Questions about Power Strips and Power Distribution Units

[Spork Schivago]

Hello,

I currently have something similar to this:

http://ak-i21.geccdn.net/site/images/large/249515.jpg


It's 15-outlet (or 16, if I miscounted). And it has served me well over the years. I have it physically attached to the back of my workbench, so no matter where I am on the workbench, I got an outlet. There's a problem with it though. It doesn't have any protection for surges or anything like that. This worries me now, because my collection of equipment is now worth a good bit. I'd hate to have to replace some of it or all of it just because of something stupid like a surge. So, I'm looking at alternatives and I come across this:

http://www.apc.com/shop/us/en/produc...5-20R/P-AP8632

Would this be a good choice to help prevent against surges? I know it's a bit pricey, but it's cheaper than replacing some of my equipment. It looks similar, and although it's meant for a rack, I bet I could attach it to my workbench in a similar matter...we're in the process of moving, in case you guys didn't know. I'm thinking in the new house, we'd also purchase and install one of those whole home surge protector units. I've been told they're not enough though and you should still use surge protectors for your important stuff. What do you guys think?

I really like how I can monitor and shut off outlets remotely with that PDU. I might use that a lot, I don't know yet. If I get it, I'd like to write a custom program that interfaced with that.

[Spork Schivago]

Re: Questions about Power Strips and Power Distribution Units

I found this on schneider-electric.us's website:

Surge protectors filter the power for surges and offer EMI/RFI filtering but do not 
efficiently distribute the power, meaning that some equipment may be deprived of the
necessary amperage it requires to run properly causing your attached equipment 
(computer, monitor, etc) to shutdown or reboot. If you need to supply additional 
receptacles on the output of your UPS, we recommend using Power Distribution Units 
(PDU's). PDUs evenly distribute the amperage among the outlets, while the UPS will 
filter the power and provide surge protection. PDUs use and distribute the available 
amperage more efficiently, allowing your equipment to receive the best available power 
to maintain operation.

So PDUs evenly distribute the amperage among the outlets...my devices don't require the same amount of amperage. Am I reading this wrong? If there's 20A total available, and the PDU has 24 outlets, does that mean each outlet gets 20/24 amps (roughly 0.83 amps) total? If one my devices require 4 amps, would it be denied? Or does it just mean if my device needs 4 amps, it'll be guaranteed to get 4 amps. Another device cannot steal that 4 amps?

I wonder how this would work with surges...I bet I'd still need something to smooth out the voltage and make sure it's a nice stable 120V, no matter what, and if a surge comes, filter it out somehow...

[stj]

Re: Questions about Power Strips and Power Distribution Units

feast your eyes on this:
http://www.olson.co.uk/international_range.htm

[budm]

Re: Questions about Power Strips and Power Distribution Units

The load dictate how much current you are going to draw from the outlet, if you have 20A feeding to the strip, and lets say you have two outlet and each outlet has 10A circuit breaker, then you can only draw 10A from each outlet.
But if the two outlets are connected in parallel and then connected to 20A breaker, then each outlet can supply up to 20A but then you are not going to be able to put the load on the other outlet because you will exceed the total current draw. because you cannot have more than 20A of current draw from both outlets.
If you want steady AC then you will need AC regulator.
You should have the box that can do surge protection and Over/under Voltage shutdown

[budm]

Re: Questions about Power Strips and Power Distribution Units

http://www.surgex.com/residential.html
http://espsurgex.com/product/axess-elite/

http://espsurgex.com/product-categor...er-protection/
http://espsurgex.com/product/flatpak/ use with your existing strip.

[Spork Schivago]

Re: Questions about Power Strips and Power Distribution Units

The load dictate how much current you are going to draw from the outlet...

Yes, I understand this. But what I'm asking is with a PDU, from the definition I gave, it sounds like if the load draws 4 amps, it's guaranteed to get that 4 amps, whereas with a power strip, perhaps if the load draws 4 amps but another load needs 2 amps, the power strip won't be able to handle it and the first load won't get enough power. Is that correct? I'm just having a hard time understanding what exactly a PDU does. I mean, how does it differ from what I currently have? Minus the whole remote monitoring stuff, is there much of a difference?

...if you have 20A feeding to the strip, and lets say you have two outlet and each outlet has 10A circuit breaker, then you can only draw 10A from each outlet.
But if the two outlets are connected in parallel and then connected to 20A breaker, then each outlet can supply up to 20A but then you are not going to be able to put the load on the other outlet because you will exceed the total current draw. because you cannot have more than 20A of current draw from both outlets.

Okay, I understand this now, thank you. So, with a PDU, is it essentially equivalent to have X amount of outlets hooked up in parallel and with a power strip, it'd be equivalent to having X amount of outlets hooked up in series?

If you want steady AC then you will need AC regulator.
You should have the box that can do surge protection and Over/under Voltage shutdown

I currently have a UPS but it's not good enough I don't think. I want something that can handle a bit more juice. I don't think the UPS was designed for the type of hardware I'm going to be powering, you know?

Also, I was looking at some of the links you posted. One shows it can handle a surge up to around 6,000 volts and 3,000 amps. What's the worst type of surge you think I could expect in a house? If there was some direct lightning strike with some power line, how much do you think could realistically get to my equipment?

[stj]

Re: Questions about Power Strips and Power Distribution Units

close lightning will hit you with an Electrostatic Field, stuff will fry even on battery's

[kaboom]

Re: Questions about Power Strips and Power Distribution Units

close lightning will hit you with an Electrostatic Field, stuff will fry even on battery's

Magnetic field- induces currents on things like audio lines connected between equip also connected via a common EGC.


All utilities (elec service, telco, CATV) need to be bonded per 250.94, 800.100, and 820.100.

https://www.youtube.com/watch?v=a5zAVo2bvJ8
https://www.youtube.com/watch?v=pzHQPgoXm30
https://www.youtube.com/watch?v=QPWmULYgONA

After a step potential event pushes current thru your TV or cable modem/computer, back to the electric service via the EGC, don't be fooled into getting a surge supressor! You need to correct the deficiency in the bonding and fully complete the electric service wiring.

[budm]

Re: Questions about Power Strips and Power Distribution Units

magnetic field- induces currents on things like audio lines connected between equip also connected via a common egc.


All utilities (elec service, telco, catv) need to be bonded per 250.94, 800.100, and 820.100.

https://www.youtube.com/watch?v=a5zavo2bvj8
https://www.youtube.com/watch?v=pzhqpgoxm30
https://www.youtube.com/watch?v=qpwmulygona

after a step potential event pushes current thru your tv or cable modem/computer, back to the electric service via the egc, don't be fooled into getting a surge supressor! You need to correct the deficiency in the bonding and fully complete the electric service wiring.

+1

[Spork Schivago]

Re: Questions about Power Strips and Power Distribution Units

Yes, I understand this. But what I'm asking is with a PDU, from the definition I gave, it sounds like if the load draws 4 amps, it's guaranteed to get that 4 amps,...

I just reread this again and it doesn't sound right at all. I'm having trouble trying to express what I mean. I guess I'm trying to say if a device is plugged into a PDU, and the device is drawing 4 amps, another device cannot come in and "steal" some of that amperage. That's my question I guess. Is that how a PDU and a regular power strip differ? Maybe a PDU is just an "intelligent" power strip...

[Spork Schivago]

Re: Questions about Power Strips and Power Distribution Units

Magnetic field- induces currents on things like audio lines connected between equip also connected via a common EGC.

What's the Equipment Grounding Conductor? Is that the wire that goes to the physical earth? The one outside of everyone's house? If the equipment isn't connected via a common EGC, we don't have to worry about a magnetic field inducing current between my various equipment? Like the cable modem having an ethernet cable plugged into my PC, if the cable modem has a separate EGC, I don't ever have to worry about a bad current going through the ethernet line to fry my PC?

All utilities (elec service, telco, CATV) need to be bonded per 250.94, 800.100, and 820.100.

I'm going to look up the NEC 250.94, 800.100 and 820.100. So, cable modem, telephone lines, incoming cable, the grounds should all be connected together, to the house ground, according to the 2014 NEC? I must be misunderstanding the top part then. I'd think we'd want a separate ground for those devices so a current couldn't be induced between them.

I'll go watch the videos now.

After a step potential event pushes current thru your TV or cable modem/computer, back to the electric service via the EGC, don't be fooled into getting a surge supressor! You need to correct the deficiency in the bonding and fully complete the electric service wiring.

What is a step potential event? Just another word for a lightning strike? I figure if something like that happened, I would need to fix stuff in the house. But the idea was to try and take preventive measures before it happens, so my expensive devices don't get damaged from it. Are you saying if I properly have my house wired, up to code, I don't need to worry about surges at all? The only time lightning could hurt would be from not having stuff properly bonded? Thanks!

[budm]

Re: Questions about Power Strips and Power Distribution Units

'Surge protectors filter the power for surges and offer EMI/RFI filtering but do not
efficiently distribute the power, meaning that some equipment may be deprived of the
necessary amperage it requires to run properly causing your attached equipment
(computer, monitor, etc) to shutdown or reboot.'
'PDUs evenly distribute the amperage among the outlets.

What is shown on post 2 is just wrong to me, the PDU cannot force evenly distribute current to the outlets.
Lets say you have 100W lamp in one outlet, and 7W Night lamp in the other outlet, are they tell me that will try to force 7W laod to be at 100W, or another way around, the PDU will reduce the current to the 100W down to 7W so the current will be even.
Do you have outlet strip with surge protection and AC line noise filter? Plug in a 100W lamp in one of the outlet, then plug in a heater (set to LOW heat) in the other outlet of the strip, do you see the 100W turns off due to the heater stealing the current from the lamp?

[Spork Schivago]

Re: Questions about Power Strips and Power Distribution Units

'Surge protectors filter the power for surges and offer EMI/RFI filtering but do not
efficiently distribute the power, meaning that some equipment may be deprived of the
necessary amperage it requires to run properly causing your attached equipment
(computer, monitor, etc) to shutdown or reboot.'
'PDUs evenly distribute the amperage among the outlets.

What is shown on post 2 is just wrong to me, the PDU cannot force evenly distribute current to the outlets.
Lets say you have 100W lamp in one outlet, and 7W Night lamp in the other outlet, are they tell me that will try to force 7W laod to be at 100W, or another way around, the PDU will reduce the current to the 100W down to 7W so the current will be even.
Do you have outlet strip with surge protection and AC line noise filter? Plug in a 100W lamp in one of the outlet, then plug in a heater (set to LOW heat) in the other outlet of the strip, do you see the 100W turns off due to the heater stealing the current from the lamp?

It was confusing me, that's why I came here, I thought maybe someone more experienced could explain it differently to me. I believe the people who gave the definition are also the people who are selling some of these units. So perhaps they were misinformed to encourage people to purchase more PDUs. I mean, really, what exactly do they do that a much, much cheaper power strip does? Besides the remote monitoring (that some units don't even have), I don't really see a difference. I was hoping they had some super surge protection built in or something.

We have small surge protectors but I don't know if they have any built in AC line noise filters. I thought my UPS is an AC line noise filter. It's a smaller UPS. It just gives me around 30 minutes or so to shut off my PC when the electricity goes out. I don't think the light bulb will turn off. But what happens if it's a much higher current and we're approaching the maximum that the surge protector is rated for? Again, it wouldn't steal any current, would it? If anything, it'd trip some breaker. I guess I didn't think my question through far enough, did I?

I have seen lights flicker before when heavy devices were turned on. Not in this house, but old houses, a long time ago. Someone would turn on the saw and the lights would flicker or maybe the AC would kick on and the lights would dim a bit, just for a second, then they'd brighten back up. I'm trying to remember where I saw that at.

[budm]

Re: Questions about Power Strips and Power Distribution Units

There no current stealing, if you draw more current than the breaker can handle, it will pop the breaker, if you try to draw more current than the UPS can provide, the UPS will shutdown. Most UPS will do the self test when you first turn on the UPS with all the loads connected to the UPS (the outlets that supply AC when the incoming AC is not present), if it senses that the current draw is higher than it can handle, it will then shutdown and beep at you to check the loads, that info is in the UPS user manual.

[kaboom]

Re: Questions about Power Strips and Power Distribution Units

'Surge protectors filter the power for surges and offer EMI/RFI filtering but do not
efficiently distribute the power, meaning that some equipment may be deprived of the
necessary amperage it requires to run properly causing your attached equipment
(computer, monitor, etc) to shutdown or reboot.'
'PDUs evenly distribute the amperage among the outlets.

What is shown on post 2 is just wrong to me, the PDU cannot force evenly distribute current to the outlets.
Lets say you have 100W lamp in one outlet, and 7W Night lamp in the other outlet, are they tell me that will try to force 7W laod to be at 100W, or another way around, the PDU will reduce the current to the 100W down to 7W so the current will be even.
Do you have outlet strip with surge protection and AC line noise filter? Plug in a 100W lamp in one of the outlet, then plug in a heater (set to LOW heat) in the other outlet of the strip, do you see the 100W turns off due to the heater stealing the current from the lamp?

It sounds like they're using "confusion" (and lies) to sell people stuff they don't need; this is not to say that legitimate cases of power "clean up" don't exist. Take the old "farm services" around here, where you've got a 7.6kV:4.8kV stepdown transformer serving a few dozen 4.8kV:240/120V transformers on multiple farms and nearby houses. It's summer- air conditioning season! Not only is there voltage drop in the typically-undersized-by-POCO transformers feeding houses, etc, but also in the 7.6:4.8 stepdowns. Between the series impedance of both of those, and the voltage drop on the 120/240 secondaries, the "120V" at such farmhouses is typically 110-115V at this time of year.

Both the 120/240 is pulled down, as usual, as well as the 4.8kV, which probably gets closer to 4.6kV.

The little 7.6:4.8kV stepdowns have much higher impedance than a "substation" transfomer; while the stepdowns certainly handle less load on their secondaries (which are the primaries of the transformers in front of the houses/barns), their higher impedance kills overall performance/voltage regulation.

So where someone needs stable 120V for something sensitive, either an "interactive" UPS, with line-freq transformer and tap-changer, an actual regulator/tap changer (miniature version of pole top unit, just for 120V), or a ferroresonant xfmr is needed.

FWIW, as most electronics have SMPSes, there's more margin for lower voltage than with a transformer-rectifier supply as in old stereo equip. The absolute worst thing for electronics is an open neutral...

As far as those old stereos, for the most part, low voltage just means lower max power output. Extreme cases of low voltage takes the output xsistors away from their idle-bias point, raising distortion. Tube stuff could be worse- bias drops a lot while B+ can remain high enough for significant plate dissipation; low-ish voltage can be OK, but too-low is bad. The filaments also cool off while plate voltage is still applied- can lead to loss of electron cloud "space charge," and residual gas/ions (no vacuum is perfect) slam into cathodes and "poison" them over time.

I just reread this again and it doesn't sound right at all.

You are right. I studied law, Ohm's Law.

if a device is plugged into a PDU, and the device is drawing 4 amps, another device cannot come in and "steal" some of that amperage.

Not on Earth, and certainly not in a parallel ckt.

What they're claiming is impossible. Load A takes 5A, load b takes 10A. Added load C now takes 5A. Total now 20A. If it's all on a 15A bkr (and all connections proper and tight), how long the bkr holds on this 5A overload depends on its time/current trip curve; it may hold anywhere from 10 to 60 minutes, depending on the particular bkr and the ambient temp of the panel the bkr is in. Cooler= longer time-to-trip, as mild/moderate overloads are handled by a thermal trip unit. Dead shorts (or even ~75A+ for certain 15A bkrs) make the trip coil drop the ckt almost instantaneously.

Modern "molded case" (the ones in a house's panelboard) bkrs have thermal-magnetic trip units.

That's my question I guess. Is that how a PDU and a regular power strip differ? Maybe a PDU is just an "intelligent" power strip...

In this case, just sounds like marketing. Almost like the "monster cable" version of a power strip.

[japlytic]

Re: Questions about Power Strips and Power Distribution Units

This topic reminds me of something about partitioned offices which the AC outlets are daisy-chained, which the outlet at the extreme end of the chain is most likely to have power problems because of significant voltage drop when outlets further away from the extreme end of the chain start drawing significant current.

Power strips arrange the wiring of the outlets in a bus configuration (daisy-chained, like as described above); however, in my theory, power distribution units arrange the wiring of the outlets in a star configuration (wiring radiating from a common point).

[kaboom]

Re: Questions about Power Strips and Power Distribution Units

Power strips arrange the wiring of the outlets in a bus configuration (daisy-chained, like as described above); however, in my theory, power distribution units arrange the wiring of the outlets in a star configuration (wiring radiating from a common point).

Which doesn't matter at all. In the short run of the bus/wiring in a typical power strip, there's plenty of conductor area such that voltage at the "far end" is perhaps a few tens of millivolts lower than the "near end."

This doesn't matter for the real cheap, nasty strips, whose undersized brass strips grip plug blades poorly and burn up. The conductor area is the least of your problems here; poorly soldered connections from the power cord wires to the strips and ckt bkr will tend to go "FPE" if/when they're loaded too much. Think coffee maker, laser printer, vacuum, etc.

As far as trying to "determine" how the item in question is different, forget it- you've been suckered. Again, questionable "audiophoolery" claims have been made, and you think you'll get into the heads of the marketing department to figure out where they're going, as if there's something legitimate.

The more you "give," the more they "take." When the marketing assholes read your silly comments, it's just like knocking on a wall to find studs; they read your pitiful "rationalization" and know immediately they've found an easy mark.

Given the same overal ckt length, a branch ckt run with #10CU will have less drop than a loop fed ckt run with #14. The two runs of #14 in parallel have less cross section than a single run of #10.

It's not some big secret or especially difficult. Try some wire tables and basic math, before haphazardly running to gOoogle.

[stj]

Re: Questions about Power Strips and Power Distribution Units

if you want a workshop strip, get a string of individually switched sockets with an RCD at the end and *maybe* a bypass switch for working on stuff that is "leaking"
just make sure it's illuminated so you know your safety is bypassed!

[Spork Schivago]

Re: Questions about Power Strips and Power Distribution Units

...Load A takes 5A, load b takes 10A. Added load C now takes 5A. Total now 20A. If it's all on a 15A bkr (and all connections proper and tight), how long the bkr holds on this 5A overload depends on its time/current trip curve; it may hold anywhere from 10 to 60 minutes, depending on the particular bkr and the ambient temp of the panel the bkr is in. Cooler= longer time-to-trip, as mild/moderate overloads are handled by a thermal trip unit. Dead shorts (or even ~75A+ for certain 15A bkrs) make the trip coil drop the ckt almost instantaneously...

So, if we were measuring the amperage on the circuit, before we add load C, we have 15A, as soon as we add load C, we see 20A being used? If we were to measure load A as soon as we added load C, load A would always draw 5A and if we were to measure load B while we added load C, load B would also be drawing 10A? And when we add load C, no matter what load C is, because it draws 5A continuously, it will always draw 5A? This part confuses me....I thought when certain things started up, they could draw more amperage than when they were running for a bit. Like ACs for example. I thought that's why sometimes, when an AC engages or whatever it is, if the breaker is rated for exactly what the AC uses or something, it can trip. Is this understanding wrong? I thought it was called input surge current or something along those lines.

In this case, just sounds like marketing. Almost like the "monster cable" version of a power strip.

That's what I'm starting to think now. Just a fancier version of what I already have. I read somewheres where a guy bought some from APC and when he was talking to them, they said they would only warrant it if it was plugged into a PDU, NOT a surge protector. APC must think there's some sort of difference here. But they were very particular as to which PDU it was plugged into. So, maybe certain PDUs do certain things different than a power strip and other ones are just fancy power strips? Or, my guess, APC just shacked up with some company that made PDUs and was trying to force users to buy stuff they didn't need.

[Spork Schivago]

Re: Questions about Power Strips and Power Distribution Units

Here, http://searchdatacenter.techtarget.c...ution-unit-PDU

they talk about load balancing power. I don't understand this anymore than the original quote I found. Isn't it the load that determines how much power is used? I can take a device I'm working on and on my programmable power supply, I can set the voltage to 5VDC and the amperage to 3 AMP. The programmable power supply will supply UP TO!!! 3 amp. It'll show how much the device is actually drawing (which is almost always less than 3 amp). Power = V * I. I guess we can change the voltage to change the power output of one of the outlets, but I wouldn't think that'd make any sense. If a device is designed to accept 120VAC, cutting it down to 110VAC, I can't really see it doing anything at all, really.

It sounds like this power load balancing stuff is just another scam as well.