Solar Geyser - what they dont tell you

[phoneJunky]

So I inherited a Solar Geyser on the home I bought and yesterday was quite a hot day. At just around 1pm I hear the noise of water running and go outside to see the geyser peeing out litres of water onto the roof. I thought the geyser had failed and rushed around to turn off the pump (pumps water from my rainwater system) and close the geyser feed stop cock. It must have spewed more than 50l of water onto the roof!
Anyway, I called the installer and was told it will happen on hot days when the water in the geyser overheats - the TP valve (temp/pressure) opens and dumps hot water, drawing cooler water in to replace it. He reckons you can pre-empt it on hot days and open the hot water tap more often during the day.

There's also the real risk of load shedding and water shortages destroying the geyser when the pump can't send cool water in to replace the hot.

With a regular electric geyser, the thermostat controls the element and mostly the TP valve is very seldom needed. With the solar geyser, you can't turn the sun off

If I were spending my $$, I would simply get a regular geyser, solar panels and a DC geyser element.
.. especially if I was already planning a solar electrical outfit.

The element is a simple drop in replacement of the AC element.

Inheriting one might be troublesome yes because you normally size the solar geyser to your usage. The general rule of thumb when I got mine was 50L per person +50L.

Also, I do think knowing what goes on in your geyser is very important. That is why I don't understand why some installers install without a geyserwise or something similar like they did my parents. I have a geyserwise and I can see if the water is going to be too hot. The geyserwise also gives it extra functionality and if the water reaches 83 degrees it automatically starts to circulate the water with increases heat loss. It will also show an errors drawing your attention to it.

Also if you know you are in for a few hot days you can also put it in holiday mode and it will try to keep the temperature down.

 

[joker08]

Normally they don't. But they gave me one of those water heaters.

Maybe it was Panasonic or something. Probably similar to what Snyper linked. I think it was like 3000 PHP or something.... But that was a long time ago. Now it is probably double that.

Anyways, would be interesting to see how the power usage compares.

These ones ? Its pretty common in india.
Powerwise they are still 2kw to 3 kw depending on how hot u want.
I have used these since my childhood. They won't work in capetown winter. Maybe in summer, but definitely not in winter.

 

[GrootBaas]

Have never had that type of issue. Guess it depends on the type of setup maybe? Dig my solar geyser, keep checking the temperature throughout the day in the geyser and in the roofpanel from the geyserwise thingie in my kitchen.

 

[wingnut771]

Well it makes hot water, wouldnt call it boiling though.

If it boiled, you would see it wasting water.

 

[RedViking]

These ones ? Its pretty common in india.
Powerwise they are still 2kw to 3 kw depending on how hot u want.
I have used these since my childhood. They won't work in capetown winter. Maybe in summer, but definitely not in winter.

Yeah, similar. Was hoping they would use less kW.

 

[Willie Trombone]

I've never liked solar geysers anyways.

When I was in the Philippines, there was this little water heater device installed next to the shower (they don't use geysers or hot water in general). I haven't seen something like it in South Africa. Water goes in, heats instantly, and goes out to the shower head warm enough for a foreigner to enjoy the hot water.

I want something like that.

I had one of these in Kaputa (Zambia) once....
I have a fundamental issue with showering with live AC cables...

 

[Willie Trombone]

Yeah, similar. Was hoping they would use less kW.

The thing with those is they only use KW while the tap is on.

 

[wingnut771]

The thing with those is they only use KW while the tap is on.

Yeah, but you need a beefy inverter to power it.

 

[Willie Trombone]

Yeah, but you need a beefy inverter to power it.

Yes, that is true.

 

[Willie Trombone]

 

[wingnut771]

Sell the monstrosity to some sucker and get this:

Geyserwise PV Solar Water Heating Kit For 200L Geyser - Sustainable.co.za

p><strong>Advantages over thermal hot water systems are as follows</strong><br /> • Any existing geyser can be converted.<br /> • No Additional plumbing is required.<br /> • No pumps necessary to circulate water.<br /> • No risk of dam

www.sustainable.co.za

 

[Speedster]

I've crunched the numbers and considered various configs on all these options. If you're only looking for water heating, EV (or flat panels) with a Geyserwise is easily the optimal option. PV only makes sense as part of a larger PV setup for your home. The PV heating kits are very expensive for what you get.

 

[Speedster]

You mean climb up to the roof on the second storey to cover the geyser for half the day every other day?

****ing mission.

If your solar heating is over-specced (as seems to be the case), you only need to get up on the roof to cover some of the pipes somewhere during the spring and again in autumn. Flat plates don't get hot enough to be an issue.

 

[wingnut771]

If your solar heating is over-specced (as seems to be the case), you only need to get up on the roof to cover some of the pipes somewhere during the spring and again in autumn. Flat plates don't get hot enough to be an issue.

Why is this?

 

[Speedster]

Why is this?

Different technologies. Flat plates max out at about 80 degrees while evacuated tubes can easily push above boiling given the right circumstances

 

[wingnut771]

Different technologies. Flat plates max out at about 80 degrees while evacuated tubes can easily push above boiling given the right circumstances

Link for flat plates? Does that mean they perform poorer during inclement weather than evac?

 

[Speedster]

Link for flat plates? Does that mean they perform poorer during inclement weather than evac?

Flat Plate Solar Heating Collectors - Sustainable.co.za

Browse our range of Flat Plate Collectors online & compare prices at Sustainable.co.za.

www.sustainable.co.za

Note that the con of flat plates is that they can burst in freezing temps. A Geyserwise pumps warm water through on cold nights to prevent this.

 

[BuckRogers]

Yes OP this is correct, I experience the same. I sometimes run the generator during load shedding on hot afternoons just to ensure the geyser panel doe not boil and lose water through the tp valve. For hot days without LS I try to manage it by switching the element off manually earlier in the morning to ensure cooler water to start the day with. Mine starts losing water when the geyser gets to the late 60's - the panel is 7 more - so middle 70's.

 

[Vis1/0N]

These needs a device like electric blinds linked to a thermistor and sun tracker to add some smarts, the current solution with TP release is built to a cost but could be supplemented with smart blinds.

Will drop efficiency though.

 

[Willie Trombone]

If your solar heating is over-specced (as seems to be the case), you only need to get up on the roof to cover some of the pipes somewhere during the spring and again in autumn. Flat plates don't get hot enough to be an issue.

I believe I have flat plates