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Go Back   SailNet Community > On Board > Gear & Maintenance > Electrical Systems > Electrical kill switch
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Thread: Electrical kill switch Reply to Thread
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Topic Review (Newest First)
05-08-2013 10:57 AM
hellosailor
Re: Electrical kill switch

I'm not sure I would say the tradesman knew his job any better than the surveyor did. In theory when the main swtich is off, everything (except perhaps the automatic bilge switch) is OFF to make sure you can't blow yourself up from a spark, among other things.

With a third dedicated engine battery, installed with no consideration for the electrical controls, that's just been skipped because it would have been an extra complication and expense. In the least there should have been another battery switch added next to the house switch, i.e "START off/on....HOUSE off/a/both/b". No matter how they did it, it would have added materials and time to the job.

And if the same a/b type switch was used for the engine battery, the "b" position could be an emergency combiner adding it to the house/both position. Why? For emergency starting, or emergency radio power, etc. Easy enough while you're working there.
05-08-2013 08:47 AM
Dog Ship
Re: Electrical kill switch

Quote:
Originally Posted by mitiempo View Post
ABYC requires a main switch on any battery with a CCA rating of 800 amps or more. (E11.7.1.2.1) Even with a smaller battery it would be foolish not to have one. It is also something a survey should flag.

Who installed the engine and left the wiring without a switch?

I would also fuse the start battery even though ABYC considers it optional on batteries dedicated to starting.
Gartside Marine installed the engine in 2008.
There is no mention of this switch being required in a Ken Rorison survey that was done prior to purchase by the p/o in 2010. I'm not sure of the size of the battery but yah at 800 amps, a hundred amps one way or the other doesn't make much difference, it would still be the same issue.
Update: I just took a look at the old survey and athough it shows the new motor it only shows the boat having two batteries, not three. The third and dedicated engine battery is mounted beside the engine near the starter, accessed through the port side sheet locker.
I would probably have never known this was wired like this until one day I started the engine and then my wife yelled up to me, "Do you want the batteries turned on?" WTF
And may I add that here is a perfect situation of a tradesmen knowing his job and a surveyor not.
05-08-2013 02:40 AM
mitiempo
Re: Electrical kill switch

Quote:
Originally Posted by Dog Ship View Post
The only thing I don't like about my set up is you can start the engine with the battery selector switch in it's off position.
It would be nice to have a night switch/kill switch somewhere so I can shut off the engines battery from inside the boat somewhere. Not being able to start the boats engine so easily would make it a little more secure.
ABYC requires a main switch on any battery with a CCA rating of 800 amps or more. (E11.7.1.2.1) Even with a smaller battery it would be foolish not to have one. It is also something a survey should flag.

Who installed the engine and left the wiring without a switch?

I would also fuse the start battery even though ABYC considers it optional on batteries dedicated to starting.
05-03-2013 12:24 PM
hellosailor
Re: Electrical kill switch

"on a boat or a plane, redundancy is a good thing."

Perhaps you've never heard of the KISS principle.

Long distance aircraft used to have four engines, for redundancy. The accepted logic was that you might lose one engine, but three were still more than you needed. Except...

The thinking changed. Four engines means four major failure nodes and now you are 16x more likely to have a failure because they compound, they don't just add up. So now all the airliners use just TWO engines. One, and the minimum number of spares, to provide some extended glide time if one fails.

Same thing on a small boat. The more stuff you've got, the more stuff that finds a way to fail. Infest it with switches, and they will all corrode and wear. Even if you buy the really expensive waterproof and vaportight kind, and then there goes the budget.

Need to cut a power line in a hurry? No problem, one damage control axe can do all sorts of good work fast. (VBG)

You may notice, you don't see THOSE around very much anymore either, do you?

No, you let the battery primary fuse work, the power goes out before you could hit a switch, and then you just attend to the problem. KISS.
05-03-2013 11:56 AM
mad_machine
Re: Electrical kill switch

on a boat or a plane, redundancy is a good thing. There is no place to pull over and start walking if it goes all pear shaped.

I can see running individual kill switches and a 3-way switch. Been around power enough to see that a few hundred amps of power can melt things you never expected -especially- if you have a short and all those amps want to get there in a hurry
05-02-2013 10:06 AM
svHyLyte
Re: Electrical kill switch

Quote:
Originally Posted by Letrappes View Post
The kill switch cuts the power to the three way switch which cuts power to the whole boat. I'm thinking it's not needed as the three way switch selects from the two banks.

On my future design for the power system I had thought about putting in an independent three way switch just for the diesel which would be separate from the main power panel. That way I can cut power to the starter without shutting down the whole boat.
One of the original twist switches did exactly that (I believe it was the after-most but am uncertain of that). Frankly, I'd loose the 3-way switch and go back to the original arrangement.

FWIW...
05-02-2013 09:56 AM
Letrappes The kill switch cuts the power to the three way switch which cuts power to the whole boat. I'm thinking it's not needed as the three way switch selects from the two banks.

On my future design for the power system I had thought about putting in an independent three way switch just for the diesel which would be separate from the main power panel. That way I can cut power to the starter without shutting down the whole boat.
05-01-2013 12:07 PM
hellosailor
Re: Electrical kill switch

Diesels can be started without...
Yeah, but push starting a boat is a real *tch.
Hey, I can push start my car too, but if someone wants to either joyride your boat or steal it, they're not going to screw around looking for a hand crank and trying to hand crank a diesel. That's usually a futile effort, you'd really have to want THAT boat to do it that way. (Easier to bring out a jumper box.)
05-01-2013 11:36 AM
svHyLyte
Re: Electrical kill switch

Quote:
Originally Posted by Letrappes View Post
I believe my boat originally had one or two batteries on a bank which lead to a kill switch that you pull out on a handle and do a quarter turn to lock out power. At some point this was changed to two battery banks with a typical A B Both Off switch. This still runs through the original kill switch.

I think in the future I will do some rewiring on the batteries and charging system and would like to remove this. Can anyone cite a reason such as ABYC recommendations for keeping this original kill switch or is it just overkill?

Thanks.
There are 3 twist switches in the port quarter cabin of the First 42. One each for each of the original batteries and a third that controlled power from either or both of the batteries to the engine starting circuit. I am not sure why one would have also installed an Off-1-2-Both switch as it offers no advantage over the original switches. Nor do I see any reason to disconnect or replace them as they--by your description-control power to the 1-2-Both switch and are/would be a positive disconnect.

FWIW...
05-01-2013 10:09 AM
deniseO30
Re: Electrical kill switch

Electrical kill switch

1 take plate off light switch near shower.
2 remove switch with wires still connected and "hot"
3 take shower
4 step out of shower while dripping lots of water on floor.
5 reach for switch and touch black wire.

If you live to tell about it! tell everyone you forgot to turn the power off when you were replacing the switch!
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