polo ralph lauren kids shoes Let’s Take a Trip Inside Low
In order to get a somewhat representative sample of what is out there, I assembled a mess of nine power bars that should hopefully cover the whole quality range from potentially dangerous to very good (within reason considering the budget) in the neighborhood of $10. Since this is a lot of bars to cover in one shot, this first part will cover four locally bought generic units.
Future parts will cover products from Kensington, Belkin, CyberPower, Tripp Lite and APC, all of which we purchased from Newegg. Hopefully, that’ll make curated sample conspirationists happy.
There is not much to see on the packaging’s front, aside from the 18″ cord length, $3 price, number of outlets, mention of the lighted switch and presence of some form of surge protection inside.
The back side provides some more details: we are told to expect 90 joules of surge suppression with an awfully high 800V line neutral protection voltage and equally high 545V clamping voltage. When you consider that bulk input caps in universal power supplies are only rated for 400 450V, it seems likely that devices connected to this bar would instead be protecting it.
Among the other details on the back is an Intertek ETL mark instead of the usual UL one. That got me curious, since I do not remember owning any equipment with an ETL mark before. I never really paid attention to those until now.
The main label does not tell us much that the packaging didn’t already cover, but it does explicitly list which UL and other agencies’ safety standards this bar is supposed to meet, complete with Intertek’s ETL mark and file number. Searching Intertek’s listings for 3155521 returned no result.
I am very much puzzled that their directory does not appear to be searchable by file number. I contacted Intertek through email to ask about this, was told they were unable to verify the product and that my inquiry was forwarded to field investigations. Not a good start.
Here comes the typical warnings about using the bar indoors in dry locations only. Many of the products we’re writing about, including this one, also state that the bar should not be used on outlets with less than 10m (30′) of wiring to the electrical distribution panel, which may seem silly since very few people can even check that. This specification is actually part of the UL 1449 surge protection device (SPD) standard, meaning that the bars’ surge protection rating is based on 10 meters worth of wiring between the surge simulator source and the outlet the device under test plugs into. Plug bars closer than that and they might not meet their spec.
The last bit of text I want to mention says that “This device features an internal protection that will disconnect surge protective device at the end of its useful life”. The reason for this is when MOVs fail, their leakage current may increase to the point where they can overheat and catch on fire. So, MOVs connected across live and neutral or ground must have a thermal shutoff fuse in series to cut off the ignition source, allowing flame retardants to put the fire out.
Lurking where the sun don’t shine are the familiar stamped sheet metal outlet terminals seen in my previous tear downs, a combination switch breaker illuminator and a small MOV hidden behind the bunched up wires. Everything is soldered at the switch except the ground wire, which gets crimped to the ground strip.
At a glance, the MOV does not appear to have a thermal fuse attached to it. Although I could not find a free copy of UL 1449, third party documents that leak fragments of it strongly indicate that such protection has been required at least since revision two. In any case, the wall of text on the previous slide explicitly states that this bar does have some form of end of life disconnect, so something should be there. We will take a closer look at that later.
Since this is the first unit in today’s crop, and this bar’s strips are easily whipped out, I am going to take a little extra time to look more closely at them.
The grounding strips are exactly the same basic design seen in my previous power bar tear downs: stamped squares with a pair of flaps providing contact, which means we can expect some degree of deformation after a plug gets inserted.
For the live and neutral strips, we have simple sheets of stamped metal parted three ways with the middle section offset in the opposite direction from the other two, a rib stamped into each section to provide some extra stiffness and help guide plug prongs through so they do not catch the strips’ edges.
The Sunbeam’s power strips are 0.45mm thick and 4mm wide at the narrowest point. Its ground strip is 0.3mm thick and 4mm wide, which feels awfully flimsy. At less than two square millimeters worth of cross section, the power strip has less metal than 14 wire. Combine that with the more resistive copper nickel alloy and you can imagine how this is definitely not a heavy duty power bar.
Before showing the aftermath on that poor ground strip, I thought some readers might be curious to see what a power strip’s outlets look like from the other side with something plugged into them. This picture is actually from the Electro I took it at a few different angles with a few bars, and just happened to get my cleanest image out of this one. If you were wondering, here is your answer! If you were not, you now have one more answer to a question you never asked.
Coming up next are the before and after shots.
These were also taken from the Electro, since its grounding flaps were tighter than the Sunbeam’s, making the deformation more evident. I could have put this slide in the EL’s section, but because I expect this to be a common design across all specimens in this story (including the major brands’), I decided to put it up front as well.
We can see that both tabs on the bottom left position have been pushed out almost flush with the cut out, and that the tips went from straight edges to somewhat bowed out. The two tabs also look slightly skewed.
When you see a warning on a power bar reminding you not to daisy chain them, this sort of wear on the metal strips is part of the reason: sufficient to provide ground and neutral for appliances, but not enough to guarantee sufficient continuity for downstream power taps. It would be interesting to measure how much of an effect insertion cycles have on the strips’ contact performance, though that’d require a high energy pulse generator and suitable measurement equipment.
From this angle, we can clearly see both of the MOV’s leads going straight across metal strips on the switch; there’s definitely no thermal cut off here. Digging out that taped device reveals a lone orange 14D331K MOV overlaid on the top left corner, with no brand or other apparent markings on it apart from UL and VDE indicators. Its other side is completely blank, save for the bulge from the other side’s lead. We see no larger lump hinting at the presence of an integrated thermal protection under its coating. These all look like red flags.
I contacted Sunbeam about this and was told they’re looking into it. Did I get a counterfeit power bar? Considering the pressure dollar stores put on their supply chain to source the cheapest stuff possible, this is definitively a possibility. It certainly does not look like a product that should be on store shelves.
Let’s see if this MOV like device has MOV like properties.
Before plugging in my 1000V multimeter and risk frying it at 3.5kV on a defective or fake MOV, I did a MOV only test run to see if the MOV warmed up as expected from dissipating somewhere in the neighborhood of 1.5W (or about 350V 40mA). Once I was reasonably confident the MOV was doing something MOV ish, I attached my meter and read 368V.
Those of you who may have looked up my multimeter’s datasheet might be screaming: “but your old meter is not True RMS” and you are absolutely correct: it uses non linear analog integration, which makes it quasi RMS. Let’s try another measurement method just to be sure.
For this re test, I added a 400V diode bridge and a 10nF 1kV cap for peak detection. I am reasonably confident in this 345V result and a little surprised the quasi RMS result over estimated by only 8%. If you are wondering why I am using RMS and DC voltages interchangeably here, this works because a square wave symmetrical about 0V (3.5kVAC clipped to 345V) has nearly identical RMS and peak voltages. The difference would go down further after accounting for the diodes’ forward voltage drop and reverse leakage current.
It looks like the MOV is real enough.
Coming out of a nearby flea market, this $8 bar raises cord length to a slightly more useful 60cm (24″) and has a similar breaker switch indicator on the front. Its back cover features an UL holographic sticker with file number E302504. Warnings include not plugging this power bar into other power taps, use indoors in dry locations only and the “do not use within 10 meters or 30 feet from the electrical distribution panel” which I bet tons of people did not know existed until now I honestly cannot remember noticing these warnings until now either. If you missed the explanation behind the 10 meters thing, revisit the Sunbeam Wall of Text slide.
I know these power bars look awfully similar overall, but this one appears to be identical to Electro’s, right down to injection molding hole placement. They do have different outer bottom molds though. Noma employs bilingual warnings, while the EL543 only has English. Moreover, the Noma lacks a 10m/30′ warning. The more obvious differences include cord length, colors and surge suppression energy ratings.