is it safe to use Power Strip OR surge protector attached to a UPS?

LOUISSSSS

Diamond Member
Dec 5, 2005
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#1
i have a big powerful UPS and it only has 6 outlets.

i know it can power more things...

is it safe to attach a power strip or a surge protector to it to connect more devices?
 
Mar 9, 2005
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#2
Most manufacturers don't recommend doing something like that. You should contact the maker of your particular unit and ask them if it's okay to do that.
 
Jan 11, 2001
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#3
I do it. I've been told you can use the power strip coming out of the UPS but never attach the power cord of a UPS to a power strip or surge supressor.

EDIT: Then again, I have a frankenstein "homeade" UPS also so the manufacturer would me me. ;)
 
Oct 6, 2008
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#4
Originally posted by: Gillbot
I do it. I've been told you can use the power strip coming out of the UPS but never attach the power cord of a UPS to a power strip or surge supressor.

EDIT: Then again, I have a frankenstein "homeade" UPS also so the manufacturer would me me. ;)
actually Ive been told its the other way.

surge strip -> UPS OK

UPS -> surge strip on UPS powered outlets NOT OK

reason is the surge strip may get faked into thinking the odd waveform from the UPS is a surge and activate, killing the UPS.

if its just a outlet strip (no surge suppression) you can use them on the UPS powered outlets.

EDIT: my APC manual doesnt recommend using ANY surge suppressor strips in the chain anywhere. it does say non surge outlets strips on the UPS outlets are OK.
 
Jan 11, 2001
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#5
Surge strips should be avoided on either end. Usually because as voltage dips, the UPS can draw more current to compensate thus tripping the surge strip. Power strips are usually just dumb multiple outlet pieces and rarely have any protection on them. Also, my reply mentions only power strip and not a surge supressor, I should have been more clear and noted I don't recommend surge strips anywhere.
 
Aug 25, 2001
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#7
My understanding is that if there is a voltage spike, and you have a surge strip connected to the battery outputs of the UPS, then the UPS will switch to battery (with a small delay), while the surge strip activates its MOVs inside, which attempt to shunt the voltages to ground. However, since it is plugged into the output of the inverter, it ends up shorting out the inverter too! Thus putting a strain on the UPS, overloading it, or possibly even damaging it.
 

LOUISSSSS

Diamond Member
Dec 5, 2005
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#8
so there really is no way to get more available outlets out of my battery-backup UPS?

other than getting another one?
 

mindless1

Diamond Member
Aug 11, 2001
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#10
If the surge strip is properly designed and rated for the load, if it still trips due to the UPS then it was supposed to trip, no matter what the UPS is doing it is not supposed to exceed the current rating. That would be an ideal situation, you wouldn't want an UPS failure to damage anything downstream just as you wouldn't want an AC powerline surge to do so.

A greater concern some manufacturers might have is that if they tell people it's ok to daisy-chain these, the total amount of current drawn could get excessive particularly if the power strip is crudely made with just strips of brass running the length for outlet contacts, or in homes with older, now corroded wall outlets. Each mechanical connector in the chain adds a tiny bit of resistance ideally but possibly a larger resistance in the worst case. The larger the resistance initially, the worse that contact will degrade over time.
 

mindless1

Diamond Member
Aug 11, 2001
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#11
Originally posted by: VirtualLarry
My understanding is that if there is a voltage spike, and you have a surge strip connected to the battery outputs of the UPS, then the UPS will switch to battery (with a small delay), while the surge strip activates its MOVs inside, which attempt to shunt the voltages to ground. However, since it is plugged into the output of the inverter, it ends up shorting out the inverter too! Thus putting a strain on the UPS, overloading it, or possibly even damaging it.
This will not happen. An MOV's function is not as a switch, not an on-off device. The MOV continuously shunts current from all voltages over it's rated voltage spec (well above 120V), which it should (for correct function of the surge protector) be doing from the UPS output too if the UPS output voltage is above that value. Voltages below it's spec will not be shunted. Obviously I am only thinking of a 110VAC mains line, the MOV will of course be equivalently higher in voltage spec on 220V lines, surge-strip (& UPS) made for those geographic markets.
 

Zepper

Elite Member
May 1, 2001
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#12
I use a non-surge (plain ordinary) power strip on the OUT side of my UPS - just don't overload your UPS. I just plug a few minor things into the strip like my USB Hub, cordless phone, etc. If you need any more protection on the out side, then your UPS isn't very good. I also plug the IN (AC) side into a surge strip. There is the potential for an MOV in the strip to fail (supposed to fail in open mode, but can occasionally fail in shorted mode). I figure that it's easier to fix MOVs in the strip than the same part inside my UPS. Since MOVs can also wear out after sufficient minor hits, they'll have to be replaced one day in any case - once again easier to fix in the strip (or just replace the whole strip) than in the UPS.

.bh.
 

Kwatt

Golden Member
Jan 3, 2000
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#13

mindless1

Diamond Member
Aug 11, 2001
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#14
Originally posted by: Zepper
There is the potential for an MOV in the strip to fail (supposed to fail in open mode, but can occasionally fail in shorted mode).
It's possible but unlikely for the sizes of MOVs we'd see in a consumer class UPS or surge protector to fail shorted and then continue to be a short in a live mains AC circuit. If the high voltage current kept flowing the heat density would make it fracture apart, if the current hadn't already tripped the circuit breaker or fuse that even a non-surge protector outlet strip should have. It might be more of a factor with a more current limited supply like that from a smaller UPS, but any UPS working properly (besides this new short) should gracefully shut down if overloaded like this. I may be idealizing too much, there's a lot of junk out there but your typical $50 APC UPS would.

 

Zepper

Elite Member
May 1, 2001
18,998
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#15
Yes, that's exactly what happens when the MOVs fail short - they blow up in a noisy, stinky death. So eventually they do go open again... ;-) Fortunately for us the power seldom goes out here - I can't recall when my UPS tripped last. And we seldom get lightning except toward the beginning and end of summer. If you live in Florida or just about anywhere along the Gulf coast, you can have thunderstorms and power outages about any given afternoon from late spring to early fall, so you have to take your power protection really seriously.

.bh.
 

JASTECH

Senior member
Oct 15, 2007
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#16
If I may "chime" in. You can not legally connect a PS to a UPS on either end. It is against code.

Thanks, JASTECH
 
Jul 13, 2005
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#17
Originally posted by: JASTECH
If I may "chime" in. You can not legally connect a PS to a UPS on either end. It is against code.

Thanks, JASTECH
who around here bothers with code.......
 

Rubycon

Madame President
Aug 10, 2005
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#18
Power strip even with MOV protection is fine. HOWEVER if it has a noise filter (chokes) WATCH OUT! These will oscillate and heat up when non sinus power is passed through them. This will shorten inverter run time sometimes substantially. It can also cause inverters in lower end ups models to become unstable and just shut off killing power to your pc. Kind of defeats the purpose of a UPS doesn't it? :p

If you need more outlets than you physically have or the ones on the UPS are covered with a wall wart, etc. sure go ahead and connect a power strip. Just make sure it does NOT have noise filtering sometimes called RF filtering, "isolation", hash filtering, etc. Your UPS will have this already BTW.
 


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