How to Turn a Solar Hot Water System On & Off

Solar Hot Water

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Solar hot water systems give homeowners the convenience of a water heating system and the efficiency of solar technology. However, hot water systems, by design, consume energy even when not in use, so there may be times when you want to turn it off for a period of time.

To turn a solar hot water system on, you need to plug it in, turn on the water supply, open all taps to remove air from the system and turn on the system itself, as well as the booster, if you have one. To turn it off, simply turn off and unplug the system, turn off the booster and switch the water supply.

In this article, we’ll be looking at the steps to safely turn your solar hot water system on and off and why you’d need to. To learn everything you need to know about turning solar hot water systems on and off, continue reading for our comprehensive guide. 

Can I Turn My Solar Hot Water System On and Off?

Yes, you can turn your solar hot water system on and off. Modern solar hot water heaters have a shut-down switch that allows the system to shut down automatically for safety purposes. You can also manually shut your solar hot water system down for maintenance or if you are going away.

Although you can turn your hot water system on and off as required, it’s always best to call your technician, installer, or manufacturer to clarify when your solar hot water system should be turned off, for what reasons, and for how long. That’s because damage from untrained maintenance is one of the most common problems with solar hot water systems.

Inside your solar hot water system, the liquid is circulated by a small pump within a loop connected to the solar collectors and the storage tank, usually consisting of 50% water and 50% Food Safe Propylene Glycol Antifreeze Mixture. Whenever the storage tank reaches maximum temperature, the pump turns off to prevent overheating and related damages (such as a rupture) to the tank.

Whenever the pump turns off, the solar collectors on the roof overheat, causing the Antifreeze Mixture to boil. The loop contains a separate tank known as the ‘expansion tank’ to take the extra volume from boiling the mixture. However, it also turns the mixture quite acidic, which isn’t good for the solar water heater’s components. Although a few times a year will not cause much impact, the storage tank and solar collectors will be damaged long-term, consequently requiring more antifreeze charges.

Some solar hot water systems have a ‘vacation mode’, which allows the small circulation pump to continue running at night, which helps the collector lose excess heat so that it does not overheat the next day. That said, it isn’t advisable to turn off your solar hot water unit without any real cause for concern.

How to Turn on a Solar Hot Water System

Unlike conventional or older kinds of water heating systems, there are varying levels of complexity involved in turning on a solar hot water system, regardless of its specific type and power source (electric or gas). As such, it is highly recommended to have these steps done by a professional. 

To turn off your solar hot water system, follow these steps: 

  1. Turn on the Water Supply – Look for the cold water inlet control valve. If your solar hot water system’s storage tank is located at the ground level, you can usually find this underneath the water heater. Twist the valve to open it (usually counterclockwise). The valve is usually right next to the storage tank for systems with a tank mounted on the roof.
  1. Remove Air From the System – Similar to conventional hot water systems, turning on all of the hot water taps inside the house is essential. After you’ve done this, locate the cold water isolation valve and fully open it, allowing all taps to flow until water freely comes out (this would mean that all remaining air has been expelled).
  1. Plug the Solar Control Unit – Split solar systems are equipped with a circulating pump responsible for moving water up into the solar collectors on the roof. Regardless of whether the hot water system is being boosted by electric or gas power for the cylinder, the solar control unit will have to be either turned on or plugged into the power source, which is usually the power point next to the storage tank.
  1. Turn on the Booster

a. Gas – Check and ensure the gas supply valve is kept on. Houses with Liquefied Petroleum Gas (LPG) will also have to ensure that the bottle that supplies the gas itself is turned on. A continuous flow water heater is usually paired with modern gas-boosted solar hot water systems and is mounted on the wall near the storage tank or onto the storage tank itself. These will require the gas system’s power supply to be turned on before ignition can occur.

Some ground solar hot water systems are still equipped with conventional-style pilot light gas booster storage tanks. These kinds of solar hot water systems are ignited differently. But in essence, after doing all the previous steps, you can ignite it by pressing down on both the pilot button and the piezo ignitor button repeatedly.

b. Electric – These solar water heaters are equipped with a gas booster or an electrical booster element. Whichever the power source is, the booster will have to be activated. For electrical boosters with a power supply that is turned on 24 hours a day, a switch can be found inside the house that usually has an indicator light.

How to Turn off a Solar Hot Water System 

Due to the sensitivity of solar technology components, expert assistance is usually needed when turning off a solar hot water system to ensure that the system isn’t damaged. 

Below are the steps to turn off the solar hot water system:

  1. Remove the Solar Control Unit’s Plug – Like most appliances, removing the plug is the first step to making sure that it stays off for the rest of the process, so pull out the one from the solar control unit.
  1. Turn off the Booster – Next, turn off the booster element, whether it’s a gas or electric, solar hot water system. A switch with a built-in indicator will have to be located for electric types. On the other hand, gas units should have their gas supply valves closed off.
  1. Switch off the Water Supply – This step is not necessarily required and only really important when you’ll be leaving the house for an extended period, in which case you should turn off the water supply. If you won’t be away for that long.

When Should I Turn My Solar Hot Water System Off? 

The main scenarios when you would need to turn off your solar hot water system are when you’re going away on holiday for an extended period. You can also turn off the system if you’re getting the unit repaired or serviced. However, your solar specialist will usually do that themselves. 

How Do I Turn off a Solar Hot Water System Booster Switch?

To turn off your solar hot water booster, you can use the manual shut-off button or switch found on the unit. If there is no button or switch, or you cannot find it, you can also turn it off at the fuse box. However, if you have concerns about your booster switch, it’s best to consult a professional first.

Here at JFK Electrical, we understand that solar systems are as delicate as they are complicated. That’s why we are always happy to speak to you if you have any questions about your system and visit your home if you have any issues. Working with trained professionals like our team helps you increase how long your solar hot water system lasts. Contact us today to speak to one of our friendly team or to book an appointment. 

Where Is the Thermostat on a Solar Hot Water System? 

The thermostat is located on the solar hot water controller, which is an additional unit that can be installed alongside your solar hot water system. Some solar hot water systems have thermostats as part of the unit, and they can be located by consulting the provided documentation or speaking with your installer. 

Can I Turn My Solar Hot Water System on and off Remotely? 

No, turning off a solar hot water system requires a hands-on approach and should be done in a specific order. This is also why it is not recommended to do this without expert or professional guidance.


This article is published in good faith and for general informational purposes only. JFK Electrical does not make any warranties about the ongoing completeness and reliability of this information. Always seek personalised advice on solar energy to ensure any recommendations suit your property and scenario.

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