beginner's DC wiring questions

[Ex-Calif]

It took me a while to get back to this and do the research but I was having a problem swallowing somone's post about aircraft wiring requiring crimp+solder. I have always been in the crimp only camp and that's how I was trained as an FAA certificated A&P.

The reasoning was always explained as the hard point created and the vibration in aircraft creating a failure point.

So...

I did the research. FAA advisory circular is the controlling document for methods and practices in aircraft repair. Specifically AC43.13-1B, chapter 11, paragraph 11-174 sub d. (you can find it pretty easy at FAA - Home

"d. Copper Terminal Lugs - Solderless crimp style, copper wire, terminal should be used and conform to MIL-T-7928. Spacers or washers should not be used between the tongues of terminal lugs."

I know this is a boating forum but I wanted to comment on this one.

[GordMay]

Soldering a properly crimped terminal is difficult, time consuming, and unnecessary.
Acceptable crimp connections are analogous to a cold weld, and are gas tight - hence, corrosion-free.
If the crimp was done poorly, solder won't save it*1.
If the crimp was done properly, solder is unnecessary*2.

*1. *In fact, soldering a crimped terminal may weaken the mechanical connection, may reduce electrical conductivity, and may damage the terminal.
Apart from the problem of solder being drawn down the cable, inside the insulation, leading to fracture failures because it’s become a single strand conductor, there is also the real possibility of making a bad (cold or dry) solder joint, which will again lead to unreliability and failure.

*2. Gas tight crimps are only achieved with use of the proper tools. One type of tool for installing crimps and terminals is the crimp manufacturer’s recommended double crimp*3, ratcheting, compound lever type tool that must go through a full crimp cycle before releasing.

*3. In the case of insulated wires, a proper crimp actually consists of two crimps: one crimp to cold weld the wire strands to the connector barrel; and a second crimp to secure the insulation to the connector. The first crimp establishes electrical continuity; the second crimp provides stress relief to prevent physical separation.

Here’s Don Casey’s take:
Sailboat Electrics Simplified: Improvement, Wiring, and Repair
By Don Casey
Sailboat Electrics Simplified ... - Google Book Search

[hellosailor]

Gord-
As Wheels notes, the silicon jelly is standard teclo practice, at least here in the States by the "children" of the late great Western Electric and AT&T. (A moment of silence in their memory, please. Of course, silence is EASY with out new phone systems.<G>) They use little "button" connectors for the small (22-24g) solid copper premises wiring, prefilled with silicon jelly. insert wires, pop the button down, good to go for 20++ years of use. But those are also "guillotine" connectors that pinch down on the wires, like a ScotchLock, not suitable for use in vibration areas.
I can't see how silicon jelly could hurt, making it metal filled with copper/nickel like antiseize would be very nice--but not so easy to find on the shelf.

And as Buddy mentions, proper practice calls for securing ALL joints to a bulkhead or other rigid mount, to prevent them from working.

Probably the biggest problem with crimps, is the "500 pieces for $5" kits sold in the auto junk shops. For sure, they're not milspec.<G> I know that once I sprung for the $50 ratcheting crimper, and the fifty-cent crimps, my crimps became way better.

[Alan Wheeler]

Gas tight crimps are only achieved with use of the proper tools.

And as HS say's above, proper crimps.

[k7cej]

I am an electrical engineer with over 30 years experience in the instrumentation industry and have been a sailor and boat owner for nearly as long. I would like to reinforce several points in this discussion:

1. Crimp connections work fine WHEN PROPERLY CRIMPED. For the normal yellow (10-12 ga.) and blue (14-18 ga.) connectors you use on branch circuits, this means using a ratcheting crimp tool. I have used the $5 non-ratcheting tool in the past and I can't tell you how many of the connectors could be easily pulled off the wire after crimping. With a ratcheting tool, it will always hold if the wire is properly stripped and passes though the entire length of the barrel.

2. Soldering is rarely advisable, due to the stress riser created where the stranded wire becomes solid. An exception would be coaxial rf antenna connectors designed to be soldered.

3. Any wire connection exposed to moisture, such as near the engine, battery, in the bilge or lockers should be terminated with a closed-end lug and covered in adhesive-lined heat shrink after crimping.

4. Butt splices should be avoided if at all possible. Sometimes they must be made when rewiring an entire run is not practical. Then use adhesive lined heat shrinkable butt connectors (crimped with a ratchet tool), AND an overall covering of adhesive-lined heatshrink. I have never had one of these connections fail when properly made up in the first place.

Regarding joint compound, grease, neverseize: most techs in my area use NOLOX on battery cable terminations. Note that it is a non-conductive dielectric grease originally designed to prevent oxidation on aluminum house wiring. In fact, by my actual measurements, all of these compounds are non-conductive, which means that if used in a connection, the mechanical forces of the connection must displace the grease to get a good, low-resistance connection.

Also regarding Never-Seize: this comes in several grades. The most common contains copper and has NO place on most boats, as it will actually contribute to corrosion of aluminum. The "silver" grade is ok; it contains nickel, not silver, and can be used on ss screws going into an aluminum mast if you want to protect from corrosion and make them easy to remove. However I prefer Tef-Gel for removable hardware, and a varnish-like paste (I can't remember its name at the moment) for screws into aluminum that don't want to vibrate loose. On almost all other screws in my boat I use Lok-Tite.

Craig
k7cej

[GordMay]

Originally Posted by k7cej

... Also regarding Never-Seize: this comes in several grades. The most common contains copper and has NO place on most boats, as it will actually contribute to corrosion of aluminum. The "silver" grade is ok; it contains nickel, not silver, and can be used on ss screws going into an aluminum mast if you want to protect from corrosion and make them easy to remove. However I prefer Tef-Gel for removable hardware, and a varnish-like paste (I can't remember its name at the moment) for screws into aluminum that don't want to vibrate loose. On almost all other screws in my boat I use Lok-Tite.
Craig
k7cej

Craig offers some good advice.

A little about ANTI-OXIDANT COMPOUNDS
Conductive & Dielectric (Non-Conductive)

Every instrumentation, power and ground connection on the boat is a potential problem. So the best approach is to prevent moisture from reaching the connections whenever possible, and to reduce electrical resistance at each static connection.

As far as I know, ALL electrical contact greases and/or anti-oxidants will APPEAR to be non-conductive, when a ‘puddle” of the compound is tested with inserted Ohmmeter leads.

Even the conductive pastes (with suspended copper, zinc, or silver particles) indicate infinite resistance under casual no-pressure measurement.

However, as installed, the paste is compressed and squeezed, and some of the particles are sheared, bridging the two contact surfaces, whilst the balance of the paste is merely displaced, and encases the joint in a protective coating which excludes moisture & air.

Due to the abrasive nature of the metal particles in conductive greases, they should never be used on sliding or “wiping” contacts.

Finally, WD-40 has no place in electrical connectors or components. WD-40 is composed of 80% Stoddard Solvent (that is similar to paraffin), 20% light lubricating oil, and a bit of fragrance. So, I advise against using WD-40 in any part of an electrical system because it leaves an oil residue. Use an alcohol-based electrical contact cleaner to remove any grease and oil that is causing conductivity problems on old connections.

[Capt Hook]

Lots of good stuff here and it'd be easy to cover things that have already been said but I'll throw a few things in the pot:
If a soldered joint is not soldered well (and it can be difficult to tell) it can be a dry joint and when it then overheats it melts the solder and falls apart where if it's crimped it is not suceptable to the same problem. It can be good to tin the wire before crimping to help avoid corrosion but if your using marine cable it shouldn't matter. Don't run cables in parallel to double the carrying capacity because if one cable becomes disconnected for any reason the other will overload and could cause fire. In this case the fuse would not protect you as the total current would still be within your design but now outside the current carrying capacity of the cable. I think it might already have been said but don't be too concerned about the current capacity of a cable. Yes look it up (you will find tables on the net) but then oversize your cable. More often than not you will be running with a battery that is not fully charged so it is important is to keep the voltage drop to a minimum so again spec a bigger cable than you think you really need. You'll now start to see that one size of cable will do most things for you. For some applications it will be far to big but that doesn't matter and for others it will be just right for the job. Now you're going to be using crimps of the same size and you're not going to run the risk of putting the wrong cable in. You can also buy a complete spool of cable of each colour you want and keep cost down. You definately need a battery isolation switch and always carry a new spare. We seem to get one of these switches go every season. One day when you can smell the cable burning but can't see where the smoke is coming from you'll need this switch. The only thing that should be connected to the battery side of his switch is your fused bilge pump. You talk of in-line fuses. Not sure exactly what you mean here but an in-line fuse to me is just that. You need panel mount fuses that are clearly marked up and easy to get at and you need spares of all sizes with you. Personally I don't like circuit breakers. It'll get expensive to carry spares of every size you've fitted and they are not quick to change in a hurry if one is faulty. Much easier and quicker to change a fuse. When it's all done and working fine get a meter and find out what current you've got in each circuit and change your fuses to suit if you want to be super safe but you'll have to allow for start up currents in motor circuits. Our cabin lights are fed with solid copper cable sandwiched between fibreglass mouldings and would be impossible to rewire without running the cable on the surface so I've made sure the ends are made off well and reused it. A final thought...... route your cables as far away from your campass as possible and then when you've finished swing your compass.
It's not a hard job just a long job .......... oh and take notes as you go and write it up cos one day you'll need it.#
Have fun.
Chris

[hellosailor]

Gord-
"WD-40 is composed of 80% Stoddard Solvent (that is similar to paraffin), "
In US English, rather than Uk English, that would be "80% dry cleaning fluid (that is similar to kerosene)"
Paraffin in both countries should still mean wax. "Paraffin oil" is apparently what we Yanks call kerosene or "lamp oil". Stoddard is similar to naphtha, aka paint thinner aka mineral spirits in the US.

Here, we put paraffin on top of jams and jellies when putting them up in jars.<G>

[Stenn]

Originally Posted by Ex-Calif

It took me a while to get back to this and do the research but I was having a problem swallowing somone's post about aircraft wiring requiring crimp+solder. I have always been in the crimp only camp and that's how I was trained as an FAA certificated A&P.

The reasoning was always explained as the hard point created and the vibration in aircraft creating a failure point.

So...

I did the research. FAA advisory circular is the controlling document for methods and practices in aircraft repair. Specifically AC43.13-1B, chapter 11, paragraph 11-174 sub d. (you can find it pretty easy at FAA - Home

"d. Copper Terminal Lugs - Solderless crimp style, copper wire, terminal should be used and conform to MIL-T-7928. Spacers or washers should not be used between the tongues of terminal lugs."

I know this is a boating forum but I wanted to comment on this one.

Hey, sorry it's hard to swallow....but neither Mil-Spec Mil-T-7928, nor your FAA "controlling document" actually says anything about practices, just describes the connector itself to be used....i.e. "solderless crimp style," but that is to differentiate it from the lug-style that is "solder only" because it isn't crimpable. "Solderless crimp style" does not mean "soldering prohibited." There are different specs that cover practices.

I will say however, after this furor inspired me to revisit the issue at work (an aerospace manufacturer of fighter avionics), rather than just rely on my old Air Force electronic technician's training, which I realized was more geared towards circuitboard repair....

....that the standard we use at work as a guide, WHMA-A-620, and all the Mil-Specs we have, including Mil-T-7928 and others, (the DoD is rolling a lot of theirs into SAE specs now) don't actually prohibit soldering the crimped connector, but say as a standard practice "not generally done" unless engineering directives specify to for a specific reason.....

.....and that's just about always the case with any of these "specs"...they leave enough "wiggle room" to allow variation of practice based on the specifics of the application and/or environment, and they always leave it to the engineer and engineering drawing to be the final say for a specific application..... the "spec" hardly ever overrules the engineer. I even found one Boeing reference on-line that talked about them not soldering crimped connections because they didn't want the safety worries of climbing around inside a fuselage with a hot soldering iron.

So none of this stuff is engraved in stone, one-size-fits-all.

In our case as skippers, the "engineering directives" come from ourselves, i.e. we are the engineers, we weigh the pro's and con's of all variables involved, i.e. vibration, moisture, salt, etc., and especially materials available and/or on hand, and then we make a decision for our own application, based on real-world circumstances.

The WHMA spec we use at work does lean towards the concern already voiced here by others, about the conductor becoming, in effect, "solid" by the wicking of solder down into the wire itself.....

"....Soldering crimp connections is normally not an approved method. However, soldering may be required when a lower resistance connection needs to be made to assure proper operation of electrical circuitry. Soldering a crimp connection may be done only when specified by engineering documentation. When the crimped connection is required to be soldered, the stranded wire shall notbe tinned prior to the crimping process..."

....and I will be the first to admit that in our particular marine application, the use of "marine" wire, which is already required to be pretinned on all conductors, would make it pretty much impossible to prevent that wicking from occurring to some degree, resulting in maybe a quarter inch of conductor becoming "solid" conductor at the connector.

But, again, in the end, we, on the boat, doing the work, taking into account what materials we have available, make the decision of which factors, which threats, which variables to focus on, and even what we "feel like" doing.

The "crimp only camp" prefers to focus on the vibration threat, and make their electrical connections in light of that.

Coming from an electronics and radio background, and not having any "adhesive shrink tubing" available (called for by others here), and not liking the "gooping up" of my electrical connections with other substances, I will carefully solder my crimped connections, trying to prevent as much of that "wicking" as possible.

I prefer to focus on the "cleanliness" and anti-corrosion qualities of my electrical connections, because those are harder to see, and I'd say more prone to cause "mystery" electrical problems, particularly RF (radio frequency) problems and things like temp-gauge-reading issues.

But this thread / discussion has given me a new-found awareness and consideration of the vibration factor that I will certainly take into account more seriously from now on, particularly closer to the engine.

Thanks,
Stenn

[hellosailor]

While we're out comparing specs...I don't have the specs, but I do have some 3M heat-shrink connectors that were designed for NASA, for use on rockets and spacecraft, which are heat-shrink with multiple solder rings inside them. When properly set (some require a special infra-red heat gun, not the conventional type) they create a SOLDER joint on two or three wires, which is then heat-shrunk and adhesive sealed--all in one operation, providing a gas-tight seal according to 3M.

So if the FAA says "no solder", the folks who fly ABOVE FAA limits, seem to have no problem soldering. At least, for some purposes.

[Ex-Calif]

Originally Posted by Stenn

<snip>.. just describes the connector itself to be used....i.e. "solderless crimp style," <snip>

Hey I'm not trying to pick a fight and as can be seen from this thread there are obviously several different practices by industry.

Advisory Circular 43-13-1B is the standard practice reference for licensed FAA mechanics - you don't do it their way and something goes wrong you can lose your ticket. As a licensed FAA mechanic I was taught by this bible and had to demonstrate wiring during my practical exam. I didn't solder anything.

Also as a "standard practice" document, by definition it is overwritten by specific application engineering instructions.

i.e. if the radio manual says solder a joint and I don't - I have failed the I.Q. test - no surprise there - LOL.

Originally Posted by Stenn

I will say however, after this furor inspired me to revisit the issue at work (an aerospace manufacturer of fighter avionics), <snip>

So none of this stuff is engraved in stone, one-size-fits-all.

Agree

Originally Posted by Stenn

The WHMA spec we use at work does lean towards the concern already voiced here by others, about the conductor becoming, in effect, "solid" by the wicking of solder down into the wire itself.....

"....Soldering crimp connections is normally not an approved method.

So normally you don't solder - I agree.

As one who has replaced many failed soldered connections and failed connections made with solid conductors. I am squarely in the multi-strand no solder camp especially where vibration is encountered.

Originally Posted by Stenn

<snip>, I will carefully solder my crimped connections, trying to prevent as much of that "wicking" as possible.

<snip>

But this thread / discussion has given me a new-found awareness and consideration of the vibration factor that I will certainly take into account more seriously from now on, particularly closer to the engine.

Good Call

[GordMay]

Originally Posted by hellosailor

While we're out comparing specs...I don't have the specs, but I do have some 3M heat-shrink connectors that were designed for NASA, for use on rockets and spacecraft, which are heat-shrink with multiple solder rings inside them. When properly set (some require a special infra-red heat gun, not the conventional type) they create a SOLDER joint on two or three wires, which is then heat-shrunk and adhesive sealed--all in one operation, providing a gas-tight seal according to 3M.
So if the FAA says "no solder", the folks who fly ABOVE FAA limits, seem to have no problem soldering. At least, for some purposes.

I don’t recall seeing the 3M product, and would appreciate any descriptive information you could provide (product brand name, or part numbers, etc)

Pacer Marine used to stock a similar product called “MULTILINK”*, which they discontinued due to excessive failure reports (from their customers & from their own fabrication shop). MultiLink combines solder, heat shrink tubing & the ability to crimp.

* “MULTILINK” SEALED CRIMPED & SOLDER CONNECTORS
http://nationalstandardparts.com/bro.../multilink.pdf

Raychem (Tyco) also have “Solder Sleeve Terminators”:
Shield Terminators Product Line Information - Tyco Electronics

NASA has (had circa 1997) a 97 page prescriptive specification for soldered connections:
SOLDERED ELECTRICAL CONNECTIONS ~ NASA TECHNICAL STANDARD
http://snebulos.mit.edu/projects/ref...D-8739-3-2.pdf