Pump Motor Selection

Around our way (Northern California, USA) we fit our deep well submersibles for domestic water supply with one of two types of control to keep the pump from running when inadequate water supply can cause overheating because lack of sufficient head makes water stay in the pump housing and heat up.

The first is a simple timer that shuts off after a certain period and allows a set period of time to lapse before starting again. The "on" period is obtained from direct experience of watching the pump perform. Timers like this are commonly sold here under the brand name "Intermatic"

The second type of device operates similarly with an added level of sophistication. In an initial calibration cycle it sets a "normal" current for operation on the system. Once this is established and set by an operator the pump will continue to run until a shutoff signal comes from something like a float switch in the tank. However if at any time the current drawn by the pump drops below some fixed proportion of full load (like 25%) the pump will shut down and not restart for a fixed period that the operator can set (like an hour or two or however long experience has shown the well needs to refill from surrounding strata. These things also require an initial amount of operator attention in order to get the current setting right and an awareness on the part of the user that conditions in the well and or pump can change over time end require some future adjustment of the controller.

I have a device of the latter type on my 440 foot deep well with a 3/4HP multistage submersible pump set at 400 ft. Tomorrow I'll try to get up to the well and find out the manufacturer and model number of this controller.

Ed Weldon

ACCORDING TO MY CALCULATIONS, YOU HAVE 260 POUNDS OF HEAD. YOU CPOULD USE PNEUMATICS, THEY ARE USED FOR THIS TYPE OF SITUATION AND ONLY PUMP WHEN THERE IS WATER ABOVE THE PUMP. YOU WOULD HAVE TO PUMP TO A STORAGE TANK AND THEN A SIMPLE JET PUMP 1/2HP PRESSURE TANK SETUP WOULD TAKE IT FROM THERE. WE USED THEM ON MULTIPLE WELLS AND THE SYSTEM WAS DESIGNED BY A PAIR OF KENYAN ENGINEERS WHOSE NAMES I NO LONGER RECALL. YOU ARE TALKING ABOUT ONE HELL OF A LIFT FOR NOT MUCH FLOW, IS THERE ANY ALTERNATIVE. EVEN IF YOUR SURFACE WATER IS POOR, RO AND CHLORINE SEEN LESS PROBLEMATIC. I HAD TO PULL A SUBMERSIBLE FRON 630' AND NEVER WISHED TO REPEAT IT. MUTISTAGE SUBMERSIBLES CAN MEAN MULTIPLE STAGE FAILURES. REPAIRS ARE EASY BUT PULLING THAT PUMP REQUIRES ASSISTANCE FROM STRONG BACKS.