Amtrol WX-401, 420 manual For example

For example, if we look at a typical pump curve for a (15) HP – (85) GPM submersible pump – we can select a pump cut-in and cut-out point on the curve which will provide optimum pump operation.

The pump curve shows pump performance as its pressure rises from cut-off ((0) head in test) to maximum head in feet.

On this curve, for a (15) Hp (85) GPM pump we can see that at approximately (100) feet the pump stops pumping and will pump up to (660) feet of head.

What we want to determine is at which point on the curve do we want to have the pump cut-in, and at which point on the curve do we want it to cut-out.

The pump operates in its best efficiency range at the mid-range of the curve.

The cut-in point can’t be too low on the curve, as this would cause inefficient operation. We should choose a point just before the curve drops off rapidly…and at a point still within the best efficiency range (60% to 80%).

The pump curve for the pump selected indicates the total pressure range of the pump or its dynamic head measured in feet of head.

The pump must have enough head, or pressure differential to:

Bring water from the level of the well to the well head at the surface of the ground.

Provide head capacity to pressurize system piping to overcome elevation (static height) and friction (friction loss) and deliver required pressure.

Since the Well-X-Trol®will control the pump operation throughout system pressurization, we must select our pump cut-in pressure and pump cut- out pressure.

For example:

In a well with water level (240) feet down in the well, system pressurization by pump will be shown on the pump curve at some point above the intersection of the line indicating (240) feet of head.

In other words, at (240) feet of head we can assume that the pump will have brought water from the pumping level of the well to the surface and pressure in the system piping will be (0) PSIG.

We now must select a pressure range (min. to max.) to establish pressurized delivery of water to the system and that we overcome elevation (static height) and friction loss of the piping.

We must select a minimum pressure at the Well- X-Trol®location that will insure enough pressure to keep water flow under pressure at the top of the system…overcoming both the static height and the resistance to flow through the piping.

We’ll do this by pre-charging the Well-X-Trol®to a pressure (P1) equal to the minimum pressure required at the Well-X-Trol®location. In addition, we’ll select a pump cut-in pressure (P2) which is at the same pressure to start the pump whenever system pressure drops to this point.

We’ll assume that a minimum system pressure at the Well-X-Trol®location of (30) PSIG. This pressure will be adequate to insure system pressurization to overcome elevation and friction loss and provide adequate pressure at the fixture.

To find this pump cut-in point on the pump curve, we’ll have to convert (30) PSIG to feet of head.

To convert PSIG to feet of head, we must multiply PSIG by (2.31).

30 PSIG x 2.31 = 69.3 or 70 feet of head

To locate this point on the pump curve, we must add 70 feet of head…the pump head required to pressurize the system to 30 PSIG…to the feet of head required to lift the water to the surface:

Minimum System Pressure	= 70 Ft. of Head
Plus Lift	= 240 Ft. of Head
* Pump cut-in point on curve	= 310 Ft. of Head

We have selected the point on the curve which will be the pump cut-in setting (P2) of 30 PSIG on the pump switch, and we will pre-charge the Well-X- Trol® to 30 PSIG (P1).

Now we will select the maximum pump cut-out point on the curve which will allow the widest possible pressure range without impairing pump performance and efficiency.

We will do this by moving up the curve to find a point that:

Is just before the curve begins to “flatten” out

And is still within the upper limits of best efficiency range of the pump

In this example, that point would be at the intersection on the curve of the horizontal line indicating (410) or (420) feet of head… let’s say (420) feet.

This is the point on the curve which will be the maximum pump cut-out for this particular pump.

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