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.

[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.

[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

[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.

[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.

[IanF]

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

[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.

[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.

[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?

[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.

[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.

[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.

[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!

[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.

[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

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