Sears 390.2508 - Manual (Page 3)

GENERAL INFORMATION
Table I: Pump Performance Chart (In Gallons Per Minute)
Pump Suction Discharge
Discharge
Pressure
Pumping Depth In Feet
Model Description Size Size P.S.I. 5’ 10’ 15’ 20’
390.2508 1/2 HP Standard S.W. Jet 1-1/4" 3/4" 40 7.3 6.2 5.2 4.2
MAJOR COMPONENTS AND
WHAT THEY DO
To Household
Water System Discharge Tee
and Priming Plug
Built-in
Check
Valve
/
Figure I
Impeller and Jet
Impeller turns with motor shaft, causirig the water to fly out
from its rim by centrifugal force. Impeller rotation creates a
vacuum which pulls in more water. Part of the water is di­
verted back to the jet where it passes through the nozzle and
venturi. This creates more vacuum to draw in more water.
In shallow wells (less than 20 feet deep), the vacuum cre­
ated at the pump is enough to pull water to the pump.
Therefore, for shallow well use the jet is built into the pump.
Air Volume Control
The air volume control (AVC) maintains the cushion of air
in Standard tanks.
Pressure Switch
The pressure switch provides automatic control.
MODEL NO. PUMP STARTS AT PUMP STOPS AT
390.2508 30 Pounds 50 Pounds
Check Valve or Foot Valve
This pump is equipped with a buUt-in check valve. Install a
foot valve in the weU on dug or cased wells. See Figure 3,
Page 4.
Tank
The tank serves two functions. It provides a reservoir of
water, some of which can be drawn through the house fix­
ture before the pump must start. It maintains a cushion of
air under pressure.
Two types of tanks are available; Captive Air® and Standard.
No air volume control is needed with Captive® Air Tanks.
PIPING
Piping in the Well
A Shallow well jet pump can be installed on a dug well,
drilled well or with a driven point. In a dug or ased well, a
foot valve and strainer should be installed for easy priming.
It should be five to ten feet below the lowest level to which
the water will drop while pump is operating (pumping
water level).
The strainer should not be too dose to the bottom or sedi­
ment may clog it. Before installing the foot valve, check to
see that it works freely.
When installed on a driven pont well, your Shallow Well
Jet Pump should have a check valve installed as shown in
Figure 2.
Discharge Tee
and Priming Plug
Relief Valve
Drive
Point
Not
to
Scale
Figure 2
For a pump at sea level, be sure the vertical distance (lift)
firom the pumping water level to the pump is not over 20
feet if the pump is over the well. This wU be less if the pump
is offset from the well.
The maximum lift of any pump decreases at the rate of about
Г less lift for every 1,000 feet elevation above sea level. For
example, if your are at 5,000 feet elevation such as in
Denver, Colorado, you would loose five feet of lift. The max­
imum depth from which oyou could pump water would
therefore be 15 feet.