Troubleshooting Danfoss Error 1027: A Quick Guide If you're staring at your Danfoss VLT display and see Error 1027, you likely have a hardware communication or power board issue. Unlike common user-fixable alarms, Error 1027 is often a "deep-level" fault indicating that the drive's internal systems aren't talking to each other correctly. What is Danfoss Error 1027?
In most Danfoss VLT documentation, such as the IBA Lift technical guide, Error 1027 is classified as a CAN telegram error or a hardware interface fault. Specifically:
Communication Breakdown: The drive's internal processors cannot send or receive data packets (telegrams) reliably.
Hardware Failure: It often points to a physical fault on the power card or the control card interface. Immediate Troubleshooting Steps
Before calling for service, you can try these basic resets to see if the error was a one-time glitch:
Power Cycle: Turn off the main AC power to the drive. Wait for the display to go completely blank (discharging the capacitors) before restoring power.
Factory Reset: If you can still access the menu, you can perform an "Initialization" by following the steps on Danfoss MyDrive Assistant to return the drive to factory defaults.
Check External Connections: Ensure that any external communication cables (like RS485 or CANbus) aren't shorted or loosely connected, as interference here can sometimes trigger internal communication alarms. Advanced Diagnosis
If the error persists after a reset, the issue is likely internal. Technicians often look for:
Faulty Control Cards: The brain of the VFD may need replacement.
Power Board Issues: On older models like the Danfoss VLT 3000 Series, internal voltage irregularities can cause the processor to "lock up" and throw interface errors.
EEPROM Errors: Sometimes the drive's internal memory (where parameters are stored) becomes corrupted, preventing the boot-up sequence from completing. When to Call Professional Support
Error 1027 is rarely a "loose wire" fix. If a power cycle doesn't clear it, it usually requires a component-level repair or a board replacement.
Experts at JustAnswer: For immediate advice from an HVAC specialist, you can consult the JustAnswer platform to see if others have resolved similar 1000-series codes.
Official Documentation: Refer to the Danfoss Quick Troubleshooting Guide for instructions on how to pull the full alarm log, which will provide more context for a service technician.
Pro Tip: If you're using a Solis inverter that shows the same code, check the Solis Service Center for specific instructions on checking DC-side polarities and MC4 connectors.
In Danfoss systems, Error 1027 typically indicates a CAN telegram communication failure.
Specifically, this error appears when a CAN telegram cannot be sent, which often points toward a possible hardware error within the communication interface. Understanding Error 1027
According to documentation for systems like the Danfoss VLT LD 302, error codes in the 1024–1279 range are related to CAN communication issues.
Cause: The controller is unable to transmit data over the CAN bus.
Hardware Component: This frequently involves the communication card or the physical wiring of the CAN network. Recommended Troubleshooting Steps
If you are seeing this error, you can attempt the following diagnostic steps:
Check Physical Connections: Inspect the CAN bus wiring for any loose connections, shorts, or damaged shielding.
Verify Hardware: Since the error notes a "possible hardware error," check if the communication module is properly seated in the drive.
Perform a Reset: You can attempt to clear the fault by pressing the [Reset] key on the LCP (Local Control Panel).
Power Cycle: Disconnect the mains supply and wait for the display to turn off completely before reconnecting.
Initialization: If the error persists, a Manual Initialization to default settings may be necessary, though this will erase custom parameter settings.
Process: Hold [Status, Main Menu], and [OK] simultaneously while powering up the drive. Danfoss VLT LD 302 HDR-V2 - IBA Lift
Danfoss Error 1027 is primarily an internal hardware or configuration fault commonly associated with the VLT Micro Drive FC 51
and certain solar inverter models. Depending on your specific Danfoss device, the error indicates a failure in the internal DC interface or a critical power board malfunction. Solis Inverters Error Meaning by Device Type VLT Micro Drive (FC 51
Error 1027 is typically labeled as an "Internal Error". It often points to a failure on the power card or a communication break between the internal control components. Solar Inverters (Solis/Danfoss variants): Code 1027 refers to a DC-INTF (DC Interface)
fault. This means the inverter has detected an issue with the internal DC power stage, often triggered by improper string connections or internal hardware damage. Solis Inverters Troubleshooting Steps Perform a Hard Reset Disconnect all AC and DC power from the unit. Wait at least 5–10 minutes for the internal capacitors to fully discharge.
Reconnect power and check if the error clears. If it recurs immediately, the fault is likely permanent hardware damage. Verify Digital Inputs (VFDs) Check if any digital input is programmed as an External Interlock
If a terminal is set for this function but is not receiving a 24V signal, the drive may trip. Ensure a jumper exists between terminal 12 (24V DC) and the programmed input. Check DC String Connections (Solar Inverters) MC4 connectors for loose connections or poor crimping.
Verify the polarity of all DC strings connected to the inverter. Measure the Voc (Open Circuit Voltage)
of PV strings using a multimeter to ensure they are within the inverter's operating range. Inspect Internal Power Board
If the error persists after a reset, it often indicates a failed power supply board or a locked-up main contactor
Check for visible signs of damage, such as blown fuses or scorched components on the internal boards. When to Seek Support
If a power cycle does not clear Error 1027, it is generally considered a non-resettable internal fault . You should contact a Danfoss Service Partner
or your supplier, as the unit may require a control card or power module replacement. parameter settings for your Danfoss model to check the error log history? Top ten VFD tech support calls - Danfoss
Danfoss Error Code 1027: Technical Fault Report In Danfoss VLT drives (such as the Error Code 1027 typically indicates a specific category of Internal Fault
that prevents the drive from starting or operating correctly Fault Description Error Type : Internal Error / System Fault. Common Trigger
: This code often appears when the drive's internal control system detects a hardware mismatch or a software-level failure that it cannot automatically resolve. Secondary Context
: In some troubleshooting contexts, a fault in this range may be associated with overvoltage conditions where the incoming supply exceeds safe operational limits. JustAnswer Immediate Troubleshooting Steps Power Cycle
: Disconnect the mains supply completely and wait for the display to turn off (allow at least 5–15 minutes for DC link capacitors to discharge) before reconnecting power. Verify Input Voltage
: Use a multimeter to check that the incoming AC mains voltage is stable and within the drive's specified nameplate range. Manual Reset : Press the
button on the Local Control Panel (LCP) to attempt to clear the alarm. Hardware Check
: Ensure all option cards and internal wiring connections are secure. Øwre-Johnsen Advanced Recovery: Manual Initialization
If a standard reset does not clear the error, you may need to perform a Manual Initialization to return the drive to factory default settings. This will erase all user-programmed parameters. MyDrive® Assistant Power off the drive. Press and hold the [Main Menu] keys simultaneously.
Power on the drive while continuing to hold the keys for 5 seconds.
Release the keys; the drive should now be in its default state. MyDrive® Assistant Recommendation
If Error 1027 persists after power cycling and initialization, it indicates a critical internal hardware failure
(likely the power board or control card). You should contact a certified Danfoss Service Department for repair or replacement. Top ten VFD tech support calls - Danfoss
Disclaimer: This guide is for general troubleshooting. Always refer to your specific Danfoss product manual and consult a qualified electrician or technician before servicing the drive.
Step 2: Verify Configuration
- Check Parameter 8-04 (Control Word Timeout Time): This is usually set in milliseconds. Compare this value to the PLC scan time. As a rule of thumb, set the timeout to at least 3-4 times the expected scan rate of the master system.
- Check Parameter 8-01 to 8-03: Ensure the protocol and address settings match the control system requirements.
Suggested short explanation for "Danfoss error 1027"
Error 1027 — Compressor start attempts exceeded
- What it means: The drive has attempted to start the compressor repeatedly but failed; the controller is now blocking further start attempts to protect the compressor and system.
- Common causes: Mechanical issue with the compressor, low suction pressure, motor overload, shorted/grounded motor windings, faulty contactor or relay, incorrect drive parameters, or power supply problems.
- Immediate steps:
- Check compressor mechanical condition and ensure no seizure.
- Verify suction and discharge pressures are within limits.
- Inspect motor windings and connections for shorts or grounding.
- Confirm contactors/relays operate correctly.
- Reset the drive after addressing causes; do not repeatedly reset without finding root cause.
- When to call service: If the fault repeats after basic checks or if you’re unsure about electrical/mechanical inspection—contact qualified HVAC/R service.
(If you want a shorter label or a one-line message for a display, use: "Error 1027 — Compressor start attempts exceeded; check compressor, motor, and power.")
Step 3: Isolate the System
- If the error occurs intermittently, disconnect other nodes on the network to see if a specific device is causing the traffic jam.
- Try bypassing switches or converters to test a direct connection between the PLC and the Drive.
Part 6: Real-World Case Study – Error 1027 on a VLT® HVAC Drive
Scenario: A 15-story office building. The primary chilled water pump (Danfoss VLT® HVAC Drive, 75 kW) triggers Alarm 1027 three times per night, stopping the pump and raising return water temperature to 14°C.
Initial diagnosis: Plant electrician replaced the Profibus cable – no change.
Our diagnostic (following the steps above):
- LED on MCA 120 (Profibus card) showed “Green flashing” → slave not in data exchange.
- PLC scanner showed no fault on other 12 drives.
- Measured resistance between Profibus A & B: ∞ ohms (open circuit).
- Found that the Profibus terminator on the last drive in the network had fallen off due to vibration.
Solution: Replaced terminator (6ES7972-0DA00-0AA0) and set active termination. Error 1027 disappeared. Added cable ties and anti-vibration mounts to all terminators.
Lesson: Always check physical termination before blaming the drive.
🔹 Step 3 – Measure Brake Resistor
- Disconnect brake resistor wires from drive terminals (+BR, -BR) or (R+, R-) depending on model.
- Measure resistance across resistor leads:
- Expected: Within ±10% of nameplate ohms (e.g., 27Ω, 39Ω).
- Fault: Near 0 Ω (short) → replace resistor.
- Fault: Infinite (open) → replace resistor (won’t cause Error 1027 but will cause overvoltage trips).