ᐅ Ground source heat pump with cooling function – controllable?
Created on: 29 Oct 2013 09:17
K
kaho674
Hello,
we would like to install a geothermal heating system with a cooling function from a well-known manufacturer in our house. It can be controlled in the upper rooms (including bedrooms). On the ground floor, it is uncontrolled because the heat has to go somewhere when the heating is on. Now my question:
In the height of summer, we would of course like to cool the rooms, but primarily the rooms upstairs. Is it possible to close the heating circuit downstairs, for example with an additional valve, so that only the upper floor is cooled in summer?
PS: Please no discussions about the pros or cons of the cooling function. Thank you.
we would like to install a geothermal heating system with a cooling function from a well-known manufacturer in our house. It can be controlled in the upper rooms (including bedrooms). On the ground floor, it is uncontrolled because the heat has to go somewhere when the heating is on. Now my question:
In the height of summer, we would of course like to cool the rooms, but primarily the rooms upstairs. Is it possible to close the heating circuit downstairs, for example with an additional valve, so that only the upper floor is cooled in summer?
PS: Please no discussions about the pros or cons of the cooling function. Thank you.
M
merlin66729 Oct 2013 13:50I would put it this way: if the entire house is well insulated, it is definitely possible to maintain a comfortable temperature (cooling requires "somewhat" more capacity).
In my case, I did a calculation:
I have an average U-value of 0.17 for a surface area of 465m² (5000 sq ft approximately) and a temperature difference of, say, 10°C (24°C (75°F) – 34°C (93°F)), resulting in around 790W of thermal heating power.
BUT:
According to my energy certificate, I gain 777kWh from solar heat in August. With an average of 7.1 hours of sunshine per day that month, that corresponds to an average solar power input of 3.4kW heating the house for 7.1 hours per day. The total cooling requirement is approximately 4.1kW — quite a bit.
For example, if you operate the underfloor heating with a supply temperature of 15-16°C (59-61°F), depending on conditions, you will already have condensation on the cold floor, besides the floor feeling cold:
At 30°C (86°F) and 50% relative humidity, the dew point is about 17°C (63°F), and at 35°C (95°F) and 50%, it is around 23°C (73°F).
This means that at 35°C (95°F) and 50% relative humidity, cooling down to 24°C (75°F) results in very high humidity (~90%).
For this reason, I combine the air/water heat pump (with integrated cooling function) with a brine preheating/cooling coil in the mechanical ventilation system.
If the air is cooled from 35°C (95°F) and 50% humidity down to 17°C (63°F), and then warmed up to 23°C (73°F) with the exhaust air, I end up with about 55% relative humidity.
Theoretically, I could also run the underfloor heating at 22°C (72°F) to stay well above the dew point (17°C / 63°F) and avoid a cold floor feeling.
Just recalculated:
With these conditions, 180m³/h (about 106 cfm) airflow – 207kg/h (about 456 lbs/h) mass flow, and an enthalpy change of 32.9, I get approximately 6.8kW of cooling power from ventilation alone, which would be quite good. However, the geothermal heat exchanger must be sized accordingly to maintain this performance continuously (temperature difference, flow rate, etc.).
In my opinion, it doesn’t make much sense to invest heavily in cooling systems unless you can also reduce indoor humidity. Otherwise, you get somewhat cooler temperatures but very high humidity.
In my case, I did a calculation:
I have an average U-value of 0.17 for a surface area of 465m² (5000 sq ft approximately) and a temperature difference of, say, 10°C (24°C (75°F) – 34°C (93°F)), resulting in around 790W of thermal heating power.
BUT:
According to my energy certificate, I gain 777kWh from solar heat in August. With an average of 7.1 hours of sunshine per day that month, that corresponds to an average solar power input of 3.4kW heating the house for 7.1 hours per day. The total cooling requirement is approximately 4.1kW — quite a bit.
For example, if you operate the underfloor heating with a supply temperature of 15-16°C (59-61°F), depending on conditions, you will already have condensation on the cold floor, besides the floor feeling cold:
At 30°C (86°F) and 50% relative humidity, the dew point is about 17°C (63°F), and at 35°C (95°F) and 50%, it is around 23°C (73°F).
This means that at 35°C (95°F) and 50% relative humidity, cooling down to 24°C (75°F) results in very high humidity (~90%).
For this reason, I combine the air/water heat pump (with integrated cooling function) with a brine preheating/cooling coil in the mechanical ventilation system.
If the air is cooled from 35°C (95°F) and 50% humidity down to 17°C (63°F), and then warmed up to 23°C (73°F) with the exhaust air, I end up with about 55% relative humidity.
Theoretically, I could also run the underfloor heating at 22°C (72°F) to stay well above the dew point (17°C / 63°F) and avoid a cold floor feeling.
Just recalculated:
With these conditions, 180m³/h (about 106 cfm) airflow – 207kg/h (about 456 lbs/h) mass flow, and an enthalpy change of 32.9, I get approximately 6.8kW of cooling power from ventilation alone, which would be quite good. However, the geothermal heat exchanger must be sized accordingly to maintain this performance continuously (temperature difference, flow rate, etc.).
In my opinion, it doesn’t make much sense to invest heavily in cooling systems unless you can also reduce indoor humidity. Otherwise, you get somewhat cooler temperatures but very high humidity.
€uro schrieb:
If you express your opinion publicly here, you have to expect some pushback, even if it’s uncomfortable! ;-)
Best regards. I’ve already faced that pushback. Your onslaught just fizzles out and annoys me. That’s why I said it beforehand, so the preachers and priests can find other targets. But for the godlike € it’s all about "public image"—because he thinks he has to protect "his" flock. I rather believe it’s all arrogance and extremely annoying. So sorry, but I won’t respond to your sermon anymore.
merlin667 schrieb:
I did a calculation for my case: I have an average U-value of 0.17 for a 465m² (5,005 ft²) surface area and a temperature difference of, say, 10°C (50°F – 62°F), which results in about 790W of thermal heating power. BUT:...From this point, I couldn’t follow anymore, but I had a good laugh. That’s what I call thinking it through thoroughly. 😎 The question is, what do you want to achieve? For example, I don’t plan to keep the entire house at 20°C (68°F) when it’s 40°C (104°F) in the shade. Our goal is to maintain the bedroom at around 24°C (75°F) when it’s, for example, 28°C (82°F) at night.
M
merlin66729 Oct 2013 15:01Um, where do you live that it’s 28°C (82°F) at night?
If your goal is to have only slight cooling, I’d say this: if the system is running and the two circulation pumps (1x brine loop + 1x underfloor heating) produce less waste heat than the cooling effect you get, it’s still better than having no passive cooling at all – even if it’s still warm, 26°C (79°F) is better than 28°C (82°F). Getting down to an (allegedly) optimal bedroom temperature of 18°C (64°F) won’t work.
If you don’t mind the few dollars of electricity per year, why not – your sleep will thank you.
To get back to your question: I already mentioned at the beginning that the heating circuit distribution manifold usually has ball valves, and you can just turn those off (how this affects the others would need to be checked separately in each case).
€ is basically not wrong in his statements, but in my example you can quickly see that when you dig deeper into it, it’s no longer so simple to explain all this in a way that’s understandable for the average user (Mollier h-x diagram, “simple” thermal calculations...).
And my calculation was definitely simplified 🙂 no energies were taken into account regarding the warming of building components, etc.
If your goal is to have only slight cooling, I’d say this: if the system is running and the two circulation pumps (1x brine loop + 1x underfloor heating) produce less waste heat than the cooling effect you get, it’s still better than having no passive cooling at all – even if it’s still warm, 26°C (79°F) is better than 28°C (82°F). Getting down to an (allegedly) optimal bedroom temperature of 18°C (64°F) won’t work.
If you don’t mind the few dollars of electricity per year, why not – your sleep will thank you.
To get back to your question: I already mentioned at the beginning that the heating circuit distribution manifold usually has ball valves, and you can just turn those off (how this affects the others would need to be checked separately in each case).
€ is basically not wrong in his statements, but in my example you can quickly see that when you dig deeper into it, it’s no longer so simple to explain all this in a way that’s understandable for the average user (Mollier h-x diagram, “simple” thermal calculations...).
And my calculation was definitely simplified 🙂 no energies were taken into account regarding the warming of building components, etc.
Well, the fact is that with this cooling function you can hardly achieve more than a 1-2 degree difference... so the desired effect will not be achieved without proper cooling.
But to answer your initial question, yes, you can close off individual rooms and thus practically concentrate the entire cooling on one room...
But to answer your initial question, yes, you can close off individual rooms and thus practically concentrate the entire cooling on one room...
Mycraft schrieb:
Well, the fact is that this cooling function can hardly achieve more than a 1–2 degree difference... so the desired effect will be absent without proper cooling... Correct, the 1–2 K (1.8–3.6°F) difference is based on past experience (dew point temperature), without considering the specific individual boundary conditions.
For the summer load case, similar principles apply as for the winter load case (heating).
If the cooling load is low, passive options (building construction) or indirect cooling can often be sufficient.
For higher cooling loads, the use of technical refrigeration is unavoidable. However, with appropriate, comprehensive planning and sizing, this can be avoided if needed.
Studies from Switzerland have confirmed this trend: heating degree days are decreasing, while cooling degree days are increasing.
The summer load case is somewhat neglected by the energy saving regulations, as the primary focus is on heating operation from a primary energy perspective. This is mainly because heating degree days exceed cooling degree days. However, the energy saving regulations refer to a standard location, which does not accurately reflect the actual site conditions.
Therefore, it is not permitted to use final results from energy saving regulations or KfW certificates for sizing heating or cooling systems or for consumption statements!
This especially affects 1.5 g. construction methods with exposed locations and roof orientations. Expecting a noticeable or lasting cooling effect from a controlled residential ventilation system is practically hopeless!
I have personally conducted practical measurements on this. Roof surface temperatures of around 90°C (194°F) are reached here, above a ventilated insulation layer about 65°C (149°F) and more.
It takes little imagination to understand how “effective” such a heating surface is during summer! ;-)
Regards
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