I have a heater that draws a continuous 18 amps and has a 20 amp plug. I created an extension cord to plug into the wall, however on one end it's a 20 amp receptacle - heater plugged into extension cord - and the other end of the cord is a normal 15 amp plug, plugged into a 15 amp receptacle in the wall. The extension cord is 12 gauge.
I used a kill-a-watt to measure the draw at the wall (the 15 amp outlet) and it's drawing 18 amps.
Is this ok for long term use? i.e. plugged in 8 hours a day straight.
UPDATE: In my haste to get this posted as I worried about the setup, I mis-spoke and need to make a correction - The outlet itself is a 20 amp outlet in the wall, BUT the make plug on the end of the extension cord is a 15 amp plug (was the only part I had at the time). Does this still pose a large risk? Here's the picture:
Update: It's no longer plugged in at the top where it was for several years. Image of extension box:
Here's a photo of the plug that goes to the heater: