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Newbie- 3 Phase Power and Inverter


RyanBM
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Hi All

 

I'm a complete newbie to backup power and alternate energy- however given the prevalence of load shedding and power outages, I need some assistance.

I received a blind quote for the following:

3kva Axpert Inverter

2x 100ah Gel Batteries

2x Solar Panels 

All other hardware and consumables

Supply and Installation

Total R15,000

When they came on site to install he said it was not possible as I have 3phase power.

I was then offered a similar system that was not automatic but that I had to plug in during power outages, which won't work for me.

My needs are simply to have basic power during outages- to run boundary lights, internal lights, 2 TV's, Router and alarm for +/- 4hours.

 

My question, do you get 3 phase inverters and if so are they seemingly different to conventional single phase inverters?

 

Tx

Ryan

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Do you have any 3 phase appliances or equipment? I highly doubt you would of this is a residential property. 

You can install the inverter on one of the phases but it will only supply power to those circuts. 

I would look at what you want the system to power during loadshedding, make sure those circus on one phase and then install the inverter on that phase. 

It is possible to use the system they quoted initially. 

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@Achmat, thanks so much for your response.

I live in Bryanston in JHB in a mini estate- so we aren't even allowed a gennie, let alone any high powered machinery- so definitely nothing requiring 3 phase.

So just to confirm:

I move all the required circuits to the phase I want to backup (selected lights and plug points) and have only this phase connected to the inverter?

Is this a straight forward operation, as I'm surprised the installer didn't suggest this approach when he came on site?

On a slightly different point, not wanting the hassle of panels for now, I requested a quote for just the inverter and batteries- this was more expensive- does this make sense?

I've attached the quotes for reference.

Tx again for your assistance.

 

RYAN MATTHEW_09 Jan 2021_1610185006.pdf RYAN MATTHEW_09 Jan 2021_1610192924.pdf

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The first quote does not seem to have the battery disconnect and change over switch which would be required with either option. 

Can't really comment on the prices as I'm not an installer or reseller. 

I think the installer will always try to oversell. Best is to know what you want and insist on the setup you want. I opted to get my own equipment and then find an installer instead of an installer that will supply everything. 

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1 minute ago, RyanBM said:

Tx for the feedback.

 

Is there anywhere to get a schematic or list of items I would need- I will buy them separately as you suggested and get them installed.

It's pretty straight forward.

First determine your budget and then what you want to achieve.

 

By the quote of what you are looking at I recon you are looking at a backup solution. You will need to calculate how long you want the backup to run and what the power draw will be if everything running from the inverter is on.

First would be an inverter. A 48v inverter would be ideal. Also consider if you ever want to upgrade beyond your initial requirements and if the inverter can accommodate this.

Batteries. Depending on budget and how long you want to be able to run on them, this would be the most costly. AGM is ok for a backup where you are not constantly cycling your batteries. Lithium would be best if you plan on expanding the system later to not just be a backup solution. Basically if you use 500w and want to be able to go through 4 hours of loadshedding you will need 2kWh of batteries. This however is not enough as they will completely empty after 4 hours. Ideally you only want to use 50% capacity of an AGM battergy or 80% to 90% of a lithium battery. For AGM batteries this would be 4kWh of batteries or 2.5kWh of lithium batteries.

Solar panels. This would be determined by the inverter in terms of minimum number of panels for the inverter to be able to generate pv electricity.

PV disconnect and fuse box. This will be between the solar panels and the inverter.

Battery disconnect and fuse. This will be between the battery and inverter

Changeover switch. To isolate the inverter in the event that you need to remove it.

Depending on how your DB is currently setup, you might need a few more circuit breakers in the DB.

Cabling. Various types of cabling to connect it all up. Mounting system for panels and other small odds and ends.

My own system is pretty big and I'm not an electrician. I investigated the options, read a lot and then started to compile a list of what I needed. I probably had 90% of what I needed before I looked for an electrician and basically told him what I needed him to do. If you come across as confident and informed, they will not try and hoodwink you into getting things you don't need or not inform you that you can use an inverter on one phase of a three phase system as you do not have any 3 phase equipment. It's like the jokes of women being taken for ride by their mechanic. There are some good installers who can provide a complete solution without trying to take advantage of the client. Maybe look through some of the threads in the Member installation section.

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19 minutes ago, RyanBM said:

@Achmat, Thanks Bud, really appreciate the info. I have lots 9f home work it seems.

Final question, why is a 48v inverter preferable? 

Lower volts will require more amps for the same watts. This will mean that you will need thicker cables for the same amount of electricity. 

A 24v system will need 70mm² cable to supply 5kw from the batteries. A 48v setup will only need 25mm² cable for the same application. 

Thicker cables are harder to work with and costs significantly more. 

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14 hours ago, Achmat said:

Lower volts will require more amps for the same watts. This will mean that you will need thicker cables for the same amount of electricity. 

A 24v system will need 70mm² cable to supply 5kw from the batteries. A 48v setup will only need 25mm² cable for the same application. 

Thicker cables are harder to work with and costs significantly more. 

Tx makes sense 

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58 minutes ago, RyanBM said:

Gents another question, can I initially just go the inverter battery route and then include panels at a later stage? 

Yes. It will then basically just be a backup solution. 

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On 2021/01/18 at 9:56 PM, Achmat said:

Lower volts will require more amps for the same watts. This will mean that you will need thicker cables for the same amount of electricity. 

A 24v system will need 70mm² cable to supply 5kw from the batteries. A 48v setup will only need 25mm² cable for the same application. 

Thicker cables are harder to work with and costs significantly more. 

@Achmatis it an issue if the battery ah rating halves when going from 24v to 48v- I'm guessing you half the output?

However, if 48v is more efficient that 24v would this suffice?

tx

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On 2021/01/20 at 10:08 AM, RyanBM said:

@Achmatis it an issue if the battery ah rating halves when going from 24v to 48v- I'm guessing you half the output?

However, if 48v is more efficient that 24v would this suffice?

tx

The magic formula is W=V*I. So if you double the voltage and half the current (I, measure in Amps) you still have the same amount of power.

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