Frequently Asked Questions

1) What is the overheat protection for my solar system?

A drainback system uses a controller with temperature sensors to monitor the performance of the solar hot water system. When the tank reaches a pre-set temperature limit, the pump turns off and the heat transfer fluid (usually water) drains out of the collector into the drainback reservoir. By removing the solar fluid from the collector, there is no danger of overheating.

Pressurized Glycol systems use a variety of techniques to try and mitigate the damage caused by overheating; including pressure relieve valves, expansion tanks, and heat dumps. All of these strategies present challenges in the operation and maintenance of the solar hot water system; therefore if you elect to use a pressurized glycol be sure your solar contractor provides a written plan for operation and maintenance including the strategy for overheat protection.

2) What is the freeze protection for my system?

Drainback systems use the same strategy for freeze and overheat protection, a controller. If the temperature sensor at the collector is not approximately 8 degrees warmer than the tank sensor, the pump does not come on, which means no solar fluid will be in the collector during freezing temperatures.

When a glycol system is used, the concentration of glycol in the heat transfer fluid has to be carefully calculated to ensure it is high enough to survive the coldest possible temperature for that environment.

3) What prevents my system from scaling or clogging inside the collector due to hard water?

Both drainback and pressurized glycol configurations are indirect or closed loop systems, which means there is a heat exchanger between the potable water and the solar fluid. All closed loop systems prevent new water or air from entering the collector, limiting the potential volume of minerals available to contribute to scaling to a very small concentration. These heat exchangers need to be large enough to provide sufficient heat exchange area otherwise the potable side of the heat exchanger can become scaled.

4) What is the maintenance required on my system?

A drainback system requires no maintenance beyond that of a regular water heater. Once or twice a year a garden hose is attached to the water heater to flush the scale from the bottom of the tank.

On a glycol system, the pH of the glycol should be checked annually and replaced along with the expansion tank when the pH falls below 7. There are several other components in the system that require inspection and testing to ensure optimal performance including pressure relief valves, check valves, and automatic air vents. Ensure your solar contractor provides a written maintenance plan or purchase a service contract if offered.

5) If I go on vacation, do I need to remember to do something to my system?

With a drainback system, there is no need for a vacation mode.

With a gylcol system, the controller needs to be set to vacation mode or the vacation by-pass valve needs to be opened; depending on the overheat strategy used by the solar contractor.

6) Are there problematic components in my system that may fail and require a service call?

The only component prone to failure in the solar loop of a drainback system is a pump. The pump typically requires replacement every 7-10 years.

There are multiple components in the solar loop of pressurized glycol systems that are prone to failure: air vent, pressure gauge, pressure relief valve, check valve, and an expansion tank. These components have a short design life and need to be replaced frequently during the 30-50 year design life of a solar hot water system.

7) If a component fails, can it be detrimental to my solar system?

With a drainback system, if a component fails, the solar fluid (approximately 5-6 gallons) will simply drain back into the reservoir. If the system uses an eagle sun controller it can only fail in the off position and therefore prevents damage to the rest of the system.

On a glycol system, if a pump fails the glycol will overheat causing the expansion tank and pressure relief valve to be compromised and both components will need to be replaced. If not corrected immediately, the glycol will continue to acidify eventually compromising the other components in the system including piping and collectors.

8) If a component fails, while under warranty, will the service call and labor be covered by the warranty? If not, will I have to pay?

In addition to the standard manufacturers warranty for parts only on all EagleSun systems, you may purchase an optional extended parts and labor warranty for an additional charge. The extended warrany is provided by Service Net and covers both parts and labor for 5 years. This benefits both the installer as well as the homeowner and must be purchased with the equipment package. Please contact your Dealer for more information and ask for additional coverage on your system.

9) What is the system design life?

An EagleSun System is designed to last 30 - 50 years.


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An EagleSun Solar Hot Water System uses heat from the sun to provide a clean, renewable energy source that will supply comfortable, reliable, hot water... without the financial or environmental costs of traditional water heating.

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