fuse panel rewire - idiots guide

robmcg

robmcg

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Anyone know or recommend an idiots guide to rewiring a new fuse panel. Just looking to tidy up the boat wiring which suffers the usual 30 years of add on equipment. Bit of a 12 volt novice but hoping it won't be a daunting task.
Rob
 
More advice to come no doubt, but for starters I would suggest making a diagram of how you plan everything to work.

Maybe invest a few quid in some cable markers. Maplin do a neat set. It is easy to get wires mixed up when you have several loose.

When you start, try to get all the negative lines together on a purpose made "neutral bar" or post. This effectively halves the job as you only then have to think about the positive supply and relevant trip protection.
 
Fuse panel

I think that fuse and switch panels are often over done. This especially if you have a master switch at the battery and on off switch on things like radio.
Fuses are designed to protect the wiring and to a lesser degree the wiring inside a radio etc. It is vital to have a fuse which will trip at a current less than the current at which a wire gets so hot as to make a fire hazard. The fuse also must have a margin of safety over the normal max load current of the service.
People however consider that it is vital to have a separate fuse for each device or service. This on the basis that failure through fuse blow of one circuit will not affect other services.
I tend to disagree in that fuse blowing or CB tripping is a very rare event.
So I reckon that many services can share the one fuse and switch. (consistent with the above requirements)
So my little boat with just VHF Nav lights and cabin lights has just one fuse at the battery.
On what might be called the control panel I have a switch for nav lights and a switch for cabin light and a socket for solar panel connection.
If you have fuses at a panel in a convenient place it is almost certain that you will have a long pair of wires from battery (switch) to the panel. These will be unprotected by fuses unless you also have a largish common fuse at the battery. So any short of the wires before the panel will give you a fire.
I get the feeling that the commercial fuse/switch boards are a con by manufacturers who love to pay to owners desire for a complex looking panel.

Anyway just a few thoughts contrary to popular opinion. Don't omit the fuse like old Maury whose only service was a mast head nav light. He refitted the light after work on the mast. Connected it to the battery and walked down the jetty to see if it was alight. The mast had squashed the wires at the hinge and provided a perfect short circuit. The wiring running from the battery then got red hot and burnt the flash new sails that were resting against the wire. Result huge insurance claim for new sails. very scary.
olewill
 
Are you rewiring the whole boat, or just replacing the panel? I did the former because having seen the bodges and corrosion in the parts I looked at, I didn't trust any of the rest of it. But maybe your actual wires are ok and you just want a neater panel.

If you're not very confident then I second the advice to draw everything out first. Including an "as it is now" diagram unless you're ripping it all out and starting from scratch.

The ultimate "neater panel" is a custom-made one :)

Pete
 
I completely rewired our boat last year to tidy up the mess behind the fuse panel and to change the corroded joints and deal with 30 years of additions and removals.

If you do a complete rewire then you will definitely need to mark the cables. The chances are you will just buy a big roll of cable (I bought 100m of marine tinned wire) and run all the cables with the same wire. On my boat each circuit had different colours in the original wiring loom, but there was no way I was shelling out for 20 different colours of cable. I mark my cable by wrapping white insulation around the cable once and stick the two sticky ends together leaving about a 2" tag, then write on it in permanent marker.

I would have everything you can on separate switches, 16 should be plenty, that way you can only turn on what you need and save power. But perhaps have some things that need to operate together on the same switch, eg I have my VHF and a small GPS (which uses almost no power) on the same fuse, the GPS supplies the data to the VHF for position etc so they are always on together.

A complete rip out is often easier than trying to patch in old wiring, as you simply start at the lamp/VHF/pump etc run it back to the fuse panel, connect the negative to the busbar and the positive to the correct switch. If your switch panel is not pre labelled plan which things you want together before you start so that you can cut the cables ends to the correct length and keep it all as neat as possible. Consider using cable ties/mounts to hold it all in position and keep it neat.

If you are keeping the old wiring you need to identify the wires from each lamp/VHF etc as it arrives at the back of the fuse panel, mark it up and then rip out all of the accumulated **** wiring that leads to nothing. Just be brave and hack it all out it is very satisfying to ditch it all and it looks much better before you have done anything with the panel.

My advice on connectors is to tin the wire, then crimp the connector on, then to solder the crimp to the connector.

Good luck

Ross
 
Ross D said:
My advice on connectors is to tin the wire, then crimp the connector on, then to solder the crimp to the connector.
Click to expand...

I don't have any personal experience, but this is usually condemned as bad practice by people whose opinions in the matter I respect. Crimps or solder are each fine, but not mixed.

Agree with everything else in your post though. It was very satisfying pulling all the ragged old cable out of my boat and replacing with new. I used a Brother label-maker (like a modern version of the old Dymo) to print cable markers for all my wiring into the new control panel.

Pete
 
prv said:
I don't have any personal experience, but this is usually condemned as bad practice by people whose opinions in the matter I respect. Crimps or solder are each fine, but not mixed.
Click to expand...

I'd be interested to know if anyone has any reasons why soldering crimps onto wires is not recommended.:confused:

It is what I have always done as it prevents any corrosion in the future causing a bad connection within the crimp. Most crimps are coated in solder, which melts into the tinned end of the wire fusing the lot together.

I suppose that the tinned wire is slightly stiffer which may fatigue and snap, but provided you have the proper strain relief (which you should have at a crimp) it will not be a problem.

Ross
 
Ross D said:
I'd be interested to know if anyone has any reasons why soldering crimps onto wires is not recommended.:confused:

It is what I have always done as it prevents any corrosion in the future causing a bad connection within the crimp. Most crimps are coated in solder, which melts into the tinned end of the wire fusing the lot together.

I suppose that the tinned wire is slightly stiffer which may fatigue and snap, but provided you have the proper strain relief (which you should have at a crimp) it will not be a problem.

Ross
Click to expand...

That is the reason
It is said that movement, vibration etc, causes the wire to work harden, fatigue and ultimately break where the soldering ends.
 
VicS said:
It is said that movement, vibration etc, causes the wire to work harden, fatigue and ultimately break where the soldering ends.
Click to expand...

As Ross said, though, there should be strain relief to prevent that.

What I heard was something about solder cold-flowing out of the crimped joint over time, leaving it loose enough to get hot. Also that the crimp is designed to pressure-weld into the copper, which it won't do if there's a layer of solder in the way.

Here's a few threads where people discuss the problem (again, I'm just reporting this, I'm not an expert on the subject):

http://www.ybw.com/forums/showthread.php?t=248440
http://www.ybw.com/forums/showthread.php?t=274438
http://www.ybw.com/forums/showthread.php?t=290768

Pete
 
Ross D said:
I suppose that the tinned wire is slightly stiffer which may fatigue and snap, but provided you have the proper strain relief (which you should have at a crimp) it will not be a problem.
Click to expand...

I quite often use solder crimps, washers with solder tabs, or a plain soldered wire to wire join. Provided they are covered with a decent bit of heat-shrink to restrict movement, there should be no problem.
 
Having read through those threads I will be sticking to my technique of tinning the end, then crimping, then soldering the crimp to the wire. This ensures that there is both a mechanical and electrical join.

Quite a number of people in the threads recommended soldered joints, because in their experience crimped ones fail and need replacing. This is also my experience of crimps onboard yachts. I agree that correctly crimped joins should not fail, but if they are not done correctly then they are likely to fail, or corrode and fail. You should definitely not tin the end and then only crimp on a connector, this is bad practice as the solder will not crimp tightly and will come loose over time.

A properly supported soldered joint is extremely unlikely to fail from vibration work hardening the solder and it snapping. The joint and any soldered part of the wire should be properly supported. Yachts are not F1 cars, my engine certainly does not rev at 25000 rpm which would shake the yacht to bits, but it does get damp and wet.

Soldering is reliable in a marine environment, where electrical problems are usually caused by poor connections rather than snapped wires.

Ross
 
The main reason for soldering crimps is if the cable gets hot, the solder melts and the joint loosens as the only physical contact with the cable is the solder, a crimp reinforces this connection.

The problem with soldering crimps is the hard spot it creates that is a source of failure in the joint.

Remember the fuse on a cable is rated at the cables design, not the solders design.

Only one or the other should be used, of course if you have adequate fuse protection nearest the battery, the worst that can happen is the fuse blows, if you don't then the boat catches fire, simples.
 
Last edited:
ColleyV8 said:
The main reason for soldering crimps is if the cable gets hot, the solder melts
Click to expand...

Even the lowest grade of solder melts at 183 C if your cable reached this temperature all of the PVC insulation would have melted off and your boat would probably already be on fire.

The whole point of why I solder and crimp and then solder the two together is to ensure a good electrical contact after years in service. The hard spot, work hardening etc can be applied to any soldered joint, and if adequately supported is not going to happen. But go over any old yacht and there will be loads of crimped connections and jobbed on bits with poor continuity and electrical problems.

If you look at any thermal image of electrical systems, the hot spot is always the poor electrical continuity at the connections.

Ross
 
ColleyV8 said:
The main reason for soldering crimps is if the cable gets hot, the solder melts and the joint loosens as the only physical contact with the cable is the solder, a crimp reinforces this connection.

The problem with soldering crimps is the hard spot it creates that is a source of failure in the joint.

l
Click to expand...

Utter nonsense.
 
Assuming that the the circuits are working OK, I suggest taking a few pictures of the existing wiring so that in months to come, you have record of when it used to work....
 
I've done my wiring twice, the second time (2 yrs later) to do it properly as I ran out of time first time around. My tips (in no particular order):

1. Leave yourself plenty of time, and then double it, especially if you are heading off for a journey.

2. As you take off existing cables from switches, fuses, bus bars etc... Mark them - white PVC tape & a permanent marker. Biro on masking tape is not good.

3. Take photos (aren't phones great) before you take anything apart.

4. Get the right tools - crimper, wore strippers, side cutters, gas soldering iron, mains soldering iron, solder sucker - it makes all the difference.

5. Buy good quality tinned copper cable, more than you think you need, in the sizes you think you will need - I find 1.5mm and 2.5mm (sq) is good for most things EXCEPT feeds to / from batteries and main isolator switches, and heavy current items.

6. Add a few extra 12v outlets while you have all the panels off

7. Hinge your switch panel so that when you need to dive in to your handiwork afterwards it is easy

8. Use things like heatshrink, adhesive heatshrink, cable ties, lacing cord and / or plastic spiral wind to keep it all tidy and to provide strain relief.

9. Make sure you leave enough wire to the switch panel so when you hinge it out it actually hinges down / to the side all the way (hard lesson :) )

9. Use bus bars for the -ve's and for any common +ves

10. I favour a switch& fuse for each item (within reason - not each individual light / 12v outlet) - so if one thing blows it doesn't take out other items/ You can guarantee that it will happen at the worst time when you can't sort it easily ( you know, lee shore, ebb, night, coming into a poorly marked rock infested harbour).

11. Spend time making all the cable runs very neat

12. As you have everything fused at the switch panel, get rid of any in-line fuses - the last thing you want to be doing is trying to take apart your boat on a lee shore, at night, etc.... to get to an inline.

13. I have found switch panels hideously expensive but the Lazilaz range are fairly priced and do the job admirably. Beware on some of the smaller ones 'cos some of the switches are on-off-on. Also I would always favour a panel with indicator lamps / LED's so you know if something is on or off.

14. Put a light where your wiring is - these are great and nicely priced and a simple pull cord switch inline gives you control. I also added a couple to my engine bay while I was at it.

15. If you are running lots of new wires around the boat, leave in pull cords (labelled) for the future.

16. Use heat shrink / adhesive filled crimps - fleabay is a great source

17. Label all your new wires, again either using a Gucci marking system or pvc tape and marker pen - the P-touch type labels go black when you use a heat gun near them (another hard lesson) to shrink heatshrink.

18. Label the back of the switch panel so when it is out you don't have to keep turning it over

19. Use single core wire in either red or black - multi-core / twin core seems like good idea but it is a fair bet that your -ve bus bar will be a distance from your switch panel so you will end up stripping the outer sheath back anyway.

20, Draw it all out first, marking cable size and colours too. Then when you do it and the inevitable changes happen, mark them up there and then - you are unlikely to remember everything afterwards. Then re-do your drawing and keep a copy on the boat.

21. Planning is key - you will be buying components and items you have never bought before and the drawing can help you calc quantities of things like heat shrink - there is nothing worse than running out and bodging it 'cos you can guarantee that you will regret your bodge on a lee shore, at night blah blah blah.

22. Think what you may add in the future (ais? RTE? Toaster?) and put the wires in now, labelled, while you have it all apart.

23. Avoid buying stuff at chandlers – fleabay and caravan sites are good value. IEM Services are especially good I found, and if you don’t see what you want on their site or need advice just phone them

These sorts of jobs are well within the capability of Mr Joe average with good planning so go for it.
 
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