EC-SWAP®: modernise your air handling units without touching your control system
In many Swiss commercial, industrial and institutional buildings, air handling units installed twenty or thirty years ago are still running. Everyone knows what to do: switch to EC motors. And yet those installations are still there. Because in a ventilation retrofit, the motor was never the sticking point.
Where the retrofit really gets stuck
When an owner requests a quote to modernise their ventilation, the quote that comes back rarely talks about the motor. It talks about everything around it:
- reworking the wiring between the panel and the unit;
- adapting or replacing the control system;
- reprogramming the ICA system, with the original integrator — when they still exist;
- new commissioning, new settings, new acceptance;
- and meanwhile, an installation at a standstill in an occupied building.
That is where the cost, the delay and above all the risk lie. A building owner is happy to improve efficiency. They are far less happy to reopen a control system that has been working for fifteen years.
The result: the project is postponed. Then postponed again. And the installation keeps consuming.
EC-SWAP®: a retrofit that stops in the right place
EC-SWAP® is a patented solution developed by Depair SA to modernise existing ventilation installations without changing the wiring or the control system.
The principle is deliberately narrow: the asynchronous motor is replaced by a high-efficiency EC motor, via a plug & play adaptation system. The existing wiring stays in place. The existing controller stays in place. The building’s control logic is not reopened.
This is not a technical limitation. It is the heart of the proposition: by removing the part of the job that is expensive and daunting, the retrofit becomes decidable.
How it works, in practice
On an older unit, the controller can only tell the fan two things: low speed, high speed. Two contactors, two windings, and nothing in between.
EC-SWAP® is a control converter: it translates the low speed / high speed signal into a control signal for an EC motor.
In other words, the controller keeps sending exactly what it sent yesterday. EC-SWAP® takes care of turning that binary command into a setpoint a modern motor can use.
That is the whole trick — and it is precisely why neither the wiring nor the programming needs to be touched.
Technical specifications
| Input | 400 V AC three-phase, 50 Hz |
| Output | 400 V AC three-phase, 50 Hz |
| Maximum current | 10 A |
| EC logic port | 24 V DC max. 50 mA · 0–10 V control max. 1 mA |
| Dimensions | 130 × 130 × 75 mm |
| Compliance | CE marking · WEEE Directive 2012/19/EU |
A unit the size of a hand, in the existing panel. That is the full extent of the work.
When control needs to go further
Command conversion covers the most common case in the existing building stock. Where the installation requires active regulation, the architecture becomes communicating.
Each air handling unit is fitted with an EC-SWAP® module, connected to one or more EC motors via MOD-IO® modules. Communication runs over a fieldbus — Modbus or BACnet/IP — with built-in protection and alarm signalling.
The whole system is modular and scalable: equip one unit, then a second, then the rest of the stock, at the pace of budgets and intervention windows. No operational disruption.
Four control modes
| Constant airflow | Maintains the set airflow whatever the air conditions (temperature, humidity, site altitude). An optional temperature/humidity measurement enables precise calculation of the actual airflow. |
| Constant pressure | Pressure sensors provide dynamic regulation and maintain duct pressure despite variations in pressure losses — filters loading up, dampers moving. |
| Fixed speed | A simple command as a percentage of the motor’s maximum speed, for installations without active regulation. |
| Air quality (CO₂ / VOC) | The ventilation speed adjusts automatically according to the measured CO₂ or volatile organic compound level. |
This last point deserves attention: it turns a constant-speed installation into demand-controlled ventilation, without changing the controller.
What this changes in operation
Up to 70% savings
On the electricity consumption of the ventilation, depending on the configuration. On installations that run all year round, the effect on operating costs is immediate and measurable.
Less noise
A notable reduction in the installation’s noise level. In an occupied building, a school or a care home, this often matters as much as the kWh in the tenant’s perception.
No heavy works
Compatible with the existing ICA system, without rewiring. Fewer contractors, less coordination, less downtime.
A building stock that becomes controllable again
An older installation that accepts air-quality-based control is an installation that regains value.
Why the subject is becoming urgent
The SIA 382/1 standard, in its 2025 edition which came into force on 1 February 2025 replacing the 2014 edition, has tightened the framework. Definitions have been harmonised with European ecodesign regulations — notably EU Regulation 1253/2014 — and the SN EN 16798-3 standard.
Above all, the standard now requires defining, for each installation, a limit value and a target value for SFP — the specific fan power, in W/(m³/s) — according to the installation type, airflow and pressure losses. The target value corresponds to 80% of the limit value.
This is precisely the indicator a motor change acts on directly: at unchanged airflow and pressure losses, every watt of absorbed power saved shows up in the SFP.
The text also explicitly emphasises the levers that reduce energy demand: variable airflow, low pressure losses, high overall supply-air efficiency, and demand-based operation.
In new buildings, these requirements are integrated at the design stage. In the existing stock — that is, the vast majority of square metres in service — an upgrade path is needed that does not require redoing everything. That is exactly the role of a well-delimited motor retrofit.
One building block in a wider system
EC-SWAP® does not live alone. It is part of the Depair ecosystem: the EC-MULTI® control gateway (up to 16 EC fans controlled), the Depair Connect remote management system for off-site supervision, and custom air handling units designed and built in Switzerland — sheet metal work and commissioning included. From Sierre, in Valais, for installations ranging from residential buildings to offices, industry, healthcare and schools.
A single point of contact for the motor, the controls, the air handling unit and the follow-up — which, on a renovation project, remains the most underrated argument.
A simple test
Do you have an air handling unit more than fifteen years old, a controller that works and an electricity bill that will not come down?
Send us the motor’s nameplate and your control diagram. We will tell you whether EC-SWAP® applies — and what it would involve.
The installer documentation and a wiring diagram (single-fan example) are available for download.
DEPAIR SA — Rue du Manège 30, 3960 Sierre — +41 27 455 16 14
