We recently purchased an existing condominium in a six-family house that was completed in December 2014.
The building has a total enclosed volume of 3,114 cubic meters (cbm), with a total living area of just under 640 square meters (sqm). Installed is an air-to-water heat pump Stiebel Eltron WPL 33 HT with the hot water storage tank SBB 1000 Wärmepumpe SOL. The heating capacity is specified as 12.38 kW at A -7/W35 and 7.45 kW at A2/W35 partial load. I am not an expert and find these figures difficult to interpret; so far, I have found little clarifying information online.
The electricity consumption for the entire building in 2016 was extremely high at 30,360 kWh (equal to 7,650 euros). Could it be that the system was significantly undersized and therefore has to run constantly? According to the seller, the construction company had to install a slope stabilization afterwards at a six-figure cost. I wouldn’t be surprised if savings were made elsewhere...
On the Stiebel Eltron website, when selecting options for new builds over 240 sqm (about 2,583 sqft), the above-mentioned pump is not recommended. This might be an initial indication of a non-ideal configuration.
In my opinion, the rental costs for various heat meters are also disproportionately high. Is it possible to replace them with individual meters, and what would the cost be? An air-to-water heat pump is supposed to be very low-maintenance. Are maintenance costs of 672 euros reasonable?
Thank you in advance for your expert feedback.
The building has a total enclosed volume of 3,114 cubic meters (cbm), with a total living area of just under 640 square meters (sqm). Installed is an air-to-water heat pump Stiebel Eltron WPL 33 HT with the hot water storage tank SBB 1000 Wärmepumpe SOL. The heating capacity is specified as 12.38 kW at A -7/W35 and 7.45 kW at A2/W35 partial load. I am not an expert and find these figures difficult to interpret; so far, I have found little clarifying information online.
The electricity consumption for the entire building in 2016 was extremely high at 30,360 kWh (equal to 7,650 euros). Could it be that the system was significantly undersized and therefore has to run constantly? According to the seller, the construction company had to install a slope stabilization afterwards at a six-figure cost. I wouldn’t be surprised if savings were made elsewhere...
On the Stiebel Eltron website, when selecting options for new builds over 240 sqm (about 2,583 sqft), the above-mentioned pump is not recommended. This might be an initial indication of a non-ideal configuration.
In my opinion, the rental costs for various heat meters are also disproportionately high. Is it possible to replace them with individual meters, and what would the cost be? An air-to-water heat pump is supposed to be very low-maintenance. Are maintenance costs of 672 euros reasonable?
Thank you in advance for your expert feedback.
I can only compare this with an air-to-water heat pump offer we received from Alpha Innotec for our single-family home with about 200 sq meters (2,150 sq ft) of heated living space. Even though this doesn’t replace a proper heat load calculation, ait roughly estimated using 45 W/sq m, which corresponds to 9,000 W or 9 kW. Considering this rough calculation, I would find 12 kW surprisingly low for more than triple the floor area. Others roughly calculate using 35 W/sq m or sometimes 50 W/sq m. Even then, 12 kW seems quite low. Couldn’t you ask for the heat load calculation? It should be clearly documented in writing.
Man, man, man... It could simply be that the heat pump is running inefficiently due to excessively high supply temperatures.
This is often caused by incorrect heating behavior.
And this rough estimate can be completely dismissed and simply forgotten. For a heat pump, having a heat load calculation is absolutely essential—room by room. If this is not done, there may be too little underfloor heating installed in a room, and at efficiently low supply temperatures, the room will not warm up adequately.
This is often caused by incorrect heating behavior.
And this rough estimate can be completely dismissed and simply forgotten. For a heat pump, having a heat load calculation is absolutely essential—room by room. If this is not done, there may be too little underfloor heating installed in a room, and at efficiently low supply temperatures, the room will not warm up adequately.
Joedreck schrieb:
Man man man.. Why so annoyed?
No one claimed that a heat load calculation is pointless or unnecessary. On the contrary, the only reliable information will be obtained from it.
Until it is available, only estimates can be made. What is wrong with that?
Since a manufacturer of air-to-water heat pumps also provides rough estimates for initial orientation until the heat load calculation is ready, their approach was explained here to give the original poster a first, although very rough, indication.
For an accurate verification of the system sizing, the heat load calculation is absolutely necessary. No claim to the contrary was made.
Joedreck, are you a professional in the field and therefore understandably irritated by rough estimates because, in your professional experience, they often cause various problems? If so, that would be important information for me as well, since I am not an expert but could then confront the air-to-water heat pump manufacturer with this...
Hi,
no, I’m not a professional. However, I’ve been interested in this as a hobby for over 7 years and, as an amateur, I’m fairly knowledgeable on the subject.
And I’m not annoyed by the people here, but rather by the heating technicians who don’t want to do the calculations and therefore mess things up a lot, as well as by landlords/builders, etc., who never care what happens because they don’t bear the costs.
In multi-family buildings, everything is often set to “as long as it gets warm.” With gas and oil systems, that still works reasonably well, but heat pumps are true low-temperature systems. Every degree higher in the supply temperature reduces efficiency, which directly costs money.
no, I’m not a professional. However, I’ve been interested in this as a hobby for over 7 years and, as an amateur, I’m fairly knowledgeable on the subject.
And I’m not annoyed by the people here, but rather by the heating technicians who don’t want to do the calculations and therefore mess things up a lot, as well as by landlords/builders, etc., who never care what happens because they don’t bear the costs.
In multi-family buildings, everything is often set to “as long as it gets warm.” With gas and oil systems, that still works reasonably well, but heat pumps are true low-temperature systems. Every degree higher in the supply temperature reduces efficiency, which directly costs money.
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