Overheat Protection

Solar water heaters are very efficient and can produce very hot water. This is a good thing! The fact that they work so well is the reason that everyone who lives in the bottom half of the country with an unshaded roof should have one.

But what if they produce too much heat?

This conversation should always start with appropriately sizing the system. In a sunny climate the 40 gallon system is appropriate for households with 1-3 people and the 80 gallon system is appropriate with households of 4+. The Sunbank produces hot water, and your hot water consumption takes heat out of the system. When this is happening, the temperature in the Sunbank typically stays between 120F – 160F in the summer – going up as the sun shines, and going down as the shower is used.

160F is too hot for a shower, you say?

Correct. That’s why every Sunbank installation should include a thermostatic mixing valve. This mechanical device is sold at every major hardware store and it automatically tempers the water down to a safe temperature.

What if you’re going on vacation?

That’s why we created “vacation mode.” The Sunbank is a passive solar water heater, meaning that it has no pumps or moving parts – it simply creates hot water when the sun shines.

Evacuated tube solar collectors painted to turn off


When you remove the consumption part of the equation and don’t use any hot water, after three or four consecutive sunny days the Sunbank will get up to boiling temperature. Before it gets there, the Sunbank temperature and pressure relief valve (T/P valve) will open to allow hot water to be pushed out of the system, protecting it from overheating.

But the T/P valve is a safety device, and shouldn’t be used for regular overheating. That’s why we  recommend that people mask half of the tube vertically with masking tape and then spray paint the other half of each tube as part of their installation process. Once the masking tape is removed, this allows you to “turn off” the system by simply rotating the tubes by hand so that the painted side is facing up. When you get home you can rotate the tubes back so that the translucent side is facing up in about 30 seconds. It’s an inexpensive, low-tech, and passive solution: just how we like it.

Give us a call!

(888) 385 0005

2020 5th St #1713
Davis, CA 95616

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All Rights Reserved


Sunbank SB-80G

80 Gallon Solar Water Heater $3,999 ($2,799 after tax credit)