Water Pump Controls Switch Pressure Differential Gap FAQs

Differential Gap Between Pump CUT-IN and Pump CUT-Out

Effects of Increasing the Difference Beween Cut-In & Cut-out Pressures
versus
Effects of Higher or Lower Pressure Range at a Water Tank Q&A

Can I increase the differential between cut-in and cut-out on the pump pressure control?

I have a 20 a Gallon water pressure tank with a submersible centrifugal water pump in frin the lake at my cottage.

I have my pressure switch set at 40-70psi (30 differential)

Is there any harm having a 30psi differential.?

I have my bladder set properly at 38 psi. On 2020-09-03 by Tim

by (mod) - increasing the pump control differential is OK; here's the effect

Tim

There's no harm in using a larger differential gap as you described as long as your pump has no trouble reaching that cut off pressure.

The effect will also be of course, that you will notice a greater water pressure drop or flow rate reduction at your fixtures before the pump comes on. If that's not a bother than you're fine.

by Tim

Great thanks for your advice!

I was just worried it would make my bladder crap [fail] on my pressure tank faster.

by (mod) - get a longer draw-down cycle by increasing the pressure range & what that does to the tank bladder

You can increase the draw-down by widening the water pressure differential between CUT-IN and CUT-OUT water pressure, but there's a limit which is the volume of your water pressure tank bladder.

Your pressure tank is rated to give you a 20 gallon draw-down volume.

You can get 20 gallons out at any of a range of pressure settings.

But when you operate at a higher pressure range - as you are doing with a 40-70 pressure control switch setting, that 20 gallons is going to be delivered at a higher pressure, which means that it is given to users faster, which means that the pump will cycle on sooner than if you operated at a lower pressure range such as 30-60 psi or 20-50 psi.

But as long as the air pre-charge in your pressure tank is set safely 2 psi below your CUT-IN pressure the system will work normally.

As long as your tank pressures don't exceed the manufacturer's permitted range you won't be harming the tank bladder.

Minimum Differential Between Pump CUT-IN & Pump CUT-OUT?

Can I set a Narrow Pressure Switch Differential of 10 psi?

I have a Goulds 1/2 hp J5 deep well pump with a 20 gal pressure tank. I am operating with a differential of 14 psi (20 / 34 CUT-IN / CUT-OUT).

Due to well limitations, the maximum pressure generated by the pump is 38 psi (pump runs forever if the cut-out pressure is raised above 38).

At this setting, the small nut is completely loosened.

I would like to operate at 24/34, but if I increase the cut-in pressure to 24 (large nut), then the cut-out pressure is also increased, and the pump runs forever (small nut still completely loose).

It seems that I am limited by the Goulds pressure control switch (which is attached to the pump and monitors the pressure by a plastic tube from the pump housing).

Any solution to this? It is a fairly new pump, so simply replacing the Goulds pressure conrol switch does not guarantee a solution, since the specs of the Goulds switch apparently do not allow one to operate with a cut-in/out differential of 10 psi. - Antony 9/14/12

Reply: don't set the pump switch Differential to a too-small number

Anthony

You're right that the "range nut"

see WATER PUMP WONT STOP RUNNING

shifts the whole water pressure cut-in/cut-out range up or down, while the "differential nut" widens or narrows the cut-in to cut-out pressure gap.

I SPECULATE that Goulds and other water pump pressure control manufacturers don't allow the range width to be less than 10 psi because you'd find that when running water in the building the pump would be cycling on and off too rapidly.

You'd be better off to leave the range so that the cut-in is at 20 psi, and then you can set the cut-out up to 34 psi.

Or call Goulds and ask if they have a switch that will operate with a narrow CUT-IN/CUT-OUT differential value.