GFI trips

[BillP]

Hi all,

Great forum and of course APC what more can one say!

In one client location I have a Symmetra RM 6000 running well.

We tried a Residual Current Detector [GFI] on the output to comply with the wiring code and it lasted three days before tripping one morning as the load isolator timed the network on.

It keeps tripping on one part of the load and I will be onsite in a few hours to do some digging around.

Is it likely to be the common mode switching currents from the RM 6000 which is doing this?

Would we be ok to de commission it and install a line interactive unit, although they aren't large enough to really cope unless say two RM 3000's would be ok perhaps.

Thanks.

[Anonymous user · Accepted solution]

Computers normally have a few mA of leakage current to the ground, because each side of the line is capacitively coupled to the ground.

Each computer's front end has a filter that's setup like this:

L--||--G--||--N
together with a pair of series reactors between the rest of the power supply and a capacitor that goes directly between L and N. Since computer power supplies are designed for global use, they pretty much all have the same design.

This common front end is designed to keep high frequency noise from getting into the mains and will inherently have some leakage current, therefore, you should have all IT loads connected to a grounded circuit and not with a GFCI.

I'm not sure about the code in Australia, but here in the US, permanently installed (i.e. refrigerators, computers, appliances) grounded fixtures are not used with GFCIs.

This is something you need to consult your an electrician or an inspector familiar with AUSTRALIAN codes.

[BillP]

Thank you for the reply, it is appreciated.

I have swapped in a LI APC ups and the fault tripping went away when it was endemic just prior.

I remember a conversation with the APC support channel engineer who said that the input to a Symmetra would cause nuisance tripping as is the case due to the MOV's / Varistors & common mode filters present along with the dual conversion process.

Apparently where the Symmetra is concerned so does the output!

The engineer reported:

Now to answer your question, it is not recommended to connect a ELCB on the input side of your UPS as it will cause nuisance tripping due to leakage currents caused by the UPS. These leakage currents are generated by MOV's and other electronic components inside the UPS which will result in tripping of your ELCB if connected on the input side.

You can place the ELCB on the output side instead and provide protection for people working with your equipments.

Actually my support channel lead me back to this online help link:

http://jpaa-en.apc.com/cgi-bin/jpaa_en.cfg/php/enduser/std_adp.php?p_faqid=1344&p_created=1010390400...

[Anonymous user]

I found this reference to an "LI APC UPS" in http://forums.isxusergroups.com/message.jspa?messageID=1917
I wonder if I could get some more details about the LI APC ups. Is LI a model indicator or a reference to a certain technology?? Thanks


"I have swapped in a LI APC ups and the fault tripping went away when it was endemic just prior. "

[TheNotoriousKMP_apc]

Steve,

My apologies as you should also have an email from me in your inbox for submitting an Answer Feedback for an APC Knowledge Base. Please close the other incident with Email Support, as I am their escalation point so it may be easier to interface w/ me directly. Here's the response that I provided in the email:

Coincidentally enough, I am also the APC Forums Admin who was in the process of contacting our Back-UPS engineers before providing a response. I noticed in your initial question that you asked for more information pertaining to the LI APC UPS. From the information I've received, LI stands for Line-Interactive, which is one of the primary UPS Topologies that we use. The XS1500 that you have is a Line Interactive UPS, as well as all of our Smart-UPS models that are not Smart-UPS RT, VT or Modular. Is there anything in particular that's occurring with the system that's raising an eyebrow to the GFCI?

[Anonymous user]

I have an APC XS1000 UPS which is powering an HP XW 4400 workstation in an industrial
application. The UPS and in turn the HP workstation are powered via a
GFCI-protected circuit. My problem is that the GFCI trips each time the
HP XW 4400 is turned on. I have tried this with several different XW
4400 workstation units with the same result.
The GFCI trips with or without the UPS in circuit.
If I use an HP 5150 model PC instead of the XW 4400 the GFCI does not trip
If I unplug the UPS prior to powering the workstation ON I can then plug in the UPS and carry on without problem.

My question is essentially this. Is there an APC product which would
provide backup power to the computer while at the same time eliminating
the tripping of the GFCI?

[TheNotoriousKMP_apc]

Do you have the inrush current of this machine? It seems to be extremely excessive to the point where it's exceeding 15A to trip the GFCI. You may have to look at a larger, double-conversion online UPS. Those would be the Smart-UPS RT or possibly a smaller scale Symmetra LX.