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FAQ GEOSystem ground heating

Private houses
The system is installed on walkways, driveways, etc.

Apartments and rental housing
The system is installed on patios, walkways by garages and footpaths, etc.

Industrial buildings
The system is installed at loading and unloading sites as well as on ramps and roads.

Public places
The system is installed at car parks, intersections, walkways, sports complexes, etc.

To heat 5 mm aq snow from -15 to 0°C and convert it to water requires 0.5 kW. The density of new snow is 0.05 g/cm³ but heavy snowfall can increase this to 0.12 to 0.18 grams g/cm³ In order to melt 1 m² of 30-40 cm thick snow you require 0.5 kW.

An annual precipitation of about 600 mm aq* means that snow accounts for about 1/3 - i.e. about 200 mm. This means that it takes at least 20 kW per year to melt 1 m² of snow.

Each time you activate the system, the plate needs to be heated up to operating temperature, which leads to increased energy consumption.

To explain we need a numeric example (50 mm thick plate):

Concrete’s heat capacity 840 J/kg x K, density 2,400 kg/m3 means that 0.42 kW is required to heat 1 Square meter from -10 (on average) to +5 °C.

If you activate the system on average 50 times per heating season, this represents total energy consumption of 21 kW per heating season.

A total of 41 kW per m²and year.

Heat loss into the atmosphere and the ground is 40-160 kW/year depending on the climate zone in which the snow melting system is located. You should expect about 80-200 kW per m2 and year with a control system. Without a control system you will require 2-3 times more energy per m2 and year.

*600 mm is just a calculation example. The exact values can be ordered at www.smhi.se.

The main purpose of a control system is to optimize energy consumption. Compared to a melting system without a control system, energy consumption over a heating season can be reduced by up to 70 %.

The control system is used mostly for large melting systems, while small systems can often be controlled with a timer, where the operating time is set between 1-6 hours each time. The alternative is continuous operation.

The automatic control system has both moisture and temperature sensors, which are installed in the ground for optimum operation.

For large areas and continuous operation of the system (all winter),insulation makes no difference.

The greatest heat loss occurs when the ground is heated i.e., from the start to desired operating temperature in the ground. Compared to total power loss, loss to the ground is 10% of all power used.

Insulation can be used in small areas, stairways, entrances, etc. The insulation makes the system react faster.

The covering layer above snow melting pipes should be as thin as possible. The layer should not be thicker than 150 mm.

Normal thickness is 50 - 100 mm.

In a snow melting system, some form of antifreeze is often used, for example glycol. The concentration of the solution depends on the desired level of antifreeze, usually 20 – 50% glycol. The lower the concentration of the mixture, the better the heat capacity of the medium.

Ethylene glycol is classified as toxic and can be replaced with propylene glycol, but take into account that propylene glycol has a lower heat capacity than ethylene glycol.

It is possible to balance the loops if a standard manifold is used. In PE manifolds, the pressure increases the farther the loop connection is from the manifold’s connection point.

Example:

  • Area 1000 m² (20 x 50 m)
  • The manifold is located on the 20 m long side
  • 40 loops with 25 mm pipes
  • 300 W/m² (cc 250 mm)

This means that we get 100 m long loops. The pressure drop in each loop is 15 kPa (according to 1.4).

Flow (V) at the beginning of the manifold is calculated using the formula:
V = W x S/C x dT
C = heat capacity of the medium. With 40% ethylene glycol is: 3.3 kJ/kg x °C.
dT = temperature drop in loops, normally 15 ºС.
W = power in watts per square meter (0.3 kW/m².
S = total area, m²

The flow of the entire manifold V = 0.3 kW/m² x 1000m²/ (3.3kJ/kg x C x 15°C) = 6.06 l/sec.

In the first 0.5 m of the manifold, the flow is 6.06-0.1515 = 5.9085 l/sec. 1 m = additional 0.1515 l/sec less, etc.

The graphs below illustrate the pressure drop for 75 and 110 pipes.

Pressure drop for a 75 mm manifold

GEOSystem Tryckfall 75 mm fördelare

GEOSystem Tryckfall 75 mm fördelare

Pressure drop for a 110 mm manifold 

GEOSystem tryckfall 110 mm fördelare

GEOSystem tryckfall 110 mm fördelare

It is necessary to have a heat exchanger when the fluid in the system contains anti-freeze such as ethylene glycol and the heating system that is to provide the heat for snow melting does not have anti-freeze.

Heat exchangers do not need to be installed in the following cases:

  • The main heating system that provides heat for snow melting has antifreeze at the same concentration needed for snow melting
  • A separate heat source is used for snow melting, for example, a separate electric boiler

Having an open or closed system is optional, regardless of whether the heat exchanger is installed or not. There are no obstacles.

A closed system is preferable, especially if the system has antifreeze.

In closed systems, it is normally sufficient with 0.5 to 1 bar.