Using an inverter as a UPS

Gnome

Gnome

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I thought this may be useful to others.

I've completed an entire build, including wiring up my apartment with backup power (I live in Cape Town).

My equipment:

Backup system:

Inverter: Cotek SK1000-224
Motivation: There is plenty of info around about this inverter but essentially it is UL listed which is very hard to get. The product is built for industrial settings, it has high efficiency, high surge rating and very high quality output. During my testing the most powerful item I tested on it was a 980Watt Robi Angle grinder which ran without issues (startup had a momentary overload light show).
Cost: R3000 from eBay (lucky find)

Batteries: 2x Excis 12v 102Ah battery
Motivation: Really this was easily available from Makro. I don't recommend these batteries. I already paid for them so I'm staying with them for now but you can do better!
Cost: R1700 each from Makro

Charger: 2x Noco Genius G7200UK 7amp smart lead acid battery chargers
Motivation: There is a lot of information available about battery chargers. What I quickly learned was that if you want to have any hope of your batteries surviving a decent amount of time, you need smart battery chargers you can leave on 24/7 and not worry about over- or undercharging. I also have a CTEK charger and on my Oscilliscope (yes I have one), both charge with the same algorithm, so overall I think I got a good deal.
Cost: R800 each from Amazon.co.uk on special (R2000 total with shipping using Postbox courier to SA).

Power cables: 50mm^2 wire from Voltex in Cape Town + 10mm lugs.
Cost: Power cable is R71 a meter, R7 a lug. I bought 2 meters.

Custom modifications:
This is an inverter, it doesn't have a change-over switch (Automatic or otherwise) and it doesn't have an automatic turn on. Additionally during my testing I found that leaving it turned on consumed too much power.

Automatic switch over: I bought a Magnecraft 3 Pole, Double Throw 15 amp relay with a 240v coil from Amazon.com

Motivation: 3 Pole means that you can connect 3 wires. Double throw means it has two positions. So you have a switch that has two positions (on/off), each with three wires (live + neutral + earth for each position). The switch is turned on by 240v AC (normal wall power). So that means you can switch between Eskom (Live + Neutral + Earth) and Inverter (Live + Neutral + Earth).

Cost: Approx R300.

How well does it work? I think I should make a video and show on my Oscilliscope also, but essentially, with a light bulb there is a slight dim. Even on my APC I get a slight dim. You can hardly tell that you are switching over, it is very quick. On my Oscilliscope it takes about 1 AC cycle.

How did I wire this:
In short, do not wire this into your DB board. The great SABS safety loop hole is that you can wire anything from a plug. So as long as your wire this from a plug it is 100% safe. You wire a normal plug so that the live and neutral connect to the relay coil wires. Additionally the live + neutral + earth wire to the Normally Open contacts.
Your inverter has a plug coming out and you wire the live + neutral + earth to the Normally Closed contacts.
Wire your output (which should go to a multiplug or something) to the common contacts on the relay (again live + neutral + earth).
DO NOT SKIP THE EARTH on ANY contacts!
Plug in the Eskom plug and you should hear a click and your multiplug will already output power (unless there is load shedding).
Plug the other outlet into your Inverter.

How to auto-turn on your inverter:
All inverters have switches, so that makes it real simple. I bought a Single Pole Double Throw 240v AC coil relay from Communica for R60. That means it takes 240V from the plug and turns on a relay. I wire the power switch so that the on wire is wired to common and then the normally closed contact goes to the switch.

This means my inverter will only switch on if:
1) It is not plugged (the relay) in OR Eskom power is off
2) The Inverter on switch is on (I didn't remove that switch I simply added a second switch in line)

How well does this work? The relay has a 10ms switch time, it is so quick I can't even hear it click over the click of turning on the plug. It works incredible well. When Eskom power goes off my inverter switches on.

How did I wire my DB?

The truth is I only care about my house lights. All my plugs stuff I just run straight from the multiplug I mentioned before (or run leads). This is to avoid any legal issues with tampering with an electrical installation.

So how did I wire my lights?
Firstly my apartment has 3 phase. In Cape Town old houses and apartments have 3 phase. It is just how it is. So my lights are on a single phase and they aren't wired through a earth leakage.

All my lights run from a single 10 amp breaker.

I bought a CBI 2 pole 10 amp breaker before this I had a single pole.
Cost: R250 from RG Jack and Son in Cape Town

Ideally my lights should also go through a earth leakage after the 10amp breaker, but I am waiting on a 3 phase earth leakage and will then use the single phase earth leakage that was begin used on *some* of my plugs (yep my install is old an dodgy, they left some plugs off the EL, ouch)

I wired the light wire straight from cable that came into the box into the 2 pole breaker (so I can still switch off lights at the DB Board). Then I bought a solid core SABS rated cable into the box and it goes straight into the 2 pole breaker at the top. The other end plugs into the multiplug. It is labelled as having backup power on my DB board.

So my lights are wired from either my house plugs or inverter VIA a plug. As far as I can tell this should be up to code, especially if I run my lights through a EL.

The ground wire goes straight through to the plug (not DB board ground). This allows it to ground to the inverter or house depending on which supplies the power. There may be a ground interrupt but at the same time, live and neutral are also broken so I think it is overall safe. (Comments welcome on this)

Final words:

I'll update with some pics if there is more interest!

Drop some comments.

Some of this stuff I based on my own knowledge, SABS documents, etc. This was a lot of work in terms of research and comments welcome if you know better. I would love to share some knowledge on this and don't mind getting some pics with a decent how to. Overall you can build a pretty impressive setup for relatively low cost. (Think I've paid about R10k so far)

Let's get the ball rolling on knowledge sharing please :)
 
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Test. Last time I tried to post this screen froze.
 
Excellent. Thanks Gnome for a great description of your setup. I want to do something very similar. I already have a 1000W inverter, 2 100Ah batteries and a 5/10amp smart charger set up, but it's still at the 'moving plugs from one socket to another' stage. I want to move it on to more like a UPS, like you have done. This has been prompted by a computer failure due to a sudden shutdown. I need to 'understand' your setup better then I can do something similar. Will get there :-)
 
inverter.jpg

This is my inverter,charger and battery. I've since added a second battery.
 
You can not feed a permanently connect circuit (i.e. lights), from an non-permanently connected circuit (inverter connected to a plug socket).

Using a relay (with a quick switching time) vs. a manual change over switch (on-off-on), also means that you can (and more than likely will) get feedback surges because of the quick and automated change over. As you have no protection to deal with this, it can, and more than likely will damage your equipment over time.

Lastly, as this is an off-grid inverter, it more than likely uses a center tap on a transformer for a earth (V-O-V Earth). It terms of SANS, it is illegal to connect this to a fixed electrical installation....

But, best of luck to you.

EDIT: Side note... Your plug has a 20A Breaker on it (~4.6kW), and you have a 1kW Inverter. Your Inverter also has no adequate protection against overloads - which also is a very bad thing.
 
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savage said:
You can not feed a permanently connect circuit (i.e. lights), from an non-permanently connected circuit (inverter connected to a plug socket).
Click to expand...
Interesting, I'm not expert here, hence asking for advice.

My lights are wired as follows: (Simply put)
Plug -> 10A Circuit Breaker (L + N) -> Earth Leakage (L + N) -> Lights L + N wires.
The earth wire from the lights go straight to the plug mentioned above.

So when Eskom power is on, this is my lights circuit effectively:
35A Breaker (3P+N) -> EL (3P + N) -> 20A Plug Breaker (1P) -> Plug socket -> Plug -> 10A Circuit Breaker (L + N) -> Earth Leakage (L + N) -> Lights L + N wires.

I'm not back feeding, perhaps you understood it, but just making sure.

I doubt that can be classified as unsafe but it may not meet the requirements. Any input on how to improve this?

savage said:
Using a relay (with a quick switching time) vs. a manual change over switch (on-off-on), also means that you can (and more than likely will) get feedback surges because of the quick and automated change over. As you have no protection to deal with this, it can, and more than likely will damage your equipment over time.
Click to expand...
I have surge plugs but if you mean brown out, my UPS detects the relay turning off as a drop out. But switching back to Eskom power is not even detected by the APC Smart UPS (it is really fast).

I'm thinking I should upload a Youtube video + Oscilliscope. The change-over is almost certainly faster than most of the off the shelf solutions. The relay isn't exactly some cheap piece of crap.

savage said:
Lastly, as this is an off-grid inverter, it more than likely uses a center tap on a transformer for a earth (V-O-V Earth). It terms of SANS, it is illegal to connect this to a fixed electrical installation....
Click to expand...
It probably is, so there is really no option to wire it to the lights with such an inverter if my understanding is correct?

savage said:
But, best of luck to you.
Click to expand...
Thanks

savage said:
EDIT: Side note... Your plug has a 20A Breaker on it (~4.6kW), and you have a 1kW Inverter. Your Inverter also has no adequate protection against overloads - which also is a very bad thing.
Click to expand...
Huh? The inverter has its own overload protection and will shutdown if there is an issue.

I don't wire my inverter into any plugs...

My setup is as follows:

Eskom power from wall plug (Completely standard plug) -> Change Over Switch
Inverter -> Loose 10A Circuit Breaker (Not wired into my panel, it is just for the UPS) -> Change Over Switch

Change Over Switch -> Multiply plug (Does not go into my DB at all), there are just some devices plugged into that plug.

Change Over Switch is a 3P 15A relay powered by Eskom power as I said. I guess I could add a fuse for the relay coil to make it more "safe".
Everything else has overload protection and I see no reason it is unsafe.

My lights are wired via a plug as I said below which you say is not legal even if it goes VIA a circuit breaker and EL.
That I think is the only concerning part here.
 
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Gnome said:
Interesting, I'm not expert here, hence asking for advice.

My lights are wired as follows: (Simply put)
Plug -> 10A Circuit Breaker (L + N) -> Earth Leakage (L + N) -> Lights L + N wires.
The earth wire from the lights go straight to the plug mentioned above.

So when Eskom power is on, this is my lights circuit effectively:
35A Breaker (3P+N) -> EL (3P + N) -> 20A Plug Breaker (1P) -> Plug socket -> Plug -> 10A Circuit Breaker (L + N) -> Earth Leakage (L + N) -> Lights L + N wires.

I'm not back feeding, perhaps you understood it, but just making sure.

I doubt that can be classified as unsafe but it may not meet the requirements. Any input on how to improve this?


I have surge plugs but if you mean brown out, my UPS detects the relay turning off as a drop out. But switching back to Eskom power is not even detected by the APC Smart UPS (it is really fast).

I'm thinking I should upload a Youtube video + Oscilliscope. The change-over is almost certainly faster than most of the off the shelf solutions. The relay isn't exactly some cheap piece of crap.


It probably is, so there is really no option to wire it to the lights with such an inverter if my understanding is correct?


Thanks


Huh? The inverter has its own overload protection and will shutdown if there is an issue.

I don't wire my inverter into any plugs...

My setup is as follows:

Eskom power from wall plug (Completely standard plug) -> Change Over Switch
Inverter -> Loose 10A Circuit Breaker (Not wired into my panel, it is just for the UPS) -> Change Over Switch

Change Over Switch -> Multiply plug (Does not go into my DB at all), there are just some devices plugged into that plug.

Change Over Switch is a 3P 15A relay powered by Eskom power as I said. I guess I could add a fuse for the relay coil to make it more "safe".
Everything else has overload protection and I see no reason it is unsafe.

My lights are wired via a plug as I said below which you say is not legal even if it goes VIA a circuit breaker and EL.
That I think is the only concerning part here.
Click to expand...

Post some pics please and some videos.

Mine is connected via the death plug, he he..... :D
Feed back into the mains
 
Gnome said:
My lights are wired as follows: (Simply put)
Plug -> 10A Circuit Breaker (L + N) -> Earth Leakage (L + N) -> Lights L + N wires.
The earth wire from the lights go straight to the plug mentioned above.

So when Eskom power is on, this is my lights circuit effectively:
35A Breaker (3P+N) -> EL (3P + N) -> 20A Plug Breaker (1P) -> Plug socket -> Plug -> 10A Circuit Breaker (L + N) -> Earth Leakage (L + N) -> Lights L + N wires.

I'm not back feeding, perhaps you understood it, but just making sure.

I doubt that can be classified as unsafe but it may not meet the requirements. Any input on how to improve this?
Click to expand...

It's not about back feeding - it's about standards and safety. You may not go from a plug, back into a DB to access the light circuits. When I switch off your 'main switch' (your 3P+N I suppose), the entire board must be off. In your case, when I switch off your 'main switch', your 10A circuit containing your lights, will still be energized. Thus, it is an unsafe installation.


Gnome said:
It probably is, so there is really no option to wire it to the lights with such an inverter if my understanding is correct?
Click to expand...

Correct. A inverter/UPS that connects to a PLUG SOCKET, can not, and MUST NOT, be seen as a permanently connected device. Therefore you may NOT connect it to permanently connected circuits (in your DB).

Such a UPS/Inverter is designed and manufactured to have appliances connected to it, not fixed electrical installations. It is illegal. SANS is also VERY clear on this, as I have previously pointed out in other threads.
 
savage said:
It's not about back feeding - it's about standards and safety. You may not go from a plug, back into a DB to access the light circuits. When I switch off your 'main switch' (your 3P+N I suppose), the entire board must be off. In your case, when I switch off your 'main switch', your 10A circuit containing your lights, will still be energized. Thus, it is an unsafe installation.
Click to expand...

Do you have a link to the relevant documents?

EDIT:
My current thinking is to move the lights out of my DB into another sub panel but really to understand what is legal would require that I read the documents.
 
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Gnome said:
Do you have a link to the relevant documents?
Click to expand...

SABS will ask you money for them. You're not allowed to share those SANS documents.

Funny that. The law references SANS, but Joe Public has to fork out money to be able to see what is legal or not. :mad:
 
Found this on an obscure web-site: View attachment SANS10142-1Amdt8.pdf

It does seem it is ok to feed power back into the board, I am refering to page 357 of that document.

However an indicator light is required showing that there is power. Is my interpretation here correct?
 
SANS (South African National Standard) 10141-1 - Available from the SABS (South African Bureau of Standards)

Just for the record...

6.1.4 All the conductors of any circuit shall originate at the same distribution board.

Your lights circuit originate at the inverter, connected to the plug socket.


6.1.9 The continuity of neutral and earth circuits shall be ensured at all times, and, except where the luminaire is used as a wireway for through wiring, the continuity shall not be disturbed during repair, replacement or removal of any appliance.

Your neutral and earth for your light circuits can be disrupted, by plugging out the inverter from the wall socket.


6.14.1.4 In a lighting circuit, a luminaire that is in a false ceiling or in a roof space 4 m above the floor where there is no ceiling, or in a floor cavity, or in a wall cavity, or in a similar position, may be fed from a socket-outlet which may be unswitched and not protected by earth leakage protection, provided that the socket-outlet a) complies with SANS 164-3 or, except in the case of residential installations, with BS 1363-2 (for 13 A fused plugs), Amdt 5

NOTE As from 1 January 2011, in terms of the compulsory specification for plugs, socket-outlets and socket-outlet adaptors (see 2.1), BS 1363-2 socket-outlets may no longer be sold in South Africa. Amdt 8

b) supplies one luminaire only, not exceeding the rating of the socket outlet,
c) is accessible for maintenance purposes, and
d) is within 3 m of the luminaire that it supplies.

6.14.1.6 In a lighting circuit, a luminaire may be fed from a socket-outlet on a wall (that may be unswitched), provided that the socket-outlet
a) complies with SANS 164-3, Amdt 5
b) is protected by earth leakage protection,
c) supplies one luminaire only, not exceeding the rating of the socketoutlet, and
d) is within 3 m of the luminaire that it supplies.

At least one 16 A socket-outlet that complies with SANS 164-1 or SANS 164-2 (see 6.15.2.1) shall be installed in the same room. Amdt 5

The above, is the ONLY exception to where a fixed light in a roof/ceiling, may be powered from a wall socket.


6.16.1.6 A socket-outlet shall supply only one fixed appliance. The use of flexible cords of length exceeding 3 m is not recommended. The reason for this recommendation is an endeavour to ensure operation of the overcurrent protective device. (But see also 6.14.1.4 for luminaires.)

SO... Not light circuits in your DB which isn't even considered a fixed appliance.


7.12.2.7 A 230 V generator with a V-O-V earth connection (centre tap on winding which is earthed), shall not be connected to a fixed electrical installation. Amdt 6

NOTE Such a generator may be used as a free-standing unit to provide power to specific appliances.

Your inverter will be classified as a generator, and pretty much any inverter not tied to the grid in some form or fashion, WILL have a V-O-V earth connection - unless of course, you've also installed a dedicated earth pin that you've forgot to mention.

There are so many issues with what you have done in terms of standards, safety, and regulations, I don't actually even know where to begin.

Posts/Installations like these really peeves me off, as it really sets an incorrect, and misleading trend. It is NOT allowed to do this, due to various reasoning, and I personally will continue to point this out in any and all posts of such installations that I see. Tomorrow, Piet Pompies finds this post through google and burns his house down / electrocute himself because he doesn't know the implications of what he is doing...
 
savage said:
Posts/Installations like these really peeves me off, as it really sets an incorrect, and misleading trend. It is NOT allowed to do this, due to various reasoning, and I personally will continue to point this out in any and all posts of such installations that I see. Tomorrow, Piet Pompies finds this post through google and burns his house down / electrocute himself because he doesn't know the implications of what he is doing...
Click to expand...

You are getting on your high horse there a bit. Although I want this installation to be compliant, I do not agree with your safety concerns. Realistically the safety concern here is that someone could shock themselves IF they open the DB board. Other than that the entire circuit is protected with both over-current and unbalanced L+N protection.

What is more, I'm endeavoring to understand the regulations and make it 100% complaint.

Lastly, this is my own house, I own it. I'm not renting it out, nor would I leave it that way in someone else's care unless it were complaint.

There is 0 fire risk here. I'm not telling anyone else to follow my advice. I'm detailing my setup for input.

savage said:
Yes - a PERMANENTLY CONNECTED UPS. Not a UPS fed from a wall socket (temporary connection). There are fundamental differences.
Click to expand...

So the big issue is that it has a plug on it?
 
Gnome said:
You are getting on your high horse there a bit. Although I want this installation to be compliant, I do not agree with your safety concerns. Realistically the safety concern here is that someone could shock themselves IF they open the DB board. Other than that the entire circuit is protected with both over-current and unbalanced L+N protection.
Click to expand...

There are rules and regulations for a reason. When your house burns down due to an electrical fault... What happens then? Not only don't you have a valid COC, but you have an electrical installation that is not compliant. Whether the fire was caused by an electrical fault or not, good luck with your insurance company.

Even when you are alone on a road, you are still compelled to adhere to the speed limit of that road.

Personally, I couldn't care less about what you do. As you say, it's your house, your safety, and your battle to fight with your insurance company / chief electrical inspector / take your pick of authoritative body. The issue is that this is a public forum, and OTHERS don't understand the implications of what you are doing.

You asked for comments - I've provided them. I can't help that you don't like them :whistle:
 
savage said:
There are rules and regulations for a reason. When your house burns down due to an electrical fault... What happens then? Not only don't you have a valid COC, but you have an electrical installation that is not compliant. Whether the fire was caused by an electrical fault or not, good luck with your insurance company.

Even when you are alone on a road, you are still compelled to adhere to the speed limit of that road.

Personally, I couldn't care less about what you do. As you say, it's your house, your safety, and your battle to fight with your insurance company / chief electrical inspector / take your pick of authoritative body. The issue is that this is a public forum, and OTHERS don't understand the implications of what you are doing.
Click to expand...

Realistically I don't believe that is the risk here (fire). I think my mayor concerns at this point are safety. And you pointed out a good safety concern. Namely that someone can get shocked if they remove the DB panel. Now I want to fix that :)

savage said:
You asked for comments - I've provided them. I can't help that you don't like them :whistle:
Click to expand...

Agree, appreciate the comments, just don't want to have an argument about it, I would rather understand the regulations and make it complaint. Doesn't help me trying to do a COC if I know it'll fail.
 
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