Hi

I've been lurking on this forum for about six months now and am now nerving myself up to take the plunge into solar. First off I would like to thank all the people who have contributed their installations and expertise. It has been a huge help.

My objectives are:
1) To reduce my dependence on Eskom and potentially save some money.
2) Provide a backup during load shedding and other outages.

From what I have read on the forum a 3kW system is a good starting point. However, I'd like to keep my options to upgrade the system open in case City of Tshwane becomes difficult, which brings me to my question:

Is it better in the long term to get a larger inverter/charger such as the Victron Quattro 48/8000 now if the budget allows and add extra panels and batteries later, or put in a smaller inverter/charger now such as the Multiplus II or Quattro 48/3000 and add a second one in parallel with more panels and batteries later given that I can just about buy 3 Multiplus II 48/3000 for one Quattro 48/8000?

I see from a previous thread that it can be quite difficult to parallel units if they have different serial numbers.

Regards

There is a lot of reading to do to catch up on the topic. 

First step is to determine your real power requirements. It is cheaper to buy lower power consumption household goods (with new warranties) than to go for a big solar investment. 

If you go too small and need to go bigger you will lose at least 50% of your initial costs when trying to sell it in the used market. So an initial R20k inverter could have been bought for R30k. 

A big concern to me is the message from prez Ramaphosa that an instruction was given to Guvament to get the solar rollout going. We can expect many stupid regulations coming our way. 

3 hours ago, alanphys said:

Is it better in the long term to get a larger inverter/charger such as the Victron Quattro 48/8000 now if the budget allows and add extra panels and batteries later, or put in a smaller inverter/charger now such as the Multiplus II or Quattro 48/3000 and add a second one in parallel with more panels and batteries later given that I can just about buy 3 Multiplus II 48/3000 for one Quattro 48/8000?

I'm tempted to say it is better to get the larger inverter, but there are two issues to keep in mind. Larger inverter means more no-load power. To use an example, a 3kVA Multiplus-II needs less than 20W to run itself, but an 8kVA quattro needs about 4 times that (thumb-suck, look in the spec sheets for actual numbers). So at night, if you are running a few stoepligte and an internet router at 200W, the 3kVA represents only 10% overhead while the 8kVA needs a good 25%. That is to say, there are some limits to how far you can push this exercise.

You may also discover, like some people in Cape Town, that the new regulations doesn't cater for your shiny Quattro. You may discover that said regulations don't want you to put in a 5kVA inverter on a 60A breaker. And so on and so forth. This in turn makes me want to tell you to get the 3kVA. But then, as you and Johan said, then there is the question of either finding another one of the same hardware revision to parallel with later, or the cost of selling and buying again.

Victron inverters tend to fetch good prices second-hand, so there is at least that. And during load-shedding... you won't have trouble selling them.

So yeah... that probably doesn't help. But I still lean towards the smaller end. If you're considering LFP batteries, I'd much rather spend more on the batteries and less on the inverter.

Edited January 20, 20206 yr by plonkster

Regarding sizing, Victron inverters can be paralleled if the are identical hardware units, with identical firmware.

The firmware compatibility is crucial, as there has been iterations of the firmware chip, and two different chips are incompatible, and there are no workarounds.

Know up front that specifying a 3kVA Victron when you make a purchase is not enough, you must specify the first four digits of the firmware chip as well, if you want to parallel a unit.

If the firmware matches paralleling two units is a piece of cake.

Your local authority will probably specify a maximum size and a list of approved inverters. Cape Town seems to have taken the lead in this, I expect other local authorities will adopt Cape Town's practices, so you'd be as well to make your system "Cape Town compliant", even if this isn't an issue that isn't pushed where you are at the moment.

In that case, the size limit is 25% of your incoming MCB size.

This is a good stage to do your sums, to see if getting a larger municipal supply ( so you'd qualify for a bigger inverter) would be worth it.

You could also consider a combination of hybrid inverter and one of many 3rd party grid-tied inverters,  just to optimize your size allowance.

This also works well and is cheaper, but it is not as rock solid a union as two hybrids.

 

 

6 hours ago, phil.g00 said:

Regarding sizing, Victron inverters can be paralleled if the are identical hardware units, with identical firmware.

The firmware compatibility is crucial, as there has been iterations of the firmware chip, and two different chips are incompatible, and there are no workarounds.

Know up front that specifying a 3kVA Victron when you make a purchase is not enough, you must specify the first four digits of the firmware chip as well, if you want to parallel a unit

@phil.g00 Are you referring to these numbers?

Thanks for the replies.

21 hours ago, Johandup said:

First step is to determine your real power requirements. It is cheaper to buy lower power consumption household goods (with new warranties) than to go for a big solar investment.

Yes, I've been through this exercise a couple of times, but each time I get a different answer depending on what I chuck into the mix. My average daily usage over the last year is 34.1 kWh with a winter peak of 39.4 kWh. The instantaneous load at any one time can be far in excess of this. The biggest culprit is the pool pump (1.5kW @ 8 hours a day) closely followed by the geyser (4 kW) and the wife's beloved dual thermofan oven (8 kW) and ceran hob (6.6 kW). If I add in, on Saturday for example, the electric mower (2 kW), leaf blower (1.5kW),  trimmer (1.5kW) and washing machine (0.5 kW), and the wife is cooking up a storm the house is potentially drawing over 20kW. Alternatively during the week when everyone is at work and school we're probably drawing less than a tenth of that.

So yes, I can install a good solar geyser and gas hob and replace the garden appliances with their petrol equivalents, but it will cost me close to R40K and I will still need some spare capacity for things like vacuum cleaner, power drill, saw etc. I can buy quite a lot of battery and panels for R40K.

The comment was made elsewhere that you need to "size the load to the batteries" and I think this is true too for the entire installation.

21 hours ago, Johandup said:

If you go too small and need to go bigger you will lose at least 50% of your initial costs when trying to sell it in the used market

Yes, this is what I'm trying to avoid.

21 hours ago, Johandup said:

A big concern to me is the message from prez Ramaphosa that an instruction was given to Guvament to get the solar rollout going.

I actually went as far as getting the requirements to connect a solar installation to the grid from City of Tshwane. Amazingly they replied. I took one look at the email and closed it again. The measly 10c/kWh they pay is simply not worth the schlep. I am not aware of any current legislation requiring compliance with these requirements. If anyone knows of anything please let me know. At the risk of getting off topic I also have in my possession a document recommending to CoT that embedded generator installations be reimbursed at a rate of 83c/kWh.

21 hours ago, phil.g00 said:

I expect other local authorities will adopt Cape Town's practices

Yes, I expect this legislation will go through once they have stopped knifing one another, which is why I want get this done now.

21 hours ago, phil.g00 said:

In that case, the size limit is 25% of your incoming MCB size.

Thanks, I'll check this.

21 hours ago, phil.g00 said:

You could also consider a combination of hybrid inverter and one of many 3rd party grid-tied inverters

I've got a friend up the road who has this set up. He is running about 6kW of panels. I'll go and have a look again.

22 hours ago, plonkster said:

But I still lean towards the smaller end. If you're considering LFP batteries, I'd much rather spend more on the batteries and less on the inverter.

Thanks, I was looking at the Pylontech US 3000. It just has to run the Fridge, Freezer and Fibre for 3-4 hours with perhaps some lights at night. Would it be adequate? The pool pump, geyser, oven, hob and outside plugs are all non-essential loads.

Thanks for the advice. Sorry, this message turned out to be a bit longer than I expected.

14 hours ago, VisN said:

@phil.g00 Are you referring to these numbers?

Yes, these numbers must be identical.

19 minutes ago, alanphys said:

Yes, I've been through this exercise a couple of times, but each time I get a different answer depending on what I chuck into the mix. My average daily usage over the last year is 34.1 kWh with a winter peak of 39.4 kWh. The instantaneous load at any one time can be far in excess of this. The biggest culprit is the pool pump (1.5kW @ 8 hours a day) closely followed by the geyser (4 kW) and the wife's beloved dual thermofan oven (8 kW) and ceran hob (6.6 kW). If I add in, on Saturday for example, the electric mower (2 kW), leaf blower (1.5kW),  trimmer (1.5kW) and washing machine (0.5 kW), and the wife is cooking up a storm the house is potentially drawing over 20kW. Alternatively during the week when everyone is at work and school we're probably drawing less than a tenth of that.

Well, ask yourself. Do I need to run the pool pump when the grid is off? Do I need to mow the lawn? If yes, is a cheap petrol mower (or a generator!) not cheaper than a larger inverter, for that once in a lifetime gardening event? Surely there is enough hot water in the geyser to last during the average load-shedding event? I'm not sure whether it is a good idea to ask whether the wife really has to cook during load-shedding... 😄

I can tell you that a very nice gas stove oven is around 15k.

Also, at 20kW, that's more than my single-phase installation can handle. The prepaid meter has overload protection built-in and relieves us of power around the 15kW mark 🙂 We rarely go there, and when we do, it's in the heart of winter. We haven't had a winter like that (in the Western Cape) since 2013.

Getting back to loads. With a 3kVA or a 5kVA hybrid inverter, if you run your geyser and pool pump during the day when you are not there, it can offset a significant part of those by using the inverter's grid-tie abilities.

26 minutes ago, alanphys said:

Thanks, I was looking at the Pylontech US 3000. It just has to run the Fridge, Freezer and Fibre for 3-4 hours with perhaps some lights at night.

It has 3kWh of stored energy. So it can run 1kW for 3 hours, 500W for 6 hours, etc etc.

If your loads are like mine, a single 3kWh might be a tad on the short side. Sadly, only you can answer this question.

Also, it is recommended that you have at least two on a 3kVA or 5kVA Multiplus, so a better idea might be 2 x US2500 units, though I do undertand that's a cool 10k extra.

1 hour ago, alanphys said:

I actually went as far as getting the requirements to connect a solar installation to the grid from City of Tshwane. Amazingly they replied. I took one look at the email and closed it again. The measly 10c/kWh they pay is simply not worth the schlep. I am not aware of any current legislation requiring compliance with these requirements. If anyone knows of anything please let me know. At the risk of getting off topic I also have in my possession a document recommending to CoT that embedded generator installations be reimbursed at a rate of 83c/kWh.

Would you mind sharing? No luck in sending emails to them and getting a reply.

I am a big believer in measuring amps - not kilowatts. Also running as well as starting amps. I have measured my hob and oven as taking 18 amps each from the dB. Definitely not inverter friendly.

You need to know what your inverter output in amps is. My 4kw gives me 16 amps with no bypass capability. The bypass capability can be a lifesaver when you need more amps and have mains available. 

51 minutes ago, PaBz0r said:

Would you mind sharing

Below is the text of the email and attached are the required forms.

Quote

The following aspects will have to be taken into consideration when planning and installing EG on sites within the City of Tshwane.
 
1.       Complete the attached Application form required for embedded generator installation. Can you please e-mail an electronic copy of the Application to [email protected] and   [email protected].  Kindly label the documents i.e Application form; single line diagram ;site layout ;control philosophy …..
2.            Please also deliver a hard copy of the Application to Antonette Nkuna at room 105 in Bothongo Plaza East, Francis Baard Street, Pretoria. Alternative room 132.   Should be submitted as soon as possible.
3.            Provide the documentation as indicated in the attached document such as copies of the Approved third party inverter type test certification.
4.            Please note the sizes of the EG installation allowed as stipulated by the NRS 097 series.
5.            Please provide a single line diagram of the proposed EG installation clearly indicating the Point of Connection (POC) to the city’s electrical network. NO INTERNET DRAWINGS AND PICTURES OF COMPONENTS ON THE DIAGRAM…
6.            Please provide figures of the minimum load at the premises.
7.            The City now has an approved FIT tariff  of 10c cents and take note of  the bi-directional metering costs in the tariff book.
8.            submit a CoC or letter of compliance to SANS 10142  by the Engineer  for the existing connection/ Premises and for the  back-up generator
 
Once the customer has provided us with the documents listed above, the evaluation process will commence for approval to enable the  go ahead for the  installation.
After installation:
1. Please provide copies of the commissioning reports.
2. A Site inspection and testing procedure for the installation will be arranged.
3. Attached also please find a copy of the Test form that is used when executing the tests on-site.
 
Also submit the control philosophy for all the applications PV systems,( if there are generators) back-up generator and council supply under following conditions:
1.            Council supply on
2.            Council supply  outage
3.            Council supply restored
 
Include the switching and synchronizing time. The operation & controls  in details.
 
Please  note that if your account is in arrears ,your application won’t be assessed.

 

NOTIFICATION FOR GRID ACCESS-EG.DOCX SSEG Tshwane Application Form Nov 2017 V4.docx Tshwane SSEG Commissioning Report with Tests Rev1 0 with CoT logo.pdf

59 minutes ago, PaBz0r said:

Would you mind sharing?

I also wanted to upload the "Impact of Small Scale Solar PV Embedded Generation (SSEG) on Tshwane’s revenue" document as well as the "Proposed Embedded Generation Policy" but the files are too large for the size limit. @PaBz0r I can send them to you directly if you want.

2 hours ago, alanphys said:

On 2020/01/20 at 12:54 PM, phil.g00 said:

In that case, the size limit is 25% of your incoming MCB size.

Thanks, I'll check this.

This is actually a NRS requirement not a City of Cape Town requirement so it essentially applicable to all municipalities as the law currently stands.  Cape Town though has gone with the strict interpretation of %ge of NMD which essentially limits inverter size to 3.5Kw and there aren't any of those on the approved NRS inverter list. 

The most recent NRS regulations will allow a 3.6kw inverter.

58 minutes ago, alanphys said:

I also wanted to upload the "Impact of Small Scale Solar PV Embedded Generation (SSEG) on Tshwane’s revenue" document as well as the "Proposed Embedded Generation Policy" but the files are too large for the size limit. @PaBz0r I can send them to you directly if you want.

Thanks for the information, I do have those two already. The others I have seen only drafts of, so thanks for this. Wonder how far we are out before they start giving deadlines for registration... 

48 minutes ago, IdlePhaedrus said:

This is actually a NRS requirement not a City of Cape Town requirement so it essentially applicable to all municipalities as the law currently stands.  Cape Town though has gone with the strict interpretation of %ge of NMD which essentially limits inverter size to 3.5Kw and there aren't any of those on the approved NRS inverter list. 

The most recent NRS regulations will allow a 3.6kw inverter.

From the webinar on Nov 29 2019 it was stated that hardware/software limiting can be used to throttle it within spec:

https://arepenergy.co.za/city-of-cape-town-webinar-nov-2019/

Good day

I'm new to the forum and solar and busy investigating solar as a means to reduce my electricity consumption (i.e. self generation) and as backup (i.e. Eskom load shedding), basically a Victron ESS type system. I came across this topic searching for info on Victron MPPT's and it enlightened me to some aspects I've not yet known about and considered, i.e. the limitation on the size of grid-tied inverter that may be installed in a standard household (60A MCB).

I'm interested in installing a Victron Multiplus II, the 5000VA one. The plan is to have my reptile room, living room plugs and lighting on AC-Out-1 (critical loads), with the rest of the house on AC-Out-2. My geyser has a 3kW element which I intend only switching on during peak solar production. My limited understanding is that a 4kW inverter can manage enough solar to power this without draw from grid. Now, if installing the 3000VA model my understanding is that, for the same setup, I'll only have enough solar to power 2.4kW of that and have to pull the 600W plus other loads shortfall from the grid?

Reading the datasheet for the Multipluss II 5000VA I however note that the Maximum Apparent Feed-in Power is only 4000VA (3200W/13.9A). Doesn't this mean that this unit actually falls within the NRS limitation of 25% of you MCB rating (0.25*60A = 15A)?

Edited January 23, 20206 yr by ewertb