The problem isn't so much the handling current, it's the arc that starts when the contacts open and close, mostly open.
The spacing and acceleration of contact separating matters to reduce plasma burn that destroys contact surfaces. With DC, there is no nulling of ignition like you have with AC at the base line (0 volts), that gives it time to put the flame out.. Plasma is generate which is a very conductive gas and since you have DC it continues to arc as the contacts pull away, until a couple of things happen, heat raising and there for pulling fresh air that helps remove the plasma and spacing of the contacts the weakens the current in the burn and thus cools it down..
Most switches derate their voltage or current to reduce the problem.
This says that the switch is rated by UL for the currents listed at
125 V AC and at 250 V AC. If the whole device using this switch was going to have a UL listing, and the currents involved are provably lower than those limits, then you wouldn't have to prove much else about this switch. I think.
Similar thing, except for CSA (Canadian standards). They sometimes let you have a little more than UL does.
This is the rating for some European standards, including Demko (Denmark), Semko (Sweden), Nemko (Norway), Fimko (Finland), and VDE (Germany/EU). Some of these standards bodies have since become part of other companies.
The micro symbol means "microdisconnection", but I'm not exactly sure what *that* means - something about the contact gap, probably.
T85 probably means an 85 C temperature rating.
Links with more info:
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(page 20)
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No. Switching DC is not the same as switching AC. When you turn the switch *off*, an arc forms at the contacts. You have to get rid of this arc before the switch is well and truly turned off. With AC, the arc is trying to put itself out 120 or 100 times a second, so it's pretty easy to get rid of the arc. DC usually never tries to put itself out, so it's harder to get rid of the arc. For DC, the contacts are usually designed to get further apart faster, and may be made out of a different material.
Doesn't work that way, at least for switch and relay contacts. You need to buy a switch that specifically has a DC rating from the manufacturer.
You also get to think about what *kind* of load you are switching. Switching 240 watts of electric heater is different than switching 240 watts of incandescent lamps; both of those are different than switching
Switches and relays I've looked at in industrial catalogs that show AC and DC contact ratings generally have the DC rating the same, or maybe 10% less, than the AC rating. AC "amps" is always kind of an average figure since it varies within each power cycle.
It's quite likely good for 10A @12VDC_resistive and _probably_ good for 10A @24VDC resistive. That's about the best answer you're going to get on USENET. Since it's offered with a 12V illumination option, it's obviously intended for some DC applications.
There are other options..
- test it yourself (test temperature rise, life, that sort of thing) and add some safety factor for production variations (such as when they shift from one factory to another in Mainland China). Do incoming inspections and spot test each lot. It might help to look at exactly how UL/CSA do their testing of switches.
- contact the supplier in Taiwan and ask them a very simple question in simple English, what is the rating at 24VDC for this exact model. They may or may not answer, or may give you a 12V rating. In any case, you'll not know less than you do now. I'd still test it, even with a positive answer, since there is no applicable safety agency approval (and, just as important, just because they're safe doesn't mean they won't fail in large numbers, in a safe manner).
- try a sample and if it looks to work and doesn't burst into flames and emit noxious fumes at 11A, say YOLO and go for it.
In any case, there is little chance of recourse if you do have problems. Even if the Taiwan company okays it's good luck in getting any satisfaction if their China factories don't measure up, unless you're using a measurable portion of their 400,000,000 unit annual capacity.
At least it appears to be** UL/CSA approved for some conditions, meaning there is some assurance decent materials are used.
** Yeah, check that out too. More than once, I've found the approvals to be expired, inapplicable to the specific product, or downright fraudulent. A product with approval markings sells for a lot more than one that doesn't have them, and approvals not only cost money but limit what raw materials that can be used, so, you know..
Best regards, Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
The more complex answer is "the switch *probably* won't melt, and the switch will *probably* be able to switch the load off and on successfully a few times, but the switch may or may not reach its design lifetime, and may or may not fail with the contacts welded closed".
If it's something you care about, or that might set your house on fire, or cause your car to die in the middle of the Interstate, or cause your airplane to fall out of the sky, or that might set your boat on fire, then you need to use a different switch.
In your other post, you said you were looking at MR-21N-3BB-R2 from
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. That's a DPST rocker switch, not illuminated.
NKK "JWMW" switches have a 10 A, 30 V DC rating, per the data sheet at
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. Mouser carries two of these switches, 633-JWMW21RA1A and 633-JWMW21RA2A , either $9 or $10 quantity one. The only difference is which way the "0 |" labels on the rocker go; one switch has "0 |" for horizontal mounting, and the other has "0 -" for vertical mounting. Both of these are a little bigger than the switch you want to use - the panel cutout for the NKK switches is 25 x 15.4 mm or 0.984 x 0.606 inches.
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If you don't like the NKK ones, how about the Arcoelectric 1350 series, which have a 20 A, 24 V DC rating, per the data sheet at
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. Digi-Key carries the C1350ARBB-602AW, $3.23 quantity one. It has an "0 -" legend for vertical mounting, and fits in a 28.4 x 23 mm cutout.
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