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7 Important Things You Need to Know After Installing a Solar Water Heater

In our previous articles in this series of ‘solar water heating,’ we discussed: 

In today’s article, we will talk about the ins and outs of solar water heating systems after you have installed your system. To ensure that your system works perfectly, you need to keep yourself abreast of the following: 

  • How does a solar water heater work?
  • How hot can solar water heater supply water?
  • How to regulate a solar water heater?
  • How come my solar water heater is not hot?
  • Does a solar water heater work in the winter?
  • How to stop solar hot water from overheating?
  • How to increase the lifespan of your water heater?

And so forth. 

Let’s discuss each one by one. 

How does a solar water heater work? 

Solar water heaters absorb solar radiation and transfer that heat to water. A solar water heating system is composed of a solar collector, a storage tank, an anti-freeze fluid, and a heat exchanger. Some systems may not need anti-freeze liquid or heat exchangers, but systems in colder regions always have them. 

The sunlight falls on solar collectors, which directly heat water or the fluid. If it is water, it is sent to the tank and from there to the plumbing system. If there is fluid in the solar collector, it is passed through the heat exchangers. The heat exchanger transfers the heat from the fluid to the water. And voila, you get hot water! 

How hot can solar water heater supply water?

Solar water heaters can supply hot water between 90°C (194°F) and 110°C (221°F). In the US, the systems are commonly set to heat water between 60°C (140°F) to 70°C (158°F). But the configurations of systems may vary, depending upon the type of heater, manufacturer, the storage tank’s material, etc. But even if the temperature is 60-70°C, it is still more than what we need for regular use, such as bathing and dishwashing. 

To make it suitable for regular use, a tempering valve is installed in the system, which mixes cold water with hot water. 

How to regulate a solar hot water heater?

Solar water heaters come with their own control system, especially if it is a direct system that requires a small electric pump for the circulation of water and working fluid. The control system consists of a thermostat and two temperature sensors—one installed at the outlet of the solar collector and another at the bottom of the storage tank. There is also another circuit that is used for starting the pump when the collector is hotter than the storage tank and vice versa. 

Most systems are calibrated for an ideal temperature. But if you need to change the temperature, you can control the temperature from the thermostat that comes with the system. If you cannot locate the thermostat, contact your installer or manufacturer. 

How come my solar water heater is not hot?

If your solar thermal is not heating water, this could be due to two reasons: 

  1. You have set the temperature too low on the thermostat. 
  2. There is something wrong with the control system. 

The issue with the thermostat is simple. Increase the temperature and wait until it heats the water. If the issue still persists, change the thermostat. 

Control systems, as discussed above, come with temperature sensors and another circuit that regulate the flow of water (or fluid) across your system. If there is a fault in either of the sensors, the water will be returned either too cold or too hot. 

If the sensor at the storage tank has fallen off or is malfunctioning, the solar collector will continue to send water down to the storage. But this will be cold water—since the flow is continuous, the solar collector cannot heat it. To ensure that the sensors work properly, inspect them and fasten them with a lug or a stainless steel clamp. If there is still an issue, replace the sensors. We recommend contacting a professional installer to pinpoint the exact cause of your thermal system not heating water. 

How to stop solar hot water from overheating?

Solar water heaters may overheat during the summer when the sunlight is plenty, but the hot water is not needed much. Overheating may also occur due to an issue in the control system. Most solar water heating systems come with a fail-safe overheating protection mechanism. But the system may still malfunction when there is something wrong with a component. For instance, the system may overheat when the temperature sensors at the collector or storage tanks give the wrong signals to the pump. Inspect your system yourself or through a professional—if the issue is in the mains or the control system, certain parts may need replacement or repair. 

Adjusting the thermostat’s temperature can also prevent your system from overheating. Another simple and effective strategy to tackle the overheating problem is to cover your solar collector. As shown in this video, you only need to buy a shadow net the size of your solar collector. After you cover your collector with the net, you would reduce the solar radiation performance by 40%; hence, the overheating won’t occur anymore. 

Does a solar hot water heater work in the winter?

Yes, all types of solar water heaters work in winter. But if you live in a colder region, where the temperature drops below the freezing point, you may need a different system than you would in a relatively warmer region. Indirect active systems are reported to work best in colder climates. 

Since water freezes at night, these systems do not use water but a non-freezing liquid (usually glycol). Systems that use fluid instead of water also feature heat exchangers. The fluid is heated in the solar collector. It then travels back to the storage, where heat exchangers transfer the heat to water. That said, the performance of solar water heaters may drop in winter. It is better to install a conventional water heater for emergency needs. 

How can I increase the lifespan of my solar water heater?

Solar water heaters are designed to last for 10-25 years. This lifespan depends on a few factors, such as the type of the system, the quality of materials used, workmanship, and the climate. Systems installed in hot climates typically last more than systems in colder and snowy climates. But with proper maintenance, you can help your system last longer. 

To ensure your system has a longer lifespan, follow these simple tips: 

  • Check the system regularly for leakage. If there are leakages in your water heater, it can affect the performance and lifespan of your system. 
  • Regularly clean the exterior of your solar collector and storage tank. Over time, the dirt and debris can accumulate over your solar collectors and tank, which can cause long-term damage to the performance and lifespan of your solar water heating system. 
  • Flush out your system once a year. This helps in removing any sediment accumulated in your storage tank over time. 
  • Perform a regular audit of the control system of your solar water heater. Make sure that all the temperature sensors, valves, and circuits are working perfectly. 
  • If your system uses glycol, make sure to replace it in time. The replacement schedule may vary from manufacturer to manufacturer, but whatever the recommended replacement schedule is, try to stick to it. If your system relies on overused fluid, it is bound to affect the performance of your solar water heater.  
  • Check regularly all the insulation covering pipes, ducts, and wiring. If they are damaged, replace them.

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