Answered question
Can a working Danfoss ECL Comfort controller be reused on another unit?
Partly, and the part that is settled is the application key. An ECL Comfort 210 or 310 is an empty shell without one: the key carries the software layout, such as A266 for heating plus domestic hot water. Keys are not locked to a serial number and move freely between controllers of the same type.
What is not settled is the mounting. Whether the base part — the socket carrying the terminal blocks — is common across the current generations has not been confirmed, and that is what decides whether reuse means unclipping a controller or rewiring an installation. Nobody should plan a job on the assumption that it swaps.
In detail
What decides it.
- Which models is this about?
- Danfoss names three current generations: ECL Comfort 120, 210 and 310. All key types, modules, accessories and current documentation remain available for those. The 100, 110, 200 and 300 are out of production — Danfoss did not say since when, so no date is given here.
- Which key fits which controller?
- The ECL Comfort 210 accepts A2xx keys. The 310 accepts both A2xx and A3xx, because A3xx applications need the extended hardware and the extra inputs and outputs that the 210 does not have. Danfoss stated this rule for the 210 and the 310. The 120 was not covered, so this page does not claim a key rule for it.
- Do the settings come across with the key?
- No. Settings and data live locally in the controller, not on the key. A controller receiving a moved key has to be configured, and a controller coming from another property should be factory reset so the previous property’s time and heating programmes do not follow it.
- How do I read the application without pulling the key?
- On the display: turn the navigation dial to Common controller settings — the gear icon — then System, then Application or System info. It shows the mounted application, for example A266.1, together with the firmware version.
- Can the firmware be updated in the field?
- Yes. From software version 1.11 onwards a newer key updates the controller automatically. Otherwise it is done over the controller’s built-in USB port with the Danfoss ECL tool on a laptop.
- Do the sensors and actuators have to change?
- Sensors are standard Pt1000 and may stay on the unit — they also still fit the discontinued generations. Valve motors are driven 3-point, or 0–10 V on specific models and modules, so an actuator matches when its signal type and voltage match.
- Is an older controller worth moving?
- Danfoss advises against reusing the ECL Comfort 100, 110 and 300: they lack modern interfaces, the relays are worn, programme cards and vital spares are no longer produced, and they support neither Danfoss Leanheat Monitor nor M-bus data logging. The 200 is out of production too, but Danfoss did not give reuse advice for it, so none is attributed here.
Unresolved
What we asked and have not been told.
Is the base part common within the 210 and 310, and where is the break against the discontinued 100, 110, 200 and 300? Danfoss treated the application key as the deciding factor throughout and never raised the base part as an obstacle — but an absence is not a confirmation, and we put the question to them directly on 15 August 2026. It has not been answered.
A second source points the other way. Stefan Carlström of Alfa Fjärrvärme AB in Malmö, Alfa Laval’s representative in Skåne, wrote on 14 August 2026 that the ECL generations “har alla olika bottenplattor så det måste göras en komplett ny el installation vid köp av nytt”. Read closely, “vid köp av nytt” describes changing generation, which does not contradict Danfoss. Read loosely, it contradicts reuse altogether. We are not going to resolve that by picking the reading we prefer.
Everything above describes a controller in your hand. None of it describes your installation.
How we know
Where this answer comes from.
Danfoss Kundeservice Danmark answered two rounds of written questions about ECL Comfort reuse under case 21372960. The answers came from Poul Henning Sørensen, Technical Support Engineer at Danfoss Climate Solutions Danmark in Silkeborg.
Answered in writing 14 August 2026.
This records what Danfoss told us about controllers and keys. It is not an official manufacturer endorsement of any particular reuse, and it does not confirm that a specific controller fits a specific unit — a professional decides that with the actual hardware in front of them.
One thing to do next
Holding a controller you cannot identify?
Send a photo of the type plate and a few lines about where it sits. PartSignal works out what it is and whether a documented equivalent exists.