ᐅ Alternative to the Weishaupt WWP LS 8 (Rotex, Kermi, etc.)?
Created on: 19 Apr 2019 13:55
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Christian K.
Hello everyone,
I am currently looking for a suitable air-to-water heat pump for our single-family house. Here are some key details:
- 200 sqm (2,150 sq ft)
- Underfloor heating
- Bonded parquet flooring
- Heating load: 7.6 kW
- Household of 4 people
- Current planned supply temperature: 35°C (95°F), target 30°C (86°F)
The heating installer is currently recommending the Weishaupt WWP LS 8 (split unit). Weishaupt also offers the monoblock WWP LA 9, but it does not have inverter technology, and the new WWP LB (bi-block). However, the bi-block requires too much space in the utility room, so it is not an option.
The LS 8 is not particularly quiet and only has 200 liters (53 gallons) of hot water storage and a 100-liter (26 gallons) buffer tank. So it is somewhat less than ideal. Therefore, I am looking for an alternative. The installer suggested a Kermi as an option, although those units are more expensive. In my opinion, a more affordable alternative might be the Rotex Compact "Ultra". It has no buffer tank but can use the domestic hot water cylinder as a buffer if necessary.
If I understand correctly, the Kermi and Rotex units are similar, with Kermi being the higher quality option. The question now is whether the Rotex is sufficient or if it would be better to go with Kermi. Or should I stick with Weishaupt or consider a completely different brand?
What are your experiences or opinions?
I am currently looking for a suitable air-to-water heat pump for our single-family house. Here are some key details:
- 200 sqm (2,150 sq ft)
- Underfloor heating
- Bonded parquet flooring
- Heating load: 7.6 kW
- Household of 4 people
- Current planned supply temperature: 35°C (95°F), target 30°C (86°F)
The heating installer is currently recommending the Weishaupt WWP LS 8 (split unit). Weishaupt also offers the monoblock WWP LA 9, but it does not have inverter technology, and the new WWP LB (bi-block). However, the bi-block requires too much space in the utility room, so it is not an option.
The LS 8 is not particularly quiet and only has 200 liters (53 gallons) of hot water storage and a 100-liter (26 gallons) buffer tank. So it is somewhat less than ideal. Therefore, I am looking for an alternative. The installer suggested a Kermi as an option, although those units are more expensive. In my opinion, a more affordable alternative might be the Rotex Compact "Ultra". It has no buffer tank but can use the domestic hot water cylinder as a buffer if necessary.
If I understand correctly, the Kermi and Rotex units are similar, with Kermi being the higher quality option. The question now is whether the Rotex is sufficient or if it would be better to go with Kermi. Or should I stick with Weishaupt or consider a completely different brand?
What are your experiences or opinions?
B
boxandroof20 Apr 2019 11:30It sounds like you’re already in a pretty good position.
Try sharing your house along with the heating load calculations in the pink htd forum, where you’ll get more expert advice.
Without plans, it’s hard to assess accurately, but the heating load seems quite high, especially since a ventilation system is planned. Heating loads often include excessive safety margins (search for crinks tool). Depending on the architecture, a BKA (building-related heating load calculation) might make sense to further reduce the supply temperature.
Personally, I would try to avoid buying an expensive air-to-water heat pump from the heating installer (they don’t last forever—you’ll likely need to replace it like any boiler) and instead review the house concept to reduce the heating load or consider planning with a horizontal ground heat exchanger (trench collector), especially if you live in a colder region; in that case, using air as a heat source might not be ideal.
Try sharing your house along with the heating load calculations in the pink htd forum, where you’ll get more expert advice.
Without plans, it’s hard to assess accurately, but the heating load seems quite high, especially since a ventilation system is planned. Heating loads often include excessive safety margins (search for crinks tool). Depending on the architecture, a BKA (building-related heating load calculation) might make sense to further reduce the supply temperature.
Personally, I would try to avoid buying an expensive air-to-water heat pump from the heating installer (they don’t last forever—you’ll likely need to replace it like any boiler) and instead review the house concept to reduce the heating load or consider planning with a horizontal ground heat exchanger (trench collector), especially if you live in a colder region; in that case, using air as a heat source might not be ideal.
C
Christian K.20 Apr 2019 15:05Thank you, it’s not that easy to get a clear overview here.
The heating technician also estimated a maximum of 6kW, but according to the energy saving regulations and the heating load calculation, I come to 7.6kW. I think somewhere between 6 and 8kW should be sufficient. As long as the air-to-water heat pump is modulating, it shouldn’t be a big issue to go with 8kW. Of course, I need to make sure that at low temperatures the required heating load is not too low and doesn’t fall below the modulation limit.
We considered a boiler room system (BKA) but discarded the idea. I am also thinking about buying the air-to-water heat pump myself and possibly having it installed by a friend who is a heating technician. I find the prices somewhat unreasonable.
The heating technician also estimated a maximum of 6kW, but according to the energy saving regulations and the heating load calculation, I come to 7.6kW. I think somewhere between 6 and 8kW should be sufficient. As long as the air-to-water heat pump is modulating, it shouldn’t be a big issue to go with 8kW. Of course, I need to make sure that at low temperatures the required heating load is not too low and doesn’t fall below the modulation limit.
We considered a boiler room system (BKA) but discarded the idea. I am also thinking about buying the air-to-water heat pump myself and possibly having it installed by a friend who is a heating technician. I find the prices somewhat unreasonable.
B
boxandroof20 Apr 2019 15:34If the heat pump modulates well, I don’t see oversizing as a critical issue.
In our energy saving regulations, it was around 7.x kW. The heating technician said 6 kW. According to the DIN standard, the room-specific heating load is 4 kW, but in reality, including domestic hot water, it’s 3 kW. Try roughly calculating this yourself based on the U-values and building envelope surface area — it’s not that difficult and helps with understanding.
For DIY installation, the 5 kW Panasonic is suitable, also because there are many tips and plans available online. If a trench collector is not an option and you want to stick with an air-to-water heat pump, I would really try to fit the Panasonic. For emergencies, there is also a 3 kW heating element included. It’s a lot of money you can save long term if you plan well and don’t just leave everything to the heating contractor.
In our energy saving regulations, it was around 7.x kW. The heating technician said 6 kW. According to the DIN standard, the room-specific heating load is 4 kW, but in reality, including domestic hot water, it’s 3 kW. Try roughly calculating this yourself based on the U-values and building envelope surface area — it’s not that difficult and helps with understanding.
For DIY installation, the 5 kW Panasonic is suitable, also because there are many tips and plans available online. If a trench collector is not an option and you want to stick with an air-to-water heat pump, I would really try to fit the Panasonic. For emergencies, there is also a 3 kW heating element included. It’s a lot of money you can save long term if you plan well and don’t just leave everything to the heating contractor.
B
boxandroof20 Apr 2019 16:16I just noticed you were the one with the cool floor plan. The heating load might be slightly higher due to the roofs and windows, but it doesn’t have to be. It’s best to calculate it yourself. Make sure to plan the windows with warm edge spacers. A ground loop collector is not an option?
C
Christian K.22 Apr 2019 21:07Thanks for the tips!
How did you calculate the heating load for each room?
I wouldn’t install it myself but rather get help from a professional and assist them. It shouldn’t be a big problem if, for example, the Panasonic system can be set up by one person. I once considered a slinky trench collector, but the plot is quite small, and even if we have to add fill (70cm (27.5 inches)), the fill needs to be added first and then the trenches dug again. Our plot is 16 by 28 meters (52 by 92 feet), so it’s not very large.
Thanks regarding the floor plan. It turned out to have a few challenges. The utility room is a bit small for the air-to-water heat pump, photovoltaic system plus battery storage, and KNX system. The children’s bathroom upstairs is a bit too small because the walls here are load-bearing and the architect didn’t take that into account. This made the shower area a bit tight, but we reduced the window size and now it fits again.
How did you calculate the heating load for each room?
I wouldn’t install it myself but rather get help from a professional and assist them. It shouldn’t be a big problem if, for example, the Panasonic system can be set up by one person. I once considered a slinky trench collector, but the plot is quite small, and even if we have to add fill (70cm (27.5 inches)), the fill needs to be added first and then the trenches dug again. Our plot is 16 by 28 meters (52 by 92 feet), so it’s not very large.
Thanks regarding the floor plan. It turned out to have a few challenges. The utility room is a bit small for the air-to-water heat pump, photovoltaic system plus battery storage, and KNX system. The children’s bathroom upstairs is a bit too small because the walls here are load-bearing and the architect didn’t take that into account. This made the shower area a bit tight, but we reduced the window size and now it fits again.
B
boxandroof22 Apr 2019 21:31The tool is suitable for a rough estimate and for sizing the heat pump. You can safely omit the domestic hot water allowances; it certainly won’t get too cold.
I had the heating load calculated for each room, which a heating engineer can do, and there are also online services available that are inexpensive. Based on that, the underfloor heating system is planned, which you should ideally check yourself.
It’s great if you have someone knowledgeable to assist you with the heat pump.
I had the heating load calculated for each room, which a heating engineer can do, and there are also online services available that are inexpensive. Based on that, the underfloor heating system is planned, which you should ideally check yourself.
It’s great if you have someone knowledgeable to assist you with the heat pump.
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