UPS plugged into Inverter?

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chrisbaker1981

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I have a Meccer Inverter that has a UPS built in, however the transfer time is not quite fast enough to keep my PC on when it switches over to battery mode.

So i plugged my separate Meccer UPS into the inverter and my PC into the UPS, this keeps the PC going for that half a second when the inverter kicks over to battery mode.

Any thoughts on this, good, bad?


Product links below

Inverter https://www.takealot.com/mecer-1200va-720w-12v-inverter/PLID38529100
UPS https://www.takealot.com/mecer-850va-line-interactive-ups/PLID53811883
 
Im sure its ok. probably not ideal, but its so quick I doubt will cause issues. I have a 720 mercer inverter for the tv area, also noticed every now and then the TV turns off on switchover, not every time. my PC has an axpert 3000VA and thank heavens it stays on
 
Is this a mecer 2400 or 1200va inverter? As I never noticed a problem on switch over. But having a ups on it shouldn't cause an issue.
 
Lupus said:
Is this a mecer 2400 or 1200va inverter? As I never noticed a problem on switch over. But having a ups on it shouldn't cause an issue.
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yep 99% power supplies dont have issue, its that 1% which is issue.

Think my raidmax psu in plex server did switch off with mecer inverter
 
Gtx Gaming said:
yep 99% power supplies dont have issue, its that 1% which is issue.

Think my raidmax psu in plex server did switch off with mecer inverter
Click to expand...
Yup never had issues with Antec, Corsair, Coolermaster but I did have an issue with a thermaltake strangely enough and that was on UPS where it would still fail on switch over.
 
So i have an Antec Gold 750 psu in my PC.

@Lupus my inverter is the 1200va version. Sometimes the switchover is ok, sometimes not.

One thing i have noticed is when the mains comes back on, and the the inverter switches back to online mode, the ups plugged in gets confused and switches off, and of course then the pc switches off. Its inconsistent..

Maybe it has to do with the inverter simulating the sinewave and confusing the attached UPS which is expecting a pure sinewave?
 
chrisbaker1981 said:
So i have an Antec Gold 750 psu in my PC.

@Lupus my inverter is the 1200va version. Sometimes the switchover is ok, sometimes not.

One thing i have noticed is when the mains comes back on, and the the inverter switches back to online mode, the ups plugged in gets confused and switches off, and of course then the pc switches off. Its inconsistent..

Maybe it has to do with the inverter simulating the sinewave and confusing the attached UPS which is expecting a pure sinewave?
Click to expand...
Could be the modified sine wave, I didn't have any issues with mine, but it seems it can be an issue, though a PSW inverter would be a better option for running PCs anyway to be honest, I did swap mine out in late 2021.
 
DrJohnZoidberg said:
I've been doing this for years, haven't had any issues yet. All pure sine wave inverters.
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Yea so thats what im suspecting, something to do with my inverter being a simulated sinewave inverter.. Maybe better to invest in a pure sinewave inverter.. Once the switch over happens though my external ups is fine it stays switched off so the inverter must be doing a good enough job in fooling the ups into thinking its receiving a sinewave
 
Lupus said:
Could be the modified sine wave, I didn't have any issues with mine, but it seems it can be an issue, though a PSW inverter would be a better option for running PCs anyway to be honest, I did swap mine out in late 2021.
Click to expand...

Can you recommend a good PSW? Preferably a quietish one that doesnt blast me with a tiny little fan running at max RPM the whole time!
 
chrisbaker1981 said:
Can you recommend a good PSW? Preferably a quietish one that doesnt blast me with a tiny little fan running at max RPM the whole time!
Click to expand...
I had three eccos, 2 1500w and the 2000w, the 1500w were great only spun up the fan every so often and even at max rpm weren't loud, if you can find them get the 1500w. I got mine from jhbgenerator.co.za in December last year.
2 forumites bought my 1500w and a colleague got my 2000w, the 2000w the fan spins when running on battery and charging, the 1500w only come on every 5 to 10 minutes.
 
Lupus said:
I had three eccos, 2 1500w and the 2000w, the 1500w were great only spun up the fan every so often and even at max rpm weren't loud, if you can find them get the 1500w. I got mine from jhbgenerator.co.za in December last year.
2 forumites bought my 1500w and a colleague got my 2000w, the 2000w the fan spins when running on battery and charging, the 1500w only come on every 5 to 10 minutes.
Click to expand...

Great thanks, looks like i should have gone with this instead of the mecer simulated sinewave.

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chrisbaker1981 said:
Yea so thats what im suspecting, something to do with my inverter being a simulated sinewave inverter.. Maybe better to invest in a pure sinewave inverter.. Once the switch over happens though my external ups is fine it stays switched off so the inverter must be doing a good enough job in fooling the ups into thinking its receiving a sinewave
Click to expand...
It has nothing to do with that.
The time it takes that "inverter" to switch over is longer than the hold-up time the PSU is able to meet.
IIRC the ATX specification requires a ~20ms hold-up time, which is a single cycle at 50Hz.
And cheap power supplies probably hardly meets that specification.
If I recall the default setting on that "inverter" is 25ms switch-over time which is why it is a stretch for many a PSU.
 
My corsair RMi 650 holds up just fine with the mecer 2400. I suspect that its better to invest in a decent PSU than another UPS to connect inline.
 
chrisbaker1981 said:
Great thanks, looks like i should have gone with this instead of the mecer simulated sinewave.

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Click to expand...
Yup for PC I would rather use pure sine
 
Gnome said:
It has nothing to do with that.
The time it takes that "inverter" to switch over is longer than the hold-up time the PSU is able to meet.
IIRC the ATX specification requires a ~20ms hold-up time, which is a single cycle at 50Hz.
And cheap power supplies probably hardly meets that specification.
If I recall the default setting on that "inverter" is 25ms switch-over time which is why it is a stretch for many a PSU.
Click to expand...
100%

For those not aware, this is also why there's a considerable price difference between "in-line" UPS's and "on-line" UPS's. The former switches over to battery within that 25ms timeframe whereas on-line runs off batteries permanently. It means no downtime and acts as a harmonics filter, but quite a bit of efficiency lost during conversions as well as $$$.
 
Gnome said:
It has nothing to do with that.
The time it takes that "inverter" to switch over is longer than the hold-up time the PSU is able to meet.
IIRC the ATX specification requires a ~20ms hold-up time, which is a single cycle at 50Hz.
And cheap power supplies probably hardly meets that specification.
If I recall the default setting on that "inverter" is 25ms switch-over time which is why it is a stretch for many a PSU.
Click to expand...
Thats why i have the pc plugged into a separate ups that is fast enough to keep the pc on without failing. Whilst it waits for the inverter to kick in, then the external ups switches off again and all good. But for some reason sometimes, something in this setup fails, sometimes when switching over to battery mode, and sometimes when switching back to online mode... The UPS works fine if just plugged into the mains directly, so thats why i suspect it has something to do with getting confused from the simulated sinewave? For the record, im not an electrician, i hate electricity.. i never touch it :)
 
chrisbaker1981 said:
Thats why i have the pc plugged into a separate ups that is fast enough to keep the pc on without failing. Whilst it waits for the inverter to kick in, then the external ups switches off again and all good. But for some reason sometimes, something in this setup fails, sometimes when switching over to battery mode, and sometimes when switching back to online mode... The UPS works fine if just plugged into the mains directly, so thats why i suspect it has something to do with getting confused from the simulated sinewave? For the record, im not an electrician, i hate electricity.. i never touch it :)
Click to expand...
The very first thing the power supply does is convert the incoming AC to DC, before it does anything.
There are usually some extra components for noise suppression and such that care about the AC wave but even if you removed those components the power supply would work perfectly.
You'd just have more line noise and a drop in power factor.

So the wave form from modified sine is not an issue.
Of course modified sine wave inverters are bad for other reasons, among them generally very low quality, struggle to maintain the correct RMS voltage and various other problems but computer power supply is one of the things that it would not matter much for.
 
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