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S&S Swan Maintenance - 12V wiring, LED lights, CAUTION and advice please
11 January 2014 - 23:57
#1
Join Date: 01 January 2011
Posts: 36

12V wiring, LED lights, CAUTION and advice please
Dear Forum,

I hope you can help with this.

During "Scotch Bonnet"s recent adventures the cabin lights, I imagine the ones we left on, scorched the roof lining and to varying degrees melted the plastic light lens of the original Hella style lights. She must have come within a whisker of having a fire to add to her worries. I had noticed scorching under the light in the forward cabin when we took delivery of "SB" in New Zealand and had an electrician look at it but he couldn't explain when it might have occurred and said all was now in order. Installed in the boat were LED globes into the original lights and I can only guess these were the problem. For whatever reason fire onboard didn't happen and the lights went on the long list of jobs to do.

As mentioned else where on the Forum choosing replacements which satisfy the necessary criteria is not straight forward. I decided on LED for all the well known reasons, after much research Hella EuroLED Warm White / Red with polished 316 stainless rim.

I hope they will look good, they weren't cheap! In the installation instructions they caution use of no larger than a 2A fuse which I suspect is associated with our previous fire issue. The old lights with the LED globes were still protected only by the 15A circuit breaker, but still why they heated up in the first place is unknown. Can I duck off on a tangent here, when we had the rigging replaced in NZ the mast was rewired and replaced all lights with LED.

Having now had the new rig installed, again with Hella LED lights on the mast, the same error SEEMS to have been perpetuated. I am trying to get from the mast builder the model number of the lights installed or better still the installation instructions to confirm this but neither when the NZ installation was done nor the recent one were the LED lights fuse protected, they are still only protected by the 25A circuit breaker. I suspect there will be specific directions that they be fused maximum 2A - 5A, I asked our mast builder who has been installing these lights for years and he has never heard of this requirement before, we'll see shortly.

But back to the cabin lights. I had thought to install a fuse block behind the electric panel with separate 2A fuses protecting each of the forward, mid and aft lighting circuits, having only 3 or 4 ceiling lights on each circuit each drawing 0.33A this should have been ok but having looked deeper I see that the little flip out reading lights are on the same circuits and they still have original globes, there are also power take offs for 12V outlets wired in to the lighting circuits. So I will have to put individual in line fuses in the roof lining for each light. I think probably the little mini blade type waterproof fuse holders, there are a lot of negative reports about corrosion and bad connections on in line fuse connectors, does anyone have any thoughts?

Challenge now is how to wire them up, the issues are: leading in to and out of the original lights are 4 wires, a positive and negative in and out, each approx 4mm diameter, the LED light has 2 x 2mm diameter pigtails, a positive and a negative (it actually has a third wire for a dimmer switch which we won't use and will tape off - would this be live, do we need to worry about leaving it loose?) So I need to join the positive in and out and a wire to the new fuse; then the negative in and out and the negative pigtail from the light; and the positive out from the fuse to the positive pigtail to the light. I have read so many different opinions of how to join wires and none really helpful about how to join 2 x 4mm and 1 x 2mm. Next question is whether we really want crimped, soldered, heat shrunk permanent joins holding the lights, and the roof lining in place? Over Christmas we found a leaking genoa sheet track and had to take down a lot of roof lining, if the lights had been wired on at this stage this would have been a problem. So do we use bullet connectors on the cabin side of the roof lining? Or bullet connectors on the underside of the roof lining and have someone hold it lowered down before connecting / disconnecting? But most books and articles I read on the subject don't recommend bullet connectors so do we install a single, probably 1A fuse block (can you buy such things?), on the underside of the deck then ring terminals on the 4mm negative in and out and positive in and out and the negative pigtail on the light and one side of the fuse? Then permanently join the other wire of the fuse and the positive light pigtail with a heat shrunk butt connector? It seems like a lot of wiring for a single light? Any experienced forum members' advice greatly appreciated as this is causing me a headache, I should have posted months ago but until now I don't think I even understood the questions properly and even now I'm not sure I've asked them clearly! For those with as little experience as me please BEWARE of LED lights, don't trust the experts and read the instructions carefully. Best wishes to all for a happy Swan filled 2014, Andrew "Scotch Bonnet" 41/39

12 January 2014 - 00:49
#2
Join Date: 01 January 2011
Posts: 36

Please disregard my last thoughts on a possible solution, it won't work! Thanks Andrew

12 January 2014 - 13:32
#3
Join Date: 02 January 2008
Posts: 1547

Dear Andrew
Would suspect that the bulbs in her when abandoned may have been a halogen type, they heat up considerably. Another possibility is corroded contact surfaces causing high resistance.
Referring to fuse sizes I would suggest that they are dependent on cable sizes, and what you actually are doing.
If you put in LEDs in an existing system the cables are oversize, and the fuses too, but I doubt that it would be necessary to reduce fuse sizes.
If you instead do a new installation with LED lights having much lower consumption, the cables will be sized accordingly, and small fuses are required.
Suggest you ask Hella whether they see a difference here.
Kind regards
Lars

13 January 2014 - 09:24
#4
Join Date: 01 January 2011
Posts: 36

Dear Lars
thank you for your reply.
I am sure the offending bulbs were LED and not halogen, I may still have one in the spares and if so will post a picture but I have been throwing them away whenever I find them!.
The Hella cabin light instruction sheet says “lamp must be protected by a fuse rated at 2 amperes maximum”, I haven’t yet been able to track down the instruction sheet for the mast lights to see what that says about fuse protection. It seems that although the boat’s light wiring is approx 4mm diameter and the pigtails on the cabin light are approx 2mm in diameter it is not only the pigtails that Hella want to protect but the lamp itself.
Your suggestion that corrosion on the contact surfaces may have caused high resistance sounds possible from my limited experience and also a reason I would have thought why it would be necessary for anyone installing LED globes to also review their fuse protection as the amp draw necessary to generate dangerous heat in an LED globe may be less than the normal amp draw, and hence fuse protection, of a conventional globe. I imagine that corrosion on a bulb’s contacts, and hence increased resistance, is almost an inevitability over time?
Kind regards
Andrew “Scotch Bonnet” 41/39

13 January 2014 - 11:42
#5
Join Date: 02 January 2008
Posts: 1547

Dear Andrew
Treating the contact surfaces occasionally with a contact spray, for example WD-40, will
improve the situation.
Kind regards
Lars

15 January 2014 - 17:01
#6
Join Date: 02 February 2007
Posts: 202

Dear Andrew,
Being french speaking I am not sure I understand all the subtleties of your memo, but...
As far as we are concerned we have installed LED lights all over the place in Soeur Anne (41-022) be it cabin lights or mast lights and have stayed with the original breakers without any problems for many years. As said by dear Professor circuit breakers are there in the first place to protect the wires, not the lamps. In cas of a short circuit the fuse is supposed to blow before the insulation on the wires start to melt... One IMPORTANT thing you must be careful about is to buy regulated LEDs or install a regulator on the light circuit, as LEDS do not like at all high voltages. If you don't you risk blowing them when the alternator is charging at 14+ volts. So, if you have the original wires I suggets you stay with the original circuit breakers.
Another point: we always weld all our wire junctions and never rely on crimped ones.
Kind regards, and all the best to Scotch Bonnet and her crew!
Philippe

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