ᐅ Maintenance Contract for Residential Ventilation System, More Affordable Filters

Points to maintain on a heat pump:

- Over time, a lot of dust and dirt accumulate on and inside the outdoor unit. This affects the compressor, which is essential for the smooth operation of the heat pump. Monoblock units also have a compressor, which must be cleaned regularly as well.

- The ventilation fins should be kept clean. For outdoor units, a pressure washer can be used for cleaning. For indoor units, the fins must be cleaned manually to remove dust and dirt.

- The most important aspect is checking the system for leaks. Refrigerant is often highly harmful to the environment. Since the liquid circulates in a closed loop, refrigerant typically only leaks if there is a gap, for example due to poor installation or vibrations of the system. Loss of refrigerant can lead to complete system failure.

- Replace or refill refrigerant if necessary. Fix any leaks.

- As a final step, the technician must perform a test to ensure the general functionality of the system.

Thank you very much for the responses; they are very helpful for non-experts.

@netuser @Mycraft
I agree with you regarding outdoor units. There might actually be some maintenance needed there. I have a brine heat pump, so there is no outdoor unit.
Is it really necessary to check the system specifically for leaks? If refrigerant were missing, wouldn’t all the heat pump’s parameters go out of range so that the system either shuts down or at least reports an error? I don’t have my car’s air conditioning checked just to see if refrigerant is still there, as long as it is working. I doubt a simple inspection can prevent refrigerant loss. Either the refrigerant has already leaked out, or there’s no leak.

@netuser
On the topic of ventilation:
I’m not familiar with the thread. A filter set from Zehnder costs about 20€ more than a cheap generic replacement. According to its specs, my ventilation system uses only 20 watts (which is surprisingly low). With those 20€ I can run my ventilation system for 126 days. So if I saved (say) 20% energy, it would take over 600 days to break even.
Furthermore, there is the risk that more expensive filters will be left in the system longer than cheaper ones, which doesn’t seem practical to me.

Some people only buy original filters for their range hood or vacuum cleaner because they fear damaging the device otherwise. Others buy the recommended descaler for their coffee machine from a Swiss manufacturer at 14€/100ml. On my Ford’s fuel cap it says, “We recommend Aral gasoline.” It’s all a matter of belief.

Gecko1927 schrieb:

Wouldn’t all the parameters of the heat pump get so messed up due to missing refrigerant that the system would shut down or at least show an error?

Eventually, yes, but leaks usually develop slowly, so only the efficiency decreases. Until, of course, the critical point is reached and the system stops working.

Gecko1927 schrieb:

I doubt that a simple inspection can prevent refrigerant from escaping.

No, the refrigerant is already gone by the time an inspection takes place if there is a leak. But inspections can prevent further environmental damage. The refrigerant is supposed to stay inside the system, not be released into the atmosphere. The rules and regulations on this are clearly defined (DIN EN 378-1).

Gecko1927 schrieb:

I don’t have my car’s air conditioning checked for refrigerant as long as it works.

Exactly, until it stops working because... well, the refrigerant is gone (which might only happen after you’ve already sold the car). Ask any workshop how often that happens—you might be surprised. Just because something isn’t commonly done doesn’t mean it doesn’t happen. There’s a whole profession (commonly known as refrigeration and air conditioning technicians) behind this for a reason.

Gecko1927 schrieb:

Either the refrigerant has already escaped, or there is no leak.

To prevent the refrigerant from eventually escaping (rubber parts become porous, metal fatigues, connections loosen due to vibration, etc.), there are maintenance intervals including leak tests, also for heat pumps. Again, this is covered by DIN EN 378.

@netuser
Some people only buy original replacement filters for their range hood or vacuum cleaner because they are afraid of damaging anything otherwise. Others purchase the descaler recommended for their coffee machine by a Swiss manufacturer for 14€/100ml (14€/3.4 fl oz). On my Ford, the fuel cap says, "We recommend Aral gasoline." It’s all a matter of belief.
[/QUOTE]

I found the mentioned post by @andimann:
https://www.hausbau-forum.de/threads/zehnder-q350-problem-diskussionsthread.41994/post-544533

You can decide for yourself whether it’s purely a matter of belief.
I found the explanation quite plausible and understandable in individual cases. It certainly doesn’t apply universally or to all filters, but that wasn’t the point! Only that such possible “side effects” should be considered before you get excited about saving 20 euros on filter purchases….

I think I will not sign a maintenance contract nor buy the original filter mats, as I have found a good alternative. I won’t run the ventilation system during the summer anyway, since the windows will be open. Many people in the house don't use the ventilation at all because of the noise. Since it’s a new build and there isn’t much ventilation in winter, I want to avoid getting mold in the apartment. Thanks for your advice!