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Old 10-14-2007, 12:21 PM
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Switch rating??

Guys,
Im having a blonde moment and wondered if someone could clear this up for me.

I want to buy 2 switches for my car and have found them but they are advertised as 220v AC 3Amp switches which also have a 12VDC LED built in. Can I use the switch on a car with 12v??


Cheers
Nick

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Old 10-14-2007, 01:10 PM
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Yes, just don't use it for more than three amps The voltage rating is a description of its insulating qualities. 220v can jump through alot more insulation than 12v can, so its just there to let you know that. But, amps are amps and they represent the actual amount of electricity that is flowing. 3amps at 220v will heat up the conductors the same (at least for practical purposes) as 3amps at 12v.

I have a couple 1400v switches in my boat out of an aircraft Waterproof and overkill
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Old 10-14-2007, 01:12 PM
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Certainly.
But, what do you wish to operate with this switch???
Anything that pulls more amperage than a dome light will need to be operated by a relay.

Use the switch to operate the relay-------the relay to operate the (fans, lights, amp, etc.)
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Old 10-14-2007, 01:50 PM
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Quote:
Originally Posted by curtis73
...
But, amps are amps and they represent the actual amount of electricity that is flowing. 3amps at 220v will heat up the conductors the same (at least for practical purposes) as 3amps at 12v.
...
I'm sorry, but I'm not sure that I can agree with that.

NAPA (Echlin) rates their toggle switches at differing amp loads, depending on voltage.
Part Mumber TG-6143

Quote:
Attributes:
Application:Universal
Features & Benefits:Two position ON-ON
D.P.D.T.
six screw terminals
10A @ 250VAC
15A @ 125VAC
35A @ 12V
silver contacts.
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Old 10-14-2007, 02:18 PM
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Thankyou very much indeed. Bryan59EC, ive already got the relays and tails as the switches are going to be used as Ignition and Start buttons for my Keyless car.

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Old 10-15-2007, 03:48 AM
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Quote:
Originally Posted by 66GMC
I'm sorry, but I'm not sure that I can agree with that.
Which is why I said (at least for practical purposes). The rating on the switch is more of a UL compliance thing than actual load capacity. I didn't see the need to further complicate the issue

In truth, a conductor can be rated higher with less voltage since there is less potential for breaching the insulation at higher temps, but the true measure of a conductor's rating is its size and/or capacity for amperage.
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Old 10-15-2007, 06:56 AM
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a switch amp rating relates (as much) to the surface area of the actual contact inside for how many times it can be "arced" open and closed and survive without pitting the contact and cause heat/resistance build up
(same as a relay rating... 10amp relay=tiny contacts...100amp relay= huge contacts)....

the NAPA example is correct
V x A = W
220V x 3 = 660watts
12V x 35 = 420watts

at 12V, watts allowed is less because as amps goes up for a given contact size continous duty heat goes up....as heat goes up so does resistance (ohms) which robs power from the circuit......

so Curtis, you are correct also

ain't electricity fun

depending on dist and coil, ign amps can easily be 20+ continous...use #10 wire for that ign on circuit

Last edited by red65mustang; 10-15-2007 at 07:26 AM.
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Old 10-15-2007, 09:07 AM
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Just incase any other UK bods look in:

Metric Size / AWG Size
mm2


0.5 / 20

0.8 / 18

1.0 / 16

2.0 / 14

3.0 / 12

5.0 / 10

8.0 / 8

13.0 / 6

19.0 / 4

32.0 / 2

52.0 / 0
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Old 10-15-2007, 08:13 PM
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Quote:
Originally Posted by red65mustang
...
ain't electricity fun
...
Aaaaaakkkk!
My head hurts...

Mmmm ... donut.
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