Dummy load 2kW+ - under development (without thermostat)
For many experiments I need very good dummy load for high RF power. After different things I chose easy solution. I use 3x50ohm dummy load and 6 resistors with 50ohm, all on nominal power 250W, together 2.25kW. The configuration is one dummy load 50ohm with 2 pieces 50ohm resistor in series, it's 150 together and this all 3x paralel with final resistance 50ohm. I tested it with 1.5kW on all HF bands with switched on both blower and for 1 minute it was enough. After 1 minute was the temperature rising up to 50°C. The cooler is 50*100*200mm aluminium, under all resistors I used thermal foil from the manufacturer KERAFOL, material S900 thickness 0.15mm. SWR on all bands (1.8 to 50MHz) under 1:1.1, tested with antenna analyzer AA-200.
More you can see from picture.