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Frequency converter for speed adjustment of DS asynchronous motors 0.75 to 75.0 kW
380 to 480 V, 3~ protection class IP21 and IP54/55

BLEMO frequency converter



The compact HVAC drive from
BLEMO - for applications with    
variable torque



This new product line is a further development of the predecessor model ER32.
The series is intended for variable torque applications in building services, sewage and waterworks, e.g. fans and pumps. It has been developed in accordance with the latest aspects of relevant standards and international regulations, including EMC, harmonics standard EN61000-3-12 and environmental compatibility, e.g. lead-free soldering and recyclability.

Device versions

The ER321 is available in two versions ER321-...K, IP21 and ER321-...G, IP54/55 with(-V2) and without(-V1) additional switches. The ER321 is designed with a 4-digit 7-segment display. 7 keys allow easy programming and control of the unit from the display. The Local/Remote button is used to switch between the display and the control terminal block. A multilingual plain text display is now available as an option.

Standard features

  • 4-digit 7-segment display
  • Optional: multilingual plain text display
  • 4 preprogrammed application macros
  • built-in PID controller
  • Modbus, METASYS N2, BACnet, APOGEE FLN P1
  • via RJ 45, RS 485,
  • optional LonWorks
  • integrated EMC filter
  • PTC thermistor input PTC
  • Maximum THDI: 35%, EN 61000-3-12
  • RoHs compliant
  • CE, UL, CSA, NOM 117, C-Tick


The ER321 series frequency inverters have a mains filter integrated in the device, are CE marked in accordance with the EU Low Voltage and EMC Directive and comply with the applicable standards for frequency inverters EN 61800-3 and -5-1.

Application areas

  • Building services engineering 
  • Pumps and fans

Your benefits

  • Usability
  • Compact design
  • Orientation towards protective functions
  • Easy maintenance
  • Permanently integrated "building" functions (fire protection mode, register monitoring, mechanical protection function, etc.)
  • Connection to building management systems

Questions about the product

What is the factory setting of the ER321 drive ?

Beschreibung  Code Wert Programmieranleitung
Ausw. Motorsteuer Pt Quadr. U/F Seite 67
Große Frequenz UL 50,0 Hz Seite 82
min. Freq LSP LL 0,0 Hz Seite 82
Taktfrequenz F300 Unterschiedlich Seite 85
autom. Rampen AU1 aktiviert Seite 85
F: Rechtslauf F111 2 Seite 90
 R: Vorwahlfrequenz F112 6 Seite 90

Guidelines for the operation of frequency converters

  1. To achieve electromagnetic compatibility, the inverter must be operated with a built-in or external radio interference filter.

  2. If shielded cables are used between the inverter and the motor, the shield must be connected to earth at both ends. Cable interruptions should be avoided if possible. If it is necessary to separate the cable, e.g. to install a motor contactor, the cable shielding must be connected through as directly as possible. It is important to ensure that the lowest possible HF impedance is achieved.

  3. The shorter the cable, the lower the radio interference and leakage current. The maximum possible cable lengths must be taken into account.

  4. To avoid interference with the control inputs, control cables should always be shielded. The shield must be connected to the cable clamp provided on the inverter. If the shield is also connected to a control device, care must be taken to ensure that the ground points have the same potential.

  5. Control cables should not cross power cables if possible. Where this cannot be avoided, a right-angled crossing is recommended.

  6. Separate laying of control and power cables should be aimed for. If the cables must be laid parallel, e.g. on the same cable route, the largest possible distance (> 20 cm) should be selected.

  7. The shielding of the laid cables should have a low HF impedance if possible. Copper braiding is therefore preferable to steel braiding.

  8. The RF contact resistance at the connection points between shielding and housing must be kept as low as possible. Dirt, paint and insulation residues on the housing and shielding in the area of the connections must therefore be removed. In principle, the cable clamps or crimp connections provided for this purpose should be used to connect the shielding. It is advantageous to use earthing cable glands.

  9. The shielding should be connected to the housing as close as possible to the cable terminals. Longer, free cable ends act as antennas.

  10. With unscreened cables, the cable wires should be twisted and output filters should be used.

How do I deactivate the motor phase monitoring (OPL) error 'EPHO'?

1. code F 605 = 0 = deactivated (page 17 and 129 in the programming instructions)

How can I use the stop button to reset an error?

1. set F735 = 0 (page 80 in the programming instructions)

2. press the stop button twice quickly.

What does my error message in the display mean?

1. The tables on page 150 in the Programming Guide are used to diagnose and correct problems when a fault, alarm or pre-alarm condition occurs. If the problem cannot be solved by the measures described in the table, contact your BLEMO dealer

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