Rpu Load Monitor Device - Harrington Hoists RHN02D-20A-20D Series Owner's Manual

3.7

RPU Load Monitor Device

The RHN hoist is equipped with the RPU Load Monitor Device. The RPU version (SLE21 or SLE22) is located
on the front cover of the RPU unit. The main function of this device is to evaluate the load conditions of the hoist
(overload protection, temperature monitoring of the hoist and trolley motors, and displaying the operating hours of
the hoist.
3.7.1 Monitoring of Load Conditions – After powering up the hoist, the RPU will run through an internal test
cycle, for approximately 4 seconds. The test will be finalized when the user initially operates the hoist in
the up or down direction. At this time the "err" light will illuminate temporarely as well as the LEDs II and
III. If the internal test cycle was completed successfully without resulting in error, the hoist will function.
3.7.2 Temperature Monitoring – The hoist and trolley motors are equipped with PTC thermistors that are
directly linked to the RPU. If an excessive motor temperature condition has developed, the RPU will not
allow the load to be lifted or lowered until the excessive temperature condition is no longer present. The
LED display on the RPU will display an "err". See
3.7.3 Count/Hour Meter – See section 6.1 for Count/Hour meter details.
3.7.4 Load Testing RHN – The RPU Load Monitoring device is designed to sense an overload of the hoist and
cut-off power when subjected to a lifting load of 110% of the rated RHN capacity. Due to this load
monitoring feature, a Crane Test function is used when conducting a load test of 125% of the rated
capacity. The crane test function temporarily changes the overload cut-off from 110% rated capacity to
137.5% rated capacity. This function can only be activated when the hoist is at a standstill and has no
overload on the hook. The DIP switches S3 must correspond to the settings shown on the lid of the
casing. This temporary load test override for both RPU versions (SLE21 or SLE22) is accomplished by
following the applicable instructions below:
For Model SLE21:
1. Remove RPU cover.
2. Press the S5 button, hold for more than 3 seconds, and release. (The S5 button is located directly
below the red "err" LED). Figure 3-16.
3. Notice the "err" LED is flashing. This will continue to flash for 30 minutes changing the overload cut-
off temporarily to 137.5% of rated capacity. After 30 minutes, the RPU reboots and the overload
cut-off returns to 110% of the rated capacity.
4. To deactivate the crane test, prior to the 30 min automatic deactivation, either press the S5 button
until the red LED no longer flashes or reboot the device.
For Model SLE22:
1. Loosen the screw on the RPU cover and remove the cover.
2. Execute the following steps in less than 12 seconds:
a. Press the S5 button for more than 3 seconds. (The S5 button is located directly below the red
b. Release the S5 button for 1 second.
c. Press the S5 button for more than 3 seconds.
3. If an error occurs in the sequence of step 2, the "err" LED flashes 3 times. After this error signal, the
crane test function can be activated again by following the sequence in step 2.
4. If the sequence in step 2 is followed correctly, then the "err" LED will flash for 30 minutes changing
the overload cut-off temporarily to 137.5% of rated capacity. After 30 minutes, the RPU reboots and
the overload cut-off returns to 110% of the rated capacity.
5. To deactivate the crane test, prior to the 30min automatic deactivation, either press the S5 button
until the red LED no longer flashes or reboot the device.
"err" LED). See Figure 3-16.
Table 7-2.
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