Two Stage Valve - Bennett 3000 Series Service Manual

531 Commercial / Industrial Electronics
Two Stage Valve Control - The two stage valves that the 3000 series dispenser uses are +24 Volt dc
valves (except for the 2 stage valves in the Satellite of a Master / Satellite system which uses 120 or 230
volt A.C. valves). These valves are used to control the flow of fuel to the hose. The valves are used to
keep people on other dispensers from getting fuel from an unauthorized hose when the submerged
pump is "on" for that product. If valves were not present then a customer on another pump could pump
fuel from the same product hose as the one you are using because that product submerged pump has
that product line pressurized.
Also, the other use of the 2 stage valve is in a preset or prepay application to slow the flow of fuel at the
end of the transaction. As an example, on a pre-pay sale (where the sale amount is collected before
fueling), the pump is "preset" by the P.O.S. In this example we will say that the customer preset the
pump for 5.000 gallons. When the customer pumps fuel it is in fast flow all the way up to the slow flow
offset that is programmed in the pump. Let's say that that was set to .2 gallons. So, at about two tenths
of a gallon until the end of the sale the pump goes into slow flow and at 5.000 gallons the valve closes
all the way and the pump stops.
So, a commercial dispenser may have only one or up to four 2 stage valves. There is one valve per
meter and the valve is mounted on the outlet of the meter.
The upper portion of the valve is where the two coils
are located along with the two plungers. The wires
that control the coils are:
Black - Fast Flow coil/plunger
Yellow– Dribble/Slow flow coil plunger
Red - +24 Volts dc
+24 Volts dc is always present on the red wire
(unless this is a 120 or 230 volt A.C. valve). The coils
are not energized until the system provides a
"ground" for those coils. When the CPU wants to
open either the fast or slow flow it turns on a Field
Effect Transistor (FET) to provide a ground for that
coil. Lets look at an example:
Example: With the valve turned " off" both
"coils" are de-energized because their legs are not
grounded. In the de-energized state the spring in the
fast flow valve pushes against the flanged sleeve
and both the fast and slow are dropped down closing
off any flow.
At the beginning of a sale, the CPU will allow only
slow flow until 9 pulses are received from both phas-
es of the pulser. It does this by grounding the slow
flow coil (energizing it raising the plunger) by turning
"on" a field effect transistor (FET). This allows a
small amount of fluid to travel through the small ori-
fice in the diaphragm, up along the grooves on the
outside of the high flow valve, and then down
through the little hole in the center of the high flow
valve. This is slow flow.
Fig 1 - 2 stage valve operation
Fig. 2 - The 2 stage valve is installed between the
meter outlet and the hose outlet.
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107932 Rev G 4-24-17