I have a concern that I happened to run across today and I am hoping that someone out there can shed some light on it for me. I am currently managing a project for the USAF here in San Antonio and I ran across something of concern today in reference to one of the Dry-Type Transformers installed at this particular project area. While walking by the XFMR, I noticed a very loud humming noise coming from the unit. I walked over and did a quick visual on it and could actually feel the heat eminating from the unit at a distance of 5 feet. I had one of the on-site technicians shut down the control (circuit breaker) and tag the unit out of service for further inspection. The case of the XFMR was too hot to touch without gloves on when we removed the front panel. I did not notice anything out of the ordinary nor did I discover any physical damage. One thing that I did notice is that the load on the XFMR was almost nil. The XFMR is a step down....480/277 to 208/120 150 kVa and is currently powering a 3 phase 120/208 400 Amp panelboard which only has a load of about 1 amp total on it!!! Is the lack of load on the transformer the problem?