Pietpower

You mentioned what you want to power but please tell how you want to power it. Example you can split the DB in two and have the inverter only feed what you want to feed. You can run it like a generator with a switchover switch and manually go over to backup. (Cheapest but presume this is not your requirement with 3D printers etc) It did cost me about R10k to split the DB and if you put that money towards a larger inverter you can put the whole house on backup while using load controls for high usage items (geyser, stove, etc) to save battery life during power outage. Less abortive installation cost. PS What advantage would a hybrid inverter have if you are not adding solar panels?

Popular belief say so but no the energy is not much less. With electrical it is also highly dependent on water usage. With electrical 200L you lose heat through the day. The geyser says 1kWh per day but with piping etc I lose about 2kWh in reality. To heat the 200L takes about 10kWh from cold. That is a loss of about 16% (2/12). Now if I use that 200L over 4 days the loss is 8/18 or 44%. If I have a 150L and heat it twice a day then the loss is probably below 10%. With a gas geyser the chimney is not ice cold so some of the energy is also lost. Maybe also 10%?? So IMHO the energy used is similar and it boils down to what you pay for electricity vs gas per kWh. Where you can really save on an electrical system is if you can put excess energy from your solar PV system into the water and then you can triple that energy with a heat pump.

Aah ok. Thought you were going to run just on gas for a while to see how long a 48kg will last.

Just guessing on figures here but cooking can take 1-2kW of energy per hob while a gas geyser can maybe be 14kW of energy or more. A 48kg for a gas geyser can easily be used up in 2 months.

Would like to know your feedback on gas usage. Please see if you can link it to water usage. For example family of 2 or 4, shower or bath, average time, etc. Thanks

My post was not in reply to your system but rather a new direction of thought. Yes I agree that the best ROI is a solar hot water system with 2 tanks. What I also have and very efficient even though my solar is a bit small. What I am saying is that when a person only have one geyser which they convert to solar vacuum it is going to be a struggle to get it operating efficiently or satisfactory. Think about this: If a family of four heat a 200L geyser with solar vacuum and don't use water sparingly in the evening then they have cold water the next morning. Now if they set the geyser timer to bump the temperature to prevent morning cold showers then solar system start with a warm temperature in the morning and you lose efficiency. How do you set up such a system to ensure morning hot showers and make use of all the solar sun power available. The only way I know is overheating the geyser water in the day to say 80C thereby effectively increasing the hot water storage volume (higher temp means you use less hot water) and then boosting the geyser temp in the morning to say 55C if necessary. A bit of a work around with varying hot water temps and maybe a slightly higher capital outlay on the solar vacuum system but no worries about cold showers. Any other methods?

If you only have only one geyser then it is not easy to get satisfaction from vacuum tube system. I think it may be a reason why so many are unsatisfied by solar water heating systems: A solar system can only heat once in a 24h period while electrical or gas is available whenever you want it to be. You may have nice hot water in the evening for showers but then find that the water is cool for the morning shower. Now you need to find ways around this. People don't want to work around problems and then just complain about the shit system. Same with a cloudy day having to manually go to a backup. One way around this is to have electrical heating in the evening to top up to desired temperature and then do the same again in the morning before showering. But now you start the day with mostly hot water in the geyser and lose most of the energy savings you could have had from the solar water system. It needs to start with as cold as possible water in the morning to have the best efficiency. Bottom line for a solar water system is you need a lot more water storage to have an efficient system. Best is if you have more than one geyser in series imho.

Could you explain the flow of water a bit. Do you have the two tanks in parallel? PS Be careful to have a one way valve or shut off valve before the geyser especially if it is Kwikot. The do not honour their warranty if they find a valve after the prv before the geyser.

Just to add some more for comparrison. Standing losses on our 200l geyser including pipework is 2kWh per day when no water is used. On your heat pump that will ad another 0.5kWh with a total of 2.5kWh We use about 150-200l of hot water a day. Instead of heating it twice a day I added another 150liters to give 350L storage. Our inlet temperature is closer to 20C (15C in winter). That is the temp to be used in the calc if all 200L in the geyser is used but when only part volume is used and then the start temp is different. We use a geyser setpoint of 65C. This effectively increases the hot water storage capacity since we use less hot water when showering. At 55C you will mix more hot water with cold water to achieve the desired temperature thus use up the hot water faster. The 150L geyser is combined with a cost effective flat plate collector and pump and in series and in front of the 200L geyser. Thus it preheats the water and the 200L geyser uses less electrical power. The cost for the added geyser, flat plate and pump with installation was about R10k. We average around 4kWh per day in summer with the above setup and it is also supplied from PV solar.

I presume that would be for about a 3kW heat pump unit? Following

To size a heat pump you need to do a proper heat load of the building. But lets say you need about 100W per sqm for heating and you heat about half of the floor area. That gives you 20kW of heating requirement. That is a big heat pump unit. With a 20kW heat pump you are going to need about 7kW of electrical power which will need a big solar system if you want to run it off solar. The problem is more at night when you still want to heat the home and only have battery power. Running a heat pump from grid power vs a pellet burner is probably gonna cost you the same in energy usage. But that is just guessing now.

Also have a POW2 sonoff running a 3kW element. Burnt the previous one and learned why they burn. Fixed my mistakes and the new one is working fine. But there are better cheaper equipment now for this purpose.

Not having the same problem but on my side the SEMS portal kW readings are wrong. Sounds like your 'general' setting is not registering or resetting or operating on another mode. There is another thread where someone mentions how bad the pvmaster app is. Goodwe support seems to be useless in my opinion.

Could you please explain this please. If all our breakers are SANS then why do you need SANS approval for an additional device? Many of us have Sonoff switches in our supplies which is not SANS rated. Is it illegal if I install that inside a DB board keeping the circuit breaker in place as opposed to installing it just outside the board? Does it matter if it is upstream or downstream of a breaker? What my logic tells me is that you have a certain size breaker to protect a certain size cable. If you remove that and replace it with the wrong size or unapproved (non SANS) then you will COC problems. If you install a contactor or breaker close to usage it should not be a problem. If you install same inside the DB is it then a problem?

Yes the tenant just pay his bill as usual and it does not matter where the power come from. There are private meter reading companies that handle that and they make money between the bulk supply rate and individual higher rates. Few questions: - With grid tied you only have power when the grid has power. Do you plan to overcome this somehow? - With residence as opposed to office block a large portion of the power usage will be at night when you don't have sun power. What is the plan for this?

Why is the power export limit set to 100W and not to 0W?

I agree it seems a lot of juice is being used. The scale on his graphs are very high at 20kW and 16kW. The graph is small but load seems to go up to 10kW. Goodwe can't supply that much so should the grid not supply the balance of 5kW? On the second graph you ask where the power is coming from. The charging battery seems to coincide with a drop in power usage. Very odd that power usage would drop when you start charging batteries.

This does not add up. Your bill can't be that high with the appliances mentioned. If you have large AC units I can maybe understand the summer usage but why would winter be that much higher? Any electric heating maybe? Did your bills drastically increase once you installed the solar system?

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COP is for heating performance EER is for cooling performance But that is now being pedantic. 🙃 Tell me more about the 18C figure please. Between 18 and say 20 C I would still heat my home. About 22C is the tip over point for me. 20-24C would be comfortable in my opinion.

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Ryan. Think about just this part for a bit. At night time you don't have any energy sources at the panel and you can't gain energy. If your geyser is at say 50C and you pump the water to the panel then it arrives at 50C. It can then not get warmer than 50C. The panel is cold and will lose energy to the environment and your panel temp will be lower that geyser temp. If you are not pumping at night and it is only unwanted flow the temp in the panel should be much lower than geyser temp as the water loses energy all the way to the panel and in the panel. Thus if you blocked the flow completely the panel temperature should settle at the outdoor ambient temperature. Best case scenario.

1.5kW for 2 hours is 3kWh of energy you add to the water. A 150l geyser can lose 1.5-2kWh over a day when including pipes. A single shower maybe takes 50l of water. To reheat that 50l from say 20C to 60C will take: (60-20) x 50 x 1.16 = 2.33kWh of energy. My guess is that 3 hours will be enough. You can lower the water temp in the geyser and reduce the heat loss but take into account that say a 50C hw temp might use double the water volume in a shower and 50% more energy to reheat.

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Can you now get away without an isolator next to the geyser (or whatever equipment.) I was under the impression an isolator is required by SANS regulation within a specific distance from equipment in order to switch off power to equipment without having to search for a DB.