I did some measurements over time to see what the range is, and the AC voltage is extremely consistent - 51.1 to 51.4V AC at 14.7 to 15.5mA. The DC is more variable, typically sitting at 16V, but ranging between 8.1 and 19.6V. That could be some sort of ground noise, so I'm considering it to be 16V DC at a very consistent 15.8 to 16.0mA.
I have tested this across multiple circuits on both sides of our service box, and it's all very much the same across all circuits.
So. Let me back up a minute and describe the situation for you.
We have a small set of four servers. Each one has had a BackUPS Pro 1000, the oldest of which is from 2012. NONE of these are under warranty, and none are involved in return situations.
The oldest one started tripping GFCIs. We were able to confirm this on multiple GFCI circuits. It did not do it every day; it was an intermittent problem, but we were able eventually to identify the bad UPS. We will call this UPS ELDA, as the server it was protecting is called elda. (It is, again, from 2012 and is NOT involved in a warranty or return situation.)
On testing, I found by using a breakout box and multimeter that UPS ELDA was putting voltage on the ground pin. Specifically, 54-57VAC at around 17mA, and 7V to 20V DC at around 19mA. Testing the other three UPSes we have of the same model on the same circuit do NOT reveal any voltage on the ground pin, so it was the outlier.
We removed UPS ELDA from service and have no longer seen any GFCI trips.
To replace it, I ordered a new UPS from Amazon. I saw that you had a pure sine wave version of the Pro1000, so I thought I would try it.
We will call this NEW UPS 1.
Before setting it up in the server room, since I had all the kit out anyway, I tested NEW UPS 1 for voltage on the ground pin. I discovered that it, too, was putting both AC and DC voltage on the ground pin, and at levels similar to UPS ELDA.
That's when I contacted support, asking if it is possible that this is normal. Support appeared to think this was not normal, and sent a replacement for NEW UPS 1.
We will call this NEW UPS 2.
I received NEW UPS 2 two days ago in apparently good condition. For obvious reasons, I decided to check it for ground pin voltage. NEW UPS 2, like NEW UPS 1, and the GFCI-tripping UPS ELDA, is putting voltage on the ground pin. Our other Pro 1000s do not put voltage on the ground pin, and I checked again yesterday for sanity purposes. (They still aren't putting voltage on the ground pin.)
As with NEW UPS 1, leaving it plugged in has not so far tripped the GFCI outlet I'm using as a tester. But the original UPS that went bad (UPS ELDA) didn't trip GFCI continually, it did so at a rate of about once every three days, and sometimes a solid week, complicating our attempts to isolate the problem considerably.
So now I am again asking:
NEW UPS 2, like NEW UPS 1, is putting both AC and DC voltage at around 16-17mA most of the time on the ground pin. This does not seem normal, and I would consider it bad engineering practice, but: is this normal?
Our servers are on GFCI/AFCI circuits and it's a code requirement in our location, so changing circuits is not an option. UPS ELDA tripped multiple different GFCI circuits, so I know that is not a failed GFCI detection or a bad GFCI breaker. (I have also finally isolated the probable bad component in UPS ELDA, a film capacitor that failed and is both performing off specification and passing DC when it shouldn't. I have ordered a replacement from DigiKey, and hope to be able to return it to service.)
What I really want to do now is return NEW UPS 1 to Amazon, NEW UPS 2 to you, and buy another non-sine-wave Pro1000, like the other three we have which do not put voltage on the ground pin. However, I'm now worried that this is a design change or parts issue and will start tripping our GFCI circuit again.
But if this piece of equipment is expected to put voltage on the ground pin, there are ways that could be done that would not create GFCI issues/voltage deltas across hot and neutral.
Is that the case? Are these UPSes expected to put voltage on the ground pin?
As I told technical support earlier, I expect this to be a tier 2 or higher issue, and do not expect an immediate response. But I do want to get it sorted, as at the moment, we have two servers on one UPS and that's bad practice in every way.
Thank you for reading through all this and for your time.