Inverter Install Compliance

[deejaypsy]

I have a question for anyone out there with the knowledge to answer...
Myself and my business partner are both time served registered electricians and are doing a lot of inverter installs at the moment due to the load shedding issues we're experiencing.
Firstly, we are battling to find any decent supplier of inverters (pure sine preferable), so if anyone can point me in the direction of someone with a quality product i'd be interested to hear...
2ndly, the kind of install we are doing is a fully automated one.
Let me explain a bit...
The client supplies the UPS (for want of a better term...an inverter battery system is basically just that anyway...)
We install it as near to the mainboard as possible, and wire it into the mains with control and protective circuitry so that in the event of a power failure, only the critical circuits that the client requests will be powered off of the inverter/ups.
We wire the inverter so that when mains is on, the earth leakage supplies all of the plug circuits (and others that are run through it) as per normal.
When the mains fails and the inverter kicks in, it too runs through the earth leakage, supplying the critical circuitry, which is usually the tv and router plug circuits and the fridge, and possibly a lighting circuit or 2 (obviously the inverter setup is spec'd correctly for the amount of load required to be run).
The pure sine inverters are a dream, and run like this perfectly...however...the modified sine wave inverters do not run through the earth leakage.
They trip the earth leakage as soon as they come in, and you cannot reset the earth leakage on a modified wave.
So the only option is to wire the critical circuits off of the earth leakage.
Now how does this hold true according to the current regulations, where they state that all plug circuits should be protected by an earth leakage?
Do i need to tell the client that he must supply a pure sine wave inverter or his installation will not be compliant, or do the regs make allowance for this kind of install?
I realise that a UPS unit is designed to plug into a plug socket (thus excluding it from a CoC as it is not part of the fixed wiring), but if my client is asking me to automate his system so that he can have lights and usually 2 different (lounge and kitchen) plug circuits running off of his UPS in the event of a power failure, then how am i supposed to proceed?
Could someone tell me what the current regs have to say about an inverter as an alternative supply?
If a generator can be connected through your mainboard by means of an ATS, then surely so can a UPS/Inverter system.
Thanx

[AndyD]

I have a question for anyone out there with the knowledge to answer...
Myself and my business partner are both time served registered electricians and are doing a lot of inverter installs at the moment due to the load shedding issues we're experiencing.
Firstly, we are battling to find any decent supplier of inverters (pure sine preferable), so if anyone can point me in the direction of someone with a quality product i'd be interested to hear...

Not sure about Plettenberg Bay but see if you can find a local Victron agent if you want a decent quality inverter.

2ndly, the kind of install we are doing is a fully automated one.
Let me explain a bit...
The client supplies the UPS (for want of a better term...an inverter battery system is basically just that anyway...)
We install it as near to the mainboard as possible, and wire it into the mains with control and protective circuitry so that in the event of a power failure, only the critical circuits that the client requests will be powered off of the inverter/ups.

So the supply side of the inverter/UPS is hardwired onto it's own MCB in the DB? And the output side of the UPS is wired into the supply side of MCB's of the final circuits it's supplying?
How big are these UPS's? (in KVA).
Are you marshalling all the UPS supplied final circuits into a clearly defined area of the DB or are you just removing the normal supply wiring of the selected circuit breakers and fitting new supply wiring that's coming from the UPS?

We wire the inverter so that when mains is on, the earth leakage supplies all of the plug circuits (and others that are run through it) as per normal.
When the mains fails and the inverter kicks in, it too runs through the earth leakage, supplying the critical circuitry, which is usually the tv and router plug circuits and the fridge, and possibly a lighting circuit or 2 (obviously the inverter setup is spec'd correctly for the amount of load required to be run).

I'm really confused how you're wiring this, can you make a sketch or drawing to show your layout and attach it?

The pure sine inverters are a dream, and run like this perfectly...however...the modified sine wave inverters do not run through the earth leakage.
They trip the earth leakage as soon as they come in, and you cannot reset the earth leakage on a modified wave.

I think you may have a wiring issue but if you can attach a drawing it will help enormously.

So the only option is to wire the critical circuits off of the earth leakage.
Now how does this hold true according to the current regulations, where they state that all plug circuits should be protected by an earth leakage?
Do i need to tell the client that he must supply a pure sine wave inverter or his installation will not be compliant, or do the regs make allowance for this kind of install?

There are certain requirements that must be met but final dedicated circuits for IT equipment can be supplied without RCD protection. In your particular case I'm dead against this because I think you may have a wiring issue so removing the RCD will be treating the symptoms and not the cause which could leave potentially dangerous circuits.

I realise that a UPS unit is designed to plug into a plug socket (thus excluding it from a CoC as it is not part of the fixed wiring)

A common misconception, just because it 'plugs in' doesn't necessarily mean it's outside of the scope of the CoC. The system design you're describing will almost certainly require a CoC regardless of it being on a plug or being hardwired.

but if my client is asking me to automate his system so that he can have lights and usually 2 different (lounge and kitchen) plug circuits running off of his UPS in the event of a power failure, then how am i supposed to proceed?

These sockets must be supplied with RCD protection.

Could someone tell me what the current regs have to say about an inverter as an alternative supply?

I'm not sure what you're asking. An inverter or UPS back-up supply is permitted as long as it's installed to be compliant.

If a generator can be connected through your mainboard by means of an ATS, then surely so can a UPS/Inverter system.
Thanx

I don't understand the question, a UPS has an internal seamless (usually 5-10mS) automatic transfer switch built into it.

[bergie]

i have also being doing a few of these installations lately and i install a small surface db next to the db. i move the 2 or 3 circuits into the new db with its own earth leakage relay.it is then supplied direct from the inverter. i have been thinking of installing a optional changeover switch,as the inverter supply might not be enough when eskom power is on. when eskom is off then obviously the customer will be careful what he plugs in.also if the inverter is faulty in future then there would be no power on those circuits until it is repaired or manually bypassed.
i would sign a coc with a seperate db but not without, unless the original db has partitions in.

[AndyD]

We use both techniques depending on the layout of the existing DB and how easy it is to achieve separation. Many instances it's just easier and quicker to install a separate enclosure.

We rarely have overload issues because almost always the inverter is supplying a pretty static critical load and often the circuits are on dedicated sockets which reduces the likelyhood of something horrific being plugged in. I guess in a domestic application the risk of accidental overload would be far greater but we don't do the domestic side.

Did you manage a sketch deejaypsy?

[deejaypsy]

Sorry Andy,
Been a crazy end to a busy week. I've gotta rush out now again for a meeting...i'll post a sketch when i get back in a coupla hours...

[deejaypsy]

Sorry Andy,
Been a crazy end to a busy week. I've gotta rush out now again for a meeting...i'll post a sketch when i get back in a coupla hours...

I hope you can make it out clearly enough?
All wiring is correctly sized and UPS circuits are marked in the board.
Your thoughts...

Seems to have come out quite small after uploading...try my dropbox link, maybe that'll be easier to see...

https://www.dropbox.com/s/kwt0z8safrvbw8v/P1100332.JPG?dl=0

[Tonye]

i have also being doing a few of these installations lately and i install a small surface db next to the db. i move the 2 or 3 circuits into the new db with its own earth leakage relay.it is then supplied direct from the inverter. i have been thinking of installing a optional changeover switch,as the inverter supply might not be enough when eskom power is on. when eskom is off then obviously the customer will be careful what he plugs in.also if the inverter is faulty in future then there would be no power on those circuits until it is repaired or manually bypassed.
i would sign a coc with a seperate db but not without, unless the original db has partitions in.

Hi Bergie. I have been checking what the regulations say & based on this have come up with a diagram. Could you possibly let me know if this would pass a coc.

http://www.power.edisplays.co.za/changeover.html

[AndyD]

[ATTACH=CONFIG]5375[/ATTACH]

I hope you can make it out clearly enough?
All wiring is correctly sized and UPS circuits are marked in the board.
Your thoughts...

Seems to have come out quite small after uploading...try my dropbox link, maybe that'll be easier to see...
https://www.dropbox.com/s/kwt0z8safr...00332.JPG?dl=0

Sorry Deejatpsy, I missed your reply until now.

I haven't been through your control circuit completely but it looks way overcomplicated, I'd go with separate RCD's for the essential and non-essential then redesign it much simpler. Even better if the essential circuits are only supplying lighting and computer equipment and other ClassII appliances then make the sockets red dedicated and do away with the RCD entirely on the essential ccts.

[AndyD]

Hi Bergie. I have been checking what the regulations say & based on this have come up with a diagram. Could you possibly let me know if this would pass a coc.
http://www.power.edisplays.co.za/changeover.html

Does your inverter not have an internal 10mSec switch?

[Tonye]

It does have an internal transfer switch which would allow an uninterrupted power supply to the mini DB. However this is for domestic use and need to allow larger loads on the mini DB when eskom mains are selected.
When used in inverter mode, the inverter circuit breaker is the primary overload protection.

I am using a 24 volt 2.4kva modified sign wave inverter with a .6 PF, together with 2 x 12v 105 amp hour deep cycle batteries. The inverter has a UPS & inverter setting ( different line low & line high detection).
It also has 2 charger settings 10A & 20A.

On mission critical equipment ie, Dstv decoder, Adsl router modem etc.. I have installed smaller UPS's,
To allow uninterrupted power while changing over.
However the modified sign wave inverter could not keep the UPS's running in online mode.
Little did I know that one requires a pure sign wave inverter to run a UPS in online mode.

I did eventually find a suitable UPS to operate on a modified sign wave. Problem solved.

I would just like to make sure that the diagram I submitted would pass a coc



I would also like to know if the diagram I submitted would pass a coc.

[deejaypsy]

Hi Bergie. I have been checking what the regulations say & based on this have come up with a diagram. Could you possibly let me know if this would pass a coc.
http://www.power.edisplays.co.za/changeover.html

Hi Tonye,
Just a question...
Why are you feeding your mini DB with a breaker that is on your main DB's EL, as the mini DB has its own EL anyway.

[deejaypsy]

Sorry Deejatpsy, I missed your reply until now.

I haven't been through your control circuit completely but it looks way overcomplicated, I'd go with separate RCD's for the essential and non-essential then redesign it much simpler. Even better if the essential circuits are only supplying lighting and computer equipment and other ClassII appliances then make the sockets red dedicated and do away with the RCD entirely on the essential ccts.

Hi Andy,
I have since modified my design to include a 2nd EL solely for the use of the critical equipment and am in the process of redesigning the control circuit to simplify it as suggested.

[bergie]

hi tonye

your diagram looks good . i do it the same way. deejay is correct though the mini db supply breaker shouldnt be on the main dbs earth leakage relay.
i use a modular changeover switch and install it in the mini db.
as you mentioned , the customer can choose to leave it on inverter but be limited with total current or changeover to eskom and have full load.

[Tonye]

My bad. have changed diagram


One problem I had, was the inverter has a floating neutral on output side. Voltage tests between live & earth 110v, between neutral & earth 110v.
Earth leakage on Mini DB showed an earth fault and would not trip.
After consulting with an electrical engineer who stated the neutral needed a reference point, I connected the neutral to main earth on the output side of the inverter.
Bingo, problem solved

[deejaypsy]

My bad. have changed diagram
[ATTACH=CONFIG]5414[/ATTACH]

One problem I had, was the inverter has a floating neutral on output side. Voltage tests between live & earth 110v, between neutral & earth 110v.
Earth leakage on Mini DB showed an earth fault and would not trip.
After consulting with an electrical engineer who stated the neutral needed a reference point, I connected the neutral to main earth on the output side of the inverter.
Bingo, problem solved

Ah hah!
This solves a problem i have been finding of an earth fault not tripping the EL.
So the solution is to earth the neutral on the load side(output) of the inverter?
This makes sense.
Thanx for the input.
The inverters i have installed are line interactive inverters so no changeover switch is required. It switches automatically on mains fail, but even when Eskom is available it runs in bypass mode, still supplying the critical load with power at the rated maximum size of the inverter...