Roof location and Pitch
The solar vacuum tubes are to be installed in a parallel array and at an angle determined by the latitude of the installation.
For optimum performance the solar vacuum tubes need to face the equator (facing north for southern hemisphere installations). Installation on angles of up to 45 degrees away from the equator do not have a major effect on the annual solar output, consequently roof locations which face less than 45 degrees away from the equator are acceptable. Solar radiance from the sun begins at about 10:00 until about 16:00 and is at its peak between 12:00 and 14:00.
If the solar vacuum tubes are installed with an east facing bias, the best solar capture is achieved in the morning, and if the installed with west facing biased, in the afternoon.
The location should not be subject to excessive shading from trees and adjacent buildings and particularly between 9:00 and 15:00. Remember that shadows are longer in winter than in summer so a location that is free of shadows in the summer may have some shadows in winter.
The solar vacuum tubes should be installed on a roof pitch greater than 8 degrees and less than 30 degrees. Where the roof pitch is greater than 30 degrees, the installation will require additional support to prevent it from moving downwards when installing and after installing. If the roof pitch is less than 8 degrees the installation will require a mounting frame to increase the pitch to above 8 degrees. Installations below 8 degrees do not thermosyphon effectively and the solar collector panel glass will not clean properly when it rains.
If the solar water heater is installed on the roof, careful inspection must be carried out to ensure that the roof can support the weigth of the entire installation system once it is filled with water.
The solar vacuum tubes have a comprehensive 5 year warranty from date of installation and subject to the following conditions:
1. Pump Circulation in a Split System
It is not always possible or convenient to place the solar water heater in a higher position than the solar collector panels or solar vacuum tubes. A circulating pump, controlled by an electronic control unit, therefore becomes necessary. The control unit using two sensors constantly monitors the temperature of the solar collector panels or the temperature of the manifold for the vacuum tubes and the solar water heater, powering the circulation pump only when the water in the solar collector panel or manifold is hotter than the water in the solar water heater.
When the temperature difference is less than the set point during the working process of the circulating pump, the pump will stop.
When the temperature of the water in the solar water heater reaches the highest set point, the controller will stop the circulating pump.
The electrical thermostat and element will automatically maintain the water temperature of the upper part of the solar water heater.
The set temperature on the thermostat must be lower than the maximum temperature attainable on the solar collector panels or solar vacuum tubes.
The circulating pump must be installed in accordance with the manufacturers instructions and ease of access for maintenance/repair.
The split system can also be installed as a thermosyphon system, if there is sufficient roof space to locate the solar water heater above the solar collector panels or array of vacuum tubes (see installation diagram).
A 12V solar circulating pump can also be used, powered by a photovoltaic collector panel.
2. Thermosyphon Circulation in a Close Coupled and Split Systems
The compulsory requirement for a thermosyphon system is that the solar water heater is placed in a position higher than the solar collector panels or a solar vacuum tubes and circulation occurs without any moving parts or auxiliary electrical energy input to the system.
This system operates according to a basic principle of physics: a liquid, if heated, becomes less dense and rises upwards.
Heated water in the solar collector panels or heated water in the vacuum tube manifold rises up into the solar water heater and displaces cold water, which travels back down to the solar collector panels of vacuum tube manifold.
When there is no solar radiation, the water in the solar collector panels or in the vacuum tube manifold, which becomes heavy, blocks the circulation and prevents the heat accumulated in the solar water heater from being dispersed.