IdlePhaedrus Posted January 29, 2020 Author Share Posted January 29, 2020 18 minutes ago, phil.g00 said: so a realizable amount of energy isn't realized for the sake of turning on a load This is what I am hoping to achieve without breaking the bank. A lot has to do with usage patterns, and that is dependant on the number of people who use water and when. Since I live alone I moved to a gas geyser when I installed the solar in 2014. For me it was cost effective as I shower once a day, and wash the dishes once a day. For a family of four it wouldn't be cost effective I don't think. I had an old style platter meter so the excess energy from the solar wasn't wasted and fully offset the cost of the gas. Now I have to limit feedback. The gas geyser is nice, but it does have a few drawbacks. It invariably runs out of gas in the middle of a shower, so you end up running around outside half naked with shampoo in your eyes to change over to the backup bottle. Also, where mine is positioned it tends to blow out when the North Wester exceeds around 30km/h, which happens quite often here in Winter. That's not much fun either. Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted January 29, 2020 Share Posted January 29, 2020 (edited) 23 minutes ago, IdlePhaedrus said: A lot has to do with usage patterns, and that is dependant on the number of people who use water and when. 45 minutes ago, plonkster said: At the cost of slightly colder water in the mornings. Many families are creatures of habit when it comes to showering. I will be shortly be relocating a roof mounted solar thermal geyser and tube unit. Where it is positioned on the roof at the moment it is North -facing on the roof ridge at the most northerly side of the roof. It stands on a frame about 5 or 6 feet proud of the roof ridge and consequently casts a shadow behind itself that makes a fair portion of the roof not ideal for PV panels. So its getting moved to be positioned flush with the roof slope, and the tubes will face due East. Why East? Well everybody in the place showers about 07H30 in the morning. So I am trying not only to get more solar panels, I am also trying to make my thermal geyser more effective in the morning. I haven't done this yet, I don't know if it will work, but I am keen to find out. I think it might be something that people should consider when installing a solar thermal geyser. Edited January 29, 2020 by phil.g00 ___ and RikH 2 Quote Link to comment Share on other sites More sharing options...
Bobster. Posted January 29, 2020 Share Posted January 29, 2020 3 hours ago, plonkster said: You'd be amazed how difficult it is to explain this to people. The largest part of your geyser's electricity consumption is due to your actual use of hot water. Cut your shower by one minute and you'd be amazed at the savings. Around 2kWh (the rated standing loss) per day is used to keep it warm. This saves water too. Something we all need to be thinking about. Quote Link to comment Share on other sites More sharing options...
P1000 Posted January 29, 2020 Share Posted January 29, 2020 (edited) 17 minutes ago, Pietpower said: Just for interest see here: https://www.kwikot.com/consumer/faq They say maximum SABS heat loss is 1.377kW (presume it should be kWh) over 24hours yet they also say that you need 2.6kWh to reheat the geyser if it was off for 24h. Those numbers changed fairly recently, so I suspect they failed to update it. Class E geysers will have standing losses of around 2.5kWh per 24hours (if you're geyser is 4 years old, you'll have one of these). The newer Class B geysers are around half that. 17 minutes ago, Pietpower said: Another thing I am wondering about: Is it worth it to insulate hot water pipes? It reduces heat loss from the pipe but adds mass. How much heat can I lose during a 5 minute shower vs the pipe and insulation will drop to ambient temp and I have to reheat the increased mass before getting hot water. Lagging will add negligible thermal mass - so yes, it is worth insulating hot water pipes. Especially since a lot of the standing loss is through heat loss to the pipes, even when the water is not running. Edited January 29, 2020 by P1000 phil.g00 and ___ 2 Quote Link to comment Share on other sites More sharing options...
___ Posted January 29, 2020 Share Posted January 29, 2020 41 minutes ago, P1000 said: Those numbers changed fairly recently, so I suspect they failed to update it. Class E geysers will have standing losses of around 2.5kWh per 24hours (if you're geyser is 4 years old, you'll have one of these). The newer Class B geysers are around half that. I remember back in 2005 when he SABS still did these things and you had an SABS mark on the geyser, the standing loss on a 150 liter Kwikot was 1.9kWh. Then I got a new one, without the SABS mark, and this one was about 2.1 I believe... which was apparently the new legal limit. That is to say, the numbers vary, and sometimes they get worse (because the manufacturer can get away with it). Quote Link to comment Share on other sites More sharing options...
Richard Mackay Posted January 29, 2020 Share Posted January 29, 2020 11 hours ago, plonkster said: Despite this, I've heard lots of anecdotal evidence of people who save hundreds per month by installing that timer. The only way I can make sense of it is that either 1) They shorten the shower because they want to give the new money-saving device an honest test, 2) Their is a massive heat loss somewhere in their system, eg water leak, 3) they actually run out of hot water during the last shower. I also believed this 'evidence' of saving on water heating but I needed to check it out for myself. So I lowered the thermostat temperature to the minimum (i.e very little cold water added if at all) Then I added a switch that I could (easily) manually switch the electricity supply to the geyser. Realising that the geyser temperature (PV) was not precise I needed to ensure that when important people had a shower the temperature had to be at the high end of the thermostat hysteresis range. The only way to do this was to anticipate when the shower was to be taken and ensure the geyser had just switched off after a heating phase.. This was meant to be a familiarising phase which was then to be automated by a timer when the algorithm was identified.. Now year/s down the line I'm still switching the geyser on/off but the good news is that when measuring the geyser power usage I find it's 5 units a day.. This should make me a happy camper (I guess) but it hasn't! Quote Link to comment Share on other sites More sharing options...
P1000 Posted January 30, 2020 Share Posted January 30, 2020 15 hours ago, plonkster said: I remember back in 2005 when he SABS still did these things and you had an SABS mark on the geyser, the standing loss on a 150 liter Kwikot was 1.9kWh. Then I got a new one, without the SABS mark, and this one was about 2.1 I believe... which was apparently the new legal limit. That is to say, the numbers vary, and sometimes they get worse (because the manufacturer can get away with it). I am pretty sure they just make sure they meet at least the legal limit, and then write the limit on the label. All of the manufacturers do that. You can still buy Class E geysers, though... On the topic of geyser timers and switching a geyser on and off: This subject I find somewhat difficult to explain to most people, but I will give it a bash. The most important thing to understand with a properly designed geyser is that the water inside is not always at a homogeneous temperature. This is due the laminar flow of the hot water from the element to the top of the geyser. This is also why the element(actually the thermostat) should be installed roughly in the middle of the geyser - so that you only need to heat half the water when the geyser is cold. Of course, the temperature will homogenize over a couple of hours, but let's say the geyser is at a low temperature and you switch on the geyser. Now the element heats water and the hottest water flows to the top of the geyser. The hot water outlet is also at the top of the geyser, so the water you use could be at a much higher temperature than the average temperature of the geyser. This means that if you can manage to heat exactly the amount of water you need and then switch off the geyser, you can eliminate most of the standing losses. That is also the reason why some solar installations seem to not work well - if you have a shower during the day, and the pump is not on some sort of delta temperature controller, it will mix the hot and cold water in the geyser so that all the water is at the same temperature. ___ 1 Quote Link to comment Share on other sites More sharing options...
PaBz0r Posted January 30, 2020 Share Posted January 30, 2020 My geyser is running at PV idle times, two slots a day and normally only comes on for the first slot. On Tuesdays this slot is also used for ironing/vacuuming etc. and in the beginning I had a 3kW element, which pushed it to importing some grid. Luckily my geyser burst and got a replacement with a 2kW element. This gave me enough room to handle most loads during a geyser slot, unless the wife really wants to also use the microwave and dishwasher at the same time Richard Mackay and IdlePhaedrus 2 Quote Link to comment Share on other sites More sharing options...
IdlePhaedrus Posted January 30, 2020 Author Share Posted January 30, 2020 The gadget has arrived, will get it installed next week or the week after. Have attached a couple of pics. The heatsink is pretty big, so I don't think there is going to be an issue there but I will keep an eye on it. Does anyone know what COM is and how that should be wired? If I need to get something extra for that I would prefer to get it before the sparky is engaged so I have everything necessary on hand. Quote Link to comment Share on other sites More sharing options...
P1000 Posted January 30, 2020 Share Posted January 30, 2020 Common is the connection to neutral. I would not use a dimmer like that on a geyser, for the reason mentioned earlier in this thread: harmonics. An inverter is also not going to like chopped current at 15A. RikH, IdlePhaedrus and ___ 2 1 Quote Link to comment Share on other sites More sharing options...
IdlePhaedrus Posted January 30, 2020 Author Share Posted January 30, 2020 38 minutes ago, P1000 said: An inverter is also not going to like chopped current at 15A. That's my biggest worry really. Have had previous harmonics issues due to other unrelated issues. But it isn't a lot of money so if it causes it problems it will simply be removed. I will report back when the deed is done (and possibly reversed)... Riaanh 1 Quote Link to comment Share on other sites More sharing options...
phil.g00 Posted January 30, 2020 Share Posted January 30, 2020 49 minutes ago, IdlePhaedrus said: That's my biggest worry really. Have had previous harmonics issues due to other unrelated issues. But it isn't a lot of money so if it causes it problems it will simply be removed. I will report back when the deed is done (and possibly reversed)... Assuming this circuit is one of those that can chop even after the peak, then theoretically, there may only be a range where it is bad. Nearly full on and nearly full off, you will probably get away with. When its chopping around the peak of the sine wave,( half-power) I'd reckon it'll be at its worst. I haven't gone into these too much though, so I might be wrong. IdlePhaedrus and ___ 1 1 Quote Link to comment Share on other sites More sharing options...
magielvdb Posted August 22, 2020 Share Posted August 22, 2020 On 2020/01/30 at 1:58 PM, IdlePhaedrus said: That's my biggest worry really. Have had previous harmonics issues due to other unrelated issues. But it isn't a lot of money so if it causes it problems it will simply be removed. I will report back when the deed is done (and possibly reversed)... And what was the outcome please supply information because a geyser maybe one of the most efficient batteries. Quote Link to comment Share on other sites More sharing options...
Hoffie Posted June 28, 2022 Share Posted June 28, 2022 My question is this:. I have a 150L normal geyser fitted with a microcare controller and 3 x 455watt solar panels. I noticed that the maximum wattage coming in is around 600 watt. I have a 3kw element in there but the water does not heat up sufficient from solar Will the water heat up more efficiently with a lower kw element? Quote Link to comment Share on other sites More sharing options...
Wanderer Posted July 16, 2022 Share Posted July 16, 2022 On 2022/06/28 at 8:51 PM, Hoffie said: My question is this:. I have a 150L normal geyser fitted with a microcare controller and 3 x 455watt solar panels. I noticed that the maximum wattage coming in is around 600 watt. I have a 3kw element in there but the water does not heat up sufficient from solar Will the water heat up more efficiently with a lower kw element? I was also looking at this at some point (but dont have one installed). I believe the voltage of the array is the most important part to be specced correctly and interestingly enough the data sheet shown a 2 kw element needed higher voltage than a 3 or 4 kw element. I also saw they recommend lower watt panels. Quote Link to comment Share on other sites More sharing options...
RikusW Posted September 14, 2023 Share Posted September 14, 2023 (edited) Just saw this today, https://www.4-noks.com/shop/elios4you-accessories/power-reducer/?lang=en was considering building something like this, I'm guessing inside is something similar to https://www.researchgate.net/figure/Standard-ac-ac-buck-converter_fig12_224125119 Edited September 14, 2023 by RikusW Quote Link to comment Share on other sites More sharing options...
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