electric connections

[little shack]

Hi folks just a quick one having to replace a relay on the engine of the boat as the old one has started working when it wants.just wondering the best way to protect the terminals from the wet and keep a nice connection.thinking of using a bit of copper slip.cheers for any help

 

[JimC]

I coat them with silicone grease or spray them with a silicone spray. The spray penetrates all round the individual strands of the wires and up beneath the insulating sleeving. It is so effective in preventing oxidation of the copper strands that I will now confidently use non-tinned wire.

 

[Barry Jones]

Another vote for silicon grease.

 

[Graham_Wright]

Copperslip will corrode and go green;-copper chloride, Vic.

 

[little shack]

thanks folks silicone grease looks the way

 

[VicS]

Copperslip will corrode and go green;-copper chloride, Vic.

Does it? I think the stuff I use as an anti-seize compound is probably polybutylcuprysil. ( one tub is .. its labelled) That's Ok

No advantage in using Copaslip ... it's not electrically conducting.

I use silicone grease on electrical connections.

 

[GrahamHR]

Does it? I think the stuff I use as an anti-seize compound is probably polybutylcuprysil. ( one tub is .. its labelled) That's Ok

No advantage in using Copaslip ... it's not electrically conducting.

I use silicone grease on electrical connections.

I didn't think silicone grease was electrically conducting either, so if Copaslip is available and silicone grease isn't, why not use the Copaslip ?

 

[CharlesSwallow]

Don't rely upon crimped-on terminals either. Use tinned wire also. Then solder on the terminals before using the silicone grease.

Chas

 

[VicS]

I didn't think silicone grease was electrically conducting either, so if Copaslip is available and silicone grease isn't, why not use the Copaslip ?

Cos its so 'orribly messy.

 

[CharlesSwallow]

I didn't think silicone grease was electrically conducting either, so if Copaslip is available and silicone grease isn't, why not use the Copaslip ?

The pressure of even the weakest terminal grip breaks through the lubrication barrier to allow a clean metal to metal contact which is then sealed against air and water getting in to cause corrosion. Great set-up!

Isn't Copaslip more appropriate in preventing seizing of automotive brake components where mineral based lubricants will perish rubber seals and silicone grease is not sufficiently viscous?

Chas

 

[greenalien]

Then solder on the terminals before using the silicone grease.

Although this seems like a good 'belt and braces' solution, it also creates a hard point where the solder ends, which is a potential point of failure if there's any vibration on the connector. A properly-made crimped connection should be perfectly adequate on its own. If you test the crimp by pulling on the cable afterwards, you'll soon find out if it's any good!

 

[Yacht Yogi]

crimping terminals

Crimping is safer than soldering. In the event of a short circuit (high current heats the wire until a fuse or circuit breaker trips) or excessive heat from a nearby fire or mechanical problem the solder can melt allowing the wire to fall out and short onto anything that happens to be around. Professionally installed wiring in vehicles, boats and aeroplanes is always crimped.

 

[CharlesSwallow]

Crimping is safer than soldering. In the event of a short circuit (high current heats the wire until a fuse or circuit breaker trips) or excessive heat from a nearby fire or mechanical problem the solder can melt allowing the wire to fall out and short onto anything that happens to be around. Professionally installed wiring in vehicles, boats and aeroplanes is always crimped.

That's because for "professionals" time is money. Perhaps I should have made it clear that I always crimp AND solder. Never just rely upon soldering a wire onto the side of a connector, of course. Most solder terminals require the conductor to be threaded through a hole and twisted, first. As to point about hard spots, these will only be a danger where movement is expected and then the wire should be clipped a couple of cms away from the joint to prevent this.

Chas

 

[Bru]

Ah, this old chestnut again!

Right, my original apprenticed trade was as a wireman on lift control systems a job which involved making hundreds of electrical connections every working day so this is how top quality reliable electrical connections are best made ...

Soldered - a strong mechanical joint must be created by wrapping the wire through or around the tab or terminal before soldering. Soldered connections are not suitable where vibration may be present

Screw terminal - strip back insulation just sufficiently to make sure it is clear of the actual connection point, never double back the wire (single or multi-strand cable). Don't tin (solder) the end of a multicore cable, it makes it brittle and prone to failure

Crimp terminal - strip back insulation as above, use the correct size crimp, again, don't tin the end of multicore cable for the same reason, get enough pressure on the crimp tool

Typical service failures ...

Solder - dry joints (insufficient flow of solder around and into joint) usually caused by too low a temperature, not enough or unsuitable flux and/or poor technique. Modern lead free solder is sh*t IMO and a leading cause of dry joints

Screw terminal - insulation trapped within the electrical connection area of the terminal, conductor failure due to movement or vibration against the fixing exacerbated by tinning the conductor in the case of multicore wiring

Crimp terminal - incorrect sized crimped connector, not enough crimping pressure, conductor failure as above

Tinning of multicore cables prior to or after crimping or connecting to a screw terminal was an instant QC failure of the job and a right rollocking for the wireman from the foreman would follow suit

Specifically with regard to crimp connectors, my employers were extremely sceptical of them back in the 1970's and carried out extensive in-house testing before introducing them. Critically, they determined that adequate crimp pressure was very difficult to achieve repeatably with hand crimp tools and invested in a lot of expensive ratchet crimp tools. Properly used, they found that crimp connectors were more reliable than soldered connections onto relays, contactors etc. as well as being faster to make

A cautionary tale ... we came within a whisker of having a serious fire on board when a soldered connection on the feed from the engine alternator to the electrical control panel failed thus sending around 30 amps up the field coil wire which promptly overheated and set fire to the insulation on the adjacent cables

 

[CharlesSwallow]

Ah, this old chestnut again!

Right, my original apprenticed trade was as a wireman on lift control systems a job which involved making hundreds of electrical connections every working day so this is how top quality reliable electrical connections are best made ...

Soldered - a strong mechanical joint must be created by wrapping the wire through or around the tab or terminal before soldering. Soldered connections are not suitable where vibration may be present

Screw terminal - strip back insulation just sufficiently to make sure it is clear of the actual connection point, never double back the wire (single or multi-strand cable). Don't tin (solder) the end of a multicore cable, it makes it brittle and prone to failure

Crimp terminal - strip back insulation as above, use the correct size crimp, again, don't tin the end of multicore cable for the same reason, get enough pressure on the crimp tool

Typical service failures ...

Solder - dry joints (insufficient flow of solder around and into joint) usually caused by too low a temperature, not enough or unsuitable flux and/or poor technique. Modern lead free solder is sh*t IMO and a leading cause of dry joints

Screw terminal - insulation trapped within the electrical connection area of the terminal, conductor failure due to movement or vibration against the fixing exacerbated by tinning the conductor in the case of multicore wiring

Crimp terminal - incorrect sized crimped connector, not enough crimping pressure, conductor failure as above

Tinning of multicore cables prior to or after crimping or connecting to a screw terminal was an instant QC failure of the job and a right rollocking for the wireman from the foreman would follow suit

Specifically with regard to crimp connectors, my employers were extremely sceptical of them back in the 1970's and carried out extensive in-house testing before introducing them. Critically, they determined that adequate crimp pressure was very difficult to achieve repeatably with hand crimp tools and invested in a lot of expensive ratchet crimp tools. Properly used, they found that crimp connectors were more reliable than soldered connections onto relays, contactors etc. as well as being faster to make

A cautionary tale ... we came within a whisker of having a serious fire on board when a soldered connection on the feed from the engine alternator to the electrical control panel failed thus sending around 30 amps up the field coil wire which promptly overheated and set fire to the insulation on the adjacent cables

Fine but how many boats can be sure that they keep ANy amount of salt away from all their electrical connections?

Chas

 

[grumpy_o_g]

Although this seems like a good 'belt and braces' solution, it also creates a hard point where the solder ends, which is a potential point of failure if there's any vibration on the connector. A properly-made crimped connection should be perfectly adequate on its own. If you test the crimp by pulling on the cable afterwards, you'll soon find out if it's any good!

Every time the crimp/solder question appears someone comes up with this myth about "you mustn't solder because it creates hard point". It is utterly and totally wrong to think crimping avoids that problem. The myth came about because people who didn't know what they were doing used far too much solder and ended up with it wicking down the cable under the insulation for some distance and usually then also didn't support the cable properly.

There is always a hard point created between the connection and the flexing cable regardless of the type of join - on a crimp it's where the mechanical crimp ends and on a solder joint it's where the solder ends. The correct thing to do is to tin the cable (even if it's already tinned) such that the solder only goes up to the insulation or just beyond. Then attach mechanically as well, whether by crimp or stud terminal or whatever. The important bit is to support the cable properly. The support provided by a heatshrink cover on a crimp terminal is not adequate unless there is no vibration present. If the terminal has some kind of clamp to hold the cable on the insulation that's better but still not enough. Don't test crimp joints by pulling on them - they aren't designed to resist in tension and you could actually weaken a perfectly good connection. Just use the right crimp on the right cable (that means both size and type) and make sure you use the right jaws in the right tool and locate everything correctly. If you are worried whether or not you're getting it right then try a few practice crimps and cut them in half with a hacksaw. You can pull on the practice crimps as well if you want but it won't prove much - if it's so loose you can feel it move you've got it really, really wrong but the fact that it doesn't move doesn't mean a guaranteed good connection.

Regarding lubrication/protection I would avoid anything that is penetrative unless it's specifically designed for the job (e.g. WD-40). I have no experience of trying it but I can't help thinking having an insulating lubricant penetrating into the connection wouldn't be a good thing.

 

[grumpy_o_g]

Brigantia, you are absolutely right about not using solder for the mechanical connection but hundreds of thousands of a/c hours suggest otherwise on not tinning the cable before crimping - I suspect the problem lies with manner of tinning. Done properly you should still be able to see the lay of the cable on the exposed conductor after tinning and the solder should stop at the insulation or within a mm or two of it at most. If you can't you need to get the excess solder off of it. Screw terminals (as opposed to stud terminals with spring/lock washers) I would simply not allow on any critical system. As far as crimp pressure is concerned I agree this is one of the biggest causes of bad crimps. The pressure should be determined by the crimping tool - it should be easy to reach the required pressure after which the tool should prevent any further compression. The AIB/AAIB have examined thousands of tinned cables in crimped connections and it has never found an issue. On Nimrods and Shackletons I have seen corrosion after salt water has wicked down the cable on an untinned crimp connection though. That's one of the reasons the Airforce tinned nearly all joints I believe. The other thing tinning does is ensures a clean contact area. If there's any significant contaminants in the cable then the tinning will either flush them out to the surface where they can be seen or it simply won't take and it will be pretty obvious. I can't believe someone would rely on a soldered connection on a cable that can take 30A - that's just stupid. Even on an aircraft where weight and space are critical that would be a crimped ring connector on to a stud terminal. At that size they actually weren't normally tinned as the cable was so big that corrosion was less of a problem (and easier to see) and the pressure from the crimping tool was huge.

 

[Csail]

look on screwfix and get self amalgimating tape.
http://www.screwfix.com/p/self-amalgamating-rubber-tape-19mm-x-10m/61749

good for loads of other things.

 

[mitiempo]

Marine wire should be tinned copper to start with - further tinning is not necessary and can interfere with the quality of the crimp.

The proper crimper is required and the better ones do not release until the crimp is complete - all crimps should pass the pull test.

Solder adds nothing to a good crimp.

ABYC allows solder as long as it is not the only means of connection. A good crimp connector has either a nylon cover or a heat shrink cover. Soldering will destroy it.

If the connector does not have heat shrink to start with adhesive heat shrink should be added.


http://www.pbase.com/mainecruising/wire_termination

 

[Bobobolinsky]

Does it? I think the stuff I use as an anti-seize compound is probably polybutylcuprysil. ( one tub is .. its labelled) That's Ok

No advantage in using Copaslip ... it's not electrically conducting.

I use silicone grease on electrical connections.

Come on Vic you're the chemist Cuprysil gives it away.

Anyway copperslip or Cuprysil will corrode the ally terminals