Quote:
Originally Posted by rickst29
The MOSFETs in the switches consume 1-2 Volts of output potential on the 'Load' circuits. Our AC heatert, without an SSR in line, consumes 1.8A at 120V. So, 2V lost at the SSR @ 1.8A is only about 5 watts.
The DC heaterside, however, runs 10.7 Amps at @ 14VDC. The 2V voltage drop creates a significant loss of power on this path: At the 12 Volt net potential after 2V loss in the SSR, we will run at only 9.2A (yielding just 110 Watts, instead of 150). This is below Norcold's minimum DC voltage limit of 13.5V, so I could need to add a Buck Boost DC regulator as well. 
Anyway - back at the SSR, the 2V voltage drop times the 9.2 Amps is creating almost 20 watts of damaging heat. (roughly 4x the amount of heat generated on the AC circuit). At least the small heatsink would seem to necessary, in order to prevent overheating and burnout. |
As I said, I successfully melted my DC side without a heat sink! But the AC side, on its own, has been fine sans heat sink. So, the math corroborates reality, at least in this instance.
Although there were many false starts, I cannot tell you all how much happier we are now that the fridge self-regulates.