UFC 3 -520-01
June 10, 2002
transformer cooling. Forced -air cooled transformers can be integrated into the facility
energy conservation design by a heat recovery syste m.
4-5.2.2 Figure 4-2 shows the installation spacing criteria for transformers rated 112.5
kVA or less. As shown, ensure these transformers have a minimum 0.3 meter (12-inch)
spacing from combustible materials or have a fire-resistant, heat-insulating barrier. This
requirement does not apply if the transformer is the nonventilating type .
Figure 4-2. Spacing Requirements for Transformers Rated 112.5 kVA or Less
Combustible
Material
Combustible
Combustible
Material
Material
Barrier
Transformer
Transformer
Transformer
305 MM(12 IN) Minimum
Completely Enclosed
Transformer Minimum Spacing
Transformer With Heat-Insulating,
Transformer, With or
Fire-Resistant Barrier
Without Ventilation Openings
4-5.2.3 Dry-type transformers rated for more than 112.5 kVA have different
requirements, depending on the insulation rating as shown in Figure 4 -3. Transformers
with less than 80 C (176 F) temperature rise rated insulation require installation in a
fire-resistant room. Transformers with greater than 80 C (176 F) temperature rise
rated ins ulation require either the spacing shown in Figure 4 -3 or a fire-resistant, heat-
insulating barrier.
Figure 4-3. Spacing Requirements for Transformers Rated Over 112.5 kVA
Combustible
Fire-Resistant
Material
Room
3.7 M (12 FT)
Transformer
Transformer
1.8 M
1.8 M
No Minimum
(6 FT)
(6 FT)
Spacing
Not Totally Enclosed,
Transformer With Less
Ventilated Transformer
Than 80 C Rise Insulation
With 80 C Rise Insulation
4-11
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