ᐅ Extremely High Pellet Consumption (200 kg in 3 Days) in a KfW 70 Multi-Family House!
Created on: 9 Nov 2016 14:35
R
rudiherbert
Hello,
I just noticed the following regarding our pellet heating system (6-family new build, KfW70 standard). This is a new build and the first winter...
The consumption in October (which was very mild here) was 1000 kg.
Currently, the consumption is 200 kg over 3 days!
Projected, that would be 2,000 kg per month!
Although temperatures have dropped somewhat, there is still no sign of a harsh winter.
Here is what I observed about the pellet heating system (Eta 20-30).
The underfloor heating temperature is 56°C (133°F) with an outside temperature of 1°C (34°F).
Supply temperature to the underfloor heating in the boiler room is only 30°C (86°F)? The return temperature is the same?
The supply temperature shown inside the apartment is 38°C (100°F) when the room thermostat is active, and 20°C (68°F) when inactive.
The buffer tank is supported by solar thermal collectors on the roof (for domestic hot water and heating).
I am certain that this consumption cannot be correct!
The new build is well insulated. The building is dry. Everyone heats reasonably and ventilates correctly.
2,000 kg of pellets per month in winter is extremely high!
In October, we used 1,000 kg.
In summer, about 500 kg per month.
Before contacting the heating technician or property management, I wanted to get some advice here.
Thank you.
I just noticed the following regarding our pellet heating system (6-family new build, KfW70 standard). This is a new build and the first winter...
The consumption in October (which was very mild here) was 1000 kg.
Currently, the consumption is 200 kg over 3 days!
Projected, that would be 2,000 kg per month!
Although temperatures have dropped somewhat, there is still no sign of a harsh winter.
Here is what I observed about the pellet heating system (Eta 20-30).
The underfloor heating temperature is 56°C (133°F) with an outside temperature of 1°C (34°F).
Supply temperature to the underfloor heating in the boiler room is only 30°C (86°F)? The return temperature is the same?
The supply temperature shown inside the apartment is 38°C (100°F) when the room thermostat is active, and 20°C (68°F) when inactive.
The buffer tank is supported by solar thermal collectors on the roof (for domestic hot water and heating).
I am certain that this consumption cannot be correct!
The new build is well insulated. The building is dry. Everyone heats reasonably and ventilates correctly.
2,000 kg of pellets per month in winter is extremely high!
In October, we used 1,000 kg.
In summer, about 500 kg per month.
Before contacting the heating technician or property management, I wanted to get some advice here.
Thank you.
AOLNCM schrieb:
In our latitude, the annual heating demand can be estimated at about 150 kWh per m² per year.
10 kWh correspond approximately to 1 m³ (35 cubic feet) of natural gas, as well as 1 liter (0.26 gallons) of heating oil and 2 kg (4.4 pounds) of pellets.
In your case, 150/10*2 = 30 kg (66 pounds) per m² per year.
30 * 550 = 16,500 kg (36,376 pounds) of pellets per year.
Depending on the heating system, insulation, and heating habits, this value may vary slightly.
That means if you end up using about 16-17 tons of pellets per year, your heating installer probably won’t find anything unusual. The reference building in my KFW-70 calculation has a heating energy demand of about 50 kWh/m² (without domestic hot water), but that would still be 5.5 tons following your calculation. If you have more glazing or something else that increases demand, that might still be realistic, especially since you also have to add hot water consumption. You only have roughly 6 heating months, so during those months the demand is quite significant. Additionally, November seems somewhat colder here compared to recent years.
Hello Saruss,
you are certainly right. If you look at the energy certificate, most modern houses will fall close to energy classes A and B, around 50 kWh/(m²·a) (50 kWh/(ft²·yr)).
Looking at comparative values, the average residential building stock in Germany can be found at about 150 kWh/(m²·a) (150 kWh/(ft²·yr)).
As a rough estimate, I have been able to reasonably assess consumption in existing buildings using this figure.
For a multi-family house like the one discussed by the original poster, the values should actually be somewhat better than for a single-family house.
However, for a new building, I would still use higher numbers for the first year, because the three weeks of continuous heating during screed drying with supply temperatures up to 55°C (131°F) significantly distort the annual average consumption.
you are certainly right. If you look at the energy certificate, most modern houses will fall close to energy classes A and B, around 50 kWh/(m²·a) (50 kWh/(ft²·yr)).
Looking at comparative values, the average residential building stock in Germany can be found at about 150 kWh/(m²·a) (150 kWh/(ft²·yr)).
As a rough estimate, I have been able to reasonably assess consumption in existing buildings using this figure.
For a multi-family house like the one discussed by the original poster, the values should actually be somewhat better than for a single-family house.
However, for a new building, I would still use higher numbers for the first year, because the three weeks of continuous heating during screed drying with supply temperatures up to 55°C (131°F) significantly distort the annual average consumption.
R
rudiherbert11 Nov 2016 11:34AOLNCM schrieb:
Hello Saruss,
you are of course right. When you look at the energy certificate, most modern houses tend to fall near energy classes A and B, around 50 kWh/(m²a) (16,000 Btu/(ft²yr)).
If you look at reference values, the average residential building stock in Germany is around 150 kWh/(m²a) (48,000 Btu/(ft²yr)).
As a rough estimate, I have been able to use this value to fairly accurately assess energy consumption in existing buildings.
For a multi-family house as in the original post, the values should actually be somewhat better than for a single-family home.
For a new building, however, I would still expect higher numbers in the first year because the three weeks of continuous heating during screed drying with supply temperatures up to 55°C (131°F) strongly distort the annual average consumption.Hello.
Thanks for the information.
So, of course, I did not multiply the November consumption by 10 months.
For 2 tons in November, I calculated the winter months November to March as 2 tons (probably more if it gets really cold). Transition months October, April, May I estimated at 1 ton each, and summer at 300 kg (because of solar collectors on the roof). That totals about 14–15 tons.
According to the KfW 70 standard and the building’s energy certificate, the kW rating is 55 kW per m². For 550 m² (5,920 ft²) in the multi-family building, that adds up to around 6 tons.
We would therefore be far above that, with about 14–15 tons!
The screed has already dried out! It was installed in spring 2016 and properly dried.
The plaster in the apartments is also dry (ventilated well over the summer, dehumidified, etc.).
The sun also warms a large part of the multi-family building through the windows.
The collectors only support heating during sunshine in the transitional and summer months!
The high supply temperature of 38°C (100°F) in the apartment also confuses me.
Best regards
Annual consumption distribution in Bavaria (e.g., Bamberg) is as follows:
January 23%
February 11%
March 8%
April 1%
May 0%
June 0%
July 0%
August 0%
September 0%
October 4%
November 11%
December 19%
Based on 2 tons in November, the calculated annual demand would be 17.5 tons — that is 4.8 kWh per kg * 17,500 kg = 84,000 kWh... per apartment this means around 7,000 kWh — without a ventilation system and including hot water, this would still be somewhat acceptable even for a single apartment.
January 23%
February 11%
March 8%
April 1%
May 0%
June 0%
July 0%
August 0%
September 0%
October 4%
November 11%
December 19%
Based on 2 tons in November, the calculated annual demand would be 17.5 tons — that is 4.8 kWh per kg * 17,500 kg = 84,000 kWh... per apartment this means around 7,000 kWh — without a ventilation system and including hot water, this would still be somewhat acceptable even for a single apartment.
R
rudiherbert11 Nov 2016 12:53BeHaElJa schrieb:
Annual consumption distribution in Bavaria (e.g., Bamberg) is as follows:
January 23%
February 11%
March 8%
April 1%
May 0%
June 0%
July 0%
August 0%
September 0%
October 4%
November 11%
December 19%
Based on 2 tons in November, this calculates to an annual demand of 17.5 tons – that is 4.8 kWh per kg * 17,500 kg = 84,000 kWh... per apartment that would be 7,000 kWh – without a ventilation system and including domestic hot water, this would still be somewhat reasonable even for a single apartment.Hello.
Thank you very much for your help.
But isn’t 17.5 tons quite a lot for a newly built KfW70 standard building with only 6 units and a total of 550 m2 (5,920 sq ft)?
According to the energy performance certificate, the building has a heat demand of 55 kWh per m2 (5.1 kWh per sq ft).
That would mean approximately 6 tons annually.
So 17.5 tons is almost three times that amount...
I suspect that the heating system (pellets with solar support) hasn’t been properly balanced. It seems to prioritize comfort (getting hot quickly) over efficiency...
That’s why the high supply temperature of the underfloor heating (currently 38°C (100°F)) doesn’t surprise me....
Regards
55 kWh/(m²*a) primary energy or final energy?
As already mentioned, pellet heating tends to calculate primary energy very optimistically.
You are, of course, right – there was a calculation error; it would be 14,000 kWh per year and apartment, or 150 kWh/m²*a (14 kWh/ft²*yr), which is rather high (not catastrophically high, but high).
I think I would bring this up at your next homeowners’ meeting and see if you can get the heating contractor to take another look and check what else can be optimized.
As already mentioned, pellet heating tends to calculate primary energy very optimistically.
You are, of course, right – there was a calculation error; it would be 14,000 kWh per year and apartment, or 150 kWh/m²*a (14 kWh/ft²*yr), which is rather high (not catastrophically high, but high).
I think I would bring this up at your next homeowners’ meeting and see if you can get the heating contractor to take another look and check what else can be optimized.
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