VDKF-LEC Alternative: Logbook vs Live Monitoring

If you are searching for a VDKF-LEC alternative, you are probably asking the wrong question. VDKF-LEC and a live monitoring platform such as ModbusCloud solve two different jobs in a refrigeration business: one documents, the other watches. This comparison shows where the line runs, which tool covers which legal and operational task, and why most refrigeration fleets end up needing both layers rather than choosing between them. You get a clear verdict, honest cost logic, and the regulatory context under the F-gas Regulation (EU) 2024/573.

Updated July 2026.

Quick verdict: documentation or monitoring?

VDKF-LEC (Leakage and Energy Control) is documentation software from the German refrigeration trade association VDKF that keeps the statutory equipment logbook required under EN 378. ModbusCloud is a monitoring platform that reads refrigeration controllers live over Modbus and raises alerts. In short:

• Choose VDKF-LEC if you need the legally sound F-gas logbook, tightness-check records, and the VDKF containment seal.
• Choose ModbusCloud if you want to see temperatures, pressures, and refrigerant-loss signals between inspection dates and be alerted.
• For a fleet of systems across multiple sites you usually need both: the logbook for compliance, the monitoring for early detection.

What is VDKF-LEC?

VDKF-LEC is vendor-neutral documentation software from the VDKF that records the operation of refrigeration and air conditioning systems in a legally compliant way. LEC stands for Leakage and Energy Control. According to the VDKF, more than 1,000 specialist companies and operators use LEC as the electronic logbook for the systems they service.

Concretely, VDKF-LEC documents refrigerant quantities per system (charge, top-up, recovery), tightness checks and their results, calculates leak rates across the equipment base, produces the climate balance (ODP, GWP, and CO2 equivalent via a built-in calculator), and maintains the printable equipment logbook per EN 378. It therefore covers the record-keeping obligations of the F-gas Regulation (EU) 2024/573 and integrates the VDKF containment seal in electronic form. The licence runs annually, from 1 April to 31 March, and the price depends on VDKF membership status.

Where VDKF-LEC reaches its limit

VDKF-LEC is deliberately a specialised documentation tool, not an operations system and not monitoring. That is its defined purpose, not a flaw. For fleet practice, though, it means three concrete limits.

First, LEC has no sensor connection. All data arrives through manual input and selection fields. Second, there is no live monitoring. A refrigerant loss only becomes visible when a technician measures it at the next tightness check and enters it, not when it starts. Third, without an interface you get double data entry, because the same values land once in the field and once in LEC. For pure documentation that is acceptable; for catching a slow leak early it is too slow.

That third limit is exactly where live monitoring fits. The scope split below shows which tool owns which task.

What ModbusCloud delivers

• Continuous pressure, temperature and energy data over Modbus
• Threshold and drift alerts between inspection dates
• Remote fleet view across multiple sites

What VDKF-LEC documents

• Refrigerant balance and tightness-check results
• Equipment logbook per EN 378
• VDKF containment seal in electronic form

What does live Modbus monitoring do?

Live monitoring is the continuous, automatic capture of a system's operating data over a fieldbus protocol, here Modbus RTU or Modbus TCP. Instead of reading values once a year, the Gateway polls the controllers every few seconds to minutes and streams the values to the cloud.

In refrigeration, the common controllers speak Modbus: Carel pCO, Danfoss AK and ADAP-KOOL, Wurm, Eliwell, and Dixell. The ModbusCloud Gateway reads suction pressure, discharge pressure, evaporating and condensing temperature, superheat, compressor runtime, and energy consumption from them. For the protocol basics, see What is Modbus.

The operational lever is early detection. A slow refrigerant loss shows up as falling suction pressure and rising superheat, long before the system fails. An alarm rule flags that drift immediately.

The economics are concrete. Refrigerant is expensive and the price keeps rising as the F-gas phase-down tightens. Finding a 5 kg leak in an R-448A system two weeks earlier saves the top-up charge, the second call-out, and in the worst case a stock loss in a cold store. This is exactly where monitoring complements the logbook: it reduces the leak volume you later have to record. To set up such rules, see Setting up automated Modbus alerts.

VDKF-LEC and ModbusCloud side by side

The table below sets both tools against the criteria that matter in fleet operation. The columns follow each tool's defined purpose, not an artificial scoring system.

Do not read the table as a winner ranking. Every "No" in the ModbusCloud column is a row where VDKF-LEC is indispensable, and vice versa. The point is the division of labour.

How monitoring data feeds the logbook

The two layers work together most cleanly when the live data flows into the documentation as evidence. The Gateway writes a timestamped, continuous record that you export for audit. That export is not a substitute for the statutory tightness check, but it documents the system's condition between inspections and gives the certified technician the trend that informs the next check.

What the Gateway reads continuously

• Evaporating and condensing temperature per circuit
• Suction and discharge pressure as a leak indicator
• Superheat drift as an early warning of refrigerant loss

The audit export complements the statutory tightness check and the F-gas logbook, it does not replace them. The mandatory inspection under EU 2024/573 remains obligatory.

Cost and the whole-fleet view

A clean cost comparison fails at the premise, because the tools do different things. VDKF-LEC runs as an annual licence whose price depends on VDKF membership; the VDKF states the current terms directly. ModbusCloud is priced as SaaS per connected system plus the one-off Gateway hardware.

So do not weigh licence against licence, but against avoided loss. A single undetected refrigerant loss over several months quickly costs several hundred euro in top-up plus call-out, and a cold-store system adds the risk of stock loss. HFC blend prices have risen sharply over recent years under the F-gas quota system. Monitoring that flags a leak two weeks earlier often pays back its annual cost with a single prevented incident per fleet.

Verdict: who needs what?

For the single-system operator who only has to meet a record-keeping obligation, VDKF-LEC or a comparable logbook is enough. For the specialist company servicing a fleet of cold-store, supermarket, or air-conditioning systems across several sites, the combination is the right path: VDKF-LEC (or an equivalent logbook) for mandatory documentation, ModbusCloud for early detection and remote supervision.

So the honest recommendation is not ModbusCloud instead of VDKF-LEC, but ModbusCloud in addition to your logbook. The logbook keeps you compliant. The monitoring keeps your systems running and reduces exactly the leak volumes that would otherwise end up in the logbook. For a first step toward live data, the Modbus gateway buyer guide helps.

Frequently asked questions

Related articles

• Refrigeration monitoring and F-gas compliance
• The F-gas Regulation 2024/573 explained
• F-gas digital logbook
• ChemKlimaSchutzV certification and logbook