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Thread: load shedding

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    load shedding

    As i mentioned before winter is coming and so is the load shedding...dont get caught this time...the prices are neg. at the moment but in a couple of weeks time there is going to be a huge demand for generators...invertors...batteries...backup battery lights...and dont forget to fill your gas bottles...this time the prices will go through the roof so dont say i didnt warn you.

    becareful of modified sine wave invertors there have been a lot of come backs and the tedelex unit promises 6-8 hours...a battery can only hold a certain amount of charge...if you only have one light connect it will only use a small amount of power...if you connect 20 light the battery will go flat quickly...use your head people you dont need to be a brain surgoen to work this one out...but i have found people rush out not thinking and just buy anything because they didnt prepare themselves....that is why i am typing this thread so you dont get caught...prepare yourself watch the TV between 6/7 and you will see the electricity demand is back in the brown again.

    if you plan on having a generator installed make sure the person carrying out the installation is suitable qualified...in fact any electrical installation must have the correctly skilled person doing various work...ie if the person is connecting in the electrical box and it has live wires only a qualified electrician is allowed to perform this work not the elconop 3 or 2 or 1 and especially not the labourer...every single skilled or semi skilled electrical worker must carry a valid compitency card around with him...which should be dispayed at all times while working on site.

    the electrical company must be registered with the electrical contractors board...they do not have to be ECA members.

    i have found another problem...a company used me to go to site and quote for work....he then informed the customer that i had all the neccessary qualifications and was registered then when the generator arrives uses anyone off the street to do the installation or carries out the installation himself...i have since been back to an installation done by this person and would highly recommend you dont use this company...i am not going to mention this companies name but will tell you that they are doing installation all over durban...my advice please make sure the person carrying out the installation is qualified...by means of card which should be worn at all times...or contact the ECA or ECB on 031-3126313 and find out if the company and staff working on site are registered and qualified to perform the work they are doing.


    lots of electrical contractors drop off staff on site who do not have the correct skills and then charge you an electricians rate.

    another problem i have found is companies pick up staff on the side of the road who then work in your house and then it normally takes 2 -3 weeks and your house or property is broken into.

    be careful electricity kills people and burns down houses and structures.

    there seem to be a lot of used car sales men selling generators at the moment because man they can bullsh*t people with their limited knowledge.

    beware of chinese junk they are short term solutions...you get what you pay for.

    if you are planning on building a house make sure you make provisions for a backup system even if you dont install it...put all the piping in...it is a small additional cost compared to what you will pay to install later...and it will look alot neater.

    dont say you i didnt warn you!

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    Bronze Member Karenwhe's Avatar
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    Hi Murdock,

    Very good post. Maybe you can explain more about "phantom load". (Don't ask me to explain it). But my husband has been in conversations about inverters and it turned out most people don't understand this and buy the wrong stuff because of it.

    When the company asked them to get first an electrician to check their "phantom load" before they buy stuff, it seems everyone wants to cut corners and end up with stuff that doesn't work, or at lease not as they thought it would, and then they blame the manufacturer.

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    i have never heard of a phantom load but they could be refering to the start up load or the load induced by a transformer for example...which is only present with the initial switch on.

    all appliances react differently...some are resistive loads which switch on and stay constant for example a kettle or toaster...then you get inductive load which might be what they are refering to an aircon is a good example because when you switch it on the compressor will not switch on imediatley but a fan will switch on which will draw a small start uo load...but when the compressor switches on the start load is a lot higher...also depending on whether it is a rotory compressor or an old piston type...if you have an window rattler for example all your lights in the house normally dim when it switches on...but with the new rotary ones the intial start up is not so servere and they are lot more economical so you can have 2 or 3 without having to upgade the electrical supply to your house.

    television sets computors and that type of appliance run on 12 volts so they have power supplies built in which when switched on draw the small load just to get them running...i would think this is the phantom load they refer to...so long as you dont switch this type of appliance off the load will stay constant.

    i had a problem in a factory many years ago where i connected a couple of big CNC lathes and a couple days later i was called back and could not understand why the circuit breaker would trip only in the mornings...when they switched the machine on...but not again and not if they switched it off then back on again...it had me puzzled then i figued it out it was the intial current drawn by the 380/220 transfomers used to power the CNC lathe.

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    just me duncan drennan's Avatar
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    Karen, I've often seen standby power (i.e. how much energy an appliance draws when turned off by in standby mode) referred to as "phantom load", but my own understanding of the term actually has to do with reactive load, or in other words power factor.

    If you follow that link you will see some graphs which demonstrate what reactive load is. Difficult to explain in words, but it has to do with how much the voltage and current wave (sine wave) line up with each other. Certain types of loads (e.g. very capacitive, or very inductive) can cause large reactive loads.

    Generators etc. are typically specified in VA, which is NOT the same as watts, while device power consumption is typically specified in watts. As a residential user you don't pay for reactive load (although I think that industrial users do) you only pay for the real load.

    Computer power supplies are one of the things that can affect the power factor (which is a measure of how much the voltage and current waves align).

    That probably sounds like gibberish to most people....so follow this link and this one for more info.
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    Bronze Member Karenwhe's Avatar
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    Aha, I think I got it.

    So, in other words, this is stuff that take current and you don't know it does and when you buy backup systems you think they will back up X load, but you have load that you are not aware of (like the computer example and other stuff that is not obvious) and then the backup system doesn't work as you though it should.

    Did I get it right .

    Here is me failing an electrical test .

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    http://en.wikipedia.org/wiki/Standby_power

    theres the link...it seems duncan was on the right track...well i learnt something new again today...the power is very small but if you have a house full of gagdets i suppose it could start adding up.

    this is the reason i do load assessment for people and i dont guess the load by calculations.

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    just me duncan drennan's Avatar
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    Well, I'm not sure about the context your husband was speaking about it. I suspect it has more to do with reactive load than standby load.

    Have a look at this picture - the "power triangle. In that picture the length of the line at the bottom of the triangle is the real power (watts) that is required. The length of the line on the right is the reactive power that is required (measures in VARs). Reactive power is not consumed, but gets passed backwards and forwards between the source and the load.

    The total amount of VA's (volt-amperes) that the source needs to deliver is the length of the 3rd side of the triangle. If you remember correctly: x^2 = y^2 + z^2 (where x is the VA's, y is the watts, and z is the VARs).

    So what that all means is that the total number of required VAs is greater than the watts delivered. Obviously this depends on the type of load that you have.

    Power factor is a number between 0 and 1 which indicates how much reactive load there is. 1 means that there is no reactive load (i.e. only real watts are delivered), 0 means that there is no real load (i.e. only VARs are delivered).

    Now here is the implication of all of that. Lets say you have a 1kW load (real power). If the load has a power factor of 1, then a 1kVA generator will be fine to drive that load. If the power factor was 0.5, then you would require a 2kVA generator to correctly drive that load.

    This is why power factor (or reactive load, or phantom load) can play an important part in choosing a generator and/or inverter.
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    Bronze Member Karenwhe's Avatar
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    Hi Duncan,

    Thanks guys. The links are helpful.

    The context was for backup systems. You see we have a site that sell prepaid meters and all of the sudden with the load shedding, got a massive amount of people wanting to buy a meter to avoid load shedding or simply a backup system for electricity.

    The avoiding part of course is not possible, but quite a few people in the public do not understand that. You don't install a prepaid meter to avoid load shedding and just because you bought your electricity prepaid it does not mean that by some miraculous way you avoid load shedding.

    So my husband went to someone he knows to find a solution and send these guys to these people. But the problem that started happening is that for those that really needed it, the solutions are expensive for the load that they need (small home offices, which are not as small as you thing, and even some homes).

    The problem was that these guys told them, you need to check your load first, you can't just buy this stuff and hope it works.

    Then you need an electrician to test your load and your "phantom loads" then you can buy and you definitely need someone that knows what they are doing to install, not just anyone but a good electrician [this was said in comparison with secondary prepaid meters which are pretty easy to install].

    So now... the problem was that people do not want the hassle and extra cost of finding out exactly what they need.

    And then they install the wrong stuff [which in that case was expensive enough as it is] to find out that it was the wrong stuff.

    Anyway, that was the context of the whole conversation.

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