TANKS AND TANKLESS WATER HEATERS
Gas, Propane or Electric Tankless Water Heaters:
Tankless water heaters are a great complement to
solar water heaters!
Be sure the Tankless unit has a “Modulation” feature to vary the flame or electric input depending on the temperature the solar water heating system is supplying.
Tankless systems rely on a great force of energy being fired onto the flow of water going by. When the flow gets to high, such as when two people take a shower at once. Solar allows tankless water heaters to overcome their greatest weakness, keeping up with a high rate of flow. Usually the solar will supply water so hot the tankless doesn’t turn on at all and when it does, it turns on a lot less.
Tankless water heaters are space saving and eliminate the need for a second tank as is usually needed with gas, propane or oil heaters. When open loop systems are appropriate, your old tank, if in good condition and large enough, may make a good solar tank. The closed loop Rheem 80 EX works great with a tankless as well.
Gas, Propane, or Oil water heater tanks:
NON-FREEZE, TEMPERATE AREAS and FREEZE AREAS:
If your gas, propane, or oil water heater is in good condition, it may be a great backup tank for your solar system as a “Two-Tank” system (see two tank diagrams). In open loop systems, using a single gas, propane, or oil water heater is less efficient when heated by solar because you will cause the solar to heat already heated water.
For the greatest solar water heating efficiency you want to start the day heating the coolest water you can. Many customers have successfully used single tank gas, propane or oil water heaters by keeping the temperature setting as low as possible during fall, winter and spring and turning the fuel to pilot or just turning it off during the warmer and summer months.
Efficiency of a solar collector is measured by the difference between the collector “inlet temperature” and the outside “ambient air temperature.” The higher the temperature entering the collector, the less efficient it is. This fact is called the “First Law of Solar” which is keep it cool. In other words, you want to start the solar heating day with ground water temperature water and not with water has already been heated by other means.
A solar tank “stratifies” overnight and can have much hotter water at the top than at the bottom. For this reason, never use a water recirculation system connected to a solar tank as it “destratifies” the tank and makes it all the same temperature in the morning.
Standard Electric water heater tanks:
NON-FREEZE and TEMPERATE AREAS:
If you have an electric water heater, it is also a great backup for solar. If you are in warmer areas not subject to freeze, you can use often your standard water heater by simply disconnecting the lower element from the upper element. Because of “stratification,” (heat rises) the tank then works in effect like two tanks, the upper part as the backup, and the lower part as the solar storage.
In colder areas, with a smaller family of for less demand, simply remove your old water heater and replace it with a Rheem, (Rudd, or Richmond) Heat Exchanger tank (81V080HE1) and use the upper element for back up. My family (now with 6 members) has done this for 21 years and we turn off the upper element during the summer, running 100% off the sun for our hot water.
For larger families, or for high demand, you may want to keep your tank for the backup and the Rheem tank, feeding it with solar heated water, will keep it off most of the time.
Remember that when there are heavy clouds or snow and no solar energy is available, your tankless or other backup will need to supply all your hot water.
We hope this helps, please call or Email with any other questions!
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