I've never found a straight answer on whether it's ok to daisy chain surge protectors. Anyone know? I've been trying to avoid it based on a warning I don't understand, but it can be tough to find power bars without surge protection.
I don't see the problem, provided that you are within the current draw limits.
Surge protectors are usually made of components that cause a short when a surge happens, protecting the equipment downstream. It usually pairs with some kind of overcurrent protection (breaker, fuse, sometimes GFCI) to protect against the short the surge protector itself caused.
Having chained surge protectors it actually quite common. You may have a surge protector in your breaker panel, then in your powerstrip, then in the power supply of the device you have plugged in. Most good quality ATX power supplies have built-in surge protection for instance. They also all tend to have overcurrent protection too. The breaker panel has breakers (duh), the power strip may have a simple breaker too, and the device may have a fuse. In the UK, the plug itself may have a fuse, plus the breaker from the utility company.
The risk from chaining surge protectors is that it increases the risk of false triggers if one of them is defective. But it may also provide better protection. All in all, I wouldn't worry too much about it. Just don't overload that power bar and whatever it is plugged in.
This has been my experience. There was a corridor between 2 FL counties known for heavy lightning strikes. I serviced small sites that had their IT equip fried (exploded, melted) once or twice a year.
Putting it behind 4-6 decent, consumer-grade surge protectors turned out to be really effective. I was a bit surprised given how lightning can jump over protection during a strike.
To illustrate the area: An XO's home was hit. Char marks lined the walls wherever wiring ran. Pipes burst all over. Nothing plugged in or wired survived. The front door was blow into the street.
His grade school kids were home at the time; they were physically fine.
There's also the fact that consumer surge protectors are incapable of determining if they're any good or not. There's a small component in there that eats the surge--a severe surge and it's destroyed, it's obvious. However, there's a range in which it no longer functions but is not destroyed. The next surge goes on down the wire.
I really wish someone would come up with some surge suppressors that have a string of field-replaceable suppressors. Periodic maintenance, replace the suppressors.
You need to know what the cable size is of the power strip and the current you are going to draw. If you have bar A with 14 ga cable plugged into the wall, and bar C With 18 gauge plugged into that, then with devices that don’t exceed C current rating (12 amps) and devices in A ( including the devices in C ) that don’t exceed A’s rating, you will be fine. The other way wall - C - A is the problem, C isn’t able to manage the full load.
Only buy known surge suppressor, there have been tear downs where the surge components were missing / fake.
Since surge comments are passive, chaining the surge components is not a problem.
Today I learned. I always thought it was some “electricity magic thing” like additional heat generated within the power strips causing issues between the connected devices, but this makes a lot more sense than whatever I was thinking of.
Although I do think I might have mixed some things up between regular power strips and those outdoors/industrial ones with a long (double/triple digit meter) rollable cable which my dad was a big user of back when he used to work in construction. Basically back when I was little he used to tell me never to plug power tools into a rolled-up “power wheel”, and I think that when I was later heard you shouldn’t daisy chain power strips I must have made that (wrong) connection.
Surge protectors do have one magical electrical thingy in them: metal oxide varistors (MOVs). They're what shunt current in an overvoltage transient and they do age with usage.
I've always known surge protectors age and eventually stop protecting from surges. But what I always wanted to know is how can you tell when it expires? I'm assumings it's based on how good/bad/stable the electricity is in your area. But still, is there any way to know when it's time to replace?
Typically surge protectors have a little light to let you know if the surge circuitry is still good. Others will fail safe, meaning the won't power on if the circuitry is bad. Cheap ones may do neither.
Either way, if your house has had a surge and other equipment has died that wasn't surge protected, probably a good time to replace all surge protectors in the house, they're not really meant to survive multiple large surges. They shunt the power destructively, just somewhere you don't care.
> they're not really meant to survive multiple large surges. They shunt the power destructively, just somewhere you don't care.
Is this a concern when buying used rackmount power conditioners (like used for live music setups?), to protect home IT gear? Can they be worn out without a sign that they are?
What I've read is that their main failure mode is that, as they age, their trigger voltage gets lower and lower, and at some point the normal line voltage is enough to trigger them all the time. And when they overheat, either due to being triggered all the time or due to diverting a large surge, they fail open and no longer have any protective effect on the circuit. High quality surge suppressors would have fuses physically touching the MOVs, so that when a MOV overheats and fails, the fuse opens and cuts power to the now unprotected output.
It's about heat. Cable has some resistance and emits heat. This heat has to dissipate somewhere. If cable is rolled out, it'll dissipate heat to the air. If "power wheel" is not rolled out, cable will heat cables around. Outer cables will dissipate heat to the air, but inner cables will not. So with enough current and enough time, this thing will melt.
You probably won't have issues charging iPhone from this thing or powering something for few seconds, so no need to go crazy about it, just something to keep in mind.
It's not very different from daisy chaining normal extension cords - safe if you know what you're doing (not exceeding the current rating on any of them). Most surge protectors are fused, making them safer to daisy-chain than normal extension cords.
> It's not very different from daisy chaining normal extension cords - safe if you know what you're doing
It’s not safe, and it’s expressly forbidden by the NEC, see 11.1.5 below:
> 11.1.5 Extension Cords
> 11.1.5.1
> Extension cords shall be plugged directly into an approved receptacle, power tap, or multiplug adapter and shall, except for approved multiplug extension cords, serve only one portable appliance.
Daisy chaining extension cords is unsafe and not recommended. Only use extension cords that you’ve inspected and are properly rated for the environment (don’t use indoor cords outside, don’t use an outdoor extension cord outdoors unless it’s GFCI protected) and power usage of the device you are powering.
Any time electricity has to flow through a splice or mechanical connection, the possibility of a loose connection causing an arc and subsequent fire exists.
It’s unlikely to happen to you specifically, but it does happen and avoiding electrical fires is a good thing if it can be avoided.
Daisy chaining power strips is also forbidden by the NEC:
> 11.1.4.2
> The relocatable power taps shall be directly connected to a permanently installed receptacle.
Yes, there is a risk of failure involved with anything electrical, but I don't see why anyone would consider chaining extension cords inherently dangerous enough to ban. It increases the number of connections, but that's a miniscule risk compared to the 5+ connections an extension cord might have on its own. The only significant risk I know is people disregarding the max amperage rating of everything in that chain.
For anecdotal experience, I've had both extension cords and wall plugs fail (nothing serious thankfully, but they did get a bit melted), but in those cases it had nothing to do with my extension cord chains, but rather an internal connection failure.
AFAIk, the rationale for extension chords is that they are sized to cause a controlled amount of voltage drop within their lenght. If you keep adding them, you will increase the drop, and many devices will react by increasing the current.
This is correct. For a 120v 12FLA load at a distance of 50’, you’re fine using a #14 cord. If you double that to 100’, you need to use #10 cord to account for the voltage drop. As voltage drop increases, the amount of current flowing through the cord increases, which can potentially heat up the insulation beyond its rated temperature.
It is probably one of those little process changes to minimize chance of catastrophic failure. Sure, the risk of the daisy chained system going poof is low, but not zero. Instead, you should try to re-work your plans so you do not need to daisy chain.
As an aside, increasing the length of extension cords can cause premature failure of some devices (mostly motorized tools, especially cheaply-made ones) if the wire gauge is inadequate, due to voltage drop.
As a general rule, I wouldn’t run tools past 50 feet on anything smaller than 12 AWG (and really, 14 AWG is the smallest I’d go for any length; anything smaller isn’t safe for most loads).
You are not supposed to. The upstream device is sized for a maximum current and daisy chaining can lead to a scenario where downstream devices are sized for larger current than upstream devices, which is avoided everywhere else in electrical distribution.
So it's fine as long as you control the strip and keep track of loads (e.g. you know your spouse will never plug a vacuum into that handy receptacle you have there), but at work your EHS team will mark you down for it.
Daisy chaining is irrelevant to the problem that you can buy 18ga "lighting-only" extensions that bear a 15A rated NEMA 15R but are limited to 8A.
Daisy chaining a power bar with it's own circuit breaker can be ideal if it prevents someone from making the mistake of using a circuit in a way that trips a panel breaker, ie preventing your spouse from plugging a vacuum into a circuit shared by several rooms.
In the UK, if I have a 6 way strip sized for 10A, which thus has a 10A plug in, I could then plug in a 4 way strip downstream with a 5A fuse, then a lamp with a 3A fuse, and that's fine. I could even connect it the other way.
If I plug in a heater pulling 10A then sure, the 5A fuse will blow.
Daisy chaining multiways will increase the resistance in the earth wire which could mean you end up with a class 1 device with a fault connecting live to earth which would only punting say 8A to earth due to a high resistance (but then your circuit's RCD would trip with that), but is it a major problem?
With the US system, do you not have wires capable of 3A (say 24 AWG) which you can connect to a normal socket which also takes a 10A vacuum?
If that lamp has a fault where it pulls 6A, what protects the 3A wire -- i.e. there's a fault with your lamp which is plugged into a 15A circuit breaker, and the lamp draws 10A, it wouldn't trip the breaker, and that nice thin 3A lamp cord would melt.
There is protection, just not at the cable itself.
UK only needed to introduce that because of their ring main architecture, which was fused at levels above a plug.
Also c.f. extension coils and pre-battery vacuums: both needed their cable full unspooled to reach their full load rating.
Yet they typically lack technical enforcement mechanism to not rely on users being literate and willing enough to RTFM.
Safety margins in what you call a 3A cable. And each circuit being fused at a lower 16A, not the 30A that my British house had.
Something like 1.5 mm2 (only a 0.5mm diameter) is able to handle 12A if the insulation survives heating up to 60 degrees and 18A if 70 degrees is acceptable. The whole circuit would have a 16A fuse at the fusebox, so you're not going to get to 70 degrees.
Far from ideal, but also very very unlikely. Because a short would be over 16A and blow the fuse. So we're talking about some situation that's far from a normal load (any device that's close to such a load would need a different cable to be certified), while still remaining right under the maximum load of the fuse that's covering the circuit.
Homes aren't burning down all over the rest of Europe all the time, while fuses in plugs aren't a thing here.
It’s less about being happy about it, and more about ignorance, industry/legal inertia, and the complete lack of me being the global benevolent dictator for life. Sure some might initially resist my efforts, but they’d come around after receiving an appropriate reeducation at my fire safety camps.
In your example there's a first undersized UPS A, then another UPS B, then whatever combination of electrical devices which power usage exceeds UPS A. You say this is problem.
If you have said combination of electrical devices, and if you're assuming we're using an undersized UPS A + the combo of devices, why does the UPS B matter?
If you're going to overload the UPS A you're going to overload the UPS A regardless of UPS B, no? Daisy chaining or not, that doesn't seem like the actual problem to a knee-jerk thinking.
"surge protector" is what Americans call a passive device that splits one outlet into several, yeah?
The danger is overloading. Back in the days when the main things you plugged in were incandescent lights and space heaters, this was probably a big issue. With computer equipment and LED lights you have to have a lot more stuff - many outlets' worth - to reach the circuit's maximum capacity.
If the circuit and "surge protectors" are rated for 1800W (15 amps x 120V), officially you should limit yourself to 80% of that for continuous loads which is 1440W, so you can supply 14 laptops or small small desktops that use 100W each, or over 200 raspberry pis on USB chargers that use 5W each, and either way you're going to need a lot of outlets before you come anywhere close to that limit.
At least that's a rough estimate. Power factor could decrease that number by up to 50% and you can use the full rating for intermittent loads; I'm not certified to know the fine print. Point is that 10 computers can easily use less power than a single space heater.
>surge protector" is what Americans call a passive device that splits one outlet into several, yeah?
Not necessarily. There are “power strips” which turn one receptacle into several. Then there are sure protectors which are typically built into power strips. So not all power strips are surge protectors but almost all surge protectors are also power strips.
> "surge protector" is what Americans call a passive device that splits one outlet into several, yeah?
Technically different, but often combined functions. The splitting bit is a "power strip", or sometimes a "power bar". The surge protection is switching off when there's a short or overvoltage in the supply, or other larger than expected power draw.
> or over 200 raspberry pis on USB chargers that use 5W each
Those little switcher bricks are horribly inefficient: the 15W one I just pulled out of a drawer draws 0.8A on the primary. Realistically you're going to max out a 15A circuit around 20-30 of those, not 96 (1440/15).
probably because it Depends, If you dont know its safer not to.
long answer (keep in mind i live in canada, im not a professional, this is just what i learned and trust, keep in mind above)
- As long as no wire/bar exceeds its max Amp your safe no matter how many things are plugged in or how long of a daisy chain, the max amp is usually listed.
- all devices should list the max amp they use, add up the amp's of all the devices connected to that wire and if its below your safe.
- if your breaker is 15 amp, virtually all normal extensions/power bars are rated for at least 15 amps which means doesnt matter what you do the breaker should* flip before any damage is done
- if breaker is above 15 amp most surge protectors have protection that will trigger if they exceed their max, most basic "splitters" and extension cords dont, eg if they dont have a switch or reset button they are pretty much guaranteed to not have this protection, be extra carful how much you load on those.
some good rules of thumb to keep in mind, look for imprints or labels that list amps, smaller wires can handle less, damaged wires can handle less then they did before and shouldn't be used, if a wire or connector warms when its in use its overloaded reduce the load on it, especially if it warms quickly.
here is a video that i liked that talks about it as well
https://www.youtube.com/watch?v=K_q-xnYRugQ
The reason it's a "bad idea" is that most surge protectors are power strips and you must be cautious when you daisy chain power strips. Likewise extension cords.
Why? Two reasons: You have to ensure the wire gauge on every link can handle the current, and at every junction (plug) the resistance is higher than in the wire itself. When electrical fires start they usually start at these plug junctions because they overheat.
The surge protectors themselves don't mind being daisy chained.
This is funny, I actually am wondering about plugging a surge protector into a UPS. I have some equipment (probably not very high power draw but I can confirm) conveniently zip tied to a peg board along with a power strip that I assume has a basic surge protector on it. One power cord leaves the whole thing, which is very clean, but power goes out a surprising amount here. Can I plug this whole thing into a UPS or should I find a replacement strip without a surge protector?
From what I remember reading, you should not do that. Only plug in PDUs or directly connect equipment to a UPS. You’re meant to put the surge protection before the UPS. I think it’s because the circuitry in surge protectors can mess with what the UPS thinks the actual load is.
I believe some UPS brands might also void parts of your warranty if you use them with a surge protector plugged in.
You can plug it in. The problems with the UPS being plugged into another UPS are related to the internal batteries and the inverters, not to the surge protection. Just don't plug in too many things and overload the UPS.
yes, as they are passive device unless in the case of a surge, which would be shorted to ground by the first one in the row (technically, the first one whose limits are lower than the surge)
The nature of surges is not simple like that - a lightning strike can easily blow MOVs and inrush limiting resistors in multiple devices. I come from a rural area and coming to someone's house with a bag of fresh MOVs and resistors is not an uncommon thing after a big storm.
I believe that it highly depends on the type of the surge protector, their ratings and the cable network involved. I do not think that it would cause issues in two surge protectors from power outlets connected in series, and depending on their rating and switching characteristics maybe both could trigger, I agree.
I believe the question is if it's safe at all to do so rather than whether the protection works or not, though I'd have to be all ears about interactions between multiple parallel surge arrestors.
