When stacking two Ventilated Transformers one above the other one, how close can the Transformers be?

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Issue:
Allocation of space for Ventilated Transformer installation

Product Line:
LV Transformers

Environment:
Applies to Ventilated Transformers by SquareD/Schneider Electric

Cause:
Ventilated Transformers require clearance space between the top surface of the enclosure and any obstruction for proper heat dissipation

Resolution:
When placing one transformer above the other – the layout must comply with National Electric Code 450.9 Ventilation – “The ventilation shall dispose of the transformer full-load heat losses without creating a temperature rise that is in excess of the transformer ratings”.

The temperature rise of the transformer is design for a 30 deg C average (40 deg c Maximum) 24 hour period. To comply with the NEC requirement it is recommended to have a minimum of 36” between the units or a barrier placed between the two units preventing excess heat from the bottom unit from directly entering the top unit. Also, it is good practice to install a metal barrier or baffle between vertically mounted Transformers to prevent heat from the lower unit from rising and heating the upper unit. This applies to EE, EX and EXN series Transformers. When using a barrier – the clearance between the units shall exceed 6”.

The installation should be verified by the Professional Engineer with the BTU’s output of the two or more transformer based on actual loading, room size and layout, and HVAC design for the room to keep both units in an environment of 30 deg C average. (40 deg C MAX) during the life of the product.