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Old 08-02-2016, 14:07   #16
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Re: 2 ground wires one terminal

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Originally Posted by bcguy View Post
I am wiring a Rule 750gph bilge pump. Wires are auto/manual and ground. I want to wire direct to a 12 v battery. I could splice the battery ground wire into the pump ground wire so that would have a single ground to attach to the terminal on the bilge pump switch or use a crimp that bites down into the bare wire using pliers. Just wondering if there is another connection method. ... thanks
Splices are bad practice. It's too easy to overload existing wiring. Splices end up hidden in wiring runs and hard to see locations.

In aerospace and automotive industries crimps are mandated for all connections. Hams tend to prefer soldering.

Ideally you crimp, seal and heat shrink. Proper ratchet matched jaw crimpers not the cheap connectors and crimp tools from walmart.

A bilge pump is a safety critical system. It should be wired accordingly.

Ideally all wiring should terminate at bus bars or dedicated terminal blocks. This is where you splice (using your words)

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Old 08-02-2016, 15:10   #17
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Re: 2 ground wires one terminal

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Originally Posted by leftbrainstuff View Post
Splices are bad practice. It's too easy to overload existing wiring. Splices end up hidden in wiring runs and hard to see locations.

In aerospace and automotive industries crimps are mandated for all connections. Hams tend to prefer soldering.

Ideally you crimp, seal and heat shrink. Proper ratchet matched jaw crimpers not the cheap connectors and crimp tools from walmart.

A bilge pump is a safety critical system. It should be wired accordingly.

Ideally all wiring should terminate at bus bars or dedicated terminal blocks. This is where you splice (using your words)

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
The only direct connection to the battery should by your emergency radio. Bilge pumps are notorious for failing/shorting/staying on. Plus they can draw enough amps to electrocute a human, let along a sailor.
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Old 08-02-2016, 15:15   #18
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Re: 2 ground wires one terminal

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Originally Posted by leftbrainstuff View Post
Splices are bad practice. It's too easy to overload existing wiring. Splices end up hidden in wiring runs and hard to see locations.

In aerospace and automotive industries crimps are mandated for all connections. Hams tend to prefer soldering.

Ideally you crimp, seal and heat shrink. Proper ratchet matched jaw crimpers not the cheap connectors and crimp tools from walmart.

A bilge pump is a safety critical system. It should be wired accordingly.

Ideally all wiring should terminate at bus bars or dedicated terminal blocks. This is where you splice (using your words)

Sent from my SM-N900T using Cruisers Sailing Forum mobile app
The only direct connection to the battery should by your emergency radio. Bilge pumps are notorious for failing/shorting/staying on. Plus they can draw enough amps to electrocute a human, let along a sailor. We crimped all electrical connections with heat sealing tubes. Never had a problem. If you want over kill, put a sealant around the crimp connector afterwards.
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Old 08-02-2016, 15:20   #19
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Re: 2 ground wires one terminal

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Plus they can draw enough amps to electrocute a human....
Don't think so.
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Old 08-02-2016, 16:29   #20
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Re: 2 ground wires one terminal

"Bilge pumps ...can draw enough amps to electrocute a human, let along a sailor."


Do tell? Exactly how many thousand horsepower is your twelve-volt bog standard dc bilge pump rated for?


And how many times have you heard of any twelve volt dc circuit, on a 12-14 AWG wire, being able to electrocute large mammals? Especially when it was fused?
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Old 08-02-2016, 16:41   #21
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Re: 2 ground wires one terminal

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"Bilge pumps ...can draw enough amps to electrocute a human, let along a sailor."


Do tell? Exactly how many thousand horsepower is your twelve-volt bog standard dc bilge pump rated for?


And how many times have you heard of any twelve volt dc circuit, on a 12-14 AWG wire, being able to electrocute large mammals? Especially when it was fused?
2 amps will do it. voltage irrelevant, or did you forget that part of your electrical engineering 101 class? Why stun guns may have millions of volts but only about .8 amps. Does not take much to put the heart into arrhythmia. Previously posted this. 5-10 amps will kill, 20-30 amps will fry, does not take much. That is why a lot of gangs will amp up(pardon pun) stun guns' amperage so the things become lethal on a 9 volt battery. Try holding your alternator and the car frame at the same time. Well maybe you better not. Yes, a 22 awg wire will usually burn out, but a lot of boats are wired with 8 awg or more for compressors, windlasses, etc. and that will transfer big loads to you. We had an Oyster in the yard that had everything wired into a 4 awg system. Bigger boats will have the equivalent of house wiring to run all their electronic components. And do not forget some boats even have transformers to provide 120 volt, 20 amp systems. Grand Banks' generators can run most houses. So guess you need to review your basic EE course materials. BTW: that is why a GUI system is worth it.
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Old 08-02-2016, 16:52   #22
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Re: 2 ground wires one terminal

True, it is the current that will kill you, but you need voltage to push that current through your skin resistance. 12V typically isn't enough to do it. You can place one hand on the battery (+) terminal and the other on the (-) or ground connection and not even feel a tingle. On the other hand, a 1.5V AA battery can kill you if you push the wires through your skin near your heart. (Or so I've been told, and I'm not going to personally test this.)

Bottom line, there are still plenty of other good reasons to use good wiring practices. Please son't splice directly into your battery cables.
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Old 08-02-2016, 17:08   #23
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Re: 2 ground wires one terminal

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2 amps will do it. voltage irrelevant, or did you forget that part of your electrical engineering 101 class? Why stun guns may have millions of volts but only about .8 amps. Does not take much to put the heart into arrhythmia. Previously posted this. 5-10 amps will kill, 20-30 amps will fry, does not take much.. (snip)


Actually, the Taser commonly carried by police officers delivers current of about 2.1 milliamperes at about 50,000 volts. Your claim of 0.8 amps is 400 times as much, and "millions of volts" is pretty out there, as well.

As to causing fibrillation, with a DC power source less than 50 volts, applied externally (skin contact), it is almost literally impossible. While electrical resistance of humans varies somewhat, by individual, electrolyte levels, etc, the lowest average is about 1,750 ohms, while 95% of the time it is over 5,000 ohms. Plug those numbers into Ohms law and see how much current 12 vdc you get.

Very low current and voltage CAN cause fibrillation or asystole, but that's done in surgery by applying the current directly to the heart muscle.

As hellosailor already asked, how many cases have their been of 12 vdc (or 24, for that matter) electrocutions?

Quote:
...a lot of gangs will amp up(pardon pun) stun guns' amperage so the things become lethal on a 9 volt battery...
Wow, I'd love to see some actual stats on that one! I think you've been watching too many movies.
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Old 08-02-2016, 17:08   #24
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Re: 2 ground wires one terminal

Sorry, reed, but I was indeed awake when that stuff was being taught to me. And while I have seen the photos the USN posted, of a sailor's wedding ring traumatically amputating his finger when it shorted out a "car" battery, and I'm very well aware that a crowbar short of a car battery can throw 3000 amps, I'm also aware that I can grab both terminals of that same battery, even with sweaty hands, and the resistance of the human body is so high that I won't even get a tingle.
A bilge pump? In a word, no. As Paul says, it ain't gonna happen that way in the real world. If you're afraid to grab the battery terminals, yourself? Slap a fresh corpse across them, and an ammeter, and see just how much current doesn't flow.
That's one reason we use 12vdc bilge pumps, instead of shopvacs connected to the inverter.
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Old 08-02-2016, 17:16   #25
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Re: 2 ground wires one terminal

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True, it is the current that will kill you, but you need voltage to push that current through your skin resistance. 12V typically isn't enough to do it. You can place one hand on the battery (+) terminal and the other on the (-) or ground connection and not even feel a tingle. On the other hand, a 1.5V AA battery can kill you if you push the wires through your skin near your heart. (Or so I've been told, and I'm not going to personally test this.)

Bottom line, there are still plenty of other good reasons to use good wiring practices. Please son't splice directly into your battery cables.
Ever hear of short circuits? Wet bodies and Ohm's law? Just breach the skin and see what happens. Or a cut that is wet. Now there is death staring you in the face. The reality is that on boats you got very wet environments, wet bodies, and probably a good chance wires will puncture the skin somewhere on our unfortunate sailor. Thus the advantage of a common ground, a gui system, and appropriate resistors. So far have not even mentioned amplifiers, shore power, nor inverters.
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Old 08-02-2016, 17:22   #26
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Re: 2 ground wires one terminal

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...a lot of gangs will amp up(pardon pun) stun guns' amperage so the things become lethal on a 9 volt battery...
Wow, I'd love to see some actual stats on that one! I think you've been watching too many movies.
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We actually operated on a kid several years ago at Mass General for the effects of being "stunned" to the point where the kid had seizures. BPD staff said the kid was attacked with a modified stun gun that was gaining popularity.
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Old 08-02-2016, 19:49   #27
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Re: 2 ground wires one terminal

Oh good grief

Using ohms law to prove the unprovable

Let's try a little experiment, get the biggest 12V battery you can find, say one that will provide at least 600 amps. Take two sharp needles and stick one in each finger and then place them on the battery posts.

Still alive???


Of course and most of us would not feel the microamps of current flowing though the body.

Lets amp in up a bit, stick the needles into your nipples and try again. Yup, still alive!

One should either understand electric theory or listen to those who do
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Old 08-02-2016, 20:16   #28
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Re: 2 ground wires one terminal

Wotname?
I rely on your experience in these matters. Do the needles really have to be sharp? I've only got some old dull rusty ones. Will that still work? Or can I use the bamboo ones?
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Old 08-02-2016, 21:38   #29
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Re: 2 ground wires one terminal

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Ever hear of short circuits?
What does this even mean??? We're talking, I think (?), about the human body completing a circuit in a 12V system. The worst-case situation is directly between +12V and ground.

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Wet bodies and Ohm's law? Just breach the skin and see what happens. Or a cut that is wet. Now there is death staring you in the face. The reality is that on boats you got very wet environments, wet bodies, and probably a good chance wires will puncture the skin somewhere on our unfortunate sailor.
I just now sprinkled salt on my tongue to where I had a seawater taste in my mouth. Using an ohmmeter and laying the probes flat on my tongue and about 1/2 inch apart, I then measured a resistance of somewhere between 500K to 1M Ohm. Assuming it was 100K, a 12V connection would provide 120 microamps.

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Thus the advantage of a common ground, a gui system, and appropriate resistors. So far have not even mentioned amplifiers, shore power, nor inverters.
I assume you meant "GFI system"? Shore power, inverters, and other high voltage systems are a completely different situation. These can be lethal if you start grabbing bare wires. But we've been talking about 12V.

And for that matter I've not seen anybody, even the OP, suggest any connection methods that would lead to accidental direct body/electrical contact. Where is this all coming from???
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Old 08-02-2016, 21:53   #30
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Re: 2 ground wires one terminal

Wow, there are some feisty folks here. Death from a battery? Hold on to the 2 terminals? Hmmmm, neither is right in my book.

Actually, if you are across a battery and your body is sweaty, you sure as heck will feel it. Takes about 3 seconds and then EOWWWW! Trust me, this ain't book learnin'. Just lean your sweaty belly against a piece of bare metal on your car while laying a wrench on the positive terminal. Or lay across a house battery bank in a Central American summer.

But kill you? Only if you have a disease that prohibits you from feeling burn pain. I call BS.
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