ᐅ Exotic combination: wood pellets plus exhaust air heat pump?
Created on: 31 Jul 2020 21:44
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RockyFranco
Hello,
First of all, thank you for providing a platform for questions like this.
I have the following issue that I’m trying to solve and hope to get some tips from the experts here.
I’m interested in a house but haven’t bought it yet.
- Viebrockhaus, so-called 3-liter house, haha. Built in 2000
- Very good quality in terms of bathrooms, floors, and materials
- Two upper floors totaling 200sqm (2,150 sq ft) with a mansard roof and a fully finished basement including an office of about 90sqm (970 sq ft)
- Now here’s the thing, hold on to your hats: the electricity bills are easily around 400€ per month, and depending on the year they use between 10,000–12,000 kWh annually. All electric, mind you. For two people!
- Radiators throughout the house. No underfloor heating! Two fireplaces, but their chimneys are located exactly opposite the technical room. They do have flaps to the hallway as well.
- Heating system: 2 x exhaust air heat pumps, Nibe Fighter 600 or 610, for the living area and one Nibe Fighter 315 for the basement/office.
- Central exhaust ventilation system from relevant rooms, with decentralized air supply openings in every room.
Clearly, the system is so inefficient that it probably runs on electric heating cartridges 90% of the time. Plus, the ventilation has to be on; otherwise, there is no efficiency at all.
I want to reduce these high costs. I’ve read that you can tweak the system with timers and turning ventilation mostly off, or trick the temperature sensors, etc. But I think all that is neither effective nor practical.
IDEA:
- Since there is LOTS of space in the technical room in the basement, including a large storage area, I’m considering installing a suitable wood pellet boiler. The chimney draft is external. The appearance doesn’t bother me.
- Combined with a modern exhaust air heat pump like the Nibe F135, which would only run occasionally.
To keep the ventilation going—I’m afraid of mold otherwise—the house was very dry and didn’t feel stuffy.
The viewing was on a 35°C (95°F) day, so it was blazing hot inside, obviously because warm air is drawn in.
What do you think about this, or is it nonsense? Would solar thermal for hot water be better? I have also thought about keeping the old Nibe just to run the ventilation function. What I don’t want is to break up 200sqm (2,150 sq ft) of flooring to install underfloor heating.
That rules out oil/gas/air-source/geothermal heat pumps.
I have also considered photovoltaic panels to cover the huge electricity costs, but that would be like casting pearls before swine and still wouldn’t be enough.
Maybe someone here has another tip.
THANK YOU VERY MUCH!
Frank
First of all, thank you for providing a platform for questions like this.
I have the following issue that I’m trying to solve and hope to get some tips from the experts here.
I’m interested in a house but haven’t bought it yet.
- Viebrockhaus, so-called 3-liter house, haha. Built in 2000
- Very good quality in terms of bathrooms, floors, and materials
- Two upper floors totaling 200sqm (2,150 sq ft) with a mansard roof and a fully finished basement including an office of about 90sqm (970 sq ft)
- Now here’s the thing, hold on to your hats: the electricity bills are easily around 400€ per month, and depending on the year they use between 10,000–12,000 kWh annually. All electric, mind you. For two people!
- Radiators throughout the house. No underfloor heating! Two fireplaces, but their chimneys are located exactly opposite the technical room. They do have flaps to the hallway as well.
- Heating system: 2 x exhaust air heat pumps, Nibe Fighter 600 or 610, for the living area and one Nibe Fighter 315 for the basement/office.
- Central exhaust ventilation system from relevant rooms, with decentralized air supply openings in every room.
Clearly, the system is so inefficient that it probably runs on electric heating cartridges 90% of the time. Plus, the ventilation has to be on; otherwise, there is no efficiency at all.
I want to reduce these high costs. I’ve read that you can tweak the system with timers and turning ventilation mostly off, or trick the temperature sensors, etc. But I think all that is neither effective nor practical.
IDEA:
- Since there is LOTS of space in the technical room in the basement, including a large storage area, I’m considering installing a suitable wood pellet boiler. The chimney draft is external. The appearance doesn’t bother me.
- Combined with a modern exhaust air heat pump like the Nibe F135, which would only run occasionally.
To keep the ventilation going—I’m afraid of mold otherwise—the house was very dry and didn’t feel stuffy.
The viewing was on a 35°C (95°F) day, so it was blazing hot inside, obviously because warm air is drawn in.
What do you think about this, or is it nonsense? Would solar thermal for hot water be better? I have also thought about keeping the old Nibe just to run the ventilation function. What I don’t want is to break up 200sqm (2,150 sq ft) of flooring to install underfloor heating.
That rules out oil/gas/air-source/geothermal heat pumps.
I have also considered photovoltaic panels to cover the huge electricity costs, but that would be like casting pearls before swine and still wouldn’t be enough.
Maybe someone here has another tip.
THANK YOU VERY MUCH!
Frank
T
T_im_Norden3 Aug 2020 10:06Joedreck schrieb:
The annual energy demand of 13,000 kWh is actually very low and comparable to new construction standards.As I understand it, this is the pure electricity consumption for heating.
13,000 / 270 = 48 kWh/m² (4.5 kWh/ft²).
This results in around 350 euros per month for heating electricity alone, which aligns with the approximately 400 euros per month total electricity costs mentioned in the first post.
This is not typical for new construction standards.
Since there are three heat pumps involved, a conservative estimate for the COP (Coefficient of Performance) would be about 2, which equals roughly 26,000 kWh of heat produced annually.
The fact that three heat pumps are operating here already indicates that there might be something wrong with the concept.
T_im_Norden schrieb:
As I understand it, this is the actual electricity consumption for heating.
13,000 / 270 = 48 kWh/m2 (4.5 kWh/ft2).
This means that just the heating costs about 350 euros per month in electricity, which fits with the approximately 400 euros per month mentioned for total household electricity in the first post.
This is not typical for new construction standards.
Since this involves 3 heat pumps, you can conservatively estimate a COP of about 2, which would amount to 26,000 kWh of heat per year.
The fact that 3 heat pumps are in operation already indicates that something is off with the concept. I strongly doubt that we have a COP of 2 here. Most of the time, the exhaust air heat pump will be supplying direct electric heating. I estimate a real heating demand of maybe 16,000 kWh hours.
However, this is relatively unimportant since, given the radiators and the existing conditions, I still recommend gas heating. It usually doesn’t make much difference, as the smallest gas heaters I know have a maximum output of 9 or 11 kW, and our demand is definitely below that.
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RockyFranco3 Aug 2020 11:56I would like to thank everyone for the constructive contributions! Let’s see how it turns out; the decision will be made this week.
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T_im_Norden3 Aug 2020 12:18Keep us updated, I’m looking forward to the solution.
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