What makes the best electrical join?

[lw395]

The most important things to me , after the integrity of the initial joint are to keep it sealed to prevent oxidation and water / moisture ingress, and to be able to re-make or at least inspect the joint at some time in the future. All joints are high on the suspect list when fault finding, so if it's totally sealed in resin or something you just don't know what's going on underneath.

So whether I've crimped or chocolate boxed it, I always tape it up tight with insulating tape afterwards. I reckon heat shrink would be equally as good or better. The other advantage is that it provides additional support to the joint and prevents movement or fatiguing, hence improving reliability that way too.

That's fair comment.
Crimps are good, but only if you have the right crimp and the right tool.
I tend to solder stuff, unless I can borrow the right crimp tool to do it properly.
Keeping the water out is key, when I had a Moto Guzzi, the only way you could keep the electrics reliable was to fill the connectors with vaseline. Poor plating I think!
Use whatever weapons seem to fit the task...
As for failure of rigid joints, that's often due to insufficient support, paticularly in things like switch panels. When you move the panel, the wiring should not be stressed at the joints, it should be anchored to the panel as a loom.
Likewise wiring on an engine should be cable tied to the engine so it all moves together, with a nicely curved loom to allow for movement/vibration.

Choc blocks can work fine. Let's face it your house is wired with little screws bearing down onto wires! Or at least mine is....

 

[ump010]

We seem to be missing one point here! In a good electrical installation there are few cable to cable joints. Cables should go direct from the switch/fuse/isolator etc to the fitting.

Where joints are necessary then properly crimped (unsoldered) connectors, marine spec. JBs and plugs/sockets are preferable.

 

[Danny Jo]

We seem to be missing one point here! In a good electrical installation there are few cable to cable joints. Cables should go direct from the switch/fuse/isolator etc to the fitting.

Where joints are necessary then properly crimped (unsoldered) connectors, marine spec. JBs and plugs/sockets are preferable.

I am coming round to this view, but can you explain why crimp connectors or junction boxes are preferable to soldered joints? Is it because they are quicker to fit or because they are easier to test if a fault develops?

Danny Jo may be a dream boat, as Scotty Twister suggests, but like many boats of her era, she was not designed around a wiring loom. So what do you do when, for example, the day comes to replace the Eberspacher and you find that the sheaf of cable supplied (to connect the heater and processor to the timer, thermostat and fuel pump) has a great fat plug on either end? Drill 32 mm holes in the one full bulkhead and five additional barriers? Hell no. Even pulling the wiring through without its plug proved impossible, so I simply cut the sheaf near the plugs and fitted them to each end of the existing sheaf of wires. Three years on, and it's still working fine. (And this year I bit the bullet and replace the plastic fuel supply pipe with the copper one supplied.)

 

[ump010]

I use crimps/JBs where it might be necessary to make a disconnection in the future, such as re-fit time etc.

Solder joints are only ok if supported, heatshrink won't do the job. There must be mechanical support to prevent movement of the cables at the junction of the solder. Close clipping a cable can do it, potting can also do it. Never do it to a cable that is liable to movement, say to an engine.

 

[ProDave]

speaking as an electrical engineer:

Don't tin wires that are either going to be inserted in a screw connector or crimped. Solder remains soft, and over time can compress and become loose in the terminal.

The other problem with soldered joints is the bit of the cable that's been soldered becomes effectively a single strand, no good at flexing, it will quickly break if flexed. I think you may be surprised at how far along the cable the solder actually wickes.

A properly done crimp connection should be stronger than the cable. If done properly with the right tool and right crimp for the size of cable, then subject to a pull test, it should be the cable that snaps, not the cable pulling out of the crimp.

Any form of joint should have the wire either side of it supported where possible to take the strain, so for a screw connection a choc box is much better than a choc block, and heat shrink with internal glue should effectively strain relief a soldered joint or crimped joint.

From a wiring regs point of view, a screw connection should only be used where it is accessible for inspection, i.e don't join two wires in a choc box, then pull that joint to somewhere you can never get to it again.

 

[rob2]

Personally, I like to use crimped automotive bullet connectors, smear them with vaseline and then heatshrink over the top. The rationale is that the vaseline will prevent corrosion and the heatshrink will keep it in place, but a good hard tug will still break the joint if needed. There are still a few chocblocs on the boat as I still haven't got round to fitting mil-spec connectors to the ridiculously small signal wires from the masthead wind sensor.

I reckon this approch will do for a couple of decades, after which you'll probably be doing a rewiring job anyway!

Rob.

 

[Forty_Two]

speaking as an electrical engineer:

Don't tin wires that are either going to be inserted in a screw connector or crimped. Solder remains soft, and over time can compress and become loose in the terminal.
.

This is so right!

I once tinned a 16mm stranded cable going in to a large fuse on a battery charger where it was fixed by a single screw clamping onto the tinned wire. All was well for a year or two then i realised it was getting very hot. Real fire causing situation, never tin a wire that is to clamped as it won't deform well & will give less contact to the clamping surface which equals heat.

 

[nedmin]

If soldered joints are suspect to breakage,what about soldered joints on armatures of electric motors.These things whirl round at 1000,s of revs per minute without fracturing.I,d solder every time.I use crimped joints as well but they are not as reliable as soldered.Some years ago when I rewound electric motors they brought out armatures where the connections to the commutator were crimped but they gave a lot of problems with bad connections.

 

[rosssavage]

Mr boeing and Monsieur airbus don't solder. It's all non-tinned crimping. That'll do for me!!

 

[misterg]

Why do you need to make a joint?

If it's to extend the cable, you'd be better off running a new, continuous length (assuming you're doing this in the luxury of you home berth with all facilities available, not at sea).

If it's something that may need to be disconnected in the future, then a junction box with choc-block connector inside, *BUT* also bootlace ferrules on the ends of the wires.

If you're using crimps, I wouldn't solder the wire first - it stops the crimp welding to the wire properly.

If you have several wires, an instrument for example, how about a multi-pole waterproof plug/socket?

e.g. Mini Buccaneer:

If I was stuck, I'd solder / heatshrink (ideally adhesive lined) though.

Don't forget your service loops and your drip loops when you're running wires...


Andy

 

[xxyyzz]

Mr boeing and Monsieur airbus don't solder. It's all non-tinned crimping. That'll do for me!!

I think that's partly due to maintenance, testing access and speed as much as anything else. You can teach crimping in half an hour, no-one will get hurt and you don't need power.

If you're ever likely to need to swap out a component then soldered-in is a pain in the bum.

Having said that I voted solder because it's the best _electrical_ connection, might not be the best physical one but that depends on where you're putting it.

 

[Danny Jo]

Thanks everyone. I've learnt a lot today.

What is particularly interesting is the near unaninimity among the professionals against soldered joints, at least when not held rigidly in place. Chief among the disadvantages are the loss in flexibility that occurs (and yes, having done many such joints, I have noticed that it extends a lot further than the bit of exposed wire that was soldered).

Also interesting are the reasons for not using solder to tin the ends of wires before inserting them into screw connectors or crimping them. From my own experience I had already concluded that crimping soldered ends was problematic. What seems less obvious is the argument for not soldering the ends going into screw connectors. Being of the generation for whom the first DIY lesson was fitting a plug to a 240v appliance, I have long concluded that a really fiercely tightened screw fixing onto a soldered end survived longer than a doubled over and twisted unsoldered end. This view was reinforced by finding ready-stripped-and-soldered terminals on cables supplied with both marine and non-marine electrical items that for one reason or another come without plugs.

I am not convinced that the plug-socket arrangement is the ideal one for long term connections - fine for joints that are regularly made and broken, thus rubbing away surface corrosions, and fine if you can get gold-plated plugs (this ain't irony - gold-plating tends to be standard on high-spec electrical equipment, and not just in the marine environment).

So my take-home messages are:

1. Use pre-tinned cable - it pays for itself in the time it saves;

2. Don't mess around joining wires if they aren't pre-tinned and you can replace the whole run;

3. Support soldered joins firmly.

 

[misterg]

I am not convinced that the plug-socket arrangement is the ideal one for long term connections - fine for joints that are regularly made and broken, thus rubbing away surface corrosions, and fine if you can get gold-plated plugs (this ain't irony - gold-plating tends to be standard on high-spec electrical equipment, and not just in the marine environment).

Just for info, the Mini Buccaneer connectors do have gold plated contacts

Andy

 

[snooks]

Crimps are a lot easier to do when you're sailing

 

[prv]

A properly done crimp connection should be stronger than the cable. If done properly with the right tool and right crimp for the size of cable, then subject to a pull test, it should be the cable that snaps, not the cable pulling out of the crimp.

That sounds good - perhaps I might rethink my plan to do all the joints in KS's refit with solder. Unfortunately, however, whenever I've attempted to crimp wires it's not been as strong as you describe. I have what I believe is a good-quality ratchet crimper, and the wires fitted snuggly in the crimps, yet I was still able to pull them out without much difficulty.

What am I doing wrong? Dodgy crimps? Is there a name to look for?

Pete

 

[NeilT]

Proper ratchet crimpers and using correct size connector for the cable is a good start - I've had a couple of sets of "krimpits" for years.
HTH
N

 

[rhumlady]

It is good to hear people saying not to tin cable ends which are to go under screws or crimps. I have been saying this for years and people look at me as if I have horns. Some of the so called gurus of the marine industry need to learn this lesson and edit there bibles appropriately. As far as equipment coming with cables pre tinned ready to be connected to choclate block or 13a plug etc the first thing I reach for is my wire cutters. My kids and my wife have also learned this lesson well.

 

[prv]

Proper ratchet crimpers and using correct size connector for the cable is a good start

Well yes, I think I'm doing that. But the cables still pull out, sometimes very easily.

I can't remember where I got my stock of crimps from - are poor quality crimps common and are they likely to cause this problem?

Pete

 

[mikefleetwood]

A few comments (difficult to add to the wisdom already provided):

If you are using a ratchet crimp tool and the wires still pull out, then you must be using the wrong size crimps for the wire used. Each colour of crimp is designed to be used with a limited range of wire sizes. Between them (red/blue/yellow), they cover the range of sizes commonly used in low voltage circuits.

The only place soldered joints should be used (except internally) is in certain high-current connectors (such as battery terminals) that are designed to have the voids filled with solder to achieve rated current.

There are several reasons why soldered joints (except as above) should be avoided in a marine environment. Where the solder ends, there is a stress point, leading to early fractures if there is any vibration. The use of solder, and the fluxes within it, tends to erode copper wire, leaving a point of weakness at the same stress point. Because solder is soft, tinning the ends of wires before crimp or screw termination will lead to eary failiures.

If at all possible use tin-plated copper wire in a marine environment. Copper wire oxidises quickly to a black powder when exposed to sea air. It is surprsing just how far this oxide travels inside a stranded wire suppsedly sealed by insulation!

Probably the ideal joint is crimped onto tin-plated stranded wire. The crimps being tin (or silver) plated brass, and the compression joint made is completely gas-tight if done correctly. Second best is probably "chocolate block" screw terminals, but only in a sealed box, and make sure they are the type with brass screws not plated steel!

 

[lw395]

Well yes, I think I'm doing that. But the cables still pull out, sometimes very easily.

I can't remember where I got my stock of crimps from - are poor quality crimps common and are they likely to cause this problem?

Pete

A particular crimp tool may only fit one brand of crimps and one size of cable.
Many have interchangeable jaws for different cables and terminals.
The crimper is trying to force everything down to a quite tightly controlled size, with zero empty space. OK a bit of metal is pushed sideways, but mostly you need to get the empty space to pretty exactly zero. 10% empty space is a non-joint and -5% means the crimper won't reach its end point.
Hence soldering is more practical for the amateur ( I include me in that bracket !)
As Snooks said crimping is easier afloat, but generally I regard crimps done afloat as a temporary fix, or OK for non critical stuff.

Another point, avoid lead free solder like the plague unless you have the right professional iron and flux to go with it. Good flux helps on all joints, I keep a flux pen (like a marker pen) from RS in my toolkit.
Most of the 12V irons are only suitable for melting rope ends, they do not get hot enough for a good joint. I have a weller TCP 12V which is thermostatically controlled by selecting the tip, it has been a good tool, although an inverter and a mains iron might be easier.
I also carry a slightly less nasty than usual diy crimp tool and some decent crimps. AMP is a good brand, anything that costs less than about 15p each usually needs soldering IMHO.