APC UTS6H and APC UPS - Site Wire Error

[wicked_apc]

Hi, I have a question about using an APC UPS with an APC UTS6H that I hoping you can help me answer. 

The UTS6H has been working fine with my EU2000i so far, so I decided to add an APC UPS.

I understand you can plug the UPS into the convenience plug on the front for power from circuit 1.  Initially I plugged the UPS into a home outlet for initial testing and things were fine, I even ran a test by turning off utility power and things worked great.

Once testing went well I set it up close to the UTS6H and plugged it into the convenience plug - the APC UPS self tested ok but I am now getting a "site wiring" error.

APC site says its due to one of the following conditions:

1. Overloaded neutral wire (>5vdc measured between Neutral and Ground).

2. Reversed polarity (hot and neutral wires are reversed).

3. Missing ground wire. (Note: this also includes using a 3 prong to 2 prong adapter)

I confirmed its not #1 or #2 which makes me focus on #3.  I see that the convenience plug is grounded to the UTS chassis as everything else is. 

I know the UTS has the white/neutral to the panel, do I need to ground the chassis of the UTS to the panel via a copper wire?

any other thoughts or suggestions?

[BillP]

Hello,

The neutral bus in the UTS is grounded to earth ground through the electrical panel, neutral to ground bond.

Also, I discussed with a co-worker and we came up with some questions.

• Please confirm what UPS model you're using. The model should be on a white sticker on the back or bottom of the unit.
• Is the UPS directly connected to the convenience outlet (no adapters, extra cabling, etc)
• Confirm that the Honda generator is not independently grounded.

Thanks.

[Anonymous user]

Has this question been answered/resolved ?

I have the exact same problem with a UTS-10BI.

The front panel convenience outlet checks fine on a test set for hot/neutral/ground/polarity. Yet the Smart UPS 1500 reports a "site wiring fault". Also a PRO-8T2 surge strip illuminates it's "building wiring fault" indicator when plugged into the same front panel convenience outlet. The outlet does work properly, the UPS picks up the load with no interruptions. There are no additional cables or adaptors between it and the outlet.

Continuity of the white neutral wire from the UTS-10BI to the main panel neutral/ground bond was checked and is good.

There are no error indications on the UTS-10BI front panel.

Measuring voltage at the convenience outlet between ground/neutral is approximately 150 volts and fluctuates.

Primary neutral bond at main panel is good.

UTS-10BI was manufactured in 2/2013.

Do I have a defective transfer switch ? I checked the main board, there does not appear to be anything obvious (ie. burnt traces, etc) - the unit functions fine with the exception of that convenience outlet not being liked by the Smart UPS.

[wayne_i_apc]

Is this a new installation or has the condition developed after previously working properly?

Neutral and ground internal to the UTS are isolated from each other as required by the National Electrical Code. As you have already verified, the neutral connection to your main panel is provided by the white wire(s) in the UTS flexible conduit. The ground connection from the UTS to the main panel is made through the metal to metal contact of the flexible metal conduit itself. Since you have measured 150 volts between ground and neutral at the UTS convenience outlet, I would suggest you measure for voltage from the flexible conduit to ground at both the UTS end and the main panel. If you find one end that does read voltage on the conduit you should check for a clean, bare (paint free) contact between the conduit connector and the case of the box in question. Another remote possibility is that your main panel case is not properly bonded to ground.

If you have installed the UTS without using the provided flexible metal conduit you should make the ground connection directly using a substantial ground wire.

[Anonymous user]

Wayne, "thank you!".

That was the issue. Yes, this is a new install. We had to use a J-box to extend the UTS-10BI mounting location on another wall adjacent (perpendicular to - in a corner) to the main breaker panel. So the J-box and conduit were PVC. When I jumpered the UTS-10BI metal conduit over to the main panel with a separate wire, the "site fault indicator" on the UPS went out. I was measuring about 33 volts between the metal UTS conduit and ground on the main panel.

So I'm going to be running a #10 (or better, depending on what I have in my 'junk box') over from the ground inside the UTS10-BI over to a ground on the main panel.

The missing piece of the puzzle was I hadn't realized that ground and neutral are separate inside the UTS-10BI. So that explains the mystery, and the need for keeping them separate going to the main panel.

Thanks again for the quick response.

best regards.

[wayne_i_apc · Accepted solution]

You're welcome! Glad I could help.