| The primary components of a drainback-type solar | | | | is often the ideal location. For a drainback system, |
| hot water system include: | | | | the collectors need to be above the level of both |
| - Solar collectors - typically installed on the roof, the | | | | the drainback tank and storage tank. |
| solar collectors gather heat from the sun. | | | | - What type of collector should I use? There are |
| - Storage tank- residential storage tanks are generally | | | | many options out there. Sustainable Future offers |
| 65-120 gallons, depending upon the number of people | | | | two types, flat plate collectors manufactured by AET |
| in the household. Hot water flows from here to the | | | | and evacuated tubes manufactured by Sunda. For |
| fixtures in your home or business. | | | | some people, it's an aesthetic decision. Flat plate |
| - Drainback tank- this small tank provides freeze | | | | collectors look more like skylights if they are |
| protection, and holds the liquids that circulate through | | | | flush-mounted. You'll need slightly less surface area if |
| the solar loop when the pump is off. | | | | you use the evacuated tubes. For residential |
| - System Controller- The system controller is a small, | | | | systems, the cost of using one versus another is |
| sophisticated computer. This computer is attached to | | | | very similar. |
| temperature sensors on the roof and in the storage | | | | - Do the collectors need to be tilted at an angle? |
| tank, as well as the circulating pump. When the | | | | Ideally, yes. However, if you prefer the look of |
| collectors are warmer than the storage tank, the | | | | flush-mounted collectors, this can be done with a |
| controller switches the system on. | | | | small decrease in the efficiency of the collectors. If |
| - Circulating Pump- The circulating pump runs the solar | | | | efficiency is of primary importance, we suggest tilting |
| loop. Water circulates through the collectors on the | | | | the collectors approximately 10 degrees more than |
| roof and gets hot. From here, the water flows down | | | | your latitude (for customers in the northern |
| to a heat exchanger where it heats the water in | | | | hemisphere). This gives a "winter bias" and makes |
| your storage tank. Cooler water then circulates back | | | | your collectors most efficient during the winter |
| up to the roof, where the cycle begins again. | | | | months when the sun is low in the sky. |
| - Flow meter- The flow meter is used to attain | | | | - What happens at night or when it's cloudy? A |
| optimum circulation, so that heat is transferred | | | | well-insulated solar hot water system will retain the |
| efficiently to your storage tank. | | | | heat in the tank overnight with no problem. If, for |
| - Pipes and Insulation- Because of the heat generated | | | | example, it's cloudy for a week in December and |
| by the solar collectors, we recommend copper pipe. | | | | you're using your hot water each day, most systems |
| PVC piping, particularly near the solar collectors, will | | | | have either a gas or electric backup to provide |
| not withstand the high temperatures generated. High | | | | supplemental heat if enough solar energy isn't |
| quality insulation surrounding the copper pipes in a | | | | available. We can also retrofit your old hot water |
| solar hot water system prevents heat loss and | | | | system. |
| makes the system more efficient. | | | | - What size storage tank do I need? This depends |
| How to choose the system that's right for you | | | | upon how much hot water you're using per day. For |
| If you're interested in a drainback-type system, you'll | | | | 3-4 people, we recommend an 80-gallon solar storage |
| want to consider the following. | | | | tank. If you have teenagers who like long showers |
| - Where should I put the collectors? If you have a | | | | or a larger family, you may need the 120-gallon tank. |
| south-facing (or near-south) roof that's unshaded, this | | | | |