Having attended many of these faults recently it has come to my attention that the poor quality of work and lack of knowledge on previous faults has left some home owners with a less than adequate system.
In light of this I am sharing my knowledge of these systems so that people have a better understanding of how they should work and also the need to use competent people and quality materials if they want a safe and efficient system that will last.
I will try and keep this as non-technical as I can and the latter section explains some of the problems I have encountered.
The solar panel hot water heating system consists of the following:
Flat Plate Solar Collectors –
The collector itself which has copper pipes that run up and down the panel and then enter the hot water tank through a black rubber hose and then into an internal coil within the hot water tank and then back down again through the other black rubber hose. The water within this pipe system is totally separate from the usable water.
It works on the basis that the sun heats the glass covered collectors which in turn heats the copper pipes running through them. The hot water can then thermo-siphon itself in and out of the tank as hot water rises, thus heating the water in the top tank as it passes around the coil.
This is a sealed system with no air in it that circulates continuously from the panel to the tank and back down to the panel. When installed it would have been filled with one of the nuts located on top of the tank. To prevent cold weather expanding and fracturing the copper pipes the system requires an anti freeze additive when being filled.
Hot Water Tank –
Located on top of the solar panel the Hot Water Tank draws water in on one side and is siphoned out from the other with the long hot and cold insulated pipes which go down into the building. Both of these pipes have a cut off tap and the cold supply will have a small bleed valve. Without any electric connected at all, the coil within the tank will heat the water around it thus providing a continuous supply of hot water.
However, while the sun can provide sufficient energy to provide you with plenty of hot water for most of the year, there may be extended periods of cloudy, cold days where your system will need a helping hand. This is provided with an Electrical Booster System which is located at the end of the tank.
Electric Booster System –
The booster is like a mini immersion heater which when the water in the tank falls below the set temperature will turn on and top up the hot water. The element has a dial which can be turned up or down depending on how hot you want your water. This should only be accessed by a competent person as there are live terminals in there. The booster system is wired directly into the fuse board of the house and you will be unaware of when it is using electric or not.
Tempering Valve –
The tempering valve is located on the immersion Water Heater in the kitchen. This adjustable 3 way valve mixes the hot and cold water so that it provides safe temperature and draws from the water tank or Water Heater.
Typical Problems identified on this site –
Having recently attended a large number of these I have found that the main problems are:
1. The flexible hoses connecting the panel to the coil within the tank have deteriorated and cracked. This will cause a leak from the coil system through the cracks and due to the lack of liquid in the system it will prevent the water from rising from the panel into the tank. This will result in the booster system kicking in all the time trying to heat all the water in the tank and run up some very high electric bills.
If you visually look at the pipes from below and you can see any staining then they need further investigation. If the system is working correctly you should be able to feel the black hoses and the one of the right should be very hot and the one on the left should be cooler as it returns to the panel.
2. Poor quality insulation on the water pipes will result in the pipe itself deteriorating in the sun and bursting. I have attended some which have only been replaced within months and are ready for replacing again. Some insulation which are covered in aluminium tape actually bake the insulation within until it dries out and disintegrates. The jobs I have done use a heavy duty product called Solarflex which has a white thick breathable membrane on the out. This is a more expensive option but has prove to withstand the extreme temperatures in Spain.
3. The electric booster not kicking in so the tank will only provide moderate hot water on cloudy days. This booster has a reset button on the thermostat which can isolate it and stop it from working. You need to have a competent person test the electrical supply for the fault which tripped the reset button first.
This list is not exhaustive but after 5 years of operation is very typical. I will also point out that these views and observations mentioned here are my own and I am sure will attract some comments from people who have already worked on these.
In anticipation of any grumbles I would say to people that if they have concerns about the system I am willing to explain my understanding completely free of charge. If you want to speak to some of the people who have had their electric bills reduced I could also arrange this so that you can make judgement for yourself.
Paul (and Millie the Pug)
This message was last edited by MPF on 28/11/2012.