The additional monitoring sensors I installed in our NMEA2000 system this winter has provided a wealth of data. One tidbit was the temperature of the two AC transformers (isolation and step-down) in our electrical system. I was surprised at the the increased temperature above the ambient engine room temperature in the transformers as I was pulling power through them to operate the two electric heaters.
At our moorage we are on a 30A/120 volt circuit. Normally, we don’t pull more than 15 to 20 amps on a steady basis. This gives a little headroom in case there are transient loads from the DC charger pulling power to service the DC side of the boat. With that steady state load, I’d routinely see a 15 to 20 degree increase above ambient in the transformers. While probably not a big issue, heat tends to accelerate the degradation of components so I thought I’d see what I could do.
The transformers are toroidal style (i.e., doughnut shape) which means there is a hole through which I can pull cooling air. I wanted the fans to only operate when the tranformers were working so I tapped into the AC power being put into the transformers. After the installation of the fans, the transformers are running about 10 degrees cooler, in the 5 to 10 degrees above ambient engine room temperature.