Electrical switches - Page 4 - Fiberglass RV


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Old 12-02-2013, 03:59 PM   #43
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Interrupting rating

[QUOTE=David Tilston;433401]

The only point I am trying to make is that current carrying capacity is not the only design consideration. Interrupting capacity is also important. This is why the DC rating is different from the AC rating for a switch.

The amperage rating and the horsepower rating of a switch differ because of the interrupting rating of the switch A SP 20 amp switch is rated for switching a 20 amp load under certain conditions but is only rated for switching a 1/2 HP motor or a 9 FLA motor . I have seen AC switches used in a DC application where the contacts weld themselves shut and not allow you to disconnect the load or the arc flash upon opening the contacts causes hot metal flying through the air. Then again what does UL know there not a government agency
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Old 12-02-2013, 04:29 PM   #44
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Originally Posted by Robert Johans View Post

Just want to ensure that my switches pass inspection...
Hey, Robert!

This looks like one of those discussions that'll go on forever...but let's face it, no answer you get here can satisfy your main concern (above).

There is a sort of building/electrical/plumbing code for RV's, established by the industry. I think compliance is more or less voluntary, but for the added layer of legal protection it offers it may be worth looking into signing on to. Link to info page.

Best of luck in your new endeavor...
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Old 12-02-2013, 04:44 PM   #45
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Originally Posted by David Tilston View Post
Byron,

What you have posted is just a comparison of two DC current ratings, lower at a higher voltage. Common sense. But the discussion is about AC ratings vs. DC ratings. If a switch is rated at 20 amps AC, it may have a much lower DC rating.

The specs that I posted are not "just plan wrong". They are determined by the manufacture through testing and research. Why do you say they are wrong?
Show the specification of one. You've got it backwards. I'll concede if you can show me the specifications on any switch that follows the lower current rating for DC than AC. I want to read the whole specifications.

Do you know why the current ratings are lower for a higher voltage using the same switch? Inductive load is why. There's this thing call "fly back". A coil (transformer, motor, relay coil, etc.etc.) when charged with a voltage and the voltage charging voltage is removed the voltage across the contacts will reverse polarity and go up until there's a bleed off path. The contacts are designed to take the bleed off as an arc and eventually will burn up. To increase the life of the contacts the higher voltage is rated at a lower current.
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Old 12-02-2013, 04:46 PM   #46
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Originally Posted by Francesca Knowles View Post
Hey, Robert!

This looks like one of those discussions that'll go on forever...but let's face it, no answer you get here can satisfy your main concern (above).

There is a sort of building/electrical/plumbing code for RV's, established by the industry. I think compliance is more or less voluntary, but for the added layer of legal protection it offers it may be worth looking into signing on to. Link to info page.

Best of luck in your new endeavor...

Not completely true. I answered his concerns, but there's always at least one person that wants to ague with any engineer.
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Old 12-02-2013, 05:07 PM   #47
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I've given my last response to this thread. Believe what you want. I tried to help the OP but the back yard mechanics have the floor.
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Old 12-02-2013, 05:10 PM   #48
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...There are also switches which are rated both DC and AC in the market( rare stuff) Usually I found out that same dual rating sw will have higher VAC rating and with lower AC amperage, also higher DC amperage with lower DC voltage rating. Here are some sws of mine in modification of Trillium. They all work good since then. In the plastic box, they are AC sws and the old big sw of 2nd photo is dual ratings, I believe 125VAC-5A and 24VAC-10 or 15A. They all were in the trailer now. Within this forum about last year, there was a topic regarding to switches that one could find out all useful info.....
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Old 12-02-2013, 05:56 PM   #49
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Good Grief, you ask about using a switch and you get a lesson in electrical engineering. The very low current for LED's might not flow across arc damaged contacts, get DC rated switches for that.

For pretty switches, get a bucket of money and go to a boat supply store.
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Old 12-02-2013, 06:29 PM   #50
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After chatting with tech support of a couple major electrical component manufacturers, I have discovered that they produce DC-rated, low voltage switches suitable for the max 15watt lighting applications in my trailers.

Nice styling with attractive trim plates.
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Old 12-03-2013, 11:17 AM   #51
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Quote:
Originally Posted by Byron Kinnaman View Post
Show the specification of one. You've got it backwards. I'll concede if you can show me the specifications on any switch that follows the lower current rating for DC than AC. I want to read the whole specifications.

Do you know why the current ratings are lower for a higher voltage using the same switch? Inductive load is why. There's this thing call "fly back". A coil (transformer, motor, relay coil, etc.etc.) when charged with a voltage and the voltage charging voltage is removed the voltage across the contacts will reverse polarity and go up until there's a bleed off path. The contacts are designed to take the bleed off as an arc and eventually will burn up. To increase the life of the contacts the higher voltage is rated at a lower current.
Byron, I showed a small portion of the old spec in my previous posting. The new spec, is available at:
http://www.neodyn.com/download/pdf/industrial/100P.pdf

But the only part that relates to the electrical part of the switch is:
15 amp at 125 or 250 VAC; 1/8, hp at 125 VAC; 1/4 hp at 250 VAC; .5 amp resistive,
.04 amp inductive at 125 VDC

So, what I take from that is that the switch is rated at 15 amps when used at 125, or 250 VAC. and 0.5 amp at 125 VDC, assuming a restive load in both cases. A fairly significant difference between the AC and DC ratings. I think, (I could be wrong) that you would find that any switch, that is rated for use in both AC and DC applications, would be rated for different current levels for AC vs DC.

I am sorry if this discussion has upset you, that was not the intent. Personally, I like being wrong. It means I have learned something new. Perhaps you should at least consider the possibility that you may be mistaken. Or are you such a great expert that being in error is impossible?

I may not be an engineer, but I am not a back yard mechanic. I am an electrical engineering tech by training, but my job is as an instrument tech.
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Old 12-03-2013, 01:51 PM   #52
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Look here:
Electronic Components and Accessories | MPJA.COM
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Old 12-14-2013, 06:15 PM   #53
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Just a quick update:

While I feel confident that a residential-style 120VAC switch could control my 15watts of LEDs without any problem, I don't believe it's strictly "up to code."

So I continued to seek a quality and attractive wall switch. I thought I had found a reasonable solution with this switch. Still cheap plastic, and a bit clunky in shape, but at least it's not one of those typical tiny RV toggles. And then I opened it up...

Yup, same exact switch, hidden under a big paddle.
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Old 12-14-2013, 06:29 PM   #54
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Good heavens....

Seems to me a lot of fuss about so little.
Look here, there might be something that suits your fancy.

You're looking for rocker switches NOT toggle switches.
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Old 12-14-2013, 06:33 PM   #55
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Luckily, I finally stumbled upon a switch made by ITC used in the marine industry. Yes, of course, it is much more expensive, but the form, fit and finish meets the standards I am trying to maintain.

On/off, and dimming capability, Good size, flush mounting, with a nice bezel.
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Old 12-14-2013, 06:34 PM   #56
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Seems to me a lot of fuss about so little.

Exactly! It's all about the details!
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