Solar Hot Water ?

I used to have bottled gas instant hot water until the price of propane rose to silly levels.

I bought a Quantum heat pump HWS second hand from a motel proprietor who found the commercial units too noisy. For the first year all went well, the unit being time clocked to come on after dark but off before bed time.

Then the compressor seized. Quantum wanted full access to our credit card before they even put the job order in. Luckily I'm a stubborn bastard and I belaboured the compressor with a 2lb lump hammer every time it tried to restart. 3 days in I eventually won and the unit has been trouble free ever since. BTW the compressor unit is completely Chinese made. Some fragment of metal must have got into the compressor, now it's likely safely away in the drier.

Last summer I added some used Beasley solar water panels aiming at the afternoon sun, and because the house doesn't have any north to north west facing roof surfaces they're on a custom rack. The system controls consist of a 20W electric solar panel on top of the water panels, a special DC pump designed to run off a small panel, and a cheap DC temperature controller set to 65C tank temperature. The panels can't overheat the tank on a 40C plus day. The pump takes bottom water from the inlet junction and feeds it back in the bottom on the other side. That way the possibly cooler water doesn't dilute the hotter water in the top of the tank. It's still useful energy. The circulating pump does not use mains power at all so is cost free to run.

Now on any sunny afternoon the panels heat the water however much they happen to do, and if the tank thermostat is over 58C the heat pump simply doesn't run. On very cloudy days the heat pump runs like normal making sure the tank always has fully heated water available every night. This is an important safety concern because we're on rain water. Everything is fully automatic and needs no regular input from me.

All in all it's a good system but I'd think twice about another Quantum unit. Luckily I got mine really cheap. If the Beasley panels crapped themselves I'd upgrade to some evacuated tube units.

Here's a link to a company that sells pumped solar units. This system was designed by a friend of mine. I would have bought his controller but he was too late and I built my solar DC system instead.

Here's another link to the DC circulating pump I used on my system.

This is the temperature controller I used, it's ridiculously cheap and I bought a spare at that price. I extended the temp sensor wire (NTC resistor) to reach the HWS from inside the laundry. The controller gives a permanent readout of tank temperature and it's quick to change the settings.

Another Stiebel Eltron heat pump owner here. Installed two and a half years ago, and not a single problem since.

We've never run out of hot water, even when there has been 8 or 9 in the house all wanting showers.

I've had a Hills evacuated tube system running for 2 or 3 years now, and it's excellent.
The brochures suggest installing a system that will be adequate in summer, and let the electric backup make up the difference in winter. However I went for a size that would be adequate during a sunny winter, with a collector angle that would increase efficiency in winter and reduce efficiency in summer. The tubes are north-facing and are mounted at such an angle that they are perpendicular to the sun's rays one month either side of the winter solstice.
I have a 30 tube collector and a 300l. tank, and have installed thermometers in the feed and return pipes to the collector as well as the top of the tank. In full sun the temperature rise between the two pipes to the collector is about 15 degrees C. The flow rate of the circ. pump is regulated to 1.25l/min, so it's just a trickle, and takes about 4 hours to raise the 300l. tank temperature by 15 degrees. When the tank temp exceeds about 80 degrees C., the pump cuts out, the water in the collector boils, and steam comes out of the air bleed on the collector. This happens occasionally in the late afternoon of a sunny summer's day.
I installed the whole thing myself, with assistance from #4 son in getting the main collector manifold onto the roof.

So there seems a 50:50 between evac tube and heat pump systems nw. Ahh so confusing !

Obviously initial price is an issue but I am looking gor lowest possible ongoing price.... that is, lowest power from grid requirement.

I figure solar is more economical in the long run, but about $5k more to install (up here at least). In my books, if I use that $5k on solar panels and install a 5kw system, should be well ahead in the long run as far as power consumption, and grid usage. Plus I have limited prime roof space for solar usage, so might as well use it for generating electricity.

Cheers,

Ken

Quote:

---

Originally Posted by VladTepes

So there seems a 50:50 between evac tube and heat pump systems nw. Ahh so confusing !

---

There is no reason why you should not be able to combine these two. You will need a decent accumulator tank, but that's god to have anyway.

Look at it this way, heat pump, too many moving parts, compressor, gas, fans, evaporator etc.... evac tube, a 40w pump, the rest is standard hot water bits, ie element and thermostat.
If your in a sunny warm environment, you can leave the system turned off for may be 6 months or more, and you only have a 40w pump running.:)

Oh and as I said, I have a heat pump.

I know what solar panels are but what are evac tubes? Jim

Have a look at the link in the first post it has an explanation

So you dont have Gas mains?

We looked deeply into replacing our Instant Gas Hot water (Rinnai) with heat pump tech...

Did the sums and came to the conclusion the Gas was cheaper...

Unit cost substantially cheaper, Gas bill is sub $100.00 a quarter including supply charge and this provides Hot water and Cook top.

Not saying this is for you...