My solar hot water is 16 tube evacuated tube system and the geyser 150L.  I fully realize it should have been at least 21 tubes.  In hind sight I should have gone the PV electric element route, but was given terrible advice by the installer on all things solar.  I found that winter generally and on cloudy days especially the water does not get hot enough on solar alone and must be boosted with the grid. 

My existing solar set up is a:

·         5Kw 48v inverter (https://shop.thesunpays.co.za/collections/axpert-inverters/products/sacolar-wifi-compatible-5kva-5kw-pure-sine-wave-axpert-type-inverter-80a-low-voltage-mppt-parallel)

·         6 x 550w panels. 

·         The battery is a Deichmann YL-S48100 48volt; 100AH; 4.8KWH.  

While changing my panels (6 panels of 550W each) into 3 strings of 2 panels each, would it make sense to add an extra 2 panels of 550W each (4 strings of 2 panels) and then, as I've seen on YouTube and read on the WWW, put the surplus electricity into the geyser?  Would I need more than an extra two panels?  I have sufficient roof space North facing for 2 panels and an East and a West facing roof for 2 panels each.  

I have also read that there are two systems for solar electricity to heat hot water.  Not 100% sure I understand it correctly, but this is what I think it to be. 

·         The first is a double element, the one element connected directly to the grid and the 2nd element is connected to the inverter output and only draws electricity when there is surplus, batteries fully charged and excess in what the house is drawing from the panels.  I would assume that all have thermostats that would prevent the geyser boiling.

·         The second is only the one element that is connected to the grid and the solar with some kind on controller to ensure that the solar system in the house doesn't fight with Eskom.  However, this element is usually downgraded to about 3KW or so. 

Bearing in mind I live in Pretoria, in doing this would I be spending too much to save too little?  Having said that I am also aware that the price of electricity as well as loading shedding will get worse before, if ever, gets better.

My ultimate aim is that my hot water should be heated by the evacuated tubes, boosted by the surplus solar power and finally the grid.

Your comments and suggestions would be welcome.

@RookieRod The max PV input is 4400 Watt. That is 8 of your 550W panels . 10 Panels 5500W is exceeding your limit by 25%. So 8x550 W Panels max.

The inverter only has 1 mppt so you cannot use different orientation roofs spaces.

I will change the Geyser element to 2kW or even lower if avialble. Then heat the geyser when excess power is avialable. a Timer on the geyser supply can be be added to assist you. I find the cost of these heating systems expensive.

As you are a pensioner and only 2 adults this should work well for you.

Overcast weather and winter is  the main reason why I never considered solar tube water warmers . 

So at the time I had an 3 kw in inverter and 1kw solar panels so powering the geyser from inverter was not an option .

So I went for gas water warmer (geyser) as we only 2 in the house and we both shower .

The cost on gas to cook and shower per month is R200 so not a train smash .

I have upgraded over time so to get away from the cost of gas best is electric geyser power from inverter solar .

So my plan is to go for 100l geyser install an 2 kw element .

Install an smart timer so it can be programed and controlled from my Android any time any place .

Install an change over witch so I have the option of powering from eskom but on rainy day the gas will be used to warm water . 

In the end there is 3 option available to warm water up but using eskom will be the last option . 

 

Edited November 3, 20232 yr by GMAC

I'm using a Geyserwise ECO unit with 2 panels in conjunction with a 20-tube tube collector.  Not marvellous in winter but from September to May is works well

There is a circulation pump powered by a 12 volt 10 watt PV panel in the pipe from the tubes

On 2023/11/03 at 3:45 PM, Chris Louw said:

@RookieRod The max PV input is 4400 Watt. That is 8 of your 550W panels . 10 Panels 5500W is exceeding your limit by 25%. So 8x550 W Panels max.

The inverter only has 1 mppt so you cannot use different orientation roofs spaces.

I will change the Geyser element to 2kW or even lower if avialble. Then heat the geyser when excess power is avialable. a Timer on the geyser supply can be be added to assist you. I find the cost of these heating systems expensive.

As you are a pensioner and only 2 adults this should work well for you.

The max PV input is 4400 Watt. That is 8 of your 550W panels . 10 Panels 5500W is exceeding your limit by 25%. So 8x550 W Panels max.

·         I currently have 6 panels.  My roof is like a “T” section.  The top of the “T” slopes facing north and south.  The upright of the “T” slopes face east and west.  No trees or any other sun obstruction on any of the slopes, just morning sun angles.  The existing 6 panels are mounted on the north slope of the right bar of the top of the “T”.  Can definitely mount one more and maybe 2, (but not sure must measure) next to the existing panels.  But facing exactly the same orientation (left side of the top bar of the “T”) as the existing 6, I can easily mount 4 extra panels on a roof on the western side of the “T”.  The existing 6 are on the eastern side of the “T”.  But I would only install another 2 panels as 8 is the maximum.

 

The inverter only has 1 mppt so you cannot use different orientation roofs spaces.

·         I would assume that my explanation above sorts this out.

 

I will change the Geyser element to 2kW or even lower if avialble.

·         I have seen on google that 1.5KW elements are freely available but assume that 1KW could be found if I try hard enough.

 

Then heat the geyser when excess power is avialable. a Timer on the geyser supply can be be added to assist you. I find the cost of these heating systems expensive.

As you are a pensioner and only 2 adults this should work well for you.

 

My idea and please comment.  

·         I install another 2 x 550w panels on the other “T” of the roof facing the same as the existing 6.

·         Change the element in the geyser to 2KW

·         Ultimately I would like in order of applying energy to heat water:

o   The 16 evacuated tubes to heat the water aided at all times by surplus power from the solar inverter.

o   I would only like grid power when the tubes and PV cannot heat the water due to continuous days of cloud cover etc. 

 

My Geyserwise controller is set to the following settings every day of the week.

·         04H01 to 10H00 at 60°C

·         10H01 to 16H00 at 50°C

·         16H01  to 21H00 at 60°C

·         21H01 to 04H00 at 50°C

·         Please comment as these were what I was told to do by the useless solar contractor.

·         I have no objection if the water temp rises to above 60°C but must not exceed whatever is the upper safety level temperature.

Finally, what equipment would I need other than the installation and coupling of the two extra panels.

@RookieRod If al the panels face the same direction the is no reason not to add another 2 panels.

The Geyser heating should be ok most of the time with a 2kW element and a 4400kW array. The time settings you use is not economical. Al my time settings from 18:00 to 06:00 is at 35 degrees. Makes no sense to me to heat water at night with utility power. If whe really need water we switch it on manualy. We are offgrid so if we heat water with solar or battery it is from 09:00 to 14:30 .As you are pensioners this should not be a problem. 

The cost of adding 2 panels depends on what needs to be changed for the extra panels. In your case you want to change to 2 panels per string . The solar combiner box will have to be upgrade. Extra wire and fuses for new strings. For the rest the normal installation cost. Hope this is the correct info you want. 

Edited November 6, 20232 yr by Chris Louw