ᐅ Heat loss per meter in district heating pipelines—can it also be expressed as a percentage?

I have an 8-meter (26-foot) long heat transfer line from my house to the garage. According to the pipe manufacturer, the district heating pipe loses 5 watts per meter at a 40°C (104°F) supply temperature. What exactly does this mean, preferably expressed as a percentage?

Thank you.

You are losing the equivalent of a 40-watt lamp that would be lit continuously. Translated into money (electricity costs), this would be about 8 to 9 euros per month while the line is in operation. Roughly estimated, I would say this applies for about 4 months per year (depending on where your house is located). So, very roughly calculated, you are looking at around 50 euros per year.

Vwgolfcabrio schrieb:

I have an 8 m (26 feet) long heat supply pipe from my house to the garage. According to the pipe manufacturer, the district heating pipe has a loss of 5 watts per meter (at 40 degrees Celsius supply temperature).
What exactly does that mean, preferably expressed as a percentage?

Thanks.

The equation is underdetermined; it depends on how much power you draw at 40 degrees Celsius supply temperature and what your average heating load is over the winter.

Do you know approximately what your annual heating demand for the building will be? And how the connection capacity to the heating network was sized (in kW)? As a rule of thumb, you can estimate about 1 kW average power for every 3000 kWh of annual demand. Assuming you have 12,000 kWh (a moderately renovated single-family house of typical size or from the early 1990s) and therefore 4 kW heating power, and assuming the 40 °C supply temperature is reached, then the loss would be 8 m * 5 W/m = 40 W, which corresponds to about 1% loss relative to the 4 kW.

Mycraft schrieb:

You lose the equivalent of a 40-watt lamp running continuously. If you translate that into money (electricity costs), it would be about 8-9 euros per month while the line is in use. Roughly estimated, I would say that’s maybe about 4 months per year (depending on where your house is located). So, very roughly calculated, you end up with around 50 euros per year.

You are calculating here with 30 cents per kWh as the operating cost for heating. We have not quite reached that level yet.

We don’t know what fuel is being used there, so we have to assume the worst. And I specifically mentioned twice in the text that the calculation is very rough 😉

Scout** schrieb:

The equation is underdetermined; it depends on the output you require at 40 degrees Celsius (104°F) supply temperature and the average output you expect over the winter.

Do you know approximately what your annual heating demand for the building will be? And what the connection capacity to the heating network was sized for (in kW)? As a rule of thumb, you can estimate about 1 kW average output per 3000 kWh demand. Assuming you have 12,000 kWh (a moderately renovated single-family house of typical size or from the early 1990s) and thus 4 kW heating output, and assuming the 40°C (104°F) supply temperature is reached, that would be 8 m (26 feet) * 5 W/m (1.5 W/ft) = 40 W, which is about 1% loss relative to the 4 kW.

I have a heat demand of about 9,700 kWh per year. The decision now is whether to place the heat pump in my utility room or in the garage. As mentioned, the garage is connected by an 8 m (26 feet) district heating pipe. The supply temperature inside the house will not exceed 35 degrees Celsius (95°F). What percentage of losses can I expect if I use the heating pipe?