Heat pump for your koi pond

  1. Why heating?
  2. Important facts
  3. Capacity planning
  4. The Ekotez heat pump
  5. References
  6. Other installations

top1. Why heating

  • For optimal temperature keeping
  • Or to shorten the winter period
  • Or to protect the pond from freezing

Advantages of heating for your koi

  • Higher temperature in winter period
  • No temperature fluctuation spring/fall and day/night
  • This means: Better immunity, Better growth, Better filter operation, Better water quality, Avoiding frost damage

Climate conditions in Japan (Niigata – where the carps come from) are different to European weather conditions. Optimal temperature conditions are only 1-3 weeks per year. And also the winter period is much longer. This has important influence on health condition and growth of your fish. The biggest problems appear in spring, but it is possible to eliminate it by heating.

Average temperatures in Niigata, Japan

Month 1 2 3 4 5 6 7 8 9 10 11 12
Max. mean temperature °C 4,9 5,1 8,8 15,4 20,6 23,8 28,0 30,3 25,4 19,4 13,6 8,1
Mean temperature °C 2,1 2,0 4,9 10,8 16,1 20,1 24,3 26,3 21,5 15,4 9,8 4,9
Min. mean temperature °C -0.5 -0.6 1,4 6,8 12,1 17,1 21,3 22,7 18,4 11,8 6,4 2,1

top2. Important facts

  • Whenever you try to heat efficiently, minimize first the heat losses. More than 90% of the heat losses are caused by the water surface and only les than 10% of the heat passes to the soil. This is the main reason, why water surface covering is so important. Pond walls insulation is often thought as improper, because it prevents the heat from accumulating in the soil and this actually causes bigger temperature fluctuation. Covers

Types that can be used:

  • Direct electrical heating with heat exchanger

    Advantages: Simple installation, Relatively low purchase price
    Disadvantages: Extreme running costs, Short operating life (for common types), Decreases the water flowage (because of the need of connecting the heat exchanger into the pump circuit), Difficult exchanger cleaning
  • Water-water exchanger, connected into the house heating circuit

    Advantages: The existing house heating system can be used (only when there is sufficient capacity).
    Disadvantages: High costs of the system reconstruction, Decreases the heating power for the proper house, Decreases the water flowage (because of the need of connecting the heat exchanger into the pump circuit), Difficult exchanger cleaning, Elevated running costs, (depends on the type of house heating used)
    Beware of the materials used on the heat exchanger (specially copper and neither the desk exchangers are appropriate – given the fact that they can easily get glazed!)
  • Independent gas or liquid gas heating with water-water heat exchanger

    Advantages: Does not decrease the power of the house heatingbr /> Disadvantages: Requires installation of new gas conduction or liquid gas tank, Higher running costs, Decreases the water flowage (because of the need of connecting the heat exchanger into the pump circuit), Difficult exchanger cleaning
    Beware of the materials used on the heat exchanger (specially copper and neither the desk exchangers are appropriate – given the fact that they can easily get glazed!)
  • Sun collectors

    Advantages: Uses natural and recoverable energy, Low running costs
    Disadvantages: High purchase costs (and extremely long payback period), Heat power output depends on sunshine (you can get the energy only when you actually do not need it and its storage is very complicated) , Problematic water temperature fluctuation between night and day, Long periods with no heat output at all, especially in winter, The system is usable for koi pond heating only as a complementary heating system.
    Beware of the materials used on the heat exchanger (specially copper and neither the desk exchangers are appropriate – given the fact that they can easily get glazed!)
  • Electrical heating cable

    Advantages: Relatively easy installation
    Disadvantages: Extreme running costs, Insufficient heat output: 10m cable length is recommended for 10m3 - heat output only 360W – but in reality you need 2000W (56m of cable) for 10m3, when the pond is covered. E.g. for 30m3 you need 167m of cable
    Difficult manipulation, Extreme purchase cost, Controversial operational safety
  • Heat pump systems

    • Soil-water

      (uses low potential warmth from the soil):
      Advantages: Low running costs, Uses natural and recoverable energy
      Disadvantages: Requires installation of soil collector or bore hole, Installation permission needed, Difficult exchanger cleaning, High purchase costs, Decreases the water flowage (because of the need of connecting the heat exchanger into the pump circuit), Special KOI solution does not exist
      Beware of the materials used on the heat exchanger (specially copper and neither the desk exchangers are appropriate – given the fact that they can easily get glazed!)
    • Water-water

      (uses low potential warmth from water: stream, river, lake, pond or underground water):
      Advantages: Low running costs, Uses natural and recoverable energy
      Disadvantages: Utilizable water source is unusual, Installation permission needed, Difficult exchanger cleaning, High purchase costs, Decreases the water flowage (because of the need of connecting the heat exchanger into the pump circuit), Special KOI solution does not exist
      Beware of the materials used on the heat exchanger (specially copper and neither the desk exchangers are appropriate – given the fact that they can easily get glazed!)
    • Air-water produced by Ekotez

      (uses low potential warmth from air):
      Advantages: Lowest purchase costs from all heat pump systems (quickest pay-back), Low running costs, Uses natural and recoverable energy, Easy installation – no special permission needed, Heat exchanger cleaning is not needed (open type; made from titanium – self cleaning effect), Low noise level, Operates as heating, but can cool as well – given the automatic mode controls and limits the temperature fluctuation, Working temperature until –25°C, High coefficient of performance, Bigger dimensions are compensated by very high efficiency.
      Disadvantages of other types on the market: Working temperature usually only until +5°C (+7°C) Lower coefficient of performance, Difficult heat exchanger cleaning, Decreases the water flowage (because of the need of connecting the heat exchanger into the pump circuit), Special KOI solution does not exist
      Beware of the materials used on the heat exchanger (specially copper and neither the desk exchangers are appropriate – given the fact that they can easily get glazed!)
      Beware of coefficient of performance (COP) indication at different ambient temperatures (most producers indicate it at ambient temperature of 20°C – means it will be lot lower at 0°C, where we indicate it)

top3. Capacity planning

  • Theoretically the heat losses can be calculated, practically for European climate zone this formula can be used:
    • 1kW of heat power output for 5m3 of water, when the pond is well covered
    • 1kW of heat power output for 3m3 of water, when the pond is not covered and only as freeze protection
  • For extremely low ambient temperatures, which appear only a few times in the winter, we recommend to use bivalent version with direct electrical heating. This is only used as additional heating, which is turned on only when needed. Its function does not affect the running costs dramatically. This solution allows you to use heat pump with lower heat output, with lower running and purchase costs.

top4. The Ekotez heat pump

The heat pump uses, what is called „green energy“ – principally it returns the lost heat back into the pond. The running costs are minimal in comparison with direct electrical heating it is only about 15% (even less then 10% when the special tariffs are used).

Comparison of heating costs for a 60m3 pond

  • The Ekotez heat pumps were specially developed for KOI ponds heating – from the design, easy installation, guaranteed functionality in very low ambient temperatures (-25°C), very low noise level to simple maintenance. The cooled air is coming in from the bottom of the pump to the top of it, so that it protects the flora in its surroundings.
  • Titanium heat exchanger does not merely any maintenance. It is immersed in the filter, directly in water flow (or on other appropriate place), so that it does not decrease the water flowage. Even the possible bivalent electrical heater is placed in the filter, as well as the titanium exchanger.
  • Thanks to the construction of the Ekotez heat pump and the way it is used, a very high COP (coefficient of performance) is achieved - in average you get 6,5kW of heat power from 1kW of electricity.
  • The air-water principal is especially convenient for this application. Better COP is achieved even in comparison with soil-water heat pump.
  • R410a is used as a coolant. In present time it is the most ecological and environment friendly coolant.
  • In contrast to other heating systems it does not pollute the environment in any way.
MORE INFO in PDF

Heat pump W160 in winter functioning, in ambient temperatures down to –20°C. Even when the temperatures are that low, the heat pump works with COP around 2.


View on an open case of the electrical management, which contains the temperature regulation, electricity consumption control and earth-leakage circuit-breaker (e.l.c.b.).

top5. References

Installment in Germany, the customer did not want the heat pump to be visible from the front view


Czech customer, who used the design of the heat pump and incorporated it into the garden.

Installment in Germany near Netherlands. The customer, thanks to good climate conditions, saves 15000 Euro every year (in comparison with electrical heating – he was using before)
 
Bivalent type (with electrical heating) in Germany. Heat exchanger installed in the filter.

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