Just no Hoval ventilation unit!!!
For anyone planning to install a heat recovery ventilation system, I can only advise against the Hoval unit! Unfortunately, we have one installed in our basement and have had nothing but problems. The first unit was replaced by customer service after the first winter because condensate water in the rotary heat exchanger froze at low temperatures. So, a new unit was installed, which runs noticeably quieter than the old one (though it’s still audible). However, almost all problems persist. The system was planned and installed by Hoval, but unfortunately, the location in the unheated storage area turned out to be very unsuitable—there were significant energy losses due to uninsulated piping. We had to cover the entire insulation cost ourselves.
I haven’t even mentioned the most serious issues yet. At lower temperatures, which can drop to minus 24 degrees Celsius (minus 11°F) where we live, the supply air temperature only reaches about 8-9 degrees Celsius (46-48°F), despite the promised 17 degrees Celsius (63°F). Because we don’t live in a mild climate like Italy, the supply air needs preheating regardless of the system used. Hoval still insists their system works without preheating. Furthermore, there is excessive moisture in the living space due to moisture recovery. At lower temperatures, the rotor speed is increased counterproductively, leading to window condensation at a relative humidity of 40-50%.
The worst part is the spread of odors and noise throughout the house. Since all exhaust air from the entire house comes into contact with the supply air in the rotary heat exchanger, the entire home ends up smelling like cooking odors or, even worse, toilet odors. Exhaust and supply air systems must be kept separate!!!
All attempts to get a response from Hoval have so far been unsuccessful.
For anyone planning to install a heat recovery ventilation system, I can only advise against the Hoval unit! Unfortunately, we have one installed in our basement and have had nothing but problems. The first unit was replaced by customer service after the first winter because condensate water in the rotary heat exchanger froze at low temperatures. So, a new unit was installed, which runs noticeably quieter than the old one (though it’s still audible). However, almost all problems persist. The system was planned and installed by Hoval, but unfortunately, the location in the unheated storage area turned out to be very unsuitable—there were significant energy losses due to uninsulated piping. We had to cover the entire insulation cost ourselves.
I haven’t even mentioned the most serious issues yet. At lower temperatures, which can drop to minus 24 degrees Celsius (minus 11°F) where we live, the supply air temperature only reaches about 8-9 degrees Celsius (46-48°F), despite the promised 17 degrees Celsius (63°F). Because we don’t live in a mild climate like Italy, the supply air needs preheating regardless of the system used. Hoval still insists their system works without preheating. Furthermore, there is excessive moisture in the living space due to moisture recovery. At lower temperatures, the rotor speed is increased counterproductively, leading to window condensation at a relative humidity of 40-50%.
The worst part is the spread of odors and noise throughout the house. Since all exhaust air from the entire house comes into contact with the supply air in the rotary heat exchanger, the entire home ends up smelling like cooking odors or, even worse, toilet odors. Exhaust and supply air systems must be kept separate!!!
All attempts to get a response from Hoval have so far been unsuccessful.
N
nachtzeche7 Apr 2011 21:51I am currently planning a mechanical ventilation system (not with the company you mentioned!) and reading your post really unsettles me!!!
1. My deepest sympathies! What a DISASTER
2. Fingers crossed that it will work out for us... it has to be possible to design it successfully, right???
Encouraging regards
nachtzeche
1. My deepest sympathies! What a DISASTER
2. Fingers crossed that it will work out for us... it has to be possible to design it successfully, right???
Encouraging regards
nachtzeche
J
JH-CADArchitekt5 Jul 2012 11:30..."There was condensate on the rotary heat exchanger which froze at lower temperatures."
...This is normal and even necessary; it certainly was not the reason for replacement!
..."Placement in the unheated storage area is not very suitable—too much energy loss due to uninsulated piping. The cost of insulation was fully covered by us."
By whom else? Were they just too stingy to plan properly?
..."At lower temperatures, with us reaching down to minus 24 degrees Celsius (−11°F), we achieve a supply air temperature of only 8–9 degrees Celsius (46–48°F) instead of the advertised 17 degrees Celsius (63°F). Since we don’t live in Italy, the supply air has to be preheated, regardless of the system used."
...Anyone installing equipment in an unheated space without insulating the supply and exhaust ducts shouldn’t be surprised! Through the uninsulated exhaust duct, already 10°C (50°F) exhaust air reaches the unit, from which heat is then recovered! How can you get 17°C (63°F) at an efficiency of 85%? This is heat recovery, not heating!
..."Furthermore, there is over-humidification of the living space caused by moisture recovery, as the rotor speed is increased counterproductively at lower temperatures."
...That has nothing to do with each other! And when it gets cold, the rotor must spin faster, or it will freeze completely!
..."Window condensation occurs at a relative humidity of 40–50%."
...That’s the joke! 40–50% relative humidity is not too high. Poor quality windows are more likely to cause condensation. In fact, 40% relative humidity is rather dry!
..."The worst issue is odor and noise distribution throughout the house. Who likes the whole house smelling like cooking or, worse, bathroom odors because the entire exhaust air from the house comes into contact with the supply air in the rotary heat exchanger? Supply and exhaust air must be separated!"
...The rotary heat exchanger includes a purge chamber! Supply and exhaust air are therefore 100% separated, just like in a plate heat exchanger! There is no recirculation! If it smells, you should turn the system on! Or clean the heat exchanger, which according to instructions should be done annually. That will prevent grease deposits! Also, ventilation systems are only approved for connection to range hoods under specific conditions that you are clearly not meeting if cooking odors get into the heat recovery system. Bathroom odors are 100% not transferred unless you urinate into the system—which it is obviously not designed for!
So where exactly is the problem?
...This is normal and even necessary; it certainly was not the reason for replacement!
..."Placement in the unheated storage area is not very suitable—too much energy loss due to uninsulated piping. The cost of insulation was fully covered by us."
By whom else? Were they just too stingy to plan properly?
..."At lower temperatures, with us reaching down to minus 24 degrees Celsius (−11°F), we achieve a supply air temperature of only 8–9 degrees Celsius (46–48°F) instead of the advertised 17 degrees Celsius (63°F). Since we don’t live in Italy, the supply air has to be preheated, regardless of the system used."
...Anyone installing equipment in an unheated space without insulating the supply and exhaust ducts shouldn’t be surprised! Through the uninsulated exhaust duct, already 10°C (50°F) exhaust air reaches the unit, from which heat is then recovered! How can you get 17°C (63°F) at an efficiency of 85%? This is heat recovery, not heating!
..."Furthermore, there is over-humidification of the living space caused by moisture recovery, as the rotor speed is increased counterproductively at lower temperatures."
...That has nothing to do with each other! And when it gets cold, the rotor must spin faster, or it will freeze completely!
..."Window condensation occurs at a relative humidity of 40–50%."
...That’s the joke! 40–50% relative humidity is not too high. Poor quality windows are more likely to cause condensation. In fact, 40% relative humidity is rather dry!
..."The worst issue is odor and noise distribution throughout the house. Who likes the whole house smelling like cooking or, worse, bathroom odors because the entire exhaust air from the house comes into contact with the supply air in the rotary heat exchanger? Supply and exhaust air must be separated!"
...The rotary heat exchanger includes a purge chamber! Supply and exhaust air are therefore 100% separated, just like in a plate heat exchanger! There is no recirculation! If it smells, you should turn the system on! Or clean the heat exchanger, which according to instructions should be done annually. That will prevent grease deposits! Also, ventilation systems are only approved for connection to range hoods under specific conditions that you are clearly not meeting if cooking odors get into the heat recovery system. Bathroom odors are 100% not transferred unless you urinate into the system—which it is obviously not designed for!
So where exactly is the problem?
M
Martin20615 Sep 2012 20:09We have been using the Hoval RS250 since October 2008, with outdoor temperatures ranging from -25°C (–13°F) to +36°C (97°F), and varying levels of humidity.
As for what happened to the original poster, one can only speculate:
It seems the planning was done by someone with little to no knowledge of ventilation technology and certainly not this device. Customer requests and restrictions imposed by the builder probably also played a role.
…"there was condensate on the rotary heat exchanger which froze at lower temperatures"…
This could be due to poor planning or execution. However, it is also conceivable that additional measures are needed when operating close to the device’s limits. A professional ventilation planner would have recommended an earth-to-air heat exchanger beforehand (even though Hoval considers it not “necessary”)… who knows, maybe someone actually did suggest that?!
…"location in an unheated storage room is not very suitable—too much energy loss due to uninsulated piping. We covered the entire cost of insulation"…
Planning mistake. Pipes carrying air at different temperatures must always be insulated. If condensation is possible (which is often the case), the insulation must also be vapor-tight. This is standard practice in ventilation planning and is included in installation kits from many ventilation suppliers.
…"at lower temperatures, with us reaching minus 24°C (–11°F), we only achieve a supply air temperature of 8-9°C (46-48°F) instead of the promised 17°C (63°F). Since we don’t live in Italy, the supply air has to be preheated regardless of the system used"…
This is certainly not a device issue. Either something is defective in the unit, or—more likely—the installation is incorrect. In our case, with a simple earth-to-air heat exchanger installed in front, the supply air temperature at –10°C (14°F) is barely one degree below the average room temperature.
…"furthermore, there is over-humidity in the living space due to moisture recovery, since the rotor speed is increased counterproductively at low temperatures"…
Over-humidity? Persistent levels above 65% relative humidity? Here too, it is probably a matter of user error, incorrect settings, or a planning/installation fault—if there is any issue at all.
…"window condensation at relative humidity of 40-50%"…
As already mentioned: if windows are fogging up at 40-50% humidity, then the windows themselves are inadequate. No controlled ventilation system can compensate for that. Even standard double-glazed windows with proper edge seals and well-installed frames should prevent this from happening, even without controlled ventilation.
…"the worst issue is the distribution of odors and noise throughout the house, or who likes the whole house smelling like fried food or worse—like toilet odors because all the exhaust air from the entire house contacts the supply air in the rotary heat exchanger. Supply and exhaust air must be separated!!!"…
Odor spread inside the house only happens if there are major leaks in the duct system or—more likely—a “short circuit” between exhaust air and fresh air intakes, meaning these openings are placed too close or in an unfavorable position.
Noise originating from the device itself indicates poor planning and installation. Such a system must be designed with vibration isolation to prevent structure-borne noise transmission and equipped with appropriate sound attenuators on the unit and, if necessary, in some duct branches. Noise transmission from room to room (e.g., carrying phone conversations) is clearly a planning error—this means the ducts were not routed in a star pattern but from room to room.
Our device is installed suspended on the ground floor, separated from other rooms by a simple apartment door, and there is no disturbing noise—not even at 100% capacity.
SUMMARY:
Even the best device is useless if planned and installed cheaply and poorly. I wouldn’t be surprised if the installer lacks ventilation engineering training and/or experience.
Regards,
-Martin-
As for what happened to the original poster, one can only speculate:
It seems the planning was done by someone with little to no knowledge of ventilation technology and certainly not this device. Customer requests and restrictions imposed by the builder probably also played a role.
…"there was condensate on the rotary heat exchanger which froze at lower temperatures"…
This could be due to poor planning or execution. However, it is also conceivable that additional measures are needed when operating close to the device’s limits. A professional ventilation planner would have recommended an earth-to-air heat exchanger beforehand (even though Hoval considers it not “necessary”)… who knows, maybe someone actually did suggest that?!
…"location in an unheated storage room is not very suitable—too much energy loss due to uninsulated piping. We covered the entire cost of insulation"…
Planning mistake. Pipes carrying air at different temperatures must always be insulated. If condensation is possible (which is often the case), the insulation must also be vapor-tight. This is standard practice in ventilation planning and is included in installation kits from many ventilation suppliers.
…"at lower temperatures, with us reaching minus 24°C (–11°F), we only achieve a supply air temperature of 8-9°C (46-48°F) instead of the promised 17°C (63°F). Since we don’t live in Italy, the supply air has to be preheated regardless of the system used"…
This is certainly not a device issue. Either something is defective in the unit, or—more likely—the installation is incorrect. In our case, with a simple earth-to-air heat exchanger installed in front, the supply air temperature at –10°C (14°F) is barely one degree below the average room temperature.
…"furthermore, there is over-humidity in the living space due to moisture recovery, since the rotor speed is increased counterproductively at low temperatures"…
Over-humidity? Persistent levels above 65% relative humidity? Here too, it is probably a matter of user error, incorrect settings, or a planning/installation fault—if there is any issue at all.
…"window condensation at relative humidity of 40-50%"…
As already mentioned: if windows are fogging up at 40-50% humidity, then the windows themselves are inadequate. No controlled ventilation system can compensate for that. Even standard double-glazed windows with proper edge seals and well-installed frames should prevent this from happening, even without controlled ventilation.
…"the worst issue is the distribution of odors and noise throughout the house, or who likes the whole house smelling like fried food or worse—like toilet odors because all the exhaust air from the entire house contacts the supply air in the rotary heat exchanger. Supply and exhaust air must be separated!!!"…
Odor spread inside the house only happens if there are major leaks in the duct system or—more likely—a “short circuit” between exhaust air and fresh air intakes, meaning these openings are placed too close or in an unfavorable position.
Noise originating from the device itself indicates poor planning and installation. Such a system must be designed with vibration isolation to prevent structure-borne noise transmission and equipped with appropriate sound attenuators on the unit and, if necessary, in some duct branches. Noise transmission from room to room (e.g., carrying phone conversations) is clearly a planning error—this means the ducts were not routed in a star pattern but from room to room.
Our device is installed suspended on the ground floor, separated from other rooms by a simple apartment door, and there is no disturbing noise—not even at 100% capacity.
SUMMARY:
Even the best device is useless if planned and installed cheaply and poorly. I wouldn’t be surprised if the installer lacks ventilation engineering training and/or experience.
Regards,
-Martin-
M
Martin20628 Feb 2015 12:16Update
We have been using the system for about 6 1/2 years now.
There is little to add to my previous statement.
The system continues to run very quietly, very reliably, and fairly efficiently (about 65W).
The indoor climate is excellent year-round (air exchange rate approximately 0.3 to 0.35).
There was a goodwill repair: Apparently, units with poor rotor bearings were delivered until 2008. After consulting with Hoval, the rotor was replaced free of charge.
Otherwise, I replace the unit filters (G4/F7), the pre-filter (G4) before the ground heat exchanger, and the filters in the exhaust air vents (G4) every six months and lightly wipe the inside of the unit with a damp cloth, cleaning the exhaust air vents.
Additionally, I check the air intake monthly for blockages caused by insects, (pollen) dust, etc., cleaning it once in spring and once in late summer (in addition to the two filter changes per year).
Other users of the Hoval system report no problems—apart from the rotor goodwill replacement for older models.
(It is unclear whether the thread starter still experiences any issues. For some reason, their account is also blocked.)
CONCLUSION:
Fully satisfied even in the 7th winter.
If it continues to perform like this for a few more years, the investment will have been worthwhile for us.
We no longer want to miss the comfortable climate provided by the controlled ventilation with heat recovery—and especially the moisture recovery/regulation.
Regards,
-Martin-
We have been using the system for about 6 1/2 years now.
There is little to add to my previous statement.
The system continues to run very quietly, very reliably, and fairly efficiently (about 65W).
The indoor climate is excellent year-round (air exchange rate approximately 0.3 to 0.35).
There was a goodwill repair: Apparently, units with poor rotor bearings were delivered until 2008. After consulting with Hoval, the rotor was replaced free of charge.
Otherwise, I replace the unit filters (G4/F7), the pre-filter (G4) before the ground heat exchanger, and the filters in the exhaust air vents (G4) every six months and lightly wipe the inside of the unit with a damp cloth, cleaning the exhaust air vents.
Additionally, I check the air intake monthly for blockages caused by insects, (pollen) dust, etc., cleaning it once in spring and once in late summer (in addition to the two filter changes per year).
Other users of the Hoval system report no problems—apart from the rotor goodwill replacement for older models.
(It is unclear whether the thread starter still experiences any issues. For some reason, their account is also blocked.)
CONCLUSION:
Fully satisfied even in the 7th winter.
If it continues to perform like this for a few more years, the investment will have been worthwhile for us.
We no longer want to miss the comfortable climate provided by the controlled ventilation with heat recovery—and especially the moisture recovery/regulation.
Regards,
-Martin-
F
Falkenjaeger4 Apr 2015 11:48I have had an RS-250 since February 2014 (wooden house, Minergie standard).
I am very satisfied.
I just had my first maintenance recently.
I was surprised at how dirty the two filters (supply/exhaust air) were.
Replacing them is really simple.
We also have an insect filter that can be easily washed (metal mesh).
However, our wooden house supplier didn’t install it very well. It’s difficult to access.
I will increase my maintenance interval to twice a year and see how dirty they get then.
During the winter months, I couldn’t resist installing an air purifier (Boneco Airwasher 1355). I measure temperature and humidity with Netatmo in four rooms.
Regards
Falkenjaeger
I am very satisfied.
I just had my first maintenance recently.
I was surprised at how dirty the two filters (supply/exhaust air) were.
Replacing them is really simple.
We also have an insect filter that can be easily washed (metal mesh).
However, our wooden house supplier didn’t install it very well. It’s difficult to access.
I will increase my maintenance interval to twice a year and see how dirty they get then.
During the winter months, I couldn’t resist installing an air purifier (Boneco Airwasher 1355). I measure temperature and humidity with Netatmo in four rooms.
Regards
Falkenjaeger
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