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Thread: Power surges and insurance

  1. #11
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    Quote Originally Posted by adrianh View Post
    Very nice - R2k isn't bad considering the protection that it offers.

    As an aside - but along similar lines. I have a nice big UPS on my PC. It works really well and it kicks in every time I forget to buy electricity :-)
    but... I have found a really interesting thing with the UPS - When the compressor starts the UPS kicks in. The compressor is of course on a different circuit in the garage and the PC is in the office. I never realized that those motors create such a huge spike that goes all over the house. I really wonder whether equipment doesn't get damaged due to those sort of spikes. Let's say by chance the compressor and the vacuum cleaner are turned on simultaneously - won't the effect be really really bad?
    Old compressor aircon units are also bad news...your lights would dim... it causes a volt drop not a surge in power...they suck electricity.

    We had an incident where every morning a 5 am the entire factory would "blink" causing all the VSD's to reset and a whole lot of other issues...the operators would have to go around and restart everything...it turns out there was a huge compressor which switched on/off causing this "blink" i got to site at 3 am...setup the recorder and waited...at 5 am on the dot ...there was the glitch on the screen ...and you heard the machine all go down.

    As soon as you start adding Aircons...pool pumps...a Jacuzzi...etc etc ...a little more consideration should be taken into the electrical installation...in most cases people dont even consider equipment installed in a domestic installation...everything is considered as general...2.5 for plugs...1.5 for lights etc etc

    Something to consider ...using a VSD to either soften the startup current or to fit a 3 phase motor (not sure if you already have a 3 phase compressor) i have a few customers who have down scaled and moved back home...unfortunately they have 3 phase equipment and only single phase power at home... simple... just use a 230 single phase to 400 3 phase inverter...way cheaper than upgrading to 3 phase power.

  2. #12
    Diamond Member AndyD's Avatar
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    Quote Originally Posted by adrianh View Post
    ... I have found a really interesting thing with the UPS - When the compressor starts the UPS kicks in. The compressor is of course on a different circuit in the garage and the PC is in the office. I never realized that those motors create such a huge spike that goes all over the house. I really wonder whether equipment doesn't get damaged due to those sort of spikes. Let's say by chance the compressor and the vacuum cleaner are turned on simultaneously - won't the effect be really really bad?
    As a rule of thumb most single phase motors that are direct-on-line will draw about 5x their run current for a very short period of time on start-up. This would include fridge, vacuum cleaner, air-con, irrigation/borehole/pool pump etc.
    The large current draw causes the voltage to drop significantly and not just on that circuit. Your UPS is probably detecting this voltage dip and jumping into battery mode. These voltage dips can cause all sorts of operational issues and reliability issues for electronics.
    The high start current only usually lasts for a few miliseconds so the chances of two motors starting simultaneously is very small in a domestic environment. If it did happen the voltage sag would be more pronounced. Unfortunately under-voltage protection relays don't help with this issue, they're more effective at protection against longer duration low-voltage events. Good practice final-circuit design helps also load balancing if you have a 3-phase supply.
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    Diamond Member adrianh's Avatar
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    Quote Originally Posted by AndyD View Post
    As a rule of thumb most single phase motors that are direct-on-line will draw about 5x their run current for a very short period of time on start-up. This would include fridge, vacuum cleaner, air-con, irrigation/borehole/pool pump etc.
    The large current draw causes the voltage to drop significantly and not just on that circuit. Your UPS is probably detecting this voltage dip and jumping into battery mode. These voltage dips can cause all sorts of operational issues and reliability issues for electronics.
    The high start current only usually lasts for a few miliseconds so the chances of two motors starting simultaneously is very small in a domestic environment. If it did happen the voltage sag would be more pronounced. Unfortunately under-voltage protection relays don't help with this issue, they're more effective at protection against longer duration low-voltage events. Good practice final-circuit design helps also load balancing if you have a 3-phase supply.
    Ahhh OK, so it is the voltage drop that causes the problem.
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    Quote Originally Posted by adrianh View Post
    Ahhh OK, so it is the voltage drop that causes the problem.
    I would suggest you do a few calculation and check cable sizes etc...incoming voltage...mains connections etc...my compressor was blinking the lights in workshop...it turns out the fuse on the pole outside my property had a bad connection.

    Even with a single phase motor starting...it shouldnt cause your UPS to switch(depending on the unit it should switch at around 180 volts ...if you have 230 volts (the standard in SA) that would mean it is a 50 volt drop...i would be scratching around for loose connections...looking at cable sizing...cable lengths...loop and line impedance tests at the compressor isolator ...etc etc.

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