is a master fuse and switch necessary?

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is a master fuse and switch necessary?

Postby mariannf » Wed Mar 09, 2016 4:18 pm

Hi all,
I am working on my first build and have a DC 12 electrical question. In a few of the schematics I have seen that a master fuse and switch are included between the battery and fuse block. I will only have the following: fantastic vent fan, cabin light, 12 volt socket charger (cigarette lighter). I was planning on just having a fuse block (ideally with built in ground block) and connecting the fuseblock to the battery directly. is there a problem with doing it this way? What is the purpose of the master fuse?
Thank in advance?
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Re: is a master fuse and switch necessary?

Postby MtnDon » Wed Mar 09, 2016 5:14 pm

Fuses or breakers are all about protecting the wires. protecting the wires is all about preventing them to overheat and melt the insulation and start a fire. The wire from the battery to the fuse block should therefore also be protected with a fuse / breaker as close to the + terminal as possible.

A disconnect can be handy to ensure that everything that is powered by the battery can be ensured to be off when placed in storage. The disconnect should be in the negative wire from the battery. There are some disconnects that connect directly to the negative terminal with the battery cable attached to it.
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Re: is a master fuse and switch necessary?

Postby Socal Tom » Wed Mar 09, 2016 6:00 pm

I use a 30 amp circuit breaker between the battery and the breake. like this one .http://www.cabelas.com/product/Manual-Reset-Circuit-Breaker/738260.uts?productVariantId=1191210&srccode=cii_17588969&cpncode=44-152311132-2&WT.tsrc=PPC&WT.mc_id=GoogleProductAds&WT.z_mc_id1=00006831&rid=20 I usually pull the neg terminal when I park for a long period to keep the battery from draining. A switch could be convenient.
I like the circuit breaker, because its inevitable that you will short something out, this way you don't need a spare ( well until it dies), it self resets once it cools down.
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Re: is a master fuse and switch necessary?

Postby H.A. » Wed Mar 09, 2016 8:42 pm

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Last edited by H.A. on Sat May 14, 2016 5:22 pm, edited 1 time in total.
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Re: is a master fuse and switch necessary?

Postby S. Heisley » Wed Mar 09, 2016 11:50 pm

When it comes to a main fuse and a battery disconnect, I agree with MtnDon. It's best to be cautious and have both. Fuses are very important. They can save your lives.

For a battery disconnect, I went really simple and easy to install and haven't been sorry yet. I went with one similar to this:

http://www.amazon.com/Qiorange-Battery- ... off+switch

It's so simple, the package told me how to install it. Then, I screwed in an eye screw into the wood nearby, ran a piece of elastic cord through it and the hole in the disconnect key and tied the cord off at the proper length to reach. That way, the key can't be lost or dropped into never-never-land and you just pick it up, plug it in and turn to connect ...Easy and it works. :thumbsup:
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Re: is a master fuse and switch necessary?

Postby Dale M. » Thu Mar 10, 2016 9:39 am

Keep in mind a master disconnect and a fuse can be either combined as same unit or two separate units.... A fuse is protection, sort of like rubber gloves when handling toxic cleaners... A master switch is simply a off/on switch....

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Re: is a master fuse and switch necessary?

Postby mariannf » Thu Mar 10, 2016 1:00 pm

thanks everyone this helps tremendously!
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