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Sanden FAQs

1. Is the Sanden “Eco®” Hot Water Heat Pump System an energy efficient hot water system? How does it compare to a conventional electric hot water system?

You can save up to 78% of your conventional electric hot water energy costs!  The Sanden “Eco®” Hot Water Heat Pump System uses only 22% of the energy required by an electric storage hot water system.

2. What are the benefits of the Sanden “Eco®” Hot Water Heat Pump System?

Not only does a Sanden “Eco®” Hot Water Heat Pump System help save on energy costs, it also delivers:

(a) The Heat Pump Unit

  • Innovative technology — up to 50% faster heat recovery than currently available Hot Water Heat Pumps.
  • Industry leading quality & performance, with the highest level of STC values of currently available Hot Water Heat Pumps.
  • Class leading warranties, backed by Sanden’s 30 years of operation in Australia.

(b) The Stainless Steel Storage Tank

  • High quality, extra long life duplex stainless steel cylinder.
  • Two x 315 litre Tank sizes to suit your space requirements (tall with a reduced diameter or short with an increased diameter)
  • Fully insulated for extremely low heat loss
  • Safety pressure and temperature relief valve
  • Mains pressure rated

3. How does a heat pump hot water system work?

The Sanden “Eco®” Hot Water Heat Pump System operates like a refrigerator in reverse. It contains a fan that forces air through an evaporator that contains a refrigerant. The heat in the air passes through the evaporator and is absorbed by a natural refrigerant, R744 (CO2), which is ozone friendly and does not contribute to global warming.

The warm gaseous refrigerant is circulated in the system via a compressor. As it passes through the compressor, its pressure rises, as does its temperature. This hot refrigerant then passes through a heat exchanger to heat the water, which is finally pumped to the storage tank.

How Heat Pump Hot Water Systems Work

4.  Which hot water system should I choose?

Sanden has 4 hot water systems to choose from, model numbers GAUS–315EQTD (short, fat tank) and GAUS–315EQTE (tall, thin tank) have a tank size of 315L, model number GAUS-250EQTA has a tank size of 250L and model GAUS-160EQTA has a tank size of 160L . Which one you choose depends on the space requirements of the location where you are installing it. Please speak to your Dealer/Installer about making the best choice for your location.

 5. I don’t understand the use of a CO2 refrigerant by the Sanden “Eco®” Hot Water Heat Pump System.  Isn’t CO2 a greenhouse gas and therefore harmful to the environment?

Yes, but CO2 has a Global Warming Potential (GWP – see below for explanation) of 1. Carbon dioxide is the baseline measurement of how it will contribute to global warming for a given mass.

Our system utilizes less than 1 kg of R744 (CO2) as a refrigerant contained in a closed system at the factory.  The installer does not need to charge the heat pump on site.

Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming.. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide (whose GWP is by convention equal to 1). A GWP is calculated over a specific time interval and this time interval must be stated whenever a GWP is quoted or else the value is meaningless.

Environmentally Safe CO2 in Sanden Hot Water Heat Pumps

See also:

6. Why does Sanden “Eco®” Hot Water Heat Pump System use CO2 as a refrigerant?

  • There is far less environmental impact (i.e. No ozone layer depletion and minimal global warming) than other commonly used refrigerants, should the system leak.
  • There is a much higher efficiency, thereby allowing more heat to be transferred to the water, for less energy used (i.e. Excellent  thermodynamic ability).

7. What is the noise level of the Sanden “Eco®” Hot Water Heat Pump System?

The unit is rated at 38dB, which is almost silent. By comparison, a whisper is around 30dB and inside a library is approximately 40dB.

8. How do I purchase a Sanden “Eco®” Hot Water Heat Pump System?

Please contact us on 1300 12 OPTI to discuss your purchase!

9. What is the life expectancy of the Sanden “Eco®” Hot Water Heat Pump System?

The Sanden HWHP is designed to last for 15 years. The high quality, weather resistant construction of the “Eco®” Hot Water Heat Pump System outdoor module carries a warranty of 3 years, whereas the high quality, extra long life stainless steel storage tank carries a class leading 15 year warranty.

10. At what temperatures will the Sanden “Eco®” Hot Water Heat Pump System operate effectively?

The Sanden HWHP will operate effectively between minus 10 and plus 43 degrees C, without the need for an electric booster element. It is also fitted with in built freeze protection, making it suitable for all climates.

11. Does the Sanden Eco® HWHP require the assistance of an electric booster element to heat water, when outside ambient temperatures are very low?

No, unlike other competitor HWHP systems, the Sanden Eco® HWHP system does not require an electric booster element

12. Can I operate the Sanden “Eco®” Hot Water Heat Pump System on Off-Peak Tariffs?

Yes, please refer to the Installation Manual for details. There are no special settings for off peak connection. Simply ensure that the off peak tariff supplies a minimum of 5 hours continuous power to the Sanden HWHP.

13. What are RECs and STCs and what are they worth?

The purchase and installation of a Sanden “Eco®” Hot Water Heat Pump System entitles you to Small-scale Technology Certificates (STCs) – formerly known as Renewable Energy Certificates (RECs). For more information: visit and

The Sanden HWHP achieves the highest level of STCs of any hot water heat pump, currently available in Australia, and these are as below:

Model Tank Type Zone 1 Zone 2 Zone 3 Zone 4 Zone 5
GAUS-160EQTA 160 L 26 25 31 33 33
GAUS-250EQTA 250 L 26 25 32 34 33
GAUS-315EQTD 315 L (short) 26 25 32 35 33
GAUS-315EQTE 315 L (tall) 26 25 32 34 33

14. Is water quality an important consideration for the Sanden “Eco®” Hot Water Heat Pump System?

Yes. Please refer to the Installation Manual for details. Importantly, no warranty applies to the heat pump unit and the storage tank, where the chloride level exceeds 200 mg/litre and the pH is less than 6.0. If in doubt, it is recommended that water chemistry information be sought from your local council or water supplier.

15. What do I do if the Sanden “Eco®” Hot Water Heat Pump System has a problem?

Firstly, review the Trouble Shooting Guide in the Installation Manual. If still unresolved, please contact the Opti Plumbing on 1300 12 OPTI.

16. If I go away from the house, can I turn the hot water heat pump off?

Yes you can. Turning off will not affect the unit. Just switch the power back on when you get back.

17. Do I need to register my warranty?

Yes.  For efficient processing of warranty claims, should they arise, please register your Sanden “Eco®” Hot Water Heat Pump System here.

18. What sizes are the Sanden “Eco®” Hot Water Heat Pump System available in?

The unit is available in four sizes as follows:

Tank size/shape No. of persons using hot water Typical dwelling type Suitable for Off-peak & Continuous tariffs? STC rebates available?
160L 1-2 Units / Townhouses Continuous only Yes
250L 2-4 Residential Both Yes
315L Tall 3-6 Residential Both Yes
315L Short 3-6 Residential Both Yes


  • “Thank you for your prompt response and the professionalism of your company. I also appreciate you explaining and marking out the problems for us as well as sending photographs of our existing piping layout and fixing the problem with the most cost effective way. I would not hesitate to recommend you and your company in future.” Glenda (Cranbourne)
  • “Thanks so much for your excellent work. You are on top of the list for preferred plumber” Ana (Frankston)
  • “Thanks for all your help with the heater. I’ll definitely recommend you to my family and friends. Since I fired the heater up again it’s been working fine.” Chris (Frankston)
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