Barry here is the result of my review:
Originally Posted by BarryD0706
I believe these pads are purely resistive so amps would decrease at lower voltages. They would have to be fed by a voltage regulator circuit (and operated at a lower voltage than supply) in order to do what you suggest.
Some definitions are in order.
Resistive Load - An electrical load which is characteristic of not having any significant inrush current. When a resistive load is energised, the current rises instantly to it's steady-state value, without first rising to a higher value. An electrical load in which voltage and current are converted to energy in the form of heat; i.e., an electrical heater, incandescent bulb.
Inductive Load - An electrical load which pulls a large amount of current (an inrush current) when first energized. After a few cycles or seconds the current "settles down" to the full-load running current. The time required for the current to "settle down" depends on the frequency or/and the inductance value of the Inductive load
Being purely resistive, a 1000 watt heater would draw 1000 watts.
My logic using a constant power requirement went like this.
Power = Volts x Amps
Power is measured in watts so a pad that draws 120 watts of power when "on" will draw 10 amp at 12 volts.
That same pad at 13 volts would be 120/13 or 9.2 amps.
For your assertion to be correct, the power requirement would have to vary and not stay fixed. As I understand it, an inductive load varies by applied voltage (like your air conditioner). As the voltage goes down the amount of amps required to turn over the compressor and fan motor goes up A LOT until everything comes up to speed.
Other threads on similar topics:
Low voltage and air conditioning
Re-thinking Hardwire Surge Guard...Opinions?