On the subject of block heaters, I'm looking for something to keep my standby diesel genset warm if the outdoor temp drops below about 50 degrees. The reasoning is that the 4-cylinder 40KW set will be required to assume up to an 11KW load 30 seconds after starting, for better or worse.
It does have an inline 1KW coolant heater that was used continuously "on" for 10 years and this kept it at 160 degrees!! well the previous user had a computer room and did not care about the cost of power, only cared that the genset would be instantly ready for the 25KW load.
The heater works by being vertically mounted and attached with 5/8" hoses, and the hot coolant rises entering the t-stat housing at the top of the engine, and flows back down through the engine, keeping it warm.
Myself, I see no earthly reason to keep it that hot, burning a KW to do it. I also hear the coolant boil inside the heater, telling me for instance it is too darn big. I attempted to put a thermostat on it, but the boiling issue troubles me, it cannot be good for the coolant. Then the thermostat, a kind used for 1600 watt space heaters, broke. It was a bi-metal snap type, and I used a hose clamp to attach its bracket to the pipe.
I know I can reduce the power of the heater by placing a half wave rectifier (big diode) in series with it. There is a nice steel pipe I can use for a contact-thermostat, so that regardless of outside temp, I could set the thing so that the engine coolant never gets below a certain temperature. I don't know where to find a decent thermostat that would use a physical contact with a pipe to detect the temperature.
The engine is small, it's a 4 liter Perkins normally aspirated diesel; would a magnet-type or other 'stick-on rubber' type for the oil pan help me out there? Or should I heat the coolant, in turn heating the whole block?