Comfosense 67 reliability

[hauntedicecreamvan]

I have a Zehnder Comfoair 180, with a Comfosense 67/CCS controller (RS232 comms). The controller has capacitive pads under the plastic faceplate, and after working fine for a couple of months with light usage it suddenly become unreliable with missed button presses, gradually getting worse to the point that it had to be operated with the plastic plate removed, and eventually mixing up key presses or phantom presses. I swapped it out for a spare Comfosense and the replacement is working fine.

 

Has anyone here experienced reliability issues with these controllers? It seems potentially quite fragile, being based on a flexible PCB which sits wedged between the plastic display surround and the front cover.

 

I don't see myself interacting with it much from now on anyway, since flow rates are commissioned, and boost is controlled via the bathroom switch input by Home Assistant based on air quality and humidity rise/fall rules.

[Mike]

Not yet. I also plan to get mine hooked up to Home Assistant in due course.

[JohnMo]

Obvious question, is why do you even need a controller - once set what is there to adjust. MVHR commission forget, except filter cleans/changes

[hauntedicecreamvan]

6 hours ago, Mike said:

Not yet. I also plan to get mine hooked up to Home Assistant in due course.

are you looking at integrating via the serial interface or just using binary inputs to trigger boost?

 

I considered the RS232 proxy approach, with an ESP32, so that I could keep the Comfosense while still allowing HA to read/set itself, but decided it was too much added complication, so just hooked up a dry-contact relay to the bathroom switch input. It would be nice to see the outputs from the various sensors and status of the summer bypass in Home Assistant though.

 

2 hours ago, JohnMo said:

Obvious question, is why do you even need a controller - once set what is there to adjust. MVHR commission forget, except filter cleans/changes

Probably not needed long-term.

 

The CA180 LUXE doesn't have any onboard display/buttons, so the Comfosense is needed to set the flow rates during commissioning, but after that its all stored in the CA180 itself so theoretically could run without it (or with something 3rd party running the reverse-engineered serial interface commands).

 

I was initially using the Comfosense schedule to set some crude time-based boost that coincide with daily shower times, but now that the relay input is configured through Home Assistant, boost logic is based on CO2 sensors in habitable rooms, an air quality/VOC sensor in the kitchen, and humidity rate of change in the kitchen/utility/bathroom - I shouldn't need to touch the Comfosense much, if at all, going forward (assuming I have thresholds set up correctly).

Edited Wednesday at 21:20 by hauntedicecreamvan

[JohnMo]

I went down the route of looking at CO2 sensors etc. 5 years in none of it is really needed - nice sales accessories. We need a CO2 monitor in master bedroom (Scotland) and I used to monitor it, all the time (very rarely look at it ever now) I tweaked MVHR flow rates to get CO2 max I was comfortable with overnight, and that's it. We have dry contact switches outside each wet room to boost and a humidity sensor in the MVHR unit.  MVHR almost never goes in to boost. It just doesn't need to, house humidity doesn't rise much for long.

[Mike]

13 hours ago, hauntedicecreamvan said:

are you looking at integrating via the serial interface or just using binary inputs to trigger boost?

 

I considered the RS232 proxy approach, with an ESP32, so that I could keep the Comfosense while still allowing HA to read/set itself, but decided it was too much added complication, so just hooked up a dry-contact relay to the bathroom switch input. It would be nice to see the outputs from the various sensors and status of the summer bypass in Home Assistant though.

It's a future project, but this approach (probably the one you found) looked promising: Zehnder ComfoAir CA350 integration

 

[hauntedicecreamvan]

On 27/08/2026 at 06:41, JohnMo said:

I went down the route of looking at CO2 sensors etc. 5 years in none of it is really needed

I need to collect some more data to draw any conclusions for my property. For humidity, it is a toss-up between letting the background rate deal with it, vs boosting, especially right now where the outside air is holding a lot of moisture - in that situation, I was finding that the boost could cause whole-house humidity levels to rise more than if I just let the background extract deal with the shower spike.

 

I think the biggest limitation of CO2 sensors is how they handle baselining of the data, and their also long-term reliability. All my CO2 sensors are "true" sensors using NDIR, but because of how they baseline based on the lowest measurements they take, you never know if they are reporting close to the actual CO2 levels or levels with a big offset. I don't know what the solution is to this, it seems they all rely on rooms being unoccupied some of the day, and supply of fresh air good enough to ensure that levels do fall to close to outside air levels. I also had one sensor fail with ridiculously high readings (measuring 2000ppm+ indoors, and 900ppm when sat on a window sill outside).