Section 4: Control Box
Wiring the Control Box
Sacksafoam I Operator’s Manual
(Version C)
14
Using Long Lines
The supplied control cable (connecting the control box and sack), fits Bambi buckets with standard length
suspension lines. The cable is sized to provide 24-volts to the injection pump when 28-volts is supplied to
the control box. If the Bambi bucket is suspended from the helicopter with an additional long line, the stand-
ard control cable may not be long enough.
If a longer control cable is required, the correct gauge can be determined by the following method (the ob-
jective is to provide 24-volts to the injection pump after accounting for the voltage drop along the cable).
Calculating Wire Gauge for Long Lines
The Sacksafoam pump draws the following current:
Small and medium series
4.5-amps
HL Series
9.0-amps
Control cables supplied with the Sacksafoam I unit meet Mil-C-27500 specifications. Individual hook-up
wires meet Mil-W-22759/16 specifications. It is recommended that any replacement wire or cable meet
these specifications. Extra cable and wire is available from SEI Industries Ltd.
Wire Specifications
With a supply voltage of 28-volts and a re-
quirement of 24-volts at the pump, the voltage
can drop four volts.
The current has to flow in both directions, so
the wire length used in the calculation will be
the distance from the control box to the sack,
multiplied by two.
Use this formula, based on Ohms law (V=IR).
Voltage drop, V
D
= Amps draw x resistance/1000
x wire length
x 2
Example:
A 100 ft. long line with a HL-7600 Bambi bucket and a 12 gauge wire, with a length of 160 ft.
from the control box to the sack.
V
D
= 9 x 1.82 x 160 ft. x 2 = 5.24 volts
1000 ft
Therefore, a 12 gauge wire would be satisfactory. It would produce a slightly low voltage at the pump (28
- 5.24 = 22.76 volts), which could be compensated for by adjusted run times shown in Section 5
Operations:
(Variation in Foam Viscosity and Using Non-Standard Voltages).
Wire specifications can be calculated in
feet or meters.
Resistance
Wire Size
(AWG #)
Ohms/1000 ft
Ohms/1000 m
18 5.74 18.83
16 4.51 14.80
14 2.88 9.45
12 1.82 5.97
10 1.18 3.87
