ᐅ Planning a Ground Loop / Water Source Heat Pump – Who Has Experience With This?
Created on: 24 Mar 2018 09:02
S
schloddy23S
schloddy2324 Mar 2018 09:02Hello dear forum members,
A few years ago, I completed my studies in building energy technology in Bremerhaven and I’m also a gas and water installer. However, I have only worked briefly in the industry, so I simply lack practical experience in this field. Of course, I have done all this theoretically, but that knowledge is now almost gone.
My wife and I are planning to build a house this year, and I have made a rough outline of the building services as a placeholder for cost estimation. Now everything is becoming more concrete quite quickly, and I realize that without advice from more experienced colleagues, I cannot fully follow my plans through to the end. I understand that people usually use informal language in forums; if anyone prefers formal address, please feel free to consider it that way and don’t take offense. That’s a bit about me and my background.
Now to the matter at hand. So far, we plan to build the following house:
- KfW40plus standard
- 150 m² (1,615 sq ft) living space
- Underfloor heating throughout
- Approx. 20 W/m² (6.1 BTU/hr·ft²), so about 3 kW (10,200 BTU/hr) heating load
- Household of 3-4 people, so about 0.8–1.2 kW (2,700–4,100 BTU/hr) additional load; I haven’t fully understood how this value is calculated, but it is commonly recommended to add 0.2–0.3 kW (680–1,020 BTU/hr) per person
- I keep reading about blackout periods (load restriction times) with special heat pump tariffs. If this is realistic and applies, I would like to include it in the calculation, e.g., heating load (or the total power?) multiplied by 1.3 or something similar
If I add all these factors together for the worst case, I end up close to 5.5 kW (18,800 BTU/hr). I was hoping to get a unit from Weishaupt or Vaillant. Weishaupt was ruled out because their hot water storage tank is, I believe, over 300 liters (79 gallons), which seems too large to me. So I am left with the Vaillant unit that has a 185-liter (49-gallon) storage tank.
The choice: flexoCOMPACT exclusive VWF 57/4 with about 5.4 kW (18,400 BTU/hr)
Now, I have also heard about modulating (and more expensive) devices from other manufacturers and wonder if it makes sense to continue with my Vaillant placeholder or if I should look further and consider other products.
I don’t want a buffer tank, but I am trying to think through every scenario. How does the system usually behave during transitional phases when the underfloor heating is just barely coming on and the heat demand is quite low? The 3 kW (10,200 BTU/hr) is really the worst case, and that level is not reached constantly. I’m concerned that the system might frequently cycle on and off. Also, I have no idea how the hot water generation with the heat pump performs.
My question here is: could you support me with your experience and share your opinion? Am I heading towards a solid plan, or is this already flawed from the start? Is the heat pump with the connected underfloor heating sufficient, or should I still include a small buffer tank? (Considering blackout times and cycling) Do you perhaps have experience with this system? Could you recommend other manufacturers? On the other hand, I have planned the other technology so far with Vaillant, and I could avoid complicated controls if I take the complete system from one supplier. I would appreciate any tip or detail at all.
Best regards
Sebastian
A few years ago, I completed my studies in building energy technology in Bremerhaven and I’m also a gas and water installer. However, I have only worked briefly in the industry, so I simply lack practical experience in this field. Of course, I have done all this theoretically, but that knowledge is now almost gone.
My wife and I are planning to build a house this year, and I have made a rough outline of the building services as a placeholder for cost estimation. Now everything is becoming more concrete quite quickly, and I realize that without advice from more experienced colleagues, I cannot fully follow my plans through to the end. I understand that people usually use informal language in forums; if anyone prefers formal address, please feel free to consider it that way and don’t take offense. That’s a bit about me and my background.
Now to the matter at hand. So far, we plan to build the following house:
- KfW40plus standard
- 150 m² (1,615 sq ft) living space
- Underfloor heating throughout
- Approx. 20 W/m² (6.1 BTU/hr·ft²), so about 3 kW (10,200 BTU/hr) heating load
- Household of 3-4 people, so about 0.8–1.2 kW (2,700–4,100 BTU/hr) additional load; I haven’t fully understood how this value is calculated, but it is commonly recommended to add 0.2–0.3 kW (680–1,020 BTU/hr) per person
- I keep reading about blackout periods (load restriction times) with special heat pump tariffs. If this is realistic and applies, I would like to include it in the calculation, e.g., heating load (or the total power?) multiplied by 1.3 or something similar
If I add all these factors together for the worst case, I end up close to 5.5 kW (18,800 BTU/hr). I was hoping to get a unit from Weishaupt or Vaillant. Weishaupt was ruled out because their hot water storage tank is, I believe, over 300 liters (79 gallons), which seems too large to me. So I am left with the Vaillant unit that has a 185-liter (49-gallon) storage tank.
The choice: flexoCOMPACT exclusive VWF 57/4 with about 5.4 kW (18,400 BTU/hr)
Now, I have also heard about modulating (and more expensive) devices from other manufacturers and wonder if it makes sense to continue with my Vaillant placeholder or if I should look further and consider other products.
I don’t want a buffer tank, but I am trying to think through every scenario. How does the system usually behave during transitional phases when the underfloor heating is just barely coming on and the heat demand is quite low? The 3 kW (10,200 BTU/hr) is really the worst case, and that level is not reached constantly. I’m concerned that the system might frequently cycle on and off. Also, I have no idea how the hot water generation with the heat pump performs.
My question here is: could you support me with your experience and share your opinion? Am I heading towards a solid plan, or is this already flawed from the start? Is the heat pump with the connected underfloor heating sufficient, or should I still include a small buffer tank? (Considering blackout times and cycling) Do you perhaps have experience with this system? Could you recommend other manufacturers? On the other hand, I have planned the other technology so far with Vaillant, and I could avoid complicated controls if I take the complete system from one supplier. I would appreciate any tip or detail at all.
Best regards
Sebastian
Pommes01 schrieb:
For these specific questions, a forum specializing in building services engineering, which is marked by a pink theme, would be more suitable. Additionally, take a look at the funding conditions of the BAFA. There is a potential subsidy of 5,000 euros (€) available. However, a certified expert will definitely need to approve the work. Doing everything yourself right to the end might actually be uneconomical.
T
toxicmolotof27 Mar 2018 14:33You should check whether a special heat pump tariff (with the mentioned blackout periods) actually makes sense. Especially considering the low heating and hot water demand (probably under 2,000 kWh per year), it might be that the extra costs for the second meter (including ongoing fees) are higher than the savings per kWh on an annual basis. If you even imagine having photovoltaic panels somewhere, the logic behind the two-meter strategy practically disappears immediately.
We have a 200-liter (about 53 gallons) hot water storage tank for 2 adults and 2 children... it works fine, but if two people want to shower one after the other for a longer time, it’s not really feasible. You should discuss this (especially with your wife!) to see if you’re willing to accept that, or you might need to wait for about half an hour in between. Otherwise, go ahead and get the 300-liter (about 79 gallons) tank. You can calculate well with that... consider the target temperature and flow rate per minute at around 38°C (100°F)... you know what I mean.
We have a 200-liter (about 53 gallons) hot water storage tank for 2 adults and 2 children... it works fine, but if two people want to shower one after the other for a longer time, it’s not really feasible. You should discuss this (especially with your wife!) to see if you’re willing to accept that, or you might need to wait for about half an hour in between. Otherwise, go ahead and get the 300-liter (about 79 gallons) tank. You can calculate well with that... consider the target temperature and flow rate per minute at around 38°C (100°F)... you know what I mean.
Similar topics