ᐅ Controlled residential ventilation & heat pumps: Viessmann vs. Vaillant vs. Zehnder?
Created on: 23 Nov 2022 14:12
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Nixwill2Hello everyone,
I want to revisit a topic that was mentioned a while ago in another thread but deserves a more detailed discussion, as it turns out to be more complicated than anticipated. Here’s our situation, and I would really appreciate hearing about your experiences. Starting with the background.
We are currently building a prefabricated house (timber construction) with a prefab home manufacturer. The plot is located in a small village, in a very old part of town. It seems like almost everyone heats with wood there. On our property, there is a wood smoke smell throughout the entire winter (we noticed this last year already, and it’s happening again this year), as if there is a campfire burning nearby non-stop.
Now, we are seriously concerned that with a mechanical ventilation system with heat recovery (MVHR), the indoor air could end up smelling the same as the outdoor air, which we definitely want to avoid. To counter this, we thought about installing a mechanical ventilation system with an activated carbon filter included. That’s why we have tentatively selected the Zehnder ComfoAir Q350 TR in the enthalpy version, since both of us already occasionally suffer from dry eyes. This system also comes from the factory with attachments for activated carbon filters.
Unfortunately, things turned out differently than expected. The house supplier is hesitant in initial discussions and is postponing the topic until the customization meeting in December. The reason given: they only work with Viessmann or Vaillant because the heat pumps come from those manufacturers. More precisely, it would be either the Viessmann Vitovent 300W or the Vaillant recoVair VAR360 ventilation system. Neither of these original systems offers a solution with an activated carbon filter.
Now to my main question. What’s your opinion on this? Our concern is not unfounded, and an F7 pollen filter doesn’t seem to be an adequate solution for this situation, does it? They immediately said that an F7 filter would be sufficient, but we don’t believe that.
Is it possible to install a Zehnder mechanical ventilation system alongside a heat pump from Viessmann or Vaillant, or not?
I don’t want to assume the worst-case scenario, but do you have any ideas on how to solve this problem if the house provider doesn’t allow any other mechanical ventilation system?
I would be very grateful for any ideas, experiences, or tips!
Best regards
For your filter box, you can either use a pre-filter followed by the activated carbon filter, just the activated carbon filter alone, or something entirely different.
There are several filter classes; the higher the number, the finer the filter. Only a coarse filter (G2 or G4) is used for outside air.
Then, before the air enters the mechanical ventilation system (usually installed inside it), you can add a "medium" filter (M5). Next comes the supply air filter (F7), which, for example, protects against pollen and is also normally installed in the mechanical ventilation system. Typically, the activated carbon filter is placed after the F7 filter in the supply air path.
This information is from the website where your box is offered:
The activated carbon replacement filter AK is designed for (or rather against) kitchen odors, car exhaust, paint fumes, and fits into the small "drawer" of the ISO filter box.
The activated carbon replacement filter AL is designed for (or rather against) agricultural odors. It also fits into the small "drawer" of the ISO filter box.
There are several filter classes; the higher the number, the finer the filter. Only a coarse filter (G2 or G4) is used for outside air.
Then, before the air enters the mechanical ventilation system (usually installed inside it), you can add a "medium" filter (M5). Next comes the supply air filter (F7), which, for example, protects against pollen and is also normally installed in the mechanical ventilation system. Typically, the activated carbon filter is placed after the F7 filter in the supply air path.
This information is from the website where your box is offered:
The activated carbon replacement filter AK is designed for (or rather against) kitchen odors, car exhaust, paint fumes, and fits into the small "drawer" of the ISO filter box.
The activated carbon replacement filter AL is designed for (or rather against) agricultural odors. It also fits into the small "drawer" of the ISO filter box.
This is a bit embarrassing for me—I searched the entire page and even googled it 🙄, shame on me! Thanks for your effort!
Thank you very much for your explanations; they help me a lot!! If I now apply what you wrote to the controlled residential ventilation system from Viessmann with the mentioned additional filter box, it sounds like this to me (viewed from outside to inside):
Outdoor air means the duct coming from outside into the controlled residential ventilation system and first going into my filter box. Here you place a G2 or G4 filter before the activated carbon filter, so as the primary contact filter 🙂. Then comes the activated carbon filter. Now we enter the controlled residential ventilation system, where the M5 filter would come next, followed by the F7 filter.
Could you omit the M5 filter in this setup, what do you think?
You mention that the activated carbon filter normally comes as the last filter after the F7. Do you think the activated carbon filter is less effective in my setup?
With this additional filter before the controlled residential ventilation system, the ventilation system itself no longer handles it—could this possibly be bad for it? It somehow sounds like it would require more effort...
Thank you very much for your explanations; they help me a lot!! If I now apply what you wrote to the controlled residential ventilation system from Viessmann with the mentioned additional filter box, it sounds like this to me (viewed from outside to inside):
Outdoor air means the duct coming from outside into the controlled residential ventilation system and first going into my filter box. Here you place a G2 or G4 filter before the activated carbon filter, so as the primary contact filter 🙂. Then comes the activated carbon filter. Now we enter the controlled residential ventilation system, where the M5 filter would come next, followed by the F7 filter.
Could you omit the M5 filter in this setup, what do you think?
You mention that the activated carbon filter normally comes as the last filter after the F7. Do you think the activated carbon filter is less effective in my setup?
With this additional filter before the controlled residential ventilation system, the ventilation system itself no longer handles it—could this possibly be bad for it? It somehow sounds like it would require more effort...
Nixwill2 schrieb:
I’m actually a bit embarrassed now, I searched the whole page and even googled it 🙄, shame on me! Thanks for your effort!!!
Thank you very much for your explanations, they help me a lot!! If I now apply what you wrote to the Viessmann mechanical ventilation with the mentioned additional filter box, it sounds like this to me (looking from outside to inside):
Outdoor air means the pipe that comes from outside into the mechanical ventilation and thus first leads into my filter box. Here you place a G2 or G4 filter in front of the activated carbon filter as a preliminary filter 🙂. Then the activated carbon filter. Now we enter the mechanical ventilation, where the M5 filter would go, followed by the F7 filter.
Do you think it would be possible to skip the M5 filter in this setup?
You wrote that the activated carbon filter actually comes last, behind the F7. Do you think the activated carbon filter is less effective in my version?
With this additional filter ahead of the mechanical ventilation, the ventilation unit itself no longer has anything to do with it, and maybe that’s not so good for it? Sounds somehow like more effort... Less effective, no; shorter lifespan, yes, because a G2/G4 filter still lets too much dirt through, causing the filter media to clog faster.
I would set it up like this: [outdoor air -> G2 or M5 at the mechanical ventilation intake -> mechanical ventilation unit -> F7 filter inside the ventilation at the supply air outlet -> activated carbon filter box].
That’s how I did it back then (roughly), my box on the right side is my G2 filter box; in your case, it should be on the left with the activated carbon filter.
Oh, you wouldn’t actually connect the box to the outside air but rather to the supply air! Is that correct?
So like this:
Outside air – M5 filter (in the mechanical ventilation system) – F7 filter (in the mechanical ventilation system) – activated carbon (in the box) – supply air into the ducts
Which brings up the question of insulation and the metal box again: would it even need to be insulated? It would basically only be exposed to the temperature of the air going into the ventilation ducts, right?
So like this:
Outside air – M5 filter (in the mechanical ventilation system) – F7 filter (in the mechanical ventilation system) – activated carbon (in the box) – supply air into the ducts
Which brings up the question of insulation and the metal box again: would it even need to be insulated? It would basically only be exposed to the temperature of the air going into the ventilation ducts, right?
Exactly, but as mentioned, you can also use G2/G4 instead of M5, since every filter increases the backpressure. This means a higher fan speed, resulting in more energy consumption, and possibly a larger mechanical ventilation system because the required air volume may no longer pass through the filters. Therefore, it is important to clearly communicate your future plans.
I hope that someone at our prefab house manufacturer is actually doing calculations for the heating system and the mechanical ventilation with heat recovery. Sometimes I feel like they are still living in their own bubble where time has stood still...
Having a mechanical ventilation system that’s too small is a problem because it will then have to run excessively. But is it possible to have one that’s too large? That’s exactly what I suspect. Both the heating system and the mechanical ventilation in our offer are always one size bigger, but I honestly have no idea if that’s necessary. Is there a rough way I can check this myself? From the building permit / planning permission, I at least have the cubic volume data for each floor—isn’t that crucial for this?
Having a mechanical ventilation system that’s too small is a problem because it will then have to run excessively. But is it possible to have one that’s too large? That’s exactly what I suspect. Both the heating system and the mechanical ventilation in our offer are always one size bigger, but I honestly have no idea if that’s necessary. Is there a rough way I can check this myself? From the building permit / planning permission, I at least have the cubic volume data for each floor—isn’t that crucial for this?
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