FAQ About Solar Hot Water Heating

Solar power solutions for smart people

Solar Hot Water Heating - Frequently Asked Questions

If you have any questions regarding solar hot water heating or solar photo-voltaic energy then please don't hesitate to ask. You may find the answers in our frequently asked questions below.

Question: Are solar water heaters and photo-voltaic systems a viable alternative to gas or electricity?

Yes. Our Solar systems can be used all year round in all regions of New Zealand. Systems can be designed to provide all of your hot water and electricity needs on clear or intermittently overcast days. If it is particularly overcast or raining, electric or gas can automatically backup your system as required.

Question: How long will it take to recoup my investment?

The NZ Solar Water Heaters are affordable hot water heaters. For a household of 4, the price of a full system may not be too much more than an electric or gas system. Depending on you location (solar activity) and current hot water usage the annual electricity or gas saving will differ. Depending on your hot water usage we estimate that, on average, it will take three to five years in savings to pay back the initial investment. From then on it is all profit, like having a pay rise.

An NZ Solar hot water collector should provide reliable operation for at least 15 to 20 years. You will definitely make considerable savings during the life of the solar hot water heater.

NZ Solar photo-voltaic systems come with a warranty that they will still produce 80% of the output in 25 years time.

Question: Can NZ Solar Water Heaters be used in cold conditions?

Yes. The Normal heat tubes and SHCMV tubes solar water heater and solar collectors can be used in temperatures as low as -40deg Celsius, although performance is reduced in such extreme conditions. Good heat output is still achieved in mild sub-zero conditions.

Question: Will Water be heated on a cloudy day?

Yes. Although the efficiency of the solar collector is reduced on overcast days it will still be able to heat water for normal use. If it is a heavily clouded day or raining, then gas or electric backup may be required to maintain water at the required temperature. This system will be automated so you don't have to worry about running out of hot water on a rainy day.

Question: Can I use a solar collector with my existing hot water system?

Normally yes.

Question: Can the Vacuum Tube Solar Heater be mounted on a flat surface?

Yes. Vacuum tube solar water heaters and solar collectors can be mounted on a flat roof or on the ground by using a stainless steel A frame, or by adding extra tubes to account for the lack of angle to the sun.

Question: How do I protect my solar system during subzero temperatures?

If you have a system that is operating in areas with subzero temperatures then freeze protection must be considered. The easiest means of preventing freezing is to use a controller with a low temperatures setting, therefore when the manifold temperature drops below a certain defined temperature (5degrees C), the pump will circulate. The pump will not have to run continually, just periodically, the frequency of which will depend on the outside temperature.

Question: Who installs NZ Solar water heating systems?

Registered craftsmen plumbers who guarantee their work install all NZ Solar systems.

Question: Can NZ Solar systems be fitted to an existing house/building?

Yes, see the specifications page for unit sizes.

Question: What happens if I go away for a period?

The system will continue automatically.

Question: What maintenance of the solar water heater and solar collector is required?

Under normal circumstances no maintenance of the system is required. Due to the shape of the tubes regular rainfall and wind should keep the tubes clean. Should a tube become broken it should be replaced. This, however, is an inexpensive and easy job. Any "handy" person can install a new tube. Normal heat tube and SHCMV tube solar water heaters and solar collectors can operate with several broken tubes.

Question: Can NZ Solar Water Heaters and Solar Collectors be used for a large-scale hot water production?

Definitely. Solar water heaters and solar collectors can be connected in series to provide large scale hot water production for commercial settings such as a school, hotel, office building etc. There is really no limit to the size of the system!

Question: How will I know if the water is being heated?

NZ Solar systems have a microcomputer with a digital readout, which gives the owner total control and ongoing information about water temperature.

Question: Can the solar water heater heat water to a high enough temperature?

Yes, the system can be designed to give you an average output temperature as high as 60-85deg C (140 - 185deg F). If you consider that when having a shower the water temperature is usually around 32-43deg C (90-110deg F), and scalding can occur at 54deg C (130deg F), this temperature output is more than sufficient. In fact in New Zealand we have to fit a thermostatic tempering valve to your house plumbing to conform to government health and safety regulations. This valve will temper water down to 55deg C.

Question: What happens if one of the tubes is broken?

The vacuum tubes can be replaced very easily. They are also fairly inexpensive. Your local distributor will stock spare tubes. The system can operate with several broken tubes, but the efficiency will be reduced, so it is recommended that broken tubes be replaced immediately.

Question: Are Vacuum Tube Collectors more efficient than flat panel collectors?

On average, yes. Vacuum tube collectors are superior to flat panel collectors in a number of ways.

  1. Due to the cylindrical shape of the vacuum tube, the sun is perpendicular to the surface of the glass for most of the day. Flat panel collectors have the disadvantage that the sun is only perpendicular to the collector at noon and thus a proportion of the sunlight striking the surface of the collector is likely to be reflected.
  2. As the name suggests, air is evacuated from the vacuum tube to form a vacuum. This greatly reduces conductive and convective heat loss from the interior of the tube. As a result wind and cold temperatures have minimal effect on the efficiency of the evacuated tube collector.
  3. NZ Solar Vacuum tube collectors can often be used in subzero temperatures without the system sustaining damage. Flat systems often require expensive and complicated "antifreeze" systems to be installed.
  4. Vacuum Tubes are strong, long lasting, and should one be broken, inexpensive and easy to replace.
  5. Due to the high efficiency absorption of solar radiation even during overcast conditions, combined with excellent insulation properties of the tube, vacuum tube collectors will heat water all year round (automatic backup may required for particularly overcast or rainy weather).
  6. Due to the various advantages of vacuum tube collector over flat panel collectors, a smaller collector can be used to provide the same heating performance. For example, a standard household of 4-5 people would usually require a 250-300L water storage tank. Depending on your location, only 2.1 - 2.8 square metres of evacuated tube surface area would be required to efficiently heat this volume of water.
  7. Flat panel solar collector can produce similar heat output to vacuum tube collector, but generally only during warm, still, sunny conditions. When averaged over an entire year, vacuum tube collector heat output per net m2 of collector area is superior to flat panel.

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