Saturday at home, installing an inverter

[IMHO]

You are right bergie, it is top loaders.

[wynn]

I am waiting for the battery that will be produced by young master Musk and the PV cells to be produced by a factory being constructed in the ELIDZ.
Right now the estimate is that one can completely go off the grid with 10Kw 24/7 for about R80,000.oo and that this price will come down in the future as competition in the market increases. Or what?

[Justloadit]

Elon still has to build his factory, expected completion date 2017.

[AndyD]

Elon still has to build his factory, expected completion date 2017.

That's still several years before Medupi is likely to be on-line

[wynn]

Here is a link to an article in the M&G about just this battery

http://mg.co.za/article/2015-05-11-p...into-a-battery

[AndyD]

“The issue with existing batteries is … that they suck.”

He's not wrong, storing power is inefficient and expensive but it's a necessary evil with load shedding and it's often cheaper and more efficient (and more neighbour-friendly) than the other option which is small generators.

[blackknight72]

Hello again, Today I found an Axpert 3KW MKS plus 24 volt system in a local shop with a price tag of R7000 Inc Vat. I checked with my contractor if it is okay to purchase that instead of the 48 volt system he chose for my system which was R2500 more expensive. He was vehemently opposed to it and was concerned that it will put a 'lot of strain' in the system 24 volt inverter. The best way he could explain the difference was by making a comparison between performance of a C 180 merc vs C 200! I was certainly not impressed with this rather unscientific explanation but lack of technical knowledge makes it difficult for me to debate on this matter. He also mentioned that I will need a minimum 8 batteries (?) to generate a pure sine wave.

I will appreciate if Andy or anyone in the forum can explain the pros and cons of using a 24 volt instead of 48 volt. Again is there any truth in saying that less than 8 cells will not create a pure sine wave?

Thanking in advance!

[bones]

any solution for hot water that doesnt
involve the sun?

spoken to many friends some say it
works some of the time others say it
is sh_t and a waste of money others
say gas is also a dead loss in winter

what size generator do i need for hot
water? got a 7kwatt 25amp generator

[IMHO]

I am changing over to gas. Yes, winter is a bugger, but for 3 months only. I get 30 days on 48kg in winter, 90 days in summer. So you average 60 days on 48kg over a full year.

That is for 2 bathrooms, used by 3 adults, plus scullery for the guest house kitchen only. No laundry or guest bathrooms. Highest price during the last year was R1100 and lowest R750 for 48kg. Shop around for gas, some outlets is very expensive. I also heard stories of unscrupulous people filling the cylinder with a percentage water to make up the weight, but I think it is the expensive guys telling the story trying to justify their prices. It is very easy to pick-up afterwards, as the cylinder is stamped with it's empty weight.

So when the gas is empty, you weigh the cylinder and see if there is a difference, indicating water. I am yet to find a cylinder with water, but then again, I did not buy from the super cheap guys yet. It is normal to have a kg of gas left and the geyser stops operating. Above is from a Rinnai 21. I now started using Paloma, which so far is far superior in operation. It will be more difficult to judge the gas consumption however, as it is installed on two guest bathrooms and these rooms is not let out very often or consistently. I will have to find a way to monitor.

If you go gas, be careful of the cheap units that does not have defrosters build in. (And all the safety gadgets) If your unit freeze in winter, you throw it away. If your municipal water pressure dips to the low side every so often, be aware that you will take cold showers. With the Rennai, I have to set the temp to a comfortable level to shower without mixing in cold water, because if you do, the change in pressure cause the geyser to shut down. My Paloma 21 however does much better in this regard and need much less water pressure.

Keep in mind that the units I am referring to use about 55w to operate and you need a UPS to make sure you can shower during a load shed.

[AndyD]

Hello again, Today I found an Axpert 3KW MKS plus 24 volt system in a local shop with a price tag of R7000 Inc Vat.

That's a good price!!

I checked with my contractor if it is okay to purchase that instead of the 48 volt system he chose for my system which was R2500 more expensive. He was vehemently opposed to it and was concerned that it will put a 'lot of strain' in the system 24 volt inverter.

The output of the inverter is rated in KVA so a 3KVA inverter will produce 3KVA output regardless of the input voltage.

The only downside in your case with using a 24v inverter rather than a 48v one is that the battery cables will need to be larger. This is one of the reasons that as the output power increases with the range of inverters so does the input voltage but with a 3kW unit it's still reasonable to use 24v input, hence the fact the manufacturers offer it as an option.

The best way he could explain the difference was by making a comparison between performance of a C 180 merc vs C 200! I was certainly not impressed with this rather unscientific explanation but lack of technical knowledge makes it difficult for me to debate on this matter. He also mentioned that I will need a minimum 8 batteries (?) to generate a pure sine wave.

I don't know how to reply to that, it's the kinda statements I'd expect a wholesaler to come out with but not really an installer

The number of batteries is immaterial as long as the inverter has sufficient to supply it with the correct input voltage. A 24v pure sine inverter will always produce a pure sine wave output regardless of the battery configuration as long as it's getting 24 volts from them. The inverter doesn't 'see' the individual batteries as such it just sees a pool of energy at a certain voltage so a 24volt inverter needs a minimum of 2x 12v batteries in series or 4x 6v batteries in series, it makes no difference which.