# Interest group forums > Energy and Resource Conservation Forum >  Manage load shedding

## IanF

Hi Guys,
With loadshedding upon us and the frequency may be going up I looked at how we should manage it. 
Loadshedding in Jhb is now scheduled at 4½ hours then lasts 5 hours.
We bought a lot of UPS so we can close down the computers and server gracefully. 
My current situation is there is no logical place to put a generator permanently we have a narrow passage at the back of the shop which gets flooded when it rains.

The current thinking is just to power on 2 computers the router modem and an inkjet printer so we can do quotes invoicing and design work during loadshedding , the main production machines ratings are 9 10 and 20amps on single phase power. And generally we can catch up production within a day after loadshedding.

So for the computers etc. I totaled up the wattage and came to 1003 watts. Then got a quote for a 5 hour invertor and battery solution this was totally out of what we can afford presently.
Then looked at the power consumption and the 80% draw was 2 power supplies to the PCs at 400 watts each. 

Now I need some opinions is it worthwhile changing the PCs  to something like an Intel NUC which only draws 65w. And would knock of at least 600w from the 1000w current setup. Does anyone have experience with them and can they handle 2 screens and 2 hard drives?

Also using the crystal balls how severe and long is this current loadshedding going to be? This makes planning so hard.

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## Houses4Rent

> Also using the crystal balls how severe and long is this current loadshedding going to be? This makes planning so hard.


Elevate your generator so it does not go for a swim when it rains.

Load shedding will be there for some years to come Eskom says. I think currently the problem of skipped planned maintenance and the resulting fallout/downtime will get worse, not better in the near future. Luckily we have 2-2.5h slots in Cape Town only, but up to 4 times a day in extreme stage 3B cases.

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## AndyD

> .........I totaled up the wattage and came to 1003 watts. Then got a quote for a 5 hour invertor and battery solution this was totally out of what we can afford presently.


Ian, rather actually measure the current draw in real life using an accurate clamp meter I think you'll find there's big discrepencies between the power stated on the label and the actual current draw. The easiest way is to use a short extension lead with a section of the outer cable sheath carefully stripped away so you can put a clamp meter around just the live or just the neutral wire to read the current. I think you'll be pleasantly surprised and may be able to specify a smaller system accordingly.

Secondly look at an inverter that you can scale the number of batteries over time. For example I've fitted 4 x 225Ah batteries to my home inverter and I'm getting around 3 hours of backup time with several lights, my home office PC's laptops and printers, my servers, router, small phone system plus the TV and entertainment PC running along with intermittant coffee machine usage. If the loadshedding situation deteriorates I can merely purchase another 4 x identical batteries and some cabling to connect them and the exact same system will then give 6 hours back-up time to the same load.

**edit**
I'd be interested to see the quotation you got but no biggie if it's a trade secret  :Smile:

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## tec0

Hi Ian, hope you are doing well. 

Perhaps it is time to upgrade to powerful notebooks? I know a good one will set you back about R11k and have all the Ram and graphics power you will ever need. Also it demands a lot less power from your inverter. My "office" is streamlined to run on about 80watts per hour. I did this by converting to LED lights and got myself a good Laptop that can handle my demand. I recommend the HP Pavilion Series they are good value for cash... Just make sure you find out how much the battery cost before making this choice. Yea it is expensive!  

Printer wise you will know best. Inverter will give you 4hours on normal PC systems but if you switch to notebooks it will last longer as it consumes much less power then a PC. Also you can lock the notebooks in a safe. As for your generator you get a Honda generator that is build for welding and put out about 30 Amps at single phase. If I recall it is a 6500 Watt system. The amps however makes it worth the R14k Perhaps placing the Generator on a few blocks of wood and cover it with plastic to avoid the rain can help things along. Just make sure to allow for cooling. I added a standard 12 radiator fan to mine due to the hellish heat as of late. 

The Honda Generator I saw at the local hardware store and is locally made. My inverter system is a simple 500Watt system running on two 12 Volt batteries. I got half of the stuff for free so I really cannot give you a cost. 

Hope this gives you some idea... Consider the needs of each computer. then see if you can find a laptop that can do the job. Not all of them need to be supper powerful right. I mean surly a simple i3 laptop can handle office work. and few programs can give a i5 a hard time and if you really must i7 will handle almost anything.

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## IanF

Andy I will try measure the actual draw and then recalculate. I just looked at the computer's psu. 
Teco I will look at the laptops as well as the NUC computers we are currently using 2 year old i5 desktops with a basic graphics card to allow for a 2 screen setup. Like most things once you are used to 2 screens it is hard without them.

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## IanF

Just realised I have an AVR with a built in meter I will use that and measure the watts.

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## wynn

We had a rep from ADT at our last CPF meeting and he said that the back up batteries in most alarm systems require about 24hrs to recharge after a 2 hr power cut, he says a lot of alarm systems start to fail after three consecutive loadsheds over three days because they don't have the time to recharge properly, he recommends putting in an inverter to a larger battery in series with the battery in the system, same with remote gates if busy.

So I would also calculate the time required to recharge the batteries on any UPS system you are installing.

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## IanF

Ok hooked up the AVR and reads 230v fine but the Amp meter doesn't move. This works to protect the laser tube so it does do what we bought it for. Anyway will work on measuring later.

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## AndyD

> We had a rep from ADT at our last CPF meeting and he said that the back up batteries in most alarm systems require about 24hrs to recharge after a 2 hr power cut,


Battery charging on a graph against time isn't a straight line. Charging the battery the last 5 or 10% can take 50% of the charging time so whilst it's possible a battery could take 24hrs (although somewhat doubtful) even if it did it would be at least 80% charged after half that time.





> he says a lot of alarm systems start to fail after three consecutive loadsheds over three days because they don't have the time to recharge properly,


 I wouldn't see any reason for this if the battery is in servicable condition and the charger is correctly matched and functioning, are you sure they're not just trying to palm off any 'fit for purpose' responsibility they may have had under their contract or service level agreement by making it your problem to install an extra back-up solution for their equipment?

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wynn (25-Feb-15)

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## IanF

OK I did some measuring. The 2 computers plus router modem and the monitors use 400w max. 
The wide format uses 120w max and rated usage of the inkjet we are looking at is 10w. So we are looking for a power of 650w for 4.5 hours.
The computers draw 400w for both computers and 4 screens so this is a big difference and negates the need to look at the NUC computers.

What other measurements do I need to do to spec an inverter setup properly. The monitor I got measures W KWh V A Hz and max watts and power factor.

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## Justloadit

There is a start up current which is extremely difficult to measure, unless you have a peak detector instrument.
This peak current draw plays havoc with inverters, which can only take an overload for a cycle or two, then shut down with an overload. So effectively get an inverter which is double the size of what you are using as a starting point. The addition of batteries does not influence the inverter, but rather the charging process.

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## AndyD

If the inverter is seamless (10 mS) when power fails I would normally spec a safety margin of 20-25% because PC's and other devices which would include motors if you have them won't restart, they'll carry on running without interruption. If you already have any small UPS's at your PC's or other equipment I'd take your consumption readings with these out of circuit because they'll be redundant if you're installing an inverter or large UPS for everything. Removing the small UPS's might drop your load requirement by up to 20%. If you're thinking of a generator then leave them in circuit because you're going to need them to carry the load whilst the genny is started.

Overload handling ability varies massively between different inverters, the unit I installed at home which I showed in another thread will tolerate a 50% overload for 5 seconds and a 20% overload for 15 seconds which would be more than sufficient for most applications. We've installed other inverters for customers such as the Victronics units which can take a 100% overload for short durations and a 50% overload for around a minute but this kind of over-specification is reflected in the price you pay for them.

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## wynn

> are you sure they're not just trying to palm off any 'fit for purpose' responsibility they may have had under their contract or service level agreement by making it your problem to install an extra back-up solution for their equipment?


I would think they are trying to sell a bigger system!

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## IanF

Thanks for the info Andy, I am busy measuring again. The wide format printer max watts cam down from 120w to 96w so that is a big difference. Just need to round up some kettle cords.

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## bones

going to do this for my laptops Ian have a look
cost is not to high so worth giving it a go

This for more lcd displays for laptop USB to VGA adapter

usb3 with power 

Ideal for use with todays Ultrabooks and thin-and-light laptops, Transcends SuperSpeed  USB 3.0 Hub transforms a single USB 3.0 port into four, instantly expanding the number of high-performance USB 3.0 devices you can connect to your computer at the same time. With the included power adapter, the Hub3 can supply high output currents of up to 2A via its dedicated fast charging port. This allows the Apple iPad and other portable devices with demanding power requirements to charge much quicker than using a standard USB port.

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## bones

Ian do you have a laser cutter 
how do you keep the thing 
from crashing?

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## IanF

Hi Bones, 
That USB adapter looks good so you can use it on the desktop as well. I will look at that later.
For the laser cutter it is a chinese one and one thing is when the power goes it just stops. Then when the power comes back you just switch it back on and it restarts in exactly the same place and finishes the job. Then we also bought a voltage regulator for the laser and it just runs no hassle and the current tube has been going for 2 years.

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bones (23-Mar-15)

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## bones

> Hi Bones, 
> That USB adapter looks good so you can use it on the desktop as well. I will look at that later.
> For the laser cutter it is a chinese one and one thing is when the power goes it just stops. Then when the power comes back you just switch it back on and it restarts in exactly the same place and finishes the job. Then we also bought a voltage regulator for the laser and it just runs no hassle and the current tube has been going for 2 years.


mine was secondhand to start with 
then got in the way of some vandals 
got it working but it freezes a lot 

power dip finally put it out of my 
misery at 3:20 pm today i am looking 
for one now any suggestions?  

got a tight budget for something 
basic

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## bones

i saw one for about R51k not 
bad looking systems 

http://am.co.za/laser

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## IanF

Bones, I have an aversion to software dongles but would go and have a demo on that machine as it is a good price. I got my machine from astroware and here is a link to a similar one. Then also get some thing to control the power spikes.
I got my last tube from perfect laser but haven't had to replace yet. They also sell machines.

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## bones

> Bones, I have an aversion to software dongles but would go and have a demo on that machine as it is a good price. I got my machine from astroware and here is a link to a similar one. Then also get some thing to control the power spikes.
> I got my last tube from perfect laser but haven't had to replace yet. They also sell machines.


will have a look our rand is not helping 
my wife pointed out we can send laser 
work out or just stop doing it she is 
right since we got 2ns hand laser we  
never recovered the cost  

will sleep on it did the laptop thing got 
to 2 elcheapo systems and only use 
the AMD for the bigger jobs but i found 
it is mostly off i dont use it 

if you thinking of doing the laptop dance 
start with one and force yourself to use 
it i3 is more then enough for basic stuff 
i did the 6gb ram thing that is a must 

powered USB hub is a must have

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## bones

right power is out laptops are 
working just fine but i cannot 
do a bloody thing because 
the ups on my printer died 
before the generator kicked 
in and something got damaged 
it doesnt want to turn on 
it is under contract they will 
fix it tomorrow 

some advice stay away from 
shitty upss

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## IanF

Bones is it a laser printer I should imagine that will kill most upss.  I hope that you don't have a big bill as some printer parts are priced like gold.

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## Justloadit

> some advice stay away from 
> shitty upss


Define a "shitty ups"?
and 
how to identify a "shitty ups"?

There are many reasons that can cause the failure, which one may not be aware off.
1. Surge - caused by lightning or disconnection of a electrical grid, as in the case of load shedding
2. Battery discharge to quickly - a number of reasons, such as to many cycles, not sufficient time for battery to charge, old battery, incorrect size battery for internal charger, unsed battery for many years now put into service, flat battery left uncharged for many days, temperature during charge and discharge.
3. Load too large for battery capacity
4. Operational start up currents exceed UPS rating
5. In coming mains out of spec to UPS, and UPS wants to run off flat battery and then shuts down
6. In coming supply unstable as in the case of a genny which is too small for the application - oscillating voltage and frequency as genny has a mechanical governor
7. Replacement battery not deep cycle battery

and so the list can go on.

In general I have found that most UPS are acceptable if used with in the specifications they were designed for, the usual discontent is the load over powers the UPS, and in the cheaper models, they used cheap batteries and not the deep cycle as is recommended. Effectively UPS were designed to allow one to save work on PCs in the case of a power failure, which occurs rarely in most countries, however in the case of RSA, this is now taking the equipment out of its design parameters.

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## bones

> Bones is it a laser printer I should imagine that will kill most upss.  I hope that you don't have a big bill as some printer parts are priced like gold.


was the laser yes but im renting
it owning them is just not 
economical anymore it will be 
the power supply 100% sure it 
is not the first time

shity ups was never meant to
keep it alive just allow it the 
30sec to switch over from 
mains to gen 

but the ups was cheap thing 
from the local pc store they 
warned me it will not hold 
the laser 

i will look into a inverter saw one
at a hardware store few weeks 
ago it is a 2kwatt system with 
large batteries it basically is a 
massive ups

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## bones

> Define a "shitty ups"?
> and 
> how to identify a "shitty ups"?
> 
> There are many reasons that can cause the failure, which one may not be aware off.
> 1. Surge - caused by lightning or disconnection of a electrical grid, as in the case of load shedding
> 2. Battery discharge to quickly - a number of reasons, such as to many cycles, not sufficient time for battery to charge, old battery, incorrect size battery for internal charger, unsed battery for many years now put into service, flat battery left uncharged for many days, temperature during charge and discharge.
> 3. Load too large for battery capacity
> 4. Operational start up currents exceed UPS rating
> ...


3 and 4 killed it im 100% sure 
im to blame for this mess 
sh_t will happen that said my 
generator normally kicks in 
asap will look why it didnt 
this time    

rsa is demadning a lot from 
our stuff they are not build 
for this mess

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## ians

It is not a wise investment using diy generators for fixed installations or electronic equipment. The sine wave is a serious issue, never mind the voltage regulation. The other issue is the frequency. Most equipment like a UPS is designed to run with a .5 hz tolerance. You can purchase UPS units which are capable of operation between 45 hz and 55 hz.

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bones (26-Mar-15)

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## CLIVE-TRIANGLE

Can someone explain why this is:
I have a small 1200 watt UPS; it only powers a few things, ADSL router, Network attached storage and an Airport Wireless access point. It is able to keep that lot going for more than 90 minutes.

Because I needed more than 90 minutes, I acquired a 2000 watt Emergency Power Supply with a generous battery bank. This I connected as the supply to the UPS.

However, when the power is off, the UPS is not supplied by the EPS; it's as if it is not there and the UPS will run on battery only. Obviously when there is mains, no problem.

I am too dumb to figure out why this is.

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## Dave A

Probably a case of the UPS rejecting the quality of the supply from the EPS. Could be voltage, frequency or wave form that's the problem.

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## AndyD

UPS's are a device that detect power failure and switch to backup batteries very quickly, so quickly in fact that the devices connected to them don't even know that there was a momentary power failure. When you have a UPS that's supplied by another UPS, because of the speed required, their sensing of power fail is so fast that both UPS's will go into battery back-up mode immediately. 

Once this happens the downstream UPS will switch back to normal mode if it is happy with the power that's being delivered to it by the upstream UPS. If the upstream UPS is delivering power that's anything less than spotlessly clean and pure sine wave then the downstream UPSis probly not going to see this as acceptable power being restored so it's staying in power fail mode.

Supplying one UPS from another UPS is something that's best avoided at all costs unless they're known to be compatible units. Even then it's a less efficient way than just having a single larger UPS. The better option would be to either extend the battery bank of your original UPS if its built-in charger can handle extra batteries or to replace the original UPS entirely with one that's the same KVA rating and has a bigger battery pack and longer run time and sell or redeploy the original one.

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## CLIVE-TRIANGLE

The EPS is no good as a UPS, it switches too slowly. So the UPS as expected does go to it's battery. However I would have thought the once the EPS has switched, it would be happy. Alas no.

Dave, the EPS is a modified wave form, so perhaps that's why.




> Once this happens the downstream UPS will switch back to normal mode if it is happy with the power that's being delivered to it by the upstream UPS.


That is what is not happening.

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## Justloadit

So when the battery of the UPS is flat, then the EPS will continue maintaining power for the duration of the charge of the EPS, should not be a problem then, until power is returned..

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## CLIVE-TRIANGLE

> So when the battery of the UPS is flat, then the EPS will continue maintaining power for the duration of the charge of the EPS, should not be a problem then, until power is returned..


That's what I was hoping for, but it doesn't happen. I have even disconnected the supply from the EPS to the UPS, then reconnected. It's simply as if it's not there. The other devices, _not_ connected to the UPS but to the second outlet on the EPS, work fine. Could it be that the UPS rejects the modified sine wave of the EPS?

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## AndyD

That is the most likely possibility, the 'modified sine' output of the EPS is not up to scratch. You could try reversing the UPS and EPS so that the EPS is downstream but if the output of the EPS is poor quality I'm not sure if this would have adverse effects on the items it's running.

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CLIVE-TRIANGLE (15-Apr-15)

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## Justloadit

Andy, not necessarily, today's equipment are made with SMPS, to maintain low cost, which work of a DC signal. The internal feedback loops with in the UPS, adjust the PWM, so that the voltage required by the equipment is maintained, this is the reason that a SMPS is rated between 95-265V. These SMPS's will work with a pure DC signal, so the fact that the supply is a modified sine wave will have no effect on the equipment. The incoming supply is first inserted through a bridge rectifier to convert to a pure DC signal, which it then uses to supply the equipment.

The only time that a "pure" sine wave is required, is when there are inductive loads involved, such as an electric motor, be it a fridge, pool pump, water pump, microwave, fluorescent lights which use a starter and a choke, very cheap LED lamps which use RC as part of it's PSU. 

TVs, decoders and most modern printers will work quite happily with a modified sine wave.

The reason that inductive loads and motors require a sine wave is due to 2 reasons, the first being that the square peak of the incoming wave is on for too long, which causes the iron in the motor to overheat because the motor was designed for a shorter peak. The 2nd reason, is the rise time from zero to peak is vertical, which changes the characteristics of the inductor filter circuit and excessive current will flow causing overheating.

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## CLIVE-TRIANGLE

:Confused:  Then I'm back to square 1.

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## Dave A

Can you post the make and model number of the UPS, Clive?

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## Justloadit

I would follow AndyD's idea, of placing the EPS after the UPS. 
So Power fail, UPS continues till battery flat, then EPS continues from there. When power returns, UPS battery charges, EPS battery charges, and load supplied by mains.

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## AndyD

> Andy, not necessarily, today's equipment are made with SMPS, to maintain low cost, which work of a DC signal. The internal feedback loops with in the UPS, adjust the PWM, so that the voltage required by the equipment is maintained, this is the reason that a SMPS is rated between 95-265V. These SMPS's will work with a pure DC signal, so the fact that the supply is a modified sine wave will have no effect on the equipment. The incoming supply is first inserted through a bridge rectifier to convert to a pure DC signal, which it then uses to supply the equipment.
> 
> The only time that a "pure" sine wave is required, is when there are inductive loads involved, such as an electric motor, be it a fridge, pool pump, water pump, microwave, fluorescent lights which use a starter and a choke, very cheap LED lamps which use RC as part of it's PSU. 
> 
> TVs, decoders and most modern printers will work quite happily with a modified sine wave.
> 
> The reason that inductive loads and motors require a sine wave is due to 2 reasons, the first being that the square peak of the incoming wave is on for too long, which causes the iron in the motor to overheat because the motor was designed for a shorter peak. The 2nd reason, is the rise time from zero to peak is vertical, which changes the characteristics of the inductor filter circuit and excessive current will flow causing overheating.


What you say is true but a power supply with active PFC and/or harmonic filters will often run warmer if the power is modified sine. This may or may not be an issue. Realistically, as you say, it's unlikely the appliance will suffer immediate damage unless is poorly designed in the first place but the lifespan of the device could be shorter running on a modified sine supply due to the higher component temperatures.

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## CLIVE-TRIANGLE

> Can you post the make and model number of the UPS, Clive?



MEISSNER XT1200 (1200VA) UPS _ TVR Computers.pdf

The EPS is the 2000 B model

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## wynn

I have decided for the time being I will start work later when the shed is from 6 to 8AM.
I will have a long lunch when it is from 12 to 2PM.
I will knock off early when it is from 4 to 6PM

Otherwise I will just grin and bear it.

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## ians

Now you getting smart. It would be interesting to hear what legal implication this would have with regards to the labour laws.

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## DanE

I do the same thing at my factory, as long as you don't work them longer than the standard weekly hours or eliminate their break times but merely shift them then you are in the clear. Easiest is to work it over a week duration and ensure staff work their 40 and you give them their 5. Aside from groaning and moaning which you'll have to endure, your in the clear.


Sent from my iPad using Tapatalk

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## Justloadit

If I am not mistaken, and I stand to be corrected on this,  employers can send staff home in the case of load shedding with out paying those hours. There is a minimum of 4 hours of wages that must be paid though. 

The real issue here is productivity. If you are a manufacturer and depend on getting product out to invoice, then this can really kill any profit you make, as the efficiency drops dramatically.
Certain expenses remain in place, such as rent, rate and taxes, insurance, telephones, loans, HP, lease etc.

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