12
Before opening DRHX
, the mains voltage must be
disconnected for at least 3 minutes
to ensure that there is no risk of
dangerous residual currents in electronic circuits or capacitors. If DRHX has no operating signal, but natural drafts through the air
handling unit cause the rotor and thus the stepper motor to rotate, there is a risk that the stepper motor will induce voltage on the
DRHX stepper motor terminals, making them dangerous to touch.
When servicing or troubleshooting the stepper motor: The stepper motor can become very hot >60°C.
Troubleshooting
- also see page 10/11, table 19 and 19.1 Fault and alarm codes
Troubleshooting
when DRHX is controlled via A/D signals (0-10 V):
Symptom
Cause
Action
Stepper motor is not
running
Lacking supply voltage
Check the voltage supply (230 V AC) to DRHX terminals
”L” and ”N” (Nominal supply voltage
is stated on the rating
plate). LED displays constant green light; see table 15.3 page 7
Check whether short-circuit protection has been activated,
external controller in the AHU.
Poor electrical connections
Check electrical connections. Make sure there are no loose
threads when connecting to the terminals, use cable shoes
(multi core).
Wrong stepper motor for DRHX
setup
Check that the DIP switch is correctly set for the selected
stepper motor size and speed.
Check that motor and controller fit: MRHX-2 = DRHX-1055,
MRHX-4, -8 = DRHX-1220
Lacking operating signal
A/D control: DRHX can be configured via the RS-485 interface register
to receive a start signal via an optional digital input. If this function is selected,
check that the DRHX has
a signal connected to the "Start/Stop” input
- digital
input Din 1, 2 or 3, depending on the configuration.
Lacking 0-10 V DC control signal
Check that DRHX receives an operating signal >1.1 V
on ”0
-
10 V In”.
Active alarm
Read active alarms via the display and remove what is causing
the alarm see page 11.
(can also be read by using DRHX-PC-Tool or via Modbus).
The stepper motor has been
stopped 5 times by the built-in
stepper motor protector because of
overloading or other alarm
Reset the alarm by disconnecting the power supply to DRHX
and reconnecting it after approx. 60 seconds.
Defective/ broken DRHX controller
Replace DRHX.
Never attempt to repair a defective DRHX controller.
Contact Hoval for support/ replacement/ repair.
Stepper motor is defective/ broken
Replace stepper motor.
Never repair a defective MRHX motor.
Contact Hoval for support/ replacement/ repair.
Stepper motor/ rotor
is running in wrong
direction
Wrong phase sequence in stepper
motor cable
Swap two phase wires in the controller DRHX. Switch the "V"
(black) and "W" (blue) cable to change motor direction (see
page 4)
DRHX cuts out due to
an alarm
Active alarm
Read active alarms via the display and remove what is causing
the alarm see page 11
(can also be read by using DRHX-PC-Tool or via Modbus).
The alarm is re-activated after reset
Repair the cause of repeated alarm activation, see page 11
The rotor stops
unintentionally
(Also see Fault code
E01 on page 11)
Internal rotor guard detects a loose
or defective belt
Tighten or replace belt
The internal rotor guard is
incorrectly calibrated
Make a re-calibration; see " Calibration test for pulley/
internal rotor guard" on page 10
External rotation guard.
/ External rotation guard is
activated even if it's not in use
See Fault code E01, page 11
