Retrofit Systems | Go-Solar

By: Hills Solar  11-11-2011
Keywords: Solar Collector

This is the first in what we intend to be a series of technical tips for solar water heating. We hope that it will be beneficial to your company. If you have any feedback we would love to hear from you in order to expand our own technical database that we can I turn pass on to others.

We have come across a few different ways in which companies are retro-fitting solar collectors to non-solar geysers. The most common of these are using a banjo valve,the Kwikot solar flange and simply teeing the return from the solar into the hot water outlet. All of these have limitations as follows:

  1. The banjo valve combines a hot water outlet with the TP valve. This allows for the hot water return from the solar collector to be connected to the normal TP valve outlet.
    1. The banjo valves are expensive.
    2. As the TP valve outlet is right at the top of the geyser,the hot water from the collector returns to the top. This results in very hot water sitting at the top of the geyser. This can result in the TP valve unnecessarily realeasing water. It also often results in the temperature of the hot water delivery at the shower being patchy.
  2. The Kwikot retrofit flange has one or two nipples inserted through the normal Kwikot flange. One of these is for the cold flow line to the solar collector and the other one for the hot return.
    1. It is a very expensive conversion bought from Kwikot.
    2. The installation is needlessly complicated and makes working on the electrical element and thermostat awkward.
    3. The danger of leaks behind the rubber gasket and through the flange is increased by the 2 extra holes.
    4. The plastic cover over the electrical box has to be cut in order to go over the pipes.
  3. Teeing out of the cold water inlet pipe to the geyser and in again at the hot water outlet pipe is very low cost and simple but results in the same problems as with the Banjo valve.

Below are some drawings of a very simple conversion that is very economical,easy to install and can be made easily or purchased from us. This enables hot water from the solar collector to be returned to the middle of the geyser,eliminating the problems outlined above. Should it be for a vertical geyser,the return pipe can be made longer and given a gentle curve to enable it to be inserted into the hot outlet and penetrate down toward the centre of the tank.

These and a number of other useful technical issues are dealt with in our one day solar water installation training course and are taken from our installation manual supplied with the course.

Keywords: Solar Collector

Other products and services from Hills Solar


Protect That Pump | Go-Solar

The pump is always installed on the flow side of the solar loop and should have a non-return valve fitted between the pump and collector. If the system is in stagnation due to a power failure or water supply problem,poor quality pumps will not withstand the resulting heat. Adhering to these guidelines and using a good quality pump with a brass housing should ensure many years of trouble free service.


Stagnation Protection | Go-Solar

Some controllers such as the SR868C8 used by Go-Solar in our solar water heaters,manages the collector temperature to try and avoid stagnation but still has an upper tank temperature limit beyond which it will shut down circulation. This results in a rumbling noise but more importantly,should the super-heated steam come directly into contact with the inner tank of the hot water cylinder,premature deterioration of the tank may occur.


Expansion Valve Discharge Pipes on Solar Water Heaters

SANS10254 calls for the discharge pipe from the Expansion Valve (EV –normally attached to the Pressure Control Valve) to be discharged to the outside of the building,to be visible and also not to be placed where the water discharge can cause a nuisance. However,with solar installations,due to the greater heat and therefore expansion variations,the fitting and positioning of these pipes require greater attention to detail.