Evacuated Tube Solar water heating

Evacuated Tube Solar water heating

 – for hot water and hydronic house heating.


Split systems – Ground tank models with roof collectors.

ultimate solar 40 tube


  • Maximum performance – Heat pipe has up to 50% more efficiency than a flat plate collector, and U tube has almost double
  • Works in all climates, including a wintery, overcast day
  • Easy to install – Split system provides solar heating without a storage tank on the roof
  • Instant unlimited mains pressure hot water with either gas or electric boosting
  • Long life materials, maintenance free
  • Designed to withstand extreme frost conditions, using closed loop system
30 tube Evacuated tube frame on a tile roof

30 tube Evacuated tube frame installed on a tile roof, ready for tubes.


Evacuated Glass Solar Tubes

Inside and outside tubes are made from extremely strong borosilicate glass that are fused together to form a vacuum between two tubes.

  1. Outer Tube – Allows the sun’s rays to pass through with minimal reflection
  2. Inner Tube – Special selective coating on the outside of the tube contributes the highest thermal efficiency and good thermal stability
  3. Evacuated Space – Stops heat loss / emission to outside of the glass tube, making these collectors particularly effective during cold and cloudy weather
  4. Selective Surface – Absorbs the maximum solar radiation to convert into heat efficiently
  5. Cylindrical Shape – Sun’s rays are perpendicular to the absorber for most of the day
  6. Fin – Transfers the heat to copper tube without heat loss
  7. Copper Conduction Tube – Passes the heat to the water / fluid inside the copper tube
  8. Barium Layer – Actively absorbs the air to maintain the vacuum between the two tubes


How does it work?

The sun’s rays pass through the outer tube, and perpendicularly strike the absorber surface on the outside of the inner glass tube.

The selective surface absorbs maximum solar radiation and converts it into heat very efficiently.

Because the sunlight is perpendicular to the absorber tubes almost all day, the sun’s energy is absorbed and transferred efficiently.

The insulation formed by the vacuum space between the outer and inner tubes minimises heat loss to the outside, whilst allowing the sun’s energy to reach the copper tube inside the inner glass tube.


Close-coupled roof tank models with mains pressure coil.

Red Circle evacuated tube hot water

Red Circle close-coupled evacuated tube solar hot water

Three convenient sizes:

250 litres system with 30 evacuated tubes and framekg$
200 litres system with 24 evacuated tubes and framekg$
165 litres system with 20 evacuated tubes and framekg$
Electrical boost element 2400w


  • Great for domestic and some commercial applications
  • Low pressure stainless tank with a high pressure heat exchange coil inside
  • “Wet tubes” use the sun’s energy to directly heat the water in the tubes.
  • Ideal for Wet backs/Wood Heaters
  • Eliminates unnecessary boosting
  • Flexible boosting options – fit as a preheater to existing gas or electric storage tanks, thermosiphon into a wood heater below, connect to an instantaneous gas heater, or use the optional 2.4kW in-tank element.
  • Mounting frame is best suited to metal roofs.   Can be mofified for fitting to tile roofs.
  • Suitable for high frost areas
  • 10 year manufacturers warranty on tanks frames and tubes.


How it works

  • Heat exchanger.

heat exchanger oil

The close coupled system uses a 30 mtr 14mm copper coil to transfer the heat from the low pressure storage tank to the mains pressure water used in the house. As the water enters the tank through the mains water supply line, it passes through the heat exchanger and extracts the heat instantly.

  • Low pressure storage.

Having a low pressure storage tank with high pressure heat exchange has many benefits.

No legionella risk.

Open vented to safely relieve the pressure from the water expanding due to heat.

Wood fire boosting ready.

Low manufacturing costs.

  • Wet tubes.

Red Circle Solar uses 1800 x 58mm high quality evacuated tubes with tri coating technology.  Our split system manifolds use the same evacuated tubes combined with a heat pipe. Wet tubes are directly heated by the sun and transfer the heat to the water that is in the storage tank using a thermosyphon.

  • Pitching frames.

The on roof system come with either a 15 deg or a 45 deg pitching frame.  Custom frames are available.

  • Solar powered tank filling kit.

The low pressure storage tank is kept flu using a 12 volt solar powered solenoid coupled with a stainless steel Reed switch float. If the tank water level drops due to evaporation, the float opens the solenoid and lets water enter the tank. Once the tank is full again, the float rises and shuts the solenoid, turning off the water. All powered by the sun!

  • Boosting.

Every solar hot water system needs boosting in the winter as the days are shorter and the solar radiation is less due to the sunlight passing through  more atmosphere.


Split-systems, and  retrofitting to existing tanks

Ultimate red circle solar water heater

  • For domestic and some commercial applications.
  • Evacuated tubes for use in a “Split system” where water is heated as it flows though the manifold and back to a storage tank.
  • Can be connected to a new or existing ground mounted electric storage tank.
  • Can be connected via pump or thermosiphon (where possible) to a new or existing in-roof tank.
  • “Dry tubes” use the sun’s energy to heat copper rods inside the tubes, which then transfer the heat to water through a heat exchange process.
  • Suitable for all roof types including tiles.
  • 10 year manufacturers warranty on the manifolds frames and tubes.


Three convenient sizes:

250 litres24 evacuated tubes
300 litres30 evacuated tubes
400 litres40 evacuated tubes


Ask for a free solar hot water quote at any time.