Brains Trust Q: best solar hot water system?

have a read through whirlpool forums:
http://forums.whirlpool.net.au/forum/143
there are many posts on this topic


personally: we have gone with a heat pump (Stiebel Eltron), which worked out cheaper than putting solar HWS on two storey house, and given the fact we have solar panels, we have "free" hot water even on days when solar HWS would not produce enough

Also keep in mind that unless there is water flowing externally of the unit, the tank itself could be in great condition. The insulation can hang out for years and mean very little in how the tank is.

Saltiest said: "Solar is really a false economy by the time you count up installation and then running costs (booster) compared to other methods."

Based on my own experience I disagree with that comment Saltiest, but it probably depends where you are, how big the tank is and how many people are using it. We're seven years into using a Rheem system with a ground level 270 ltr storage tank. Installation was straightforward because we designed it into our build - collectors are right above tank on a north-facing roof with ideal slope and no shade. They feed into the tank below, which is out of the weather and easily accessed for maintenance.

It heats up fast if we do need to use the booster, which has only been about twice each winter, maybe two hours max each time. We're in the midwest, so cloudy skies lasting long enough to need the booster are rare anyway. That's also a big tank for only two of us using it. Power bill dropped noticeably from running a 50ltr electric before we got the Rheem.


Good luck with finding a replacement GPA - sounds like you've had a pretty decent run with them. Those rooftop tanks you've had have to survive pretty harsh conditions, it amazes me they last as long as they do. I hope ours hangs in as long as your Solarhart did.

Steel tanks tend to develop multiple rusted pinholes that leak very slowly, but often the leak will come and go as the hole will fill up with rust. You can turn off the water during the night and the leaks can sometimes self heal, for a while at least.
Stainless tanks tend to develop leaks along the seam where they are welded together. You can drill a hole in the outer shell to let the water leak out in a controlled manner so it doesn't get into any controls. Check closely around the fittings to make sure the leak isn't coming from a pipe that threads into the tank.
I'm a plumber and I've never seen a tank completely burst, a small steady stream but not burst.
Heat pumps work well but they make some noise, like a very loud refrigerator or worse, so they need to be located away from living areas and often put on a timer so they don't come on in the middle of the night. Several PV panels can pay for a heat pump to run and this strategy is certainly valid, the price will be similar to solar hot water. One thing to consider is the heat pumps usually have a lot of electrical controls, switches and PC boards that can fail while solar hot water systems are simpler but not immune to problems either, it's a trade off. A heat pump will stop making hot water in very cold weather while the solar hot water will still work in very cold air as long as there is sun.
I'm in the same boat and still trying to figure exactly which way to go, leaning towards solar hot water because of the noise issue.

I am pretty sure that the cost of solar systems went up when the government were offering rebates for them.

Did they go back down in price? I am assuming that there's no more rebates for them.

I've had a 400lt Conergy Solar set-up for a year. Ground mount (panels on roof) and instantaneous booster. Very happy so far. The newly installed bath with test out it's capabilities.
But did I read that Conergy went bust?

^^^
Thanks Stephen - we are metro Perth Northern suburbs. We have a filter on the input that gets changed every few years - but could be well overdue. 18yrs and 10yrs life may suggest that the mineral content of the water is OK - however the corrosion is at the pipe fittings as you suggest...

As always, sh!t like this happens just as you get in front with your bills... then 'smack!' another unplanned expense...

Copper fittings should never be threaded straight into a steel tank, a dielectic problem with corrosion can occur, use a 6" brass nipple between or a dielectric union. Copper into stainless steel apparently not such a problem but I wouldn't do it. Use the all brass dielectric unions if you can find them.
Are you sure this isn't the problem? not the tank?

I was in the game for a long time , stainless steel tanks good in low pressure and water that is low in TDS and chloride. If you have hard water and high pressure stay away from stainless tanks.. Glass lines steel tanks can handle high pressure and hard water .Like any other products their are glass lined tanks and stainless tanks not all are equal. Solahart manufacturer in Perth and are a good product. Stay away from evacuated tubes in my opinion more hype than substance , stiebal do make a quality heatpump. Go for tank and panels roof mounted simple system with little to go wrong if installed correctly.

We've had a solarheart system since July 1996 still going strong, it's gas boosted not electric, and we only have the gas on, for a half hour or so, when the water gets too cold. A gas bottle lasts more than a year, and it's also doing the cooking.
We get it serviced every 5 years, anode and safety valves replaced.
I haven't done the numbers, but that seems like a good investment to me.

When it comes time to replace, I'd like a modern instantaneous inline gas booster, apparently they are smart enough to handle high incoming temperatures without overheating. So you're only boosting the water you use.

About tanks, 29 years of plumbing I've probably replaced a few hundred water heaters. The glass lining is sort of a gimmick I believe, it's not glass like a bottle but rather fiberglass I think whatever it is it's very thin, I've cut old tanks apart and there is no "glass" visible.
Gas storage tank water heaters have the shortest life because the flame is burning straight upon the steel on the bottom of the tank, hot water causes minerals in the water to change from solution to actual globs of minerals that accumulate on the bottom of the tank, over time the tank can become up to half full of deposits. This problem is worse on gas tanks and least on electric and solar storage tank water heaters. Over time gas tanks nearly always develop leaks on the bottom. The problem can be largely remedied by fitting a ball valve with a hose connection fitting on the drain at the bottom of the tank and letting it blast out the debris every 6 months, write the date when serviced on the side of the tank to remind yourself. Don't turn off the water just open the ball valve and let it flow until no more stuff comes out. If you don't do it regularly the minerals will attach to the tank and will not flush out.
Changing anode rods is something I have never done, often there is no room to pull out the rod and put another in, the cost also seems prohibitive to me.
if you have hard water there are well and water softener companies that can analyze the water and install a special filter for the particular problem.
Rinnai instantaneous gas heaters are very popular in the states, the owners like them because they are mostly very reliable and never run out of hot water. The savings are not really that great and the cost of the unit and install for a retrofit from a different type of heater may not pay for itself for a very long time if at all. If you have teenagers they will take very, very long showers and end up using more fuel than anticipated as the tankless never runs out of hot water. The instructions state the Tankless heater must be flushed with vinegar every year. To do this the unit must be installed with a special valve kit that has three way ball valves and hose fitting connections. A bucket is filled with vinegar and a small pump with washing machine hoses is connected to the heater and the vinegar is allowed to pump thru the heater for an hour or so. I have never seen anyone actually do this but I have read about them getting jammed up.
If you live in a no freeze area solar is especially good as the system and controls can be simpler. A split system with a ground mounted tank will be easiest to service and replace if necessary while the panels should last much, much longer. The Solahart type system with thermosyphon seems well though out but inevitably the tank will fail and that really means replacing the whole unit instead of just the tank which will be more expensive for the unit and the install as it's on the roof.

We bought a Conenergy Solar Stainless from
one earth outlet com au
about 2 years ago
We have had nothing but trouble from this solar hot water system
and the company have NO interest in after sales service and are down right obnoxious

I installed a 350 Lt heat transfer stainless steel solar hot water system with 30 evacuated tubes from Sunergy last September, the system is fantastic except when it boils for an hour or so during the early afternoon, it sounds like there is a storm outside.
These systems don't use the water in the storage tank, it only uses it to heat the fresh water being passed through it, I have never switched the heating element on yet and going on its performance during overcast or rainy days, I doubt if I ever will need to use it.
I'm a shift worker, so I am always the last to have a shower out of a family of four females and myself, doesn't matter what time of the morning I get home, the waters always hot.
This is my first solar hot water system, I'm stoked, but kicking myself for wasting money buying gas for the last 26 years.
There are quite a few of these type of systems on Ebay, for me the main thing is that it's a heat transfer system with evacuated tubes.