TRANSFORMER ROOM FORCED AIR VENTILATION DESIGN CALCULATION (2025)

Can anybody suggest a design computation of a transformer room ventilation (forced air) with the following data?

Transformer area - 4.00m(L) x 3.00m(W) x 4.00m(H)
Location - at the side of the building
Transformer size
1000kVA, 13.8/0.415kV, 60hz
iron losses - 1,800 watts
copper losses at nominal load - 12,100 watts
Ambient Temp - about 30-35 deg C

We need to construct this room.

Thanks
Arvin

I'm sure there is a calculation method available. I would search the IEEE standards at

thanks guys, will try to look into the ieee website and HVC forum.

regards,
Arvin

In case you're still working on this --

We use a "rule of thumb" of 5cfm per kVA of transformer, which is conservative, but helps account for issues that hinder the performance of the blower. This would give you a value of 5000 cfm forced air ventilation. You should place the intake and exhaust on opposite sides of the room, with intake low and exhaust high.

If you take the total heat losses into the room, (13900 Watts) and calculate the heat load at 3.4 Btuh/watt this gives you a heat load of 47,460 Btuh which at approximately 12000Btuh/Ton of cooling would require an A/C unit sized at 4 Tons of cooling. A small split system would suffice which at the rule of thumb of 400cfm/ton would mean about 1600cfm of conditioned air. If you have a chilled water system, you could further reduce the amount of air depending on the water temperature and if you had a dedicated VAV box for the room.

As "AllGreek2me" stated however, (and if you can ventilate the room with air at an entering temperature sufficiently low at all times of the year to maintain the 30-35 degrees C), you could do it with just exhaust and outside or precooled air, but the air volume you would have to move would increase dramatically. 5000cfm is quite conservative, but not extraordinarily so.

Best of luck.