ᐅ Air-to-air heat pump vs. air-to-water heat pump vs. trench ground collector – Differences
Created on: 12 Dec 2019 10:33
N
Neubau2020
Hello,
I am currently trying to decide how the heating energy should be generated.
Here in the forum, I came across the horizontal ground loop collector, which I find very interesting. In conversations with two prefabricated house suppliers, I mentioned that I am considering generating energy with a horizontal ground loop collector. Both times, the response was, "We’ve heard of horizontal ground loop collectors, but never installed one."
One offer included an air-to-water heat pump (Luxhaus KfW55), and the other included an air-to-air heat pump with controlled residential ventilation (Streif Haus KfW40). The house will have two levels, no basement, around 190 m² (2,045 sq ft), on a fairly flat plot with no special features.
I am wondering how the horizontal ground loop collector differs technically and in price from the air-to-water heat pump.
Is the technology inside the house the same, or are there other factors to consider, such as system size and design?
Is the main difference simply that instead of the external unit of the air heat pump, I install the trench and lay the pipes?
What is the price difference?
What about the long-term difference in energy consumption? The air heat pump needs to run continuously on electricity to draw in air—how does it work with geothermal energy from the horizontal ground loop in this regard?
Lastly, a question regarding the air-to-air heat pump:
The sales representative from Streif Haus said that if I wanted to switch from the air-to-air heat pump to an air-to-water heat pump, it would cost about 10,000 euros more. Is that a realistic estimate?
I am currently trying to decide how the heating energy should be generated.
Here in the forum, I came across the horizontal ground loop collector, which I find very interesting. In conversations with two prefabricated house suppliers, I mentioned that I am considering generating energy with a horizontal ground loop collector. Both times, the response was, "We’ve heard of horizontal ground loop collectors, but never installed one."
One offer included an air-to-water heat pump (Luxhaus KfW55), and the other included an air-to-air heat pump with controlled residential ventilation (Streif Haus KfW40). The house will have two levels, no basement, around 190 m² (2,045 sq ft), on a fairly flat plot with no special features.
I am wondering how the horizontal ground loop collector differs technically and in price from the air-to-water heat pump.
Is the technology inside the house the same, or are there other factors to consider, such as system size and design?
Is the main difference simply that instead of the external unit of the air heat pump, I install the trench and lay the pipes?
What is the price difference?
What about the long-term difference in energy consumption? The air heat pump needs to run continuously on electricity to draw in air—how does it work with geothermal energy from the horizontal ground loop in this regard?
Lastly, a question regarding the air-to-air heat pump:
The sales representative from Streif Haus said that if I wanted to switch from the air-to-air heat pump to an air-to-water heat pump, it would cost about 10,000 euros more. Is that a realistic estimate?
guckuck2 schrieb:
Well, never say never. Installing a foundation for a wall, pergola, or sunshade sail in the ground can be tricky if pipes are everywhere.The pipes are actually buried at least 1.5 meters (5 feet) deep... I can’t think of anything that would be concreted in that deep. Building above them is no problem.
A large pool might be an issue though..
S
sichtbeton8213 Dec 2019 13:15We recently installed a ground collector (four loops, each 300 m (984 feet) of DA32 pipe). Here are some brief notes and tips:
- Check the water resources regulations to see if a building permit / planning permission is required. Usually, only a notification is needed.
- Are there specific local requirements regarding distances to neighboring properties in your federal state / region?
- Is the soil suitable? (Key factor: thermal conductivity of the ground)
- The energy for these shallow loops is drawn from solar and precipitation heat. Does the soil receive enough sunlight and allow sufficient infiltration? (Areas above the loops should not be built over or sealed later)
- Other types also exist, such as trench collectors, ground heat baskets, energy columns...
- Material: Use high resistance to stress crack PE 100-RC (lifetime decreases above 25°C (77°F); if solar regeneration is planned, consider switching to PE-X)
- Pipe wall thickness is a tradeoff: thinner walls mean lower thermal resistance but larger bending radius; thicker walls offer better durability and protection.
- I recommend electrofusion coupling (E-couplings) for welding. For this, the pipe must typically meet class SDR11.
- When installing multiple loops, try to keep lengths approximately equal (maximum deviation 10%).
- Multi-service house entry systems are available that already accommodate two ground heat pipes.
- Pay attention to installation spacing and depth, e.g., distance to wastewater pipes, foundations, etc.
- Heat transfer fluid: premixed solutions down to -40°C (-40°F) are quite expensive. It’s best to mix yourself for a lower freeze point. We use -15°C (5°F) since our heat pump switches off at -5°C (23°F) anyway.
Good luck!
- Check the water resources regulations to see if a building permit / planning permission is required. Usually, only a notification is needed.
- Are there specific local requirements regarding distances to neighboring properties in your federal state / region?
- Is the soil suitable? (Key factor: thermal conductivity of the ground)
- The energy for these shallow loops is drawn from solar and precipitation heat. Does the soil receive enough sunlight and allow sufficient infiltration? (Areas above the loops should not be built over or sealed later)
- Other types also exist, such as trench collectors, ground heat baskets, energy columns...
- Material: Use high resistance to stress crack PE 100-RC (lifetime decreases above 25°C (77°F); if solar regeneration is planned, consider switching to PE-X)
- Pipe wall thickness is a tradeoff: thinner walls mean lower thermal resistance but larger bending radius; thicker walls offer better durability and protection.
- I recommend electrofusion coupling (E-couplings) for welding. For this, the pipe must typically meet class SDR11.
- When installing multiple loops, try to keep lengths approximately equal (maximum deviation 10%).
- Multi-service house entry systems are available that already accommodate two ground heat pipes.
- Pay attention to installation spacing and depth, e.g., distance to wastewater pipes, foundations, etc.
- Heat transfer fluid: premixed solutions down to -40°C (-40°F) are quite expensive. It’s best to mix yourself for a lower freeze point. We use -15°C (5°F) since our heat pump switches off at -5°C (23°F) anyway.
Good luck!
L
ludwig88sta19 Dec 2019 08:47Yesterday, besides the currently favored air-to-water heat pump or gas heating, I also came across the horizontal ground heat exchanger heat pump. I have the following questions:
Main concern: I imagine laying it myself after renting an excavator is feasible, but in the strip where the horizontal ground heat exchanger is installed, no plants will grow later due to frost. How far does this cold effect extend, i.e., how wide is the exclusion zone around the ground heat exchanger for plants, trees, bushes, etc.?
Secondary issue: Do I always have to hire a paid expert beforehand to assess whether my soil is even suitable?
Another question, since it is also included here by the original poster: When installing an air-to-water heat pump, do you also install a controlled mechanical ventilation system with heat recovery, or is the controlled mechanical ventilation only used with ground source heat pumps?
Main concern: I imagine laying it myself after renting an excavator is feasible, but in the strip where the horizontal ground heat exchanger is installed, no plants will grow later due to frost. How far does this cold effect extend, i.e., how wide is the exclusion zone around the ground heat exchanger for plants, trees, bushes, etc.?
Secondary issue: Do I always have to hire a paid expert beforehand to assess whether my soil is even suitable?
Another question, since it is also included here by the original poster: When installing an air-to-water heat pump, do you also install a controlled mechanical ventilation system with heat recovery, or is the controlled mechanical ventilation only used with ground source heat pumps?
N
nordanney19 Dec 2019 08:54ludwig88sta schrieb:
Is it common to install an air-to-water heat pump and then also a mechanical ventilation system with heat recovery, or is the mechanical ventilation system only used with ground-source heat pumps? A mechanical ventilation system with heat recovery can always be installed—even with a gas heating system or storage heaters. You need to distinguish between ventilation (which is like opening windows) and heating.
L
ludwig88sta19 Dec 2019 09:03nordanney schrieb:
A controlled ventilation system can always be installed – even with a gas heating system or night storage heaters. You need to distinguish between ventilation (which is like opening windows) and heating.Okay, thanks! I only thought about it because with an air-to-air heat pump, the ventilation also heats the rooms. But I guess that’s true.
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