ᐅ Retrofitting an enthalpy exchanger – any experiences?

Hello and good morning to the forum! After reading along for a long time, I’ve decided to register because I’d like to ask about the collective knowledge here 🙂. A brief introduction about me/us: we moved into our house (prefabricated, timber frame construction) in 2023. So far, the building services (Viessmann split heat pump and Zehnder Comfoair E 350) have been running well through the winter, but like many others, we have a problem with too low relative humidity. An inquiry with Zehnder revealed that replacing the standard heat exchanger with the appropriate enthalpy exchanger (we were given the article number) is possible. Now to my question:
Has anyone done this with this ventilation system? I’ve only found guides for the Comfoair Q350 model.
I also have a quote from a technician, which comes to about 1750 euros (including 2 hours of installation and the exchanger). That seems quite high to me. I’ve already found out that the part itself costs around 1000 euros 😉 but the installation didn’t seem too complicated.
Before we start experimenting, I’d rather ask here first.
And if anyone has done this themselves, it would be great if you could share your experience — was there a noticeable improvement? One more thing I’m concerned about: the E350 has no pre-heating coil. The heat exchanger by Zehnder is only described for use down to -6°C (21°F) outside temperature. What happens if it gets colder? Do you have to switch off the ventilation to prevent damage?
Thanks in advance for reading, I’d be happy if anyone can share any insights. Good luck Bubo

Unplug the unit, remove the front panel (4-6 screws), pull out the old heat exchanger from the frame, slide in the enthalpy exchanger, put the front panel back on, done. You can vacuum inside once more in between. Takes about 10 minutes.

A preheating coil is usually not necessary.

MayrCh schrieb:

Preheating registers are usually not necessary.

In winter, when it’s cold, they are more likely needed. I believe my Vaillant system goes into "frost protection" mode at around -4°C (25°F), which means it shuts off. The user manual should specify how each manufacturer handles this. If the temperature here drops to -6°C (21°F), I would expect the system to simply shut down and not restart even if you try to override it. It would only start running again once it gets warmer.

I believe the average temperature must have been around -4°C (25°F) over the last 24 hours. Otherwise, my Vaillant system would have been shutting down intermittently for about a week this winter, but it was only two days.

Thanks to you too for the information 🙂. I think we will get one of those and try to install it ourselves.

MayrCh schrieb:

Unplug the unit, remove the front panel (4-6 screws), pull out the old heat exchanger on the belt, slide in the enthalpy exchanger, put the front panel back on, done. You can vacuum inside in between. Takes about 10 minutes.

A preheating coil is generally not necessary.

Basically, this is the procedure. However, I would still recommend doing this only after the warranty period has expired, or at least making sure to reinstall the original block if the main unit breaks down unexpectedly before the technician arrives, so as not to void the warranty.