Can someone explain how or direct me to informtion regarding the power signatures of AC motors (pumps) responds as load (head) increases? I have a pump in my aquarium that is rated at 120watts, but installed with the plumbing it only draws about 55 watts (measured with a kill-a-watt device). This surprised me, but apparently it shouldnt. Any details would be great, but i'd really love the technical side/equations. Thanks!!
your kill-a-watt-device is designed to measure the direct power consumption as is in an electrical circuit. This works great for lamps and heaters. now since you have a pump in your circuit you need to consider that this is an inductive device. Such devices cause a phase shift between voltage and current in your circuit which gives you messed up readings. the other extreme would be a highly capacitive device.
