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In order to assist you in understanding the ‘tricks of the trade’,selecting the correct solution to your specific Back-
A generator petrol or diesel, is for most of the application and requirements still the lowest cost initial investment.
A Generator do have the inconvenience of noise, refilling the fuel and starting it up when required.
The starting up of a generator can also be triggered by a short time UPS , for instance in hospitals and clinics a short time UPS will be used to supply power for a short period to start up a generator.
There is no fixed rule to guide one here, but I would suggest that a system that requires about 20kW continuous and/or use approximately 100kW.h per day or more, an other alternative than a Generator becomes costly unpractical and space wise unpractical.
For instance companies or factories which run heating machines or 3 phase machinery or a office building block /Shopping mall use so much power that using an Inverter/UPS systems as a power back-
For such big systems, it could be the best to connect the critical management items, such as computers, a few lights and a servers onto a UPS uninterrupted Power Supply system and connect the main power requirements onto a generator system.
Please read the page first -
A short time UPS, is a typical UPS bought from computer shops or various suppliers. The UPS is designed for 10-
You get various kinds of UPS, Online,Off line, Short term, Extended time etc. For this purpose we divide it into 2 groups only, it is either Extended time UPS or a Short time UPS. This does not mean it is a small UPS by any means.
A Hospital might have a 100kVA 3 Phase UPS, banks, will have 100-
It is off course possible, that a 10kVA short time UPS used in an application where only 1kVA is used, will give 10x longer backup time, ie 300 minutes or 5 hours.
The limitations with using these UPS units for power backup during load shedding is 2 fold
People often do the mistake to buy a UPS, even thou they advertised as “solutions to load shedding” and add additional external batteries . This will not work, initially is does work, but within a few months those batteries do not hold charge and they damaged. Make sure, when you buy an UPS that is it a ups with External battery connection facilities and it has the ability to recharge the external batteries. Look at the specs
The table 1 above is a typical part of the spec sheet of a short term UPS, note is specify time of backup at full load, varied between 14 minutes and 20 minutes only
The most important aspect of backing-
How much battery power you would need, would depend upon the number of appliances and the length of the power cut. With Load shedding of up to 4-
If Load shedding last longer (6 hours plus) then you will have to start considering running your fridge off the reserve backup power, and this significantly increases the costs.
A UPS is a DC AC Power inverter, with a build in battery charger and an automatic transfer switch all combined, thus all dc ac power inverters and are not UPS systems and suitable for use as power back-
A discreet build up UPS for power backup -
A discreet DIY UPS power backup system can be build up, thus using 3 components
This simple system works well for occasional load shedding's, you will typically charge the batteries up during periods of healthy power, When a load shed occur you can then plug your appliances into the inverter . This works well, it has a bit of inconvenience it is the simplest and cheapest form of having power for power back-
An Extend time UPS and DC AC Power inverter with charger
An Extended time UPS and a Inverter-
Another difference is, the UPS will unusually not allow for Peak power overloads, it will be limited tot the power it is deigned for, where a Inverter-
In order to choose the correct size of unit, you need to know and understand the following requirements.
The best way is to check your own appliances and see what you think you can live with (or without!) over a period of say 4 hours. Once you have established the appliances and the wattage that they draw, you can use our template to gauge the cost of your specific application. You peak total power possibly used at one moment determines the physical inverter/UPS inverter size
Batteries is the main energy source, as a rule of thumb 1x 100A.h 12V battery store approximately 700W.h of useable energy. Thus if you have a TV of 100W which need to run for 5 hours..that would be 5 hours x 100W= 500 W.h
From the same, if you have a TV and lights adding up to 300W, which you will need to run for 5 hours, this is 300W x 5 hours= 1500W.h , you will thus need 2 x 100A.h batteries etc. This will be discussed in detail on another page
The backup UPS/inverter unit, is then sized according to you maximum peak load I.e if you load is 800W, you need a 1kW backup inverter unit, if you have 3kW load, you need an Backup Inverter unit, which has a rating higher than that ie, 3kW or 5kW
Please refer to our site on power inverters for choices
In countries other than South-
In some of these situations we thus require an additional source of energy-
Nb: I need to highlight here that purely for occasional load shedding periods of up to 4-
We will discuss solar power backup solutions in more detail on another page “solar power backup solutions”
This page is only a guideline introduction to various power backup power solutions, more detail about each is discussed within the relevant pages as per the site hierarchy. Please feel free to send us an email or give us a call, we will gladly assist [email protected]
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