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-   -   Where can I get a 12V timer switch? (http://www.sailnet.com/forums/gear-maintenance/85640-where-can-i-get-12v-timer-switch.html)

MedSailor 03-30-2012 09:44 PM

Where can I get a 12V timer switch?
 
I want to install an engine oil pan heater and it would be most convenient if I could have it on a timer switch. I have other items that would be amenable to a timer switch such as the propane solenoid.

Can I use one of these household ones or does it have to be a 12V switch?

http://4.bp.blogspot.com/_UMjiMMHrE4...mer+switch.jpg

I've owned cars that had the defroster on a timer (that was not adjustable) so I suppose this could be an option, though I'm not sure how to find one of those either.

MedSailor

asdf38 03-30-2012 10:15 PM

Re: Where can I get a 12V timer switch?
 
I don't see why not. Mind the current rating of course. When it comes to relays switching power DC is harder than AC but 12V is so much less than 120V that it should basically cancel. In-fact as a reference point the Bluesea switches I just put in my panel have this rating:

10A@250V AC, 15A@125V AC, 15A@12V DC

Note the 15A rating is the same for 125V AC as it is for 12V DC. That should roughly hold across other switches. The challenge with DC is that the voltage is constant whereas AC always crosses 0. If the switch arcs after breaking current the AC will extinguish when it crosses 0.

Waltthesalt 03-31-2012 01:34 AM

Re: Where can I get a 12V timer switch?
 
I agree. It's a spring timer and contacts. Having a lower voltage only means you've got extra margin on the insulation. I think if there's any issue its using the switch in a humid marine environment where it's internals may corrode.

mitiempo 03-31-2012 02:03 AM

Re: Where can I get a 12V timer switch?
 
Lower voltage but higher current probably.

MedSailor 03-31-2012 03:27 AM

Re: Where can I get a 12V timer switch?
 
Quote:

Originally Posted by Waltthesalt (Post 852878)
I agree. It's a spring timer and contacts. Having a lower voltage only means you've got extra margin on the insulation. I think if there's any issue its using the switch in a humid marine environment where it's internals may corrode.

A spring with contacts. That makes sense.

The second part you mention, that you have an extra margin, makes me think otherwise though. It takes a lot more copper to transmit amps without heat than it does at 120V. That's why boat cables are so big. If it's rated for 20A at 120V it may not take 20A at 12V without melting, right?

It's late, I'm not sure I have that last bit right. Might have to run it by Ohm's law after coffee in the morning and see how it stands up to the light of day...

MedSailor

tap 03-31-2012 05:15 AM

Re: Where can I get a 12V timer switch?
 
If it's rated for 20A at 120V then it will do 20A at 12V too. The issue is that a 1kW heater that uses 120V would draw about 10A or so. If it used 12V, it would be need near 100A.

ron_hudson 03-31-2012 07:56 AM

Re: Where can I get a 12V timer switch?
 
Could you not use an electronic timer or at least hook it up to see if it works . Could you go through an inverter?

Tanley 03-31-2012 09:30 AM

Re: Where can I get a 12V timer switch?
 
LED lighting, soundproof, Sailor's Solutions Inc.

hellosailor 03-31-2012 01:50 PM

Re: Where can I get a 12V timer switch?
 
The spring timers are almost impossible to find these days, but Ace hardware still carries them, and their web site sells them for about 1/3 less than the stores--with free delivery to your local store. (Great logic, huh?)

Electronic timers could be a problem if they are all solid state (no relay) and intended for use with AC. You'd have to check with the maker for specifics.

bljones 03-31-2012 06:44 PM

Re: Where can I get a 12V timer switch?
 
Why would you want it on a timer?
Unless you are seriously sub-zero for extended periods, there really is no need for proplonged or timed use on a pan heater- besides, since most spring timers have only an hour duration, if you will be gone from the boat for any length of time, the timer is almost useless.If you want a warm pan for ease of starting, simply plug your heater in before starting, while you are prepping the boat for departure.
If you are aboartd, and want to periodically warm up the oil for whatever reason, what I would do is set my watch, my alarm clock, the alarm on my laptop, whatever, plug in the heater, and when the alarm goes off unplug it. Done. For free.


Or just solve the whole problem by rolling Baffin Island style- start your motor in October. Don't shut it off until May.


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