H15 trim

[Anonymous user]

Periodically, my H15 unit goes into trim mode (possibly from seeing a voltage higher than 124V). Looking at the display, I see that the Vin (voltage in) is 124 and the Vout (voltage out) is 117. The unit stays in trim mode until I turn on a device plugged into the H15. Then, the unit goes out of trim. The Vin remains at 124 and the Vout becomes 124 as well. Is this normal? I'm concerned that during long off times of connected components, the unit is working unnecessarily to trim voltage. Not sure if this will effect the life of the unit. Please advise. Thanks

[BillP]

What do you have the AVR range set to (wide, normal, narrow)?

Either way, it shouldn't affect the life of the unit. It's more of an issue if it goes in and out of trim/boost repeatedly, all day long, because that will wear out the relay faster. Otherwise what you're describing doesn't sound like an issue in terms of life expectancy.

[Anonymous user]

Hi Buzz. It is currently set to narrow. But why is the unit staying in trim mode when there is no need (i.e. after input voltage returns to 124)?

Actually, the unit is not going in and out of trim. Once in trim, it stays there (despite normal voltage being supplied) until there is a load placed on the unit by turning on a component plugged into the H15 (like my TV). Then the trim turns off immediately.

I'm in the room the H15 is in very frequently. It is unusual for the unit top go into trim, maybe once or twice per week. I notice it because it stays in trim until I turn something on.

This unit has a wiring ok light issue and it will be replaced by APC when units without this issue are available. I wasn't sure if this trim situation is typical of H15's, or if there is something odd with this H15.

[BillP]

Yeah, I gotcha. Basically it goes into trim mode due to high(ish) voltage - 125v on narrow - and it stays in trim until the hysteresis threshold (5v) has been reached. Then you turn your TV or whatever on, which causes a very brief sag in the voltage, so brief the unit's display may not even reflect it. Afterward the voltage goes back to 124v, but because of that very brief sag, it's outside of the hysteresis window and 124v is acceptable (below 125v) so it stays "online" without trimming at that point. Sounds like normal behavior, I tested it myself and it does the same thing. 🙂

I'm not sure how familiar you are with hysteresis, but basically it's a window where the unit will stay performing as it is so it doesn't keep switching back and forth when the voltage fluctuates slightly but rapidly. In this instance, the window is 5v, so once the unit starts trimming at 125v, it won't stop trimming until the voltage is reduced by 5v to 120. For example, you wouldn't want the unit to keep going in and out of trim mode with the voltage changing slightly from 124 to 125, as electricity is wont to do. The brief sag in voltage when you turn on your equipment reduces the voltage enough to get it to stop trimming, and then the voltage is fine at 124v again. Make sense?

[Anonymous user]

Buzz, I understand your post. I also changed the setting from narrow to normal. Same thing is happening. Is this still normal?

What is the window on the normal and wide setting (is it still 5v)? Is the window the same for boost and trim? Thanks!

P.S. At what voltage does the H15 begin trimming voltage in narrow, normal and wide? At what voltage does the H15 unit begin boosting voltage in narrow, normal and wide?

Message was edited by: apcme

[BillP]

Yes, it's most likely still normal, since the hysteresis windows are larger with the wider AVR ranges. Here are the ranges:

Narrow: 102-132v, regulates to 120 +/- 5%
Normal: 97-139v, regulates to 120 +/-10%
Wide: 92-145v, regulates to 120 +/- 15%

Playing with an H15BLK, here's where boost/trim seem to kick in: (apparently I can't make nice table-like layout)

AVR Setting / Boost / Trim / Hysteresis
Narrow: 113v / 125v / 5v
Normal: 110v / 128v / 10v
Wide: 108v / 130v

Hysteresis was harder to determine on wide since it regulates to +/-15%... but it would stay in trim/boost mode for awhile even back at 120v before going back to normal operation. Sometimes I had to bring it below 120v, where it would start to boost and then realize voltage was fine before coming online.

I'd leave it on narrow, personally.

[Anonymous user · Accepted solution]

Thanks Buzz. This information is helpful.