ᐅ Company Lüumel, trench collector (horizontal ground heat exchanger)
Created on: 3 Dec 2015 06:58
D
daytonaHello everyone,
does anyone have general experience, both positive and negative, with the company Lüumel from Coswig?
I currently have an offer for a heat pump with a horizontal ground loop. I have already read quite a bit about this online. I would be interested in hearing about your experiences here as well. Unfortunately, my offer is not very detailed, so I will get in touch with the company. But maybe some of you here in the forum can help in advance:
How does the seasonal performance factor (SPF) or energy consumption compare to other heat pump systems?
Have you had a simulation or calculation of the SPF done?
What is the impact or buildability of the buried pipes in the garden, for example regarding load-bearing or drive-over capacity?
Is a heat meter absolutely necessary?
What are the pros and cons of a horizontal ground loop? (I know this is a very general question)
does anyone have general experience, both positive and negative, with the company Lüumel from Coswig?
I currently have an offer for a heat pump with a horizontal ground loop. I have already read quite a bit about this online. I would be interested in hearing about your experiences here as well. Unfortunately, my offer is not very detailed, so I will get in touch with the company. But maybe some of you here in the forum can help in advance:
How does the seasonal performance factor (SPF) or energy consumption compare to other heat pump systems?
Have you had a simulation or calculation of the SPF done?
What is the impact or buildability of the buried pipes in the garden, for example regarding load-bearing or drive-over capacity?
Is a heat meter absolutely necessary?
What are the pros and cons of a horizontal ground loop? (I know this is a very general question)
Good morning,
I can’t say much about the trench collector, only about the company Lüumel, as we ourselves have a heat pump with a ground collector from them. If I had known about the trench collector back then, I probably would have chosen it over the ground collector, since with the ground collector a lot of space is lost where you are not allowed to build or plant trees/shrubs.
I’ll start with the question about the heat meter.
We don’t have a heat meter or a separate electricity meter. In hindsight, I regret this a bit because I can’t monitor the share of electricity used for heating or the system’s efficiency.
I have been reading the electricity meter almost daily since October 28, 2014. Until October 28, 2015, we used a total of 6300 kWh for both household electricity and heating. In summer (heating only for hot water), the daily consumption was about 7 kWh. In winter, the usage is certainly higher, so I estimate around 3000 kWh for household electricity and about 3300 kWh for heating for a living area of 125 m² (1345 sq ft) (this is only an estimate since we don’t have sub-meters). However, this number needs some context:
1.) In the first year, we heated more than necessary to remove moisture.
2.) It was found that too little refrigerant was filled, so only the first part of the ground collectors was used. This then caused icing and ground heaving in the area of the ground collectors during winter.
For the last 35 days, I have a comparison with the previous year for the first time. During these days, we used 25% less electricity and therefore an estimated 50% less electricity for heating. Currently, the weather is quite warm for this time of year. Last year was also mild in these 35 days, but still somewhat cooler than this year.
I can’t say exactly what caused the reduced consumption (milder weather, optimized heating settings, more refrigerant). Probably a combination of all three.
As I mentioned above, our lawn heaved significantly in winter (about 25-30 cm [10-12 inches]) and sank back again in summer. Behind the garage, at the edge of the collectors, we have a passageway for trash bins, etc. This path was completely broken apart by the heaving and sinking. We are negotiating with Lüumel about this. They claim that we were not allowed to build over this area and that at least 1 m (3 ft) clearance should have been maintained (although their brochure does not clearly state this, because according to the brochure you are allowed to build over permeable surfaces). I then wonder why the permeable lawn heaved by 30 cm and what would have happened with a permeable path?
However, in my opinion, they should have also filled the refrigerant correctly. Since they supposedly cannot do this properly during non-heating periods, they need to come back in winter. Since I think both sides share some blame, we are trying to reach a compromise. We will repair the passage ourselves and, in exchange, receive 2-3 free maintenance visits or something similar. We’ll see how that turns out.
In our neighborhood, there is a second system from Lüumel where the collectors are covered by a path, and there were no problems there.
About the heating system itself:
- relatively straightforward
- direct expansion (DX) system
- maintenance required due to the amount of refrigerant (maintenance cost about 170 €)
- stratified storage tank
The stratified storage tank definitely has advantages but also a major drawback. On cold winter days, the hot water becomes very hot (>70°C [158°F]). You have to be very careful to avoid burns.
I hope this is helpful. I am happy to answer any further questions.
I can’t say much about the trench collector, only about the company Lüumel, as we ourselves have a heat pump with a ground collector from them. If I had known about the trench collector back then, I probably would have chosen it over the ground collector, since with the ground collector a lot of space is lost where you are not allowed to build or plant trees/shrubs.
I’ll start with the question about the heat meter.
We don’t have a heat meter or a separate electricity meter. In hindsight, I regret this a bit because I can’t monitor the share of electricity used for heating or the system’s efficiency.
I have been reading the electricity meter almost daily since October 28, 2014. Until October 28, 2015, we used a total of 6300 kWh for both household electricity and heating. In summer (heating only for hot water), the daily consumption was about 7 kWh. In winter, the usage is certainly higher, so I estimate around 3000 kWh for household electricity and about 3300 kWh for heating for a living area of 125 m² (1345 sq ft) (this is only an estimate since we don’t have sub-meters). However, this number needs some context:
1.) In the first year, we heated more than necessary to remove moisture.
2.) It was found that too little refrigerant was filled, so only the first part of the ground collectors was used. This then caused icing and ground heaving in the area of the ground collectors during winter.
For the last 35 days, I have a comparison with the previous year for the first time. During these days, we used 25% less electricity and therefore an estimated 50% less electricity for heating. Currently, the weather is quite warm for this time of year. Last year was also mild in these 35 days, but still somewhat cooler than this year.
I can’t say exactly what caused the reduced consumption (milder weather, optimized heating settings, more refrigerant). Probably a combination of all three.
As I mentioned above, our lawn heaved significantly in winter (about 25-30 cm [10-12 inches]) and sank back again in summer. Behind the garage, at the edge of the collectors, we have a passageway for trash bins, etc. This path was completely broken apart by the heaving and sinking. We are negotiating with Lüumel about this. They claim that we were not allowed to build over this area and that at least 1 m (3 ft) clearance should have been maintained (although their brochure does not clearly state this, because according to the brochure you are allowed to build over permeable surfaces). I then wonder why the permeable lawn heaved by 30 cm and what would have happened with a permeable path?
However, in my opinion, they should have also filled the refrigerant correctly. Since they supposedly cannot do this properly during non-heating periods, they need to come back in winter. Since I think both sides share some blame, we are trying to reach a compromise. We will repair the passage ourselves and, in exchange, receive 2-3 free maintenance visits or something similar. We’ll see how that turns out.
In our neighborhood, there is a second system from Lüumel where the collectors are covered by a path, and there were no problems there.
About the heating system itself:
- relatively straightforward
- direct expansion (DX) system
- maintenance required due to the amount of refrigerant (maintenance cost about 170 €)
- stratified storage tank
The stratified storage tank definitely has advantages but also a major drawback. On cold winter days, the hot water becomes very hot (>70°C [158°F]). You have to be very careful to avoid burns.
I hope this is helpful. I am happy to answer any further questions.
Hello,
thank you very much. That already answers some questions. However, a few new ones have come up:
If I understand correctly, you don’t have a separate electric meter for the heat pump? I’ve heard somewhere that heating electricity can be discounted by the supplier and supplied and billed through a second meter. That would, of course, also make it easier to determine consumption separately from the household electricity.
The offered heat quantity meter costs around 900€ (about $970). From my point of view, this is quite an expensive luxury just to track your own statistics. Based on the current situation, I would rather tend to cancel it for cost reasons.
You mentioned the topic of layered storage: don’t you have to maintain >70°C (158°F) anyway for legionella prevention, and aren’t all water-carrying parts insulated, as far as I know?
thank you very much. That already answers some questions. However, a few new ones have come up:
If I understand correctly, you don’t have a separate electric meter for the heat pump? I’ve heard somewhere that heating electricity can be discounted by the supplier and supplied and billed through a second meter. That would, of course, also make it easier to determine consumption separately from the household electricity.
The offered heat quantity meter costs around 900€ (about $970). From my point of view, this is quite an expensive luxury just to track your own statistics. Based on the current situation, I would rather tend to cancel it for cost reasons.
You mentioned the topic of layered storage: don’t you have to maintain >70°C (158°F) anyway for legionella prevention, and aren’t all water-carrying parts insulated, as far as I know?
For the separate meter, check out the following pages starting here:
https://www.hausbau-forum.de/threads/solar-pv-wirtschaftlicher-Gesichtspunkt.13659/page-6
We decided against it, but in hindsight, we should have had the electricity submeter installed.
€900 for a heat meter is quite a sum, I would have hesitated as well. If you make changes to the heating settings, you never have the same conditions to accurately compare whether your adjustments had a positive or negative effect. You can only get a somewhat reliable comparison with an electricity meter and a heat meter. Whether you recoup that €900 is of course questionable.
You don’t have the legionella problem with a layered storage tank, since the domestic hot water is not heated in the water storage but only during the flow through the heating water. As far as I know, 60°C (140°F) is sufficient to prevent legionella. The temperatures over 70°C (158°F), sometimes up to 80°C (176°F), in the layered storage tank (in winter) are really quite hot. Last year I tried to soften the heating curve so it wouldn’t get so hot in winter, but I only succeeded to a limited extent.
In summer, however, you need to make sure to roughly stick to the heating system’s set times for domestic hot water heating. Otherwise, you keep heating the entire heating water in the storage tank to temperatures you don’t actually need.
https://www.hausbau-forum.de/threads/solar-pv-wirtschaftlicher-Gesichtspunkt.13659/page-6
We decided against it, but in hindsight, we should have had the electricity submeter installed.
€900 for a heat meter is quite a sum, I would have hesitated as well. If you make changes to the heating settings, you never have the same conditions to accurately compare whether your adjustments had a positive or negative effect. You can only get a somewhat reliable comparison with an electricity meter and a heat meter. Whether you recoup that €900 is of course questionable.
You don’t have the legionella problem with a layered storage tank, since the domestic hot water is not heated in the water storage but only during the flow through the heating water. As far as I know, 60°C (140°F) is sufficient to prevent legionella. The temperatures over 70°C (158°F), sometimes up to 80°C (176°F), in the layered storage tank (in winter) are really quite hot. Last year I tried to soften the heating curve so it wouldn’t get so hot in winter, but I only succeeded to a limited extent.
In summer, however, you need to make sure to roughly stick to the heating system’s set times for domestic hot water heating. Otherwise, you keep heating the entire heating water in the storage tank to temperatures you don’t actually need.
S
Sebastian793 Dec 2015 13:06Quick question: Why don't you install a submeter for the heat pump in the distribution board? The device probably costs around 50-100 euros, and then you can monitor exactly how much power it consumes.
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