Why is my UPS always trimming if the high voltage threshold has not been reached?

[Anonymous user]

Hello,

I got a new BR1300G, upon plugging it I noticed that the fan came on and that the unit is constantly trimming the voltage down to 120, with the AVR light being on. My input voltage is 133 and the powerchute software is set to intervene at 136. Why is AVR activating?

I live in Mexico and our nominal input is 127V, with 133-136V not being abnormal... I've purchased APC units for as long as I can remember and I've never had a problem with this. I actually have a 4 year old 1300G unit that's been working fine.

Any ideas? why is it trimming even if the software is set to 136v?

Thanks

[BillP]

Hello,

The 136V is when the UPS would intervene by going to battery rather than trimming. Take a look at this user's guide -> http://www.apcmedia.com/salestools/EALN-7V5MXA/EALN-7V5MXA_R1_EN.pdf

You'll see on PDF page 8 (which is the last page) and you'll see that Automatic Voltage Regulation kicks in at 126V. Depending on how sensitive your equipment is to the 11.5% voltage trim, then you can set the voltage transfer range which is the setting you're referring to either higher or lower.

The older unit likely has different firmware and perhaps different AVR ranges for example. I'll have to see if there is anything to do in order to change when the UPS trims..

Edit: - I don't think there is much we can do on preventing the UPS from trimming. I have to assume either the voltage where the older UPS is slightly lower depending on the circuit it's ok or they have different firmware versions that causes them to trim at different voltages.

[Anonymous user]

Thanks for your reply,

Not sure if I understood though, what are my options? I assume that it's not healthy for the UPS to leave it trimming the voltage all the time?  Can the AVR range be modified?

[BillP]

Well, to begin, can you confirm the exact SKUs of the two UPS units you have? I'd just like to be sure to help explain any differences in behavior. This model number should be on the white sticker on the rear, perhaps where you discovered "BR1300G."

I ask because we have BR1300G and BX1300G and BX1300G does not have trim, only boost. Thus, this might explain why your other UPS is not trimming but this one is.

And no, the AVR transfer range is modifiable, only the voltage transfer range (when the UPS goes to battery because of high/low input voltage). You could try to change the sensitivity of the UPS but I don't think it will change the behavior.

[Anonymous user]

You are correct, the old one is the BX1300G and the new one is the BR1300G.

Regarding my question about the letting the BR1300G trim all the time. Is that a no no?

Thanks

[Anonymous user]

With the line interactive architecture within these smaller UPS, there is really no harm for it to be doing some form of trimming, even on a full time basis; this type of ups utilizes a multi-tap transformer to actively regulate small changes in voltage (IE those within the acceptable range whereby it's designed to remain online, versus going to battery), which means the current is just flowing thru a different winding on the main transformer.

[Anonymous user]

I see, I was searching around and came across someone asking about AVR being on all the time, and here's what a random person replied:

"AVR Trim should not damage the UPS. However, it will cause the transformer and other components to thermal cycle more often, which is what usually kills electronic devices. Depending on the frequency of events and the desired service level it may not be worth worrying about."

Though he didn't cite any sources, that's the reason I ask... I don't want to find out that what its supposed to be protecting my gear is also slowly killing it.

Thanks for your reply,

Cheers

[Anonymous user]

Well, I can relate to some of what that source is saying, but only to a certain degree: Firstly I don't agree with the "thermal cycling" statement as that would only apply if there were dramatic changes in the UPS load, which during the AVR process isn't happening. I do want to point out that if the incoming "overvoltage" level is sitting right on the threshold where the ups is designed to do a tap change on the transformer, and slight up and down fluctuations up/down are causing the ups to constantly (many times a minute) kick in and out of a trim response there will be some wear and tear on the relays that do the tap switching and will steal life off of them..... so its best to address any such overvoltage (or under) with local electrical facilities personnel right away when you observe this on your ups.

[BillP · Accepted solution]

I am trying to get more feedback from our Back UPS support team but it sounds like BX1300G is the best option to avoid problems with trimming. I think boost functionality (versus trim) probably generates the most heat which could cause premature problems too but I would think the more use particular electronics and components get, no matter what it is - since I am sure the UPS is not tested in constant trim mode for years - could potentially affect the UPS over time. I can't say I have anything other than my UPS experience to back that up - I am just talking out loud.

I am also trying to track down more feedback on this dilemma of offering a 120V UPS in Mexico without considering it may be constantly trimming..

I think if anything, this could be swapped for a BX1300G..