SMT750I , Questions before purchase

BillP · ‎2021-06-29

Hello, i am in the process of purchasing a new UPS, exactly the one mentioned in the topic SMT750I, but before, i need to know:

Does it have any fan? this is the most important thing i need to be sure, as i need a 100% silent unit.

Can the display be turned off?

I read that at standby, this unit consumes around to 60w, is this true? even when nothing is drawing power?

Thanks.

BillP · ‎2021-06-29

SMT750/SMT750I units do not have a fan.
Recent firmware revisions have introduced the ability to turn the display off. You'd need to enable the feature in the LCD menu and I think it goes off after a few minutes or something like that. I
60W is high. Keep in mind, this answer depends on if the battery is fully charged or not. The battery charger wattage is 49W so if the battery is fully discharged with no load, it'd draw at least that most likely. We also have a UPS efficiency calculator (located here -> http://www.apc.com/tool/?tt=5) and you can look up your UPS model there and compare the model to itself. If you do that, then you'll get a graph on the right where you can look at UPS system losses and you can show it at 0% load. If I do that, I see 8W is the answer. So, with no load and battery fully charged, the UPS power consumption would be 8W.

See Answer In Context

BillP · ‎2021-06-29

Hello, i am in the process of purchasing a new UPS, exactly the one mentioned in the topic SMT750I, but before, i need to know:

Does it have any fan? this is the most important thing i need to be sure, as i need a 100% silent unit.

Can the display be turned off?

I read that at standby, this unit consumes around to 60w, is this true? even when nothing is drawing power?

Thanks.

BillP · ‎2021-06-29

SMT750/SMT750I units do not have a fan.
Recent firmware revisions have introduced the ability to turn the display off. You'd need to enable the feature in the LCD menu and I think it goes off after a few minutes or something like that. I
60W is high. Keep in mind, this answer depends on if the battery is fully charged or not. The battery charger wattage is 49W so if the battery is fully discharged with no load, it'd draw at least that most likely. We also have a UPS efficiency calculator (located here -> http://www.apc.com/tool/?tt=5) and you can look up your UPS model there and compare the model to itself. If you do that, then you'll get a graph on the right where you can look at UPS system losses and you can show it at 0% load. If I do that, I see 8W is the answer. So, with no load and battery fully charged, the UPS power consumption would be 8W.

BillP · ‎2021-06-29

Yes, Line Interactive Smart UPS like this one have AVR. I see the answer in this user's guide -> http://www.apcmedia.com/salestools/SCON-7NBSEM/SCON-7NBSEM_R5_EN.pdf Refer to PDF page 9.

BillP · ‎2021-06-29

Sorry, i only see the threshold for battery transfer, there is no mention of at what voltage AVR trims or boosts..

BillP · ‎2021-06-29

Sorry, my error. The voltage transfer ranges listed there are the only ones that you can adjust via the LCD or the NMC so I had that on the brain. The AVR transfer points I don't have readily accessible unfortunately..it also may change between firmware revisions.

hkpolice_apc · ‎2021-06-29

I have this unit running in my house (120v version) and it's NOT 100% silent. While there are no running fans, the battery charger and or transformer emits buzzing electrical noise all the time. Depending on how quiet the ambient noise is, you might not be able to hear it like if there's a desktop running nearby, but if it's dead quiet at night and you're trying to sleep you will notice it. I also have an SMT1500 unit and it makes a much louder buzzing noise noticeable much further away. This seems to be the norm for these new SMT unit whereas the older SUA units are generally quieter.

BillP · ‎2021-06-29

Ok, while looking at the shop, i seen bigger unit, SMT1000I , can you please verify if this one also comes fanless?

Thanks hkpolice, i'll be aware of it when i get the unit, hope it does not end bothering too much...

BillP · ‎2021-06-29

Anything larger than a 750 typically has a fan. SMT1000I has a fan.

BillP · ‎2021-06-29

Okay, will definitely go for the 750 then.

I can't find the transfer time ms, do you know it?

BillP · ‎2021-06-29

Depends on the sensitivity. If its at high (default), you'll see 2-4ms, 4-6ms for medium, and 6-8ms at low sensitivity. The more THD (total harmonic distortion) on the input, the longer the transfer time.

BillP · ‎2021-06-29

Finally received the unit, everything seems ok, only thing i noticed, is that when it's on battery, with an average amount of load, it emmits a sound like water bubbles, like brbrbrbrbrbr... does this is normal?

BillP · ‎2021-06-29

You'll hear some type of noise while the inverter is operating but I can't say it sounds like water bubbles to me..

BillP · ‎2021-06-29

Maybe water bubbles was not the correct word, more like some type of electric noise...

It fluctuates, when there is no load, it's almost silent, but when there is 150 or more watts, it's more pronounced..

I'll try to make a video as soon as i can get a mic, just to make sure it's normal...