DIRAHRAV
2025-01-01 20:31:21
- #1
The plan was to heat the house with 2 granny flats, 450 m² living space, and KW 75 as flexibly and energy-efficiently as possible. The offer of the Brötje combo via the installer seemed to fit. The gas heating was supposed to handle the domestic hot water since, when enough sunlight is available, the 11 kW photovoltaic system has enough surplus. In dark, cold periods, the heat pump doesn’t bring much. Moreover, I did not want to produce domestic hot water for 50 minutes at 0 degrees outside when 3 bathtubs were required. (no electric reheating, instantaneous water heaters were not planned)
Furthermore: 55° flow temperature at 16 kW, i.e. full power, and 3° outside temperature pull the COP well below 2. Gas is considerably cheaper in this scenario and can also save CO2. More on that later. The gas heating is to run at temperatures below 2 degrees, maybe also lower if the COP is clearly determined. In this way, an electric heating element is not necessary.
Brötje designed the hydraulics and all parameters. However, during installation it quickly became clear that the planning was not thorough. The hydraulic scheme with redundant 3-way valves, unnecessary mixing units, and electrically incoherent specifications made the project a problematic case.
1. The gas boiler could not produce domestic hot water. When the gas boiler switched on, the heat pump’s DHW pump also ran. Because it was stronger, water flowed backward from the gas boiler, which went into fault. The solution was to disconnect the expensive and unnecessary DHW pump of the heat pump electrically.
2. Now: The heat pump ran until the set value. The gas boiler started. Since the outdoor thermostat was missing and the regulation is usually done by the heat pump, the gas boiler ran constantly with a flow temperature of 60 degrees. It only provided a maximum of 11 kW. To produce more, the flow temperature had to be manually increased to 70°+. Reason: The pump does not modulate and remains at about 0.4 m³. Not very efficient. This was then changed. Now the temperature adapts somewhat. Depending on the outside temperature, it modulates between 50 and 55° with controlled water flow. However, it cycles frequently. It pumps 15 kW into the storage although only 9 kW is drawn. With my 300-liter storage, it stops after about 15 minutes. Instead of 55°, it should run at 40–45° if properly adjusted, which would raise the efficiency to over 4–5.
3. Since the gas heating now at least works for transition, the heat pump produces domestic hot water, which I did not want.
Now it was found that there is a second hydraulic calculation without three-way valves in the domestic hot water circuit. This is still to be changed. The Brötje specialist then had concerns. He said the DHW pump of the heat pump is needed to supply enough DHW to the heat pump during the defrost phase. So, both pumps with heat pump and DHW push water into the heat pump for defrosting. This could fill a C hose. He did not know that the heat pump has a hot gas defrost with energy supply via the scroll compressor.
4. I had to notice that the heat pump did not modulate. If it runs at all, it always does so at 16 kW. After a phone call with a colleague, the Brötje specialist made an adjustment. And behold, the heat pump modulates sometimes. But only when it gets really cold. At, for example, 8 degrees, it still blows with 16 kW and fills the storage in 5 minutes at 4–5 kW consumption. With 400 liters and 4° delta T, only about 1.9 kW are needed. With over 10 kW, it takes almost 10 minutes. So the heat pump cycles on average over 60 times a day. Furthermore, it modulates only up to max 50%, i.e. 8 kW. (A good scroll compressor ideally runs between 40–60%)
I did not want to contradict the Brötje specialist’s argument that the scroll compressor must run at full load for a time at the start (10 minutes!) to get warm, in order not to completely drive him away.
5. I still hope for improvements. I tried to calculate the COP given in the heat pump. I have a heat meter and a second calibrated power meter.
The external power meter shows a 20% higher power consumption than the heat pump indicates. The heat pump is individually fused. Nothing else connected, no circulation pumps on it, because of the heat pump tariff. No electric auxiliary heater.
The heat meter shows 5% less.
Calculating this based on the specified COP, I currently run the heat pump only down to 5°, COP 3.9 to 3.2.
The average COP without condensing heat and reheating is thus currently well below 3, rather around 2.5. Such a performance is not eligible for subsidies under BAFA.
In conclusion:
It may be that the heat pump operates differently in SOLO mode. But it is clear that operation, algorithm, and experience from refrigeration technology are missing. Heating engineers and refrigeration compressors seem not to like each other.
The hybrid concept is currently economically unrivaled for buildings before EN 2007 for air-water heat pumps. The heat pump can be designed small and without heating rod down to 2 degrees. Gas or oil in condensing technology, if available, is efficient. Usage can be adapted depending on gas and electricity prices. The storage tank does not need to be large in case of a shutdown in heat current tariff. Legionella protection in winter with fossil energy is considerably cheaper than with the heat pump.
Suppliers are relieved from the enormous power peaks because the provision does not have to be tripled due to the simultaneity factor.
At high power loads in winter, a lot of gas power plants, which are very inefficiently written off, have to push electricity. They do not run in cogeneration. Thus they do not achieve 40% efficiency. In total, including transmission and transformer losses, gas heating is significantly more CO2-saving.
I now also see a change of mind at Brötje, new gas boilers to design hybrid solutions.
Problem: The danger that such a system first will not run properly. See my Brötje NEO 18 B, 16 kW. An upgrade NEO 16 C 16 kW might perhaps work.
The heating installers, and I see this in comparisons, are inflexible and stubborn in their explanations. They lack practical basic experience from refrigeration technology.
Heat pumps are the right way. If drilling deep enough is possible, and expense for trench collectors and other island solutions is feasible, it also works for poorly insulated buildings. Collector lines at 400 m depth with 15° into the apartments would also be a solution. This would also allow efficient operation with temperatures up to 50°.
Now I have the Brötje NEO 18 B, 16 kW on my hands. Also the feeling that Brötje tinkers more than they professionally plan. The device is basically not bad. Although way too expensive for what is inside. Never mind, it is no better at the competition. The heat pump delivers domestic hot water through insulated pipes into the house. Inside, however, lines have only 25% insulation. Not everything IP56. Unfortunate. Extremely high installation effort. The heating room is almost 120 cm deep. Condensation shaft with gravel 100 x 100 cm, 100 cm deep.
Everything must fit here. The fan is very quiet. Excellent. The flow in the heat exchanger also fits. But little effort went into insulating the scroll compressor. With some professional insulation, I got almost 6 dB out. Now you hardly hear anything during normal operation. The scroll compressor itself makes a good standard impression. Would not bet on knowing it. Probably purchased externally.
In China, the outdoor unit in an identically built model costs max. 5 to 10% of the retail price. I therefore at least expect programming at least at standard level. Even if this sounds unqualified: I believe it can be done much better.
I could point out a number of other problems with my project, but Brötje is not alone involved in those.
I know a little and see that a layperson is quickly overwhelmed. A poorly functioning system will not be adjusted without a well-founded complaint. The heating installer is almost as overwhelmed. The manufacturer’s colleagues are primarily interested in making their machine look good. Many systems that go out of control could be brought on track with simple adjustments by specialists. Essentially, it does not matter which manufacturer the parts are from; they are mostly the same. Optimal on-site adjustment is just as important as the correct performance profile the heating installer must specify. But he is usually overwhelmed with that. Low flow temperatures, changed control behavior, and assessment of building losses are too often poorly estimated. You don’t have to calculate everything. Enough experience usually suffices.
In that sense: let’s see.
Furthermore: 55° flow temperature at 16 kW, i.e. full power, and 3° outside temperature pull the COP well below 2. Gas is considerably cheaper in this scenario and can also save CO2. More on that later. The gas heating is to run at temperatures below 2 degrees, maybe also lower if the COP is clearly determined. In this way, an electric heating element is not necessary.
Brötje designed the hydraulics and all parameters. However, during installation it quickly became clear that the planning was not thorough. The hydraulic scheme with redundant 3-way valves, unnecessary mixing units, and electrically incoherent specifications made the project a problematic case.
1. The gas boiler could not produce domestic hot water. When the gas boiler switched on, the heat pump’s DHW pump also ran. Because it was stronger, water flowed backward from the gas boiler, which went into fault. The solution was to disconnect the expensive and unnecessary DHW pump of the heat pump electrically.
2. Now: The heat pump ran until the set value. The gas boiler started. Since the outdoor thermostat was missing and the regulation is usually done by the heat pump, the gas boiler ran constantly with a flow temperature of 60 degrees. It only provided a maximum of 11 kW. To produce more, the flow temperature had to be manually increased to 70°+. Reason: The pump does not modulate and remains at about 0.4 m³. Not very efficient. This was then changed. Now the temperature adapts somewhat. Depending on the outside temperature, it modulates between 50 and 55° with controlled water flow. However, it cycles frequently. It pumps 15 kW into the storage although only 9 kW is drawn. With my 300-liter storage, it stops after about 15 minutes. Instead of 55°, it should run at 40–45° if properly adjusted, which would raise the efficiency to over 4–5.
3. Since the gas heating now at least works for transition, the heat pump produces domestic hot water, which I did not want.
Now it was found that there is a second hydraulic calculation without three-way valves in the domestic hot water circuit. This is still to be changed. The Brötje specialist then had concerns. He said the DHW pump of the heat pump is needed to supply enough DHW to the heat pump during the defrost phase. So, both pumps with heat pump and DHW push water into the heat pump for defrosting. This could fill a C hose. He did not know that the heat pump has a hot gas defrost with energy supply via the scroll compressor.
4. I had to notice that the heat pump did not modulate. If it runs at all, it always does so at 16 kW. After a phone call with a colleague, the Brötje specialist made an adjustment. And behold, the heat pump modulates sometimes. But only when it gets really cold. At, for example, 8 degrees, it still blows with 16 kW and fills the storage in 5 minutes at 4–5 kW consumption. With 400 liters and 4° delta T, only about 1.9 kW are needed. With over 10 kW, it takes almost 10 minutes. So the heat pump cycles on average over 60 times a day. Furthermore, it modulates only up to max 50%, i.e. 8 kW. (A good scroll compressor ideally runs between 40–60%)
I did not want to contradict the Brötje specialist’s argument that the scroll compressor must run at full load for a time at the start (10 minutes!) to get warm, in order not to completely drive him away.
5. I still hope for improvements. I tried to calculate the COP given in the heat pump. I have a heat meter and a second calibrated power meter.
The external power meter shows a 20% higher power consumption than the heat pump indicates. The heat pump is individually fused. Nothing else connected, no circulation pumps on it, because of the heat pump tariff. No electric auxiliary heater.
The heat meter shows 5% less.
Calculating this based on the specified COP, I currently run the heat pump only down to 5°, COP 3.9 to 3.2.
The average COP without condensing heat and reheating is thus currently well below 3, rather around 2.5. Such a performance is not eligible for subsidies under BAFA.
In conclusion:
It may be that the heat pump operates differently in SOLO mode. But it is clear that operation, algorithm, and experience from refrigeration technology are missing. Heating engineers and refrigeration compressors seem not to like each other.
The hybrid concept is currently economically unrivaled for buildings before EN 2007 for air-water heat pumps. The heat pump can be designed small and without heating rod down to 2 degrees. Gas or oil in condensing technology, if available, is efficient. Usage can be adapted depending on gas and electricity prices. The storage tank does not need to be large in case of a shutdown in heat current tariff. Legionella protection in winter with fossil energy is considerably cheaper than with the heat pump.
Suppliers are relieved from the enormous power peaks because the provision does not have to be tripled due to the simultaneity factor.
At high power loads in winter, a lot of gas power plants, which are very inefficiently written off, have to push electricity. They do not run in cogeneration. Thus they do not achieve 40% efficiency. In total, including transmission and transformer losses, gas heating is significantly more CO2-saving.
I now also see a change of mind at Brötje, new gas boilers to design hybrid solutions.
Problem: The danger that such a system first will not run properly. See my Brötje NEO 18 B, 16 kW. An upgrade NEO 16 C 16 kW might perhaps work.
The heating installers, and I see this in comparisons, are inflexible and stubborn in their explanations. They lack practical basic experience from refrigeration technology.
Heat pumps are the right way. If drilling deep enough is possible, and expense for trench collectors and other island solutions is feasible, it also works for poorly insulated buildings. Collector lines at 400 m depth with 15° into the apartments would also be a solution. This would also allow efficient operation with temperatures up to 50°.
Now I have the Brötje NEO 18 B, 16 kW on my hands. Also the feeling that Brötje tinkers more than they professionally plan. The device is basically not bad. Although way too expensive for what is inside. Never mind, it is no better at the competition. The heat pump delivers domestic hot water through insulated pipes into the house. Inside, however, lines have only 25% insulation. Not everything IP56. Unfortunate. Extremely high installation effort. The heating room is almost 120 cm deep. Condensation shaft with gravel 100 x 100 cm, 100 cm deep.
Everything must fit here. The fan is very quiet. Excellent. The flow in the heat exchanger also fits. But little effort went into insulating the scroll compressor. With some professional insulation, I got almost 6 dB out. Now you hardly hear anything during normal operation. The scroll compressor itself makes a good standard impression. Would not bet on knowing it. Probably purchased externally.
In China, the outdoor unit in an identically built model costs max. 5 to 10% of the retail price. I therefore at least expect programming at least at standard level. Even if this sounds unqualified: I believe it can be done much better.
I could point out a number of other problems with my project, but Brötje is not alone involved in those.
I know a little and see that a layperson is quickly overwhelmed. A poorly functioning system will not be adjusted without a well-founded complaint. The heating installer is almost as overwhelmed. The manufacturer’s colleagues are primarily interested in making their machine look good. Many systems that go out of control could be brought on track with simple adjustments by specialists. Essentially, it does not matter which manufacturer the parts are from; they are mostly the same. Optimal on-site adjustment is just as important as the correct performance profile the heating installer must specify. But he is usually overwhelmed with that. Low flow temperatures, changed control behavior, and assessment of building losses are too often poorly estimated. You don’t have to calculate everything. Enough experience usually suffices.
In that sense: let’s see.