Just to clarify and in response to the reply that someone had written but seemingly than deleted... .
Since I received it via email, I'm sure others did.
I did not say to use a under rated cord, or bad cord.
I 100% agree, with you on that part, the cord needs to be properly rated and in fine shape.
In fact, in my other posts, I warn about the fact that just checking voltage wont save one from a fire or detect a bad connection.
I've had a couple over the years nearly melt, so I now monitor voltage and current 100% of the time, to see that the connections are well.
All I said was, that a longer cord (assuming properly rated) on our block heaters will NOT cause and increase in current as if it was an electric motor / tool, causing the tool to burn up from low input voltage and too high of an operating current since it's a constant power / inductive device.
Our block heaters are resistive elements, not inductive.
Once you start lowering the applied voltage to it (via voltage drop over an extension cord), the current drops as well.
So the heater is less effective.
Just ohm's law ...
The inverse of what happens with a motorized electric power tool.
Longer the cord, the lower the applied voltage, the higher the input current, and more heat in the motor... lower the voltage enough, or operate at the point long enough, and the motor over heats. That's what the real danger is with a long extension cord with an electric motorized power tool... both to the tool and cord set... the current sky rockets and exceeds the cords rating, due what you expect normal operating current to be...
Our block heaters do not do that... longer cord, they draw less current, and they generate less heat in the water jacket.
So if we expect the block heater to draw ~6 amps with a full 120Vac applied to it, but have to go to a longer cord, get the heaviest you can, to make the heater as effective as you can. .
But the current isn't going to go past the 6amps. . in fact it will go down with a longer cord.
Again, unlike the heater, the power tool say rated at 10amp, but put a long extension cord on the power tool, and it can go up to 50% higher than that, and as it gets hot, still increase more... and it finally runs away and will go over double. . burning up the cord and motor.