Solar flat panel piped correctly?

[Rowan1982]

Hi all, I'm a solar rookie in South Africa where we get a lot of sun.
Where we are renting there's an old flat panel solar geyser. Interested to know if its been piped correctly? From the brief research I've done it may not have been and could be piped the wrong way round with the hot going into the cold side of the geyser?
We appear to be getting some hot water from the solar but possibly not as efficient as it could be?
Any advice greatly appreciated. Thanks so much pics attached

[azdave]

Seems like the "cold" line leaving the tank (4th photo) should go to the bottom of the collector.

[Ampster]

My only comment is that the transition through the roof is relying on caulking instead of flashing to water proof where the pipes enter the house. Expansion and contraction will work that seam loose and may creat a leak. I would have insulated the hot water pipe as well.

[J.P.M.]

You have what's called a thermosiphon system. They operate on the idea that warm(er) water (or perhaps water/glycol in this case) is less dense than cold(er) fluid. When the fluid is heated in the flat plate, it becomes less dense and rises against gravity through the collector and back to the storage tank.

This may be a direct or an indirect type system.

In an indirect system, the heated fluid may go through some piping/tubing arrangement in the tank that keeps the (non freezing) working fluid - usually glycol/water - separate from the potable water that also acts as a heat exchanger (HX) that transfers the heat from the circulating fluid to the potable water in the tank. Those are generically called "indirect" systems.

It's also possible to have a system where the potable water circulates directly through the collector without a HX and without a separate working fluid. Those type systems are generically called "direct" systems. Direct systems are easier to build and maintain but one freezing event can wreck the system.

The thermosiphon principle generally and usually works well with either type system and eliminates the need for a pump.

If used in a climate where freezing is even a remote/rare occurrence, an indirect system is often/usually used to avoid failures from burst piping due to freezing water that will occur with direct type systems. There are other ways to avoid freezing, but indirect systems are the most reliable way to avoid freezing problems and failures.

Looks like the co. that marketed/sold the system is still around but their info on thermosiphon systems doesn't allow me to determine if their thermosiphon systems are direct or indirect. The product blurbs such as they are don't mention a tank HX, or anything about closed loop. Hard for me to tell if this system has a HX or not. If I had to guess, I'd say it doesn't, but stress that's no more than a guess.

Either way, direct or indirect, while the system as it is currently configured will work, it looks to me like it's plumbed backwards or at least less than optimally.

Whether direct (where potable water circulates directly thorough the collector) or indirect (where a secondary and non freezing fluid circulates through the collector and to a HX inside the tank), and also assuming the tank connection labeled "To Panel Cold Side" is correct, that connection should be plumbed from the tank connection labeled " To Panel Cold Side" to the lower left (NE) corner of the collector when looking at the collector from the north looking toward the south pole - that is, plumbed all the way to the lowest elevation of the collector.

The line with the heated working fluid, whatever it is, (that is, the collector outlet or return line to the tank) should then run from the upper right (SW) corner of the collector to the tank at a connection that goes either into the internal heat exchanger (if present), or if a direct system, directly into the tank. Either way, that connection should be as high on the tank as possible.

The outlet from the tank should be as low an elevation on the tank as possible. The return to the tank should be at as high an elevation on the tank as possible. Doing it that way will help thermal stratification in the tank and improve thermal efficiency a bit.

The collector inlet and outlets should be on opposite sides of the collector to help with flow distribution of the fluid through the collector. That will improve efficiency and help avoid/keep hot spots from maldistribution of flow to a minimum.

In the meantime, Ampster makes sound comment with respect the roof sealing and penetrations as well as the lack of insulation. Whoever installed that job ought to first learn to read instructions and then be castrated with a dull butter knife and no anesthetic for the barn job. Insulate the lines with ~ 2.5 cm thickness of closed cell foam. The stuff works great but it quickly degrades in sunlight. To avoid that degradation, wrap the insulation with aluminum tape - NOTE: NOT duct tape.

One more point: Even though it's usually not good idea on thermosiphon systems, partly because they're not needed, somebody that did a barn job on the plumbing and piping logic may know just enough to be dangerous and put a check valve in the system. If they did and the system is functioning poorly, that may be one reason why. Thermosiphon systems work on a very low pressure drop. Commonly available check valves usually need a relatively large opening pressure compared to thermosiphon line/flow pressure drops and so may slow flow appreciably or stop it altogether. Also, if the plumbing is reversed/corrected as described above and there is a check valve in the system and its direction is not reversed, the system will not work at all. If the system is corrected, make sure a check valve is not present.

Read up on thermosiphon systems to make all the above spoor more clear.

Good luck.

Welcome to the neighborhood.