minimum run time

System

I rely upon deep well (~300-400 feet) pumping for some mountain property, and have replaced my own jet, deep jet, and submersible pumps and maintained a variety of wells and systems for myself and others. Domestic wells are quite common here in rural and even suburban New Mexico, and the water table can fluctuate with seasons and annual rainfall drastically. There are pump controls that will sense and deal with this situation automatically, but many manufacturers have minimum run time requirements per pump cycle in order to obtain maximum life span for their AC submersible centrifugal models. The reason for this is to allow the start winding in the motor to cool properly before the next cycle, since it pulls a lot of current in order to develop enough starting torque to quickly bring the motor up to an efficient running speed. In order to meet this requirement, one should evaluate the flow rate vs. tank storage capacity to make sure the pump runs long enough and with adequate flow to allow the water passing through it to cool it down. This means that a larger pump or flow rate will need a larger storage tank to allow the manufacturers minimum time to be met before the pressure switch cuts out. An advantage of the large gravity storage system is that it will not normally require the pump to turn on and off again in a short amount of time, and the float or pressure switches that control such a system can be set to allow for a minimum pump cycle far in excess of manufacturer resommendations. I don't know if any of the DC pumps have this same issue, does anyone else?

K.D.