These systems have two main advantages:
It's also important to consider the disadvantages:
These systems have three main advantages:
It's also important to consider the disadvantages:
With any solar-powered heating system, whether it's for the domestic hot water supply or space heating, a diversion load can be essential to safety and the system's lifespan.
Since a pressurized system has a solar loop which is completely filled with fluid (the industry standard being a mix of water and propylene glycol), it is very important to get all the air out of the system when you're setting up. This is doubly important because the solar fluid only needs to be checked every 10 or 15 years, so it's going to be in there a long time before you look at it again.
If you think a drainback solar hot water system fits your needs, you must consider a wide variety of rules, limitations and requirements, as outlined below.
The choice of collector array for drainback systems is more complicated than for a pressurized system: some evacuated tube collectors cannot be used at all (check with the manufacturer) and any collectors that use serpentine riser tubes are also ruled out.
It doesn't matter whether you're installing a huge solar thermal system to heat the water for an entire community or a small residential setup to lower your power bills: you'll need a storage tank to keep hot water in. And since the sun has an annoying tendency to be weaker in winter and disappear at night, that tank needs to be insulated to keep your water hot as long as possible.
Solar thermal installations use liquid-to-liquid heat exchangers exclusively: on one side, there's the solar fluid that travels from the collector; on the other there's the water being heated.
The pumps used in solar thermal installations come in both AC and DC models. It is important to choose a model that not only fits your electrical supply but which is also compatible with the rest of the system, in terms of construction materials.
