 400C
under full load.
Vertex Edge System
42
User Manual
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