Frequently Asked Questions
What if I use a lot of hot water at night?
That’s fine. The Sunbank solar water heater is installed in such a way that you always have hot water; either as a pre-heater to your existing water heater or as a stand-alone system with a backup electric heating element installed in the Sunbank (not eligible in California). And the Sunbank tank is very well insulated. If you use a lot of hot water at night then you will use the heat stored in the Sunbank and then the backup heater will kick in for any hot water consumed in excess of the amount stored.
What happens to the temperature when I take a shower?
The Sunbank typically stays in the 100F-160F temperature range. Your Sunbank may be at 140 degrees when you take a 10 minute shower at 2 gallons per minute. That means you have used 20 gallons of hot water thus introducing 20 gallons of 60 degree ground water into your Sunbank tank. For an 80 gallon tank that means you have used 1/4 of the heat which would drop the temperature of the tank by 20 degrees (140-60 X .25) to 120F. In reality you would be using less than 2 GPM of hot water because you would mix down 140 degree water to 120 so that it doesn’t scald you. You would actually use 15% less hot water or 1.71gpm (140/120 X 2) and therefore be left with 123F in the tank. Any water temperature over ground water temperature means gas or electricity savings. And when your Sunbank is over your backup temperature set point you are not using any fossil fuel to heat that water.
What if the water gets too hot, won't it burn me?
The Sunbank should always be installed with a thermostatic mixing valve, otherwise knows as an anti-scald valve. This is a common spring loaded mechanical device that automatically mixes hot water down to a set point. We recommend a set point that is comfortable for showering, typically 110F – 120F, so that you can turn on the hot water in your shower without the need to do extra mixing at the tap. Other than the obvious benefit of not being burned, the mixing valve also saves hot water. If you have 140 degree water in your Sunbank, for example, and are mixing it down to 120, then you are using 1.71 gallons of solar heated water in order to get 2 gallons of hot water. This, in effect, extends your hot water capacity.
What is the water temperature first thing in the morning?
The Sunbank solar water heater has a very well insulated tank. When sized correctly (you have enough storage and solar production to roughly match your consumption), the Sunbank typically stays in the 100F-160F temperature range. If you go to sleep when the tank is 140F and it is 70F ambient air temperature, you will have roughy 130F water temperature the next morning. In the winter, if it is 30F overnight you may lose roughly 20F. Any water temperature over ground water temperature means gas or electricity savings. And when your Sunbank is over your backup temperature set point you are not using any fossil fuel to heat that water.
How do I keep it from freezing in the winter?
The Sunbank collector and tank are both protected from freezing by their insulation. The tank has 55mm of high density polyurethane insulation. The collector tubes each have a heat pipe which contain a small bit of anti-freeze solution in it. That, combined with the fact that the tubes are evacuated means they are freeze protected to -35° below zero.
External plumbing is the most vulnerable point for freezing. The first point here is that we recommend PEX tubing instead of copper as PEX tubing does not burst when frozen. Your PEX must be well insulated and for prolonged freezing temperatures should include thermostatic heat tape in the insulation bundle or a re-circulation pump with a timer set to run for 5 minutes during the night in the winter. The added benefit of the re-circulation pump is that you can also use it to deliver hot water instantly your shower. In the case of a power outage where these freeze protections fail, we recommend a freeze protection valve be installed as a last line of defense.
Why not 100% solar?
Solar water heaters, when designed correctly, produce an average of 75% of the necessary hot water per year in a 4 season climate. The correctly sized solar water heater will handle 100% of your water needs in the summer but less during the winter. If you wanted a solar water heater that provided 100% of your heating capacity year round in a 4 season climate, you would have to install a system that could provide 100% of your hot water in the winter. This is not a cost efficient strategy as you would have excess heat capacity in the summer.
A year round 95% solar solution is possible in places that do not experience a significant winter, like Florida, parts of the South, the Southwest, coastal California, etc. Even so, we recommend that the system be installed with a controller and auxiliary heater for those times when there is excess demand and/or a long period of rainy weather.
Can I use this with a tankless or on demand water heater?
Absolutely! That is a very efficient installation scenario because you avoid the standby losses of a conventional tank water heater. Most all modern tankless water heaters accept pre-heated water, or are “solar ready,” but check with the manufacturer before installation so that it doesn’t void your tankless water heater warranty. They can be sensitive systems, and sometimes manufacturers will want to make sure your water is not too hard, also, in order to honor their warranty.
It’s worth mentioning that when comparing a tankless system to a solar water heater, from an economical perspective there is almost no comparison. Tankless water heaters are relatively expensive to install, so while they may cost the same as a solar water heater they still burn gas or consume electricity and are 75% less efficient than a solar water heater.
What are the criteria to place one at my house?
The only thing you truly need is a place to put the Sunbank. Roof mount or ground mount, with a ground mount often being preferable as it will usually make the installation easier, avoid roof penetrations and shorten the plumbing run. Preferable you would have a at least 4 hours of direct sunglight per day and a relatively simple chase to your existing plumbing or existing water heater if pre-heating.
Will it work on a cloudy day?
The Sunbank works even on cloudy days. The only days that you will not get solar gain are those in which the sky is black and it is either raining or snowing all day.
Can I paint it?
You can paint the it any color under the sun. As long as the tubes don’t get painted the Sunbank will work fine.
Is there any maintenance needed?
The only maintenance needed is the replacement of the Magnesium anode which, depending on you water quality, is every 3-5 years.
Can I heat my pool with it?
The Sunbank is designed to heat a relatively small volume of water from ground water temperature to well over 120 degrees. There is a different technology designed to heat pools which heats a large volume of water only a few degree. This technology is “lower tech” than the Sunbank, not able to heat domestic water, and thus less expensive per BTU than a solar water heater. Feel free to contact us and we can tell you more about solar pool heaters.
Will I have to worry about snow sticking to it and piling up?
In normal conditions you will not have to worry about snow on your Sunbank. There are spaces between the tubes for snow to fall between and if snow does stick to the curved surface then it will quickly melt or evaporate off.
Would I have to cut down trees to put one in?
It is optimal to have at least 6 hours of full sun per day or more, but the Sunbank will still make valuable heat in indirect sun and if it only has direct sunlight for, say, 4 hours. Any solar energy you absorb is free and contributes to your savings.
Give us a call!
(888) 385 0005
2020 5th St #1713
Davis, CA 95616
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80 Gallon Solar Water Heater $3,999 ($2,959 after tax credit)