What NMC settings determine Undervoltage condition?

[Anonymous user]

One of my units (an S20 BLK) often reports an Undervoltage condition. Here's its current Overview NMC screen:

As you can see, the input voltage is 115V. Here's what the Configuration/Power screen looks like:

Does the NMC use the values in this screen to determine how it defines an under/over-voltage situation? If so, I'm guessing some combination of the 100VAC Low Transfer Voltage setting and the "High" Sensitivity setting is telling the UPS to treat 115VAC as an under-voltage condition, but how is that being calculated?

[BillP · Accepted solution]

Hi stevejenkins

This UPS has automatic voltage regulation (AVR) inside. Here is what I found out:

Low Voltage Cutoff (Upward, Downward)                          106, 100 VAC        

Double Boost to Single Boost (upward, downward)           110, 106 VAC

Single Boost - On Line    (Upward, Downward)                 117, 113 VAC

On Line - Trim      (Upward, Downward)                           126,122    

High Voltage Cutoff - Trim to battery  (Upward, Downward) 134, 130

So single boost in Highest threshold will be 117vac, 115vac Medium and 113vac low. Seems like it's boosting your voltage since its at 115 cause the thresholds are fairly tight.

If you're concerned, we can lower the voltage transfer ranges a few notches which also affects the AVR transfer ranges.

[Anonymous user]

Awesome, Angela. Those ranges are helpful data (bookmarking thread... NOW). I'm actually OK having the thresholds tight. This is powering an Xbox, a PS3, and AppleTV, a Plasma TV, and a high-end AV Receiver, so a tight range is fine by me to protect all that AV equipment.

Just for my geekiness, based on what you said, am I right in understanding the following?

1. The values shown in my screen shots are the "Voltage Transfer" values, meaning the Upper and Lower VAC values at which the UPS switches completely to On-Battery (and NOT using AVR trim)
2. The AVR transfer ranges are influenced by the Voltage Transfer values

If #2 is correct, is there a "fixed" mathematical relationship between the Voltage Transfer values and each of the AVR levels you stated? Meaning, are the AVR trim settings some percentage of the voltages shown on the UPS/Power tab? If so, how are those calculated (what's the percentage)?

Thx!

Steve

[BillP]

Yes, you're correct. 14.6% is the percentage.

[Anonymous user]

Awesome. 14.6, huh? Nothing like a nice round number.