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Solar Hot Water Controllers

If you’re installing a solar hot water system on your home, the controller is possibly one of the most daunting pieces of equipment you will need to purchase. For DIY installations and professional services alike, the solar hot water controller is one of the most complicated but critical parts of any renewable energy-powered system. 

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Thankfully, the systems of today have never been easier or cheaper to access, install, and control on and off of the utility power grid.  Here’s what you need to know about solar hot water controllers for the installation, use, and ongoing success of your solar hot water system.  

About Solar Hot Water Systems

Alright, before we get carried away with the ins and outs of your solar hot water controller, let’s look at the system as a whole to get a better idea of where each piece fits in. For those that are unfamiliar, a “solar hot water system” is an environmentally friendly way to heat your home’s water supply that generally consists of:

  • Thermal solar panels (or thermal solar collectors)
  • A heat transfer system (fluids and exchanger)
  • The water tank
  • Water pumps
  • And a system controller.

To operate, solar collectors harness the heat from the sun and transfer it to a home’s water supply through a heat exchange system. Hot water tanks may be located either adjacent to the collector on the roof, or separately in or around a home or building. 

Do you need a solar hot water controller? 

Not all solar hot water systems include a hot water controller, and passive systems (those without a physical controller) can be installed at a reduced upfront cost. In most instances, homeowners prefer to install a solar hot water controller (in an active system) for a better overall experience.  

With a controller, system pumps can be more easily controlled with a digital screen and thermostat and can incorporate boosts from other power sources.   

Other Names for Solar Hot Water Controllers

Solar hot water controllers are continuously becoming more refined and have adopted several monikers along the way. Your local provider may refer to the controller as a “solar controller,” “thermostat,” “pump controller,” “system controller,” or other names.

Alongside other smart home features, advanced solar hot water controllers may empower owners to control their system via a smartphone app, computer, tablet, and more. 

Passive vs. Active Solar Water Heating Systems

Before we move any further, it is crucial to understand the difference between passive and active solar hot water systems, as only the latter of the two includes a controller. In a passive solar hot water system, a home’s water tank is typically kept in direct sunlight, which heats the supply in preparation for use.

Passive solar systems lack the mechanics of active systems and rely on gravity to transport water in and out of the home. Conversely, active systems are usually slightly more expensive but also more efficient, as they utilize pumps to effectively deliver hot water. 

Active systems can also use environmentally-friendly anti-freeze liquid to heat a home’s water and are therefore more suitable for climates with freezing temperatures. In a passive installation, the water is more likely to freeze which can cause drastic damages to the system, home, and property at large. 

What Exactly Does a Solar Hot Water Controller Do?

Okay, so in an active solar hot water system, you might be wondering what exactly the “controller” controls? Well, depending on the make and model, most solar hot water controllers are designed to:

  • Adjust pump speed for optimal gain
  • Display and control hot water temperature
  • Analyze system performance and energy efficiency 
  • And measure exact available and potential hot water quantities

In a product purchase, you typically get what you pay for with a solar hot water controller. While some low-use homeowners may not need the performance data supplied by advanced systems, large building and high-demand business owners (such as laundromats, food service, etc.) will likely want to find a premium solar hot water control system. 

How to Use a Solar Hot Water Controller 

Not surprisingly, every solar hot water controller will be slightly different. However, systems are almost always built to be user-friendly, with nothing more than a few buttons and a display screen to control your home’s hot water supply. 

If you have any questions about how to operate a specific solar hot water controller, we recommend contacting the manufacturer for any information that cannot be found within the included purchase materials. Below, we will outline some of the most common features of solar hot water controllers to showcase how to efficiently manage your system. 

Adjusting the Thermostat

In advanced, user-friendly systems, adjusting the thermostat of a solar hot water controller is essentially the same as adjusting the ambient temperature of your home. Simply locate the display screen to find the current and set water temperatures, adjusting accordingly via the knobs, buttons, or other control toggles.

If your solar water heating system does not feature a thermostat with a temperature display, finding the actual resting temperature of our hot water tank will require a thermometer. Simply run the hot water of a sink or tub (without activating the cold water handle) and take the temperature of the water after it has been running for about 30 seconds.  

After this, you will be able to adjust your thermostat as necessary using your solar hot water controller. Somewhat obviously, systems set to higher water temperature will have to work much harder and use up more energy than systems at, below, or near the factory standard of 49°C (120°F).  

Direct and Indirect Circulation Systems 

Within the realm of active solar hot water systems, there are two distinct types of circulation: direct and indirect.  In a direct circulation system, water is transferred directly from the collectors to the water supply just like in most passive gravity-fed installations. Here, direct circulation is mainly suitable for homes in locations where outside temperatures rarely go below freezing.

For more variable climate zones, indirect circulation systems are preferred for effective solar hot water control. The non-freezing transfer fluid used in an indirect system can keep a building’s water supply safe during cold temperatures, often with the assistance of a gas or electric booster alongside the heat exchanger. 

In both direct and indirect circulation systems, the solar hot water controller and thermostat are the primary pieces of equipment used to regulate the system. Indirect systems are generally a bit more expensive than direct systems, but may be the only choice for residents in cooler parts of the country. 

Gas and Electric Boosts

During the evening and throughout long bits of little sunlight, solar hot water systems can be equipped with an electric or gas boost to maintain high temperature levels for a home’s water supply. Powered by utility or onsite renewable energy, gas and electric boosts can generally be utilized directly on the solar hot water controller or by use of a separate control station. 

In general, a gas or electric boost will be installed at the same time as the collectors, but it is not uncommon for retrofits to be added to underperforming systems. The debate as to whether to choose a gas or electricity powered boost largely depends on local availability, utility pricing, property budget, and user preference. 

Troubleshooting 4 Common Solar Hot Water Controller Problems 

Like most solar energy systems, solar hot water heaters generally run problem-free for the majority of their operating lives. Solar energy is generated passively, and hot water systems are typically limited to a few moving parts that require little to no maintenance and upkeep. 

When things go wrong, however, it is good to know the cause and a solution to get your system back on track. Below we will outline some of the most common solar hot water controller troubleshooting scenarios. 

Controller Not Working 

As the worst of the worst, it is tough to see what is going wrong with your system if the controller itself is not working. While some controllers may just need a new battery, those wired into your home’s electrical may need a bit more attention if the system is unresponsive. 

If your solar hot water controller is not working properly, it may have become damaged due to a voltage surge, corrosion on system parts, or short circuiting. After double-checking to make sure that your controller is plugged in and set to the “on” position, consult the manufacturer’s included materials or customer service hotline for specific troubleshooting issues regarding your solar hot water controller. 

Circulation Pump Problems 

As its primary function, the solar hot water controller dictates the way a heating system’s circulation pump works.  The circulation pump is prone to a number of issues, including clogging and blockages from debris build-up as well as valve and part malfunctions. 

As a circulation pump ages, lower operating efficiencies identified by the controller may indicate the presence of a leak, too much air trapped inside the collector (faulty discharge valve), or another part failure. In some instances, you will be able to tighten loose valves or apply a bit of lubricant to old parts, while more serious issues will likely need the assistance of a professional plumber.    

To prevent circulation pump and controller problems, we recommend monitoring the system annually with a full inspection of the wires, pipes, and other connecting parts. So long as the system is free of damages, rust, corrosion, and breaks, your controller can largely be ignored throughout most of the year. 

Solar Input Issues

Second to the circulation pump in terms of common problems, DIY installers and licensed companies alike have experienced many issues with the amount of solar energy input in many thermal hot water systems. Although solar panels are manufactured to be tough and efficiently generate energy for decades, there are some external factors that simply cannot be controlled. 

If your controller has indicated that no solar input is present, one or more of your collectors may have become damaged. While most panels can handle weather conditions that are quite heavy, oversized hail, debris build-up, golf balls, and other foreign objects can potentially damage a panel and lower its efficiency (or completely eliminate the possibility of production). Likewise, critters such as birds and squirrels may chew on wires, hoses, or cables used in the installation. 

Before doing anything to troubleshoot your solar input issues, ensure that your system is powered off to avoid potential safety hazards. In order to avoid voiding your warranty on a solar thermal installation, systems are almost always required to have professional repairs made in the event of a damaged item.  

Not Enough Hot Water, or None at All

When a system cannot effectively heat enough water for a home, the issue may or may not be detected on your solar hot water controller. For instance, if your controller is displaying ordinary hot water conditions, but your tank has a room temperature supply, then there is likely an issue with the sensory hardware or software of the thermostat’s controller. 

If your controller is working properly and not enough hot water is being produced, then the problem will most likely be within the heat exchanger. The inability to heat water effectively may be the result of many different issues including:

  • Debris buildups, clogs, and backups in water or exchange fluid pipes
  • Leaks in the system (water or heat exchange fluid)
  • Frozen water within the system
  • Or damage to valves, pipes, joints, and electrical components thought the system

There are troubleshooting guides built into many new solar hot water controllers which can take you through a series of steps for the right solution. Always ensure that your system is turned off before performing any actual maintenance, and we strongly encourage owners to utilize professional services if they are unsure about any step of the process.

If your controller indicates that the hot water levels are rising in your tank but simply not at a fast enough rate or long enough duration, then you may have an issue with the size and quality of your system components. Solar hot water systems typically include a well-insulated tank and enough power input and boosting options to always provide homeowners with enough hot water.    

Solar Hot Water Controller FAQ

And finally, before we conclude this resource, here are a few answers to some of the most frequently asked questions about solar hot water heating and control. 

How does a solar hot water service work?

A solar hot water service works by efficiently transferring the heat of the sun to a building’s water supply. Special solar collectors are used to heat the water (or an antifreeze heat transfer fluid) on a property before sending it to the rest of the home.

How do I control the temperature of my solar water heater?

Depending on the type of system, the temperature of a solar water heater can most often be controlled by the piece of equipment known as the solar hot water controller. With a similar appearance and functionality of a traditional thermostat, it is generally very easy to control the temperature of a modern solar water heater.

Are solar hot water systems worth it?

In most instances, yes, solar hot water systems are worth it for saving money on the costs to run a home. By utilizing the free and abundant energy of the sun, solar hot water systems are able to operate free of charge, only costing users money when assisted with a gas or electric boost. In general, the higher your hot water demand is, the more “worth it” a solar hot water system will be in terms of long-term costs. 

How hot is the water from a solar water heater?

As a standard, most solar water heaters bring the temperature of a home’s water supply to a steady 49°C (120°F). At the point of use, this temperature can be adjusted alongside cold water knobs or settings. Of course, most solar water heaters allow you to adjust the standing temperature of your home’s hot water to fit the performance demands of your property. 

Can I turn off my solar hot water heater?  

Yes, for safety reasons, most solar hot water controllers come with a shut-down switch to automatically power off the entire solar hot water heating system. Turning off your hot water heater may become necessary and urgent if your system is damaged, leaking, or experiencing other problems. 

Why is my solar hot water not working?

If your solar hot water heater is not working, feel free to use our troubleshooting information featured above. Of course when in doubt, the best thing you can do to safely and efficiently get your hot water heater working again is to call a local professional. A specialty contractor may be able to diagnose and guide you through your specific issue over the phone or come by for a system repair. 

Final Thoughts 

Although you may never need to know all there is to know about solar hot water controllers, we hope that this guide has helped you understand the concepts and functionality of most modern systems. With a high-quality solar hot water controller, the power of the sun is in the palm of your hands and you may effectively run your system to perfectly fit in with your property’s solar potential and hot water demand.