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soon1
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Join Date: Jun 2009
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UPS

01/11/2017 10:22 PM

Hi ,

when main source to ups turn off,ups take over rcd at DB trip.

please kindly help.

thanks.

chew
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JE in Chicago
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#1

Re: ups

01/11/2017 10:57 PM

is that all the information you can give?

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SolarEagle
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#2

Re: ups

01/11/2017 11:06 PM

The RCCB should be installed before the UPS in the Circuit Breaker panel, if the UPS causes it to trip, it means the leakage current inside the UPS is exceeding the trip current allowed by the RCD...so check the leakage of your UPS unit and the size of your RCD....one is probably at fault...

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JE in Chicago
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#4
In reply to #2

Re: ups

01/11/2017 11:12 PM

you got all that from that? ∴

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SolarEagle
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#6
In reply to #4

Re: ups

01/11/2017 11:23 PM

Just spitballin'....

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Brave Sir Robin
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#9
In reply to #4

Re: ups

01/12/2017 12:57 PM

I think SE really is Cleo.
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SolarEagle
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#10
In reply to #9

Re: ups

01/12/2017 4:05 PM

...haha

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soon1
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#3

Re: ups

01/11/2017 11:09 PM

Hi jerlyn

It is an online ups.

When we turn off the ups incoming to let the battery take over .

It trip the output supply rcd .

Thanks
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SolarEagle
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#5
In reply to #3

Re: ups

01/11/2017 11:22 PM

..."Some UPS units (particularly smaller cheaper units) don't produce a very accurate sine wave - in fact they are pretty awful, but do the job in hand and are good enough to drive the IT equipment connected to them. However sensitive things like RCDs etc will not tolerate them and do what yours is doing - switch off.

Another option is relating to the connection of the supply/inverter and earth in the ups. Under normal conditions the RCD relies on an imbalance in the L-N conductors due to electricity taking an alternative path back to the source - through the earth/CPC/person etc. This works due to N and E being joined to complete that path. Inside your UPS the inverter may not have a connection to the earth at all. This will allow an induced voltage to appear between N & E which some RCDs can detect - probably the ones with an earth tail. It also means that when the UPS is under operating load (from the batteries) the RCD is unlikely to function as intended. "...

http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=55339

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Andy Germany
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#12
In reply to #5

Re: ups

01/13/2017 4:50 AM

GA

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67model
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#14
In reply to #3

Re: ups

01/13/2017 5:09 PM

It may be one particular load.

Isolate all loads. Put system onto battery power.

Switch on each load in turn.

Energising a certain load may be found to cause trip. Check energising that load on its own without other loads.

You might find you do not need any loads to cause a trip, just cable capacitance!

While 50/60Hz fundamental currents may not exceed RCD trip current on mains sinusoid power, harmonics 3rd,5th etc will pass more current through capacitance. Basic inverters give out rectangular plus & minus pulses with high harmonics.

Splitting the load between several RCDs may solve problem. Perhaps RCD at each power outlet socket, with high operate current RCD, 100mA or more at UPS outlet.

Since you gave no kVA/volts/amps for UPS or description of load connections, I can suggest no more.
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RAMConsult
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#7

Re: ups

01/11/2017 11:24 PM

Something is not right. If the main source turns off, where is the current to trip the RCD coming from?? I suspect you have some large motors or capacitors on circuits in your DB which are backfeeding the panel and your UPS in an unbalanced fashion, which fools the RCD.

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PWSlack
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#8

Re: ups

01/12/2017 2:49 AM

The RCD trips because the vector sum of the live and neutral currents downstream of it exceeds its trip setting, inferring that this level of current is flowing in the earth conductor.

Look in particular for (an) inadvertent connection(s) between neutral and earth downstream of the RCD. Once de-energised, a multimeter, some effort and some patience is all that is needed to find it.

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#11
In reply to #8

Re: ups

01/13/2017 4:15 AM

<...this level of current is flowing in the earth conductor...> ...which might be formed by a human being.

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rwilliams
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#13
In reply to #11

Re: ups

01/13/2017 8:53 AM

similar to an ungrounded 220v heater...
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67model (1); Andy Germany (1); Brave Sir Robin (1); JE in Chicago (2); PWSlack (2); RAMConsult (1); rwilliams (1); SolarEagle (4); soon1 (1)

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