Back-UPS 1500

[RichardH_apc]

Hi,

I'm an owner of a Back-UPS 1500 (home use). I've had this unit for approx. two years and it has worked flawlessly. I use this unit to provide back-up power to my home network equipment - network switches, servers and firewall. Also connected to this UPS, is a standard PDU bar. Attached to the mains lead for this PDU is an RCD plug with a "Test" button. Today, I accidentally hit this button which in turn tripped the main RCD to the house, instead of just tripping the RCD on the mains cable to the PDU. Along with this, the UPS switched to battery mode, which I'm a little concerned about. In theory, loss of power should switch the unit to battery, but in this case where there was possibly earth leakage after pressing the test button, should the UPS itself not have tripped?

I'm not an electrician so any advice I can get on this would be greatly appreciated.

One last note - I have recently moved all of my IT equipment to an 18u metal server rack (inc. the UPS with external battery). I'm concerned about grounding/earthing, where in the unfortunate event that there is a wiring fault and the cabinet itself becomes live, how would I link the cabinets earth lug to the UPS mains lead earth wire?

Thanks and regards,

Richard

[BillP]

Hi Richard,

I cant really speak for the RCD, as to why it may have tripped the main breaker. It would appear the Main Breaker observed something similar to a direct short. As for the UPS, it will certainly transfer to battery power once the RCD removes the electrical source, as it is designed to do so. Once the UPS switches to battery, it essentially electrically isolates itself from the electrical circuit. In theory, the unit can safely be removed from the electrical outlet and carried around while On-battery, without fear of electrical shock.

Schneider Electric does manufacture a Smart-UPS line of UPS which have EPO capabilities if this is something you are interested in having. The Back-UPS 1500 however, does not have this capability.

As for fears of properly grounding the 18U rack, you may connect a small ground wire between the rack and the center screw of your electrical wall plate where the UPS is plugged in. Although the UPS disables the Neutral/Hot blades during transfer to battery as to not back-feed, the ground reference is still actively connected.

If in doubt, I would suggest checking with your local electrical code for approved methods of grounding.

Secret Squirrel

[RichardH_apc]

Hi,

Thanks for your very helpful response! In regards to grounding the rack, I live in the UK so there isn't an accessible earth connection on the face plates of the sockets. This may sound a little crazy, but I've got a three pin plug in which I've removed the live and neutral pins from, leaving just the earth, with an earth wire attached. I haven't actually used this, but in theory, if I attached the other end of this wire to the cabinets earth stud and then plugged the plug into a wall outlet - do you think this will provide ground to the cabinet?

Thanks again!

Regards,

Richard

[BillP]

Yes in theory this should provide the ground connection your looking for however of course, I must advise you you check with your local electrical code to ensure you meet the local requirements.

Secret Squirrel

[RichardH_apc]

Perfect, thanks for that! I'll check that out also. In regards to the earth wire in the mains lead to the UPS, if I was to attach a standard PDU bar with an internal earth connection to the UPS, would connecting the earth stud on the PDU to the earth stud of the rack be the same as running an earth wire direct from the wall outlet? Would the earth connection from the mains lead to the PDU link to the earth wire of the mains lead to the UPS? Which in theory if it does, I can use the same earth connection as the UPS uses?

Thanks again,

Regards,

Richard

[BillP · Accepted solution]

Yes, essentially it would be the same electrical point.

Secret Squirrel