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.
R
rudiherbert11 Nov 2016 13:09BeHaElJa schrieb:
55 kWh/(m²*a) primary energy or final energy?
As mentioned before, pellet calculations for primary energy always tend to look very favorable quickly.
You are of course right – I made a calculation error; it would be 14,000 kWh per year per apartment or 150 kWh/(m²*a) – which is rather high (not catastrophically high, but high).
I think I would bring this up at your next homeowners’ meeting and try to get the heating contractor back to see what else can be optimized. Hello.
According to the energy certificate, it is primary energy!
The usable area of the multi-family house is about 950 m² (10,230 sq ft), the total living area of the apartments is 550 m² (5,920 sq ft).
I calculated based on 550 m².
Was that a mistake???
I also believe that the usable area within the insulated building envelope requires heating. I experienced higher heating costs during the first year as well. Although the screed may be dry in itself, there is usually more moisture in the house compared to the second year.
Otherwise, I find a 38°C (100°F) supply water temperature quite high; our heating system doesn’t even reach that at -20°C (-4°F). However, I am not familiar with your underfloor heating system or how closely the pipes were installed.
Overall, a faulty configuration could be to blame (for example, an incorrect heating curve), causing the system not only to have too high a supply temperature but also to be “choked” by valves in the individual apartments. It is also theoretically possible that someone in one of the units keeps windows open and takes hot baths three times a day.
Otherwise, I find a 38°C (100°F) supply water temperature quite high; our heating system doesn’t even reach that at -20°C (-4°F). However, I am not familiar with your underfloor heating system or how closely the pipes were installed.
Overall, a faulty configuration could be to blame (for example, an incorrect heating curve), causing the system not only to have too high a supply temperature but also to be “choked” by valves in the individual apartments. It is also theoretically possible that someone in one of the units keeps windows open and takes hot baths three times a day.
I don’t think that a 38°C (100°F) supply temperature is too high; on the contrary, it actually seems too low to me.
He has a wood-fired boiler. These need to operate at higher temperatures (60°C / 140°F) to prevent soot from forming on the heat exchanger. He also has solar thermal.
The system will probably have a return temperature lift.
There are two ways to transfer heat into the rooms: either with a high flow rate and a small temperature difference between supply and return, or by pumping more slowly with a higher temperature difference for heat transfer.
Due to their design, heat pumps typically use the first method, while wood combustion requires the second.
It’s best to speak with the person who designed the system or a qualified heating engineer.
He has a wood-fired boiler. These need to operate at higher temperatures (60°C / 140°F) to prevent soot from forming on the heat exchanger. He also has solar thermal.
The system will probably have a return temperature lift.
There are two ways to transfer heat into the rooms: either with a high flow rate and a small temperature difference between supply and return, or by pumping more slowly with a higher temperature difference for heat transfer.
Due to their design, heat pumps typically use the first method, while wood combustion requires the second.
It’s best to speak with the person who designed the system or a qualified heating engineer.
You can achieve a low supply temperature, as you mentioned, by using a mixing valve. A high supply temperature is rather unusual in underfloor heating systems due to their design. If the temperature is already high at 0°C (32°F), then at -15°C (5°F) outside, it would reach around 60°C (140°F), which either results in uncomfortably hot floors or extreme stop-and-go cycling. This cycling is also detrimental to the system. If there is a buffer tank to prevent frequent cycling, you can still mix down to a lower temperature! However, if the underfloor heating system is designed for higher temperatures, it can be difficult to change the heat source later.
Of course, you should discuss this with your heating engineer. In my experience, my installer just aimed for "as long as it’s warm," without concern for efficiency, and we hadn’t contractually agreed on a maximum energy consumption. I had to optimize the heating curve and basically all other system settings myself.
Sent from on the go
Of course, you should discuss this with your heating engineer. In my experience, my installer just aimed for "as long as it’s warm," without concern for efficiency, and we hadn’t contractually agreed on a maximum energy consumption. I had to optimize the heating curve and basically all other system settings myself.
Sent from on the go
R
rudiherbert11 Nov 2016 15:51AOLNCM schrieb:
I don’t think the 38°C (100°F) supply temperature is too high; on the contrary, it seems too low to me.
He has a wood-fired heating boiler. These need to operate at higher temperatures (60°C (140°F)) to prevent soot from forming on the heat exchanger. He also has solar thermal.
The system probably has a return temperature lift.
There are two ways to transfer heat into the rooms: either a high volume flow with a small temperature difference between supply and return, or slower pumping with higher heat transfer.
Due to their design, heat pumps require the first method, and wood combustion the second.
It’s best to talk to the person who designed the system or a qualified heating engineer.Thanks for your information.
So, you also don’t think that around 2-3 tons in the winter months, 1 ton in the transitional season (projected to about 15 tons per year) is too high for a KfW 70 multi-family house (6 units, living area about 550m2 (5,920 sq.ft), building area 950m2 (10,225 sq.ft))?
According to the energy certificate, the building should require 55 kW primary energy. That would be about 6 tons of pellets per year. Not nearly three times that amount…
Thanks!
Similar topics