Where can I find a DC rated pull chain switch?

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blw2

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I finally decided to upgrade the bathroom fan in my RV.  Went cheap and ordered one of those Heng's Vortex retrofit fans.  I figure that'll be a lot easier than replacing the whole thing, and will work good enough. 

It came in today, and as I look at it it really wants a pull chain switch in place of the push button, so it's easier for DW and kids to reach it.  Seems easy enough, but now I can't find a source for a DC rated switch pull chain switch.  I've searched amazon, ebay, and a google web search.  I found one that had a DC rating of 0-10VDC.... which really doesn't make sense to me....

My gut tells me that any of the AC rated ceiling fan switches will probably be fine, but I do understand that DC switching is more 'demanding' than AC...so I want to be smart about it.

I have no idea how many amps the thing will pull, but the push button switch in it is rated 4A at 14VDC

Any ideas where I might find one to order?
 

xrated

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Many of the small switches will have a dual rating printed on them.....one for rated amps AC, and the other for rated amps DC.  The DC amperage rating will be less than the AC amperage rating so check them closely!  Do you know what the current rating is for the retrofit fan at 12VDC?......should be a nomenclature sticker on the fan somewhere.
 

Back2PA

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I gave up trying to find an inline DC switch for my TPMS booster and bought an AC switch at Home Depot. I miss Radio Shack  :-\
 

blw2

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Sun2Retire said:
I gave up trying to find an inline DC switch for my TPMS booster and bought an AC switch at Home Depot. I miss Radio Shack  :-\

yeah, me to.  I started missing the old Radio Shack about 10 years before they went away for good.  I don't know when it started changing really....there was a period of time I didn't shop them...maybe there wasn't one nearby, or i just didn't have a need... I don't know..... anyway, at some point it went from aisles of parts and adapters down to about 4 sets of drawers
 

BIG JOE

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I'l step up and admit I've use Many AC switches of all types.. for DC applications and have had No Issues. The only requirement is the needed... AMP rating. (?)

I currently have an on/off Pull Chain Light switch, from Home Depot, hard wired into the 12v power source wire to our 3 speed Fantastic Fan in the Bathroom. Fan speed knob on #1, 2, or 3.. Pull the Chain.. fan comes on.. pull the chain.. fan turns off. (?)
 
S

sightseers

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amperage is the important thing in fuses and switches and wire.  a 10 amp fuse does not really care if it's a/c or d/c.
 

Great Horned Owl

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sightseers said:
amperage is the important thing in fuses and switches and wire.  a 10 amp fuse does not really care if it's a/c or d/c.

NONSENSE

While the switch doesn't care when it is on, while being switched off, it very much cares. When it is switched off, the contacts arc. If the current is AC, both the current and voltage will pass through zero within a maximum of 1/120 second. That will extinguish the arc. If the current id DC, the arc will last much longer, and will soon destroy the contacts.

In some switched, the contacts bounce when the switch is closed. Often, there may be multiple bounces. With AC, that isn't very significant. With DC, there will be an arc with each bounce. Again, the contacts will self destruct.

The blade type of contact found in the typical pull chain switch has virtually zero contact bounce, but the contacts open fairly slowly. Fortunately, the wiping action tends to clean the contacts each time they are opened or closed.

There many possible type of ratings on switches. Incandescent lights and old tube type TVs have a huge current surge when switched on. Motors have a big, slow surge when switched off. Because there is a considerable expense incurred by the manufacturer for each rating, they will typically only apply rating for those situations that the switch will most likely encounter.

The pull chain switches are most commonly used for 120 VAC lights and fans. It would not last very long in a 120 VDC circuit. However. there is very little arcing in a 12 VDC circuit. I would think that it would work just fine.

Joel
 

blw2

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Thanks everyone.

Great Horned Owl said:
.... The blade type of contact found in the typical pull chain switch has virtually zero contact bounce, but the contacts open fairly slowly. Fortunately, the wiping action tends to clean the contacts each time they are opened or closed.

this, I didn't know.  For my need maybe it's something positive at least...

Great Horned Owl said:
  .... Because there is a considerable expense incurred by the manufacturer for each rating, they will typically only apply rating for those situations that the switch will most likely encounter.
.....

I hadn't really considered the reason why the rating isn't listed for these things, but that makes sense.


I guess I'll have to either live with the push button
or
do as several of you have and just use what I can find.  I was never overly concerned about doing it, but I'd rather do it "right" if I could...
I recon the most likely worst thing to happen would be the switch eventually starts acting flaky.  Could cause fire or other problems I suppose, but my gut tells me this probably is not likely.  Seems like lots of you agree....
 

judway

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>>the push button switch in it is rated 4A at 14VDC<<

Just get a pull chain switch defined above or greater than the 4A. Just make sure it will fit in the space. Switch should be available at the sources mentioned in the other posts.
 

John From Detroit

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If you can not find one easily just divide A/C by 2 and you will be darn close.

Most pull chain switches are rated 15 amps A/C and .. Well. you won't be drawing 7 amps DC. Voltage rating is more important and a 120 vac switch will do 12 vdc no problem .
 

Great Horned Owl

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John From Detroit said:
If you can not find one easily just divide A/C by 2 and you will be darn close.

Most pull chain switches are rated 15 amps A/C and .. Well. you won't be drawing 7 amps DC. Voltage rating is more important and a 120 vac switch will do 12 vdc no problem .

That might be approximately true (depending on the type of contact) for DC over 30 or 40 volts. However, with 12 VDC, there is virtually no contact degradation doe to arcing. Only the heating is a concern, so the 12 VDC current rating would be the same as the 120 VAC current rating. There is no need to cut the rating in half.

Joel
 

ChasA

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Hey Brad.  Just get a 3/4" dowel and put a crutch tip on it. No need for extra work.
 

Gary RV_Wizard

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In my opinion this question is being way over-done technically.  Accurate technical statements aren't always helpful when the problem is simple (I'm often guilty of that myself).  At low DC amps, as with a fan motor,  you can't go too far wrong with any pull-chain switch you are likely to find in a local store.
 

BIG JOE

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Gary RV_Wizard said:
In my opinion this question is being way over-done technically.  Accurate technical statements aren't always helpful when the problem is simple (I'm often guilty of that myself).  At low DC amps, as with a fan motor,  you can't go too far wrong with any pull-chain switch you are likely to find in a local store./quote]

I agree Gary  :)) I'm also guilty at Over-Thinking things at times .... ;) :)
 

blw2

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yes, it started as a simple question, one that so far nobody knows a source for what I was looking for.....
and it is beat maybe a bit to hard perhaps...
but I do think it's an interesting discussion
points to a lot of us not knowing finer points of the things we do, myself included,
and that we're often willing to do a bit of "Star Trek Engineering"....
 

Great Horned Owl

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Gary RV_Wizard said:
In my opinion this question is being way over-done technically.  Accurate technical statements aren't always helpful when the problem is simple (I'm often guilty of that myself). 

This is mostly true. However, the inverse is not. When erroneous technical information is posted, even if there is no impact on the question at hand, there is still a risk that somebody will read it, believe it. and try to apply it to a similar but different situation. The consequences are unpredictable.

Joel
 
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