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APPENDIX B — POTENTIOMETER ADJUSTMENT
Fig. C — 3-Speed ECM
Adjusting the low, medium, and high potentiometers requires
the use of a multi-meter capable of measuring 0~5 vdc (See
Fig. C).
1. Only trained and qualified individuals should attempt to
adjust or service components on any electrical compo-
nent. Failure to follow safety rules could result in electri-
cal shock or hazard.
2. Unit must be powered to perform the following proce-
dure. If main power is not available, connecting a tempo-
rary 24-v-40VA power supply to parallel with a
secondary outputs of the unit’s transformer is recom-
mended.
3. Set the electrical multi-meter to volts direct current (vdc)
on the 0~5 or 0~20 vdc scale.
4. Attach black (negative) lead of meter to the DC common
terminal, labeled “L2” above the potentiometer and to
the left of the orange relay.
5. Attach the red (positive) lead of the meter to the red wire
that bridges the 0-10 vdc outputs: high, medium, and
low.
6. High Speed: Close high speed relay by applying 24-v to
the high terminal. Using a small screwdriver, turn the
VR3 potentiometer so the meter measures 4.51 vdc. This
will set the ECM speed to 90% of maximum for high
speed. Open the high speed relay.
7. Medium Speed: close medium speed relay by applying
24-v to the medium terminal. Using a small screwdriver,
turn the VR2 potentiometer so the meter measures 3.53
vdc. This will set the ECM speed to 70% of maximum
for medium speed. Open the medium speed relay.
8. Low Speed: Close low speed relay by applying 24-v to
the low terminal. Using a small screwdriver, turn the
VR1 potentiometer so the meter measures 2.06 vdc. This
will set the ECM speed to 40% of maximum speed for
low speed operation. Open the low speed relay.
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