A question about lights and switches and splicing into cables. (1 Viewer)

[CamperJack]

Lets say I have two puck lights wired in parallel in the ceiling, which come on via one switch.

I then have a pair of wall mounted reading lights with their own switches built into the bases.

Could I splice into the positive and negative wires running to the puck lights (using a scotch lock for example) to power the reading light?

Could the reading light then be switched on while the ceiling lights are switched off and vice versa?

Thanks in advance for answering what must be another of my obvious questions! I hope everyone is keeping well with everything that's going on. Working on my van while the pub is closed is keeping me sane (as I have ever been ). I've been building draws today. I'll not be doing that again in a hurry! Draws are hard.

 

[Jev88]

It may depend on how the existing lights are wired. Will power reach the reading lights if the main light is powered off?

 

[CamperJack]

It may depend on how the existing lights are wired. Will power reach the reading lights if the main light is powered off?

Nothing is pre-existing. This is how I plan to light the back of my van, above my bed. I’ve not installed any lights yet.

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[Mr Chrysalis]

I don’t trust scotch locks. I’d prefer to run new wires from a separate fuse, or from a piggy back fuse if you don’t have a spare
Amazon product ASIN B07ZKJHB3V

 

[JohnJan]

As above, use a dedicated wire/fuse.

 

[Googlebot]

I always use scotch locks.

Much quicker and easier and as long as they are accessible, I don’t see the issue.

Sorry, I know some people hate them.

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[funflair]

Lets say I have two puck lights wired in parallel in the ceiling, which come on via one switch.

I then have a pair of wall mounted reading lights with their own switches built into the bases.

Could I splice into the positive and negative wires running to the puck lights (using a scotch lock for example) to power the reading light?

Could the reading light then be switched on while the ceiling lights are switched off and vice versa?

Thanks in advance for answering what must be another of my obvious questions! I hope everyone is keeping well with everything that's going on. Working on my van while the pub is closed is keeping me sane (as I have ever been ). I've been building draws today. I'll not be doing that again in a hurry! Draws are hard.

If your reading lights are powered from the wires to the ceiling lights then Yes you will be able to switch them all on together assuming the reading light switches are in the on position then you can switch them off individually but you can not have the reading lights on without the ceiling lights, just think of it as a master switch and two slave switches at the reading lights.

Have a look at Wago connectors, https://www.wago.com/gb/electrical-...stallation-terminal-blocks-and-connectors/221

 

[tonyidle]

I always use scotch locks.

Much quicker and easier and as long as they are accessible, I don’t see the issue.

Sorry, I know some people hate them. ☹

With a passion . They cut the wire to which they are attached, they're huge by comparison with any alternative, and they are incredibly ugly. And that's when used in a dry location. Get them damp and they open up a whole new world of fault potential.

 

[Googlebot]

With a passion . They cut the wire to which they are attached, they're huge by comparison with any alternative, and they are incredibly ugly. And that's when used in a dry location. Get them damp and they open up a whole new world of fault potential.

I don’t disagree, that’s why I hide them and keep them dry.

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[Lenny HB]

I always use scotch locks.

Much quicker and easier and as long as they are accessible, I don’t see the issue.

Sorry, I know some people hate them. ☹

Terrible things very unreliable. If you want an easy reliable way of connecting wires use Waco connectors and they are much easier to use.

 

[Pausim]

I have stopped using Scotchlok and now use Wago connectors.

Wago 221 Series Compact Wiring Connectors

The new Wago 221 series wiring connectors are 40% smaller than the 222 series, helping to further reduce space inside junction boxes. The compact, tool-less design is a great way of connecting cables. They are suitable for use with stranded and solid cables and are ideal for use in domestic or...

www.expertelectrical.co.uk

 

[Bucket]

Lets say I have two puck lights wired in parallel in the ceiling, which come on via one switch.

I then have a pair of wall mounted reading lights with their own switches built into the bases.

Could I splice into the positive and negative wires running to the puck lights (using a scotch lock for example) to power the reading light?

Could the reading light then be switched on while the ceiling lights are switched off and vice versa?

To keep it simple, you want to access a light cable that is always live and splice off that to your new lamp, as long as that has it's own switch it will operate independently. If there's no switch built-in, add one in parallel on the live line. Make sure you retain continuity by running the circuit back to where you started. As others advise, if in doubt use an in-line fuse holder.

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[Pausim]

You are more likely to find a permanently live wire at the switch than at the light (except if the switch is part of a 2 way system where you can turn the lights off and on at different places).

 

[Bucket]

You are more likely to find a permanently live wire at the switch than at the light (except if the switch is part of a 2 way system where you can turn the lights off and on at different places).

My expertise is domestic installations and I'm less sure about vehicles. In the home a modern lighting circuit has the live and return looping in and out of the ceiling roses so we would always look up there for a viable spur. Switches can be investigated as mentioned but usually they are too tight for this purpose.

 

[Pausim]

My expertise is domestic installations and I'm less sure about vehicles. In the home a modern lighting circuit has the live and return looping in and out of the ceiling roses so we would always look up there for a viable spur. Switches can be investigated as mentioned but usually they are too tight for this purpose.

I have no doubt you are correct re domestic circuits but think 12V motorhome circuits are different.

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[Bucket]

I have no doubt you are correct re domestic circuits but think 12V motorhome circuits are different.

Can't argue with that. However electricity behaves the same and the same basic rules apply. By all means investigate a light switch if it's closer and accessable.

 

[Ian Bosman]

Lets say I have two puck lights wired in parallel in the ceiling, which come on via one switch.

I then have a pair of wall mounted reading lights with their own switches built into the bases.

Could I splice into the positive and negative wires running to the puck lights (using a scotch lock for example) to power the reading light?

Could the reading light then be switched on while the ceiling lights are switched off and vice versa?

Thanks in advance for answering what must be another of my obvious questions! I hope everyone is keeping well with everything that's going on. Working on my van while the pub is closed is keeping me sane (as I have ever been ). I've been building draws today. I'll not be doing that again in a hurry! Draws are hard.

The better way than scotch locks is to splice into the wires and solder then insulate, that way you have a much lower resistant connection and safer. Scotchlocks eventually have corrosion at the join which is a very small piece of copper alloy, probably brass, pinching the internally wiring, great for a temporary job but not a permanent job. All my wiring in my van has been by soldered spliced joints ie remove the insulation for a short length, separate the internal wire strands into two, push through the gap the new wire, solder that up then insulate with insulation tape ensuring it is well past the exposed wires.
Yes you do have to do it for both positive and negative wires. As to whether you can have all on at the same time depends on the circuit fuse or trip as to the loa possible but bear in mind LED lights run at very low current rates so if you are replacing, say tungsten with LED then you would be OK most likely.

 

[Pausim]

The better way than scotch locks is to splice into the wires and solder then insulate, that way you have a much lower resistant connection and safer. Scotchlocks eventually have corrosion at the join which is a very small piece of copper alloy, probably brass, pinching the internally wiring, great for a temporary job but not a permanent job. All my wiring in my van has been by soldered spliced joints ie remove the insulation for a short length, separate the internal wire strands into two, push through the gap the new wire, solder that up then insulate with insulation tape ensuring it is well past the exposed wires.
Yes you do have to do it for both positive and negative wires. As to whether you can have all on at the same time depends on the circuit fuse or trip as to the loa possible but bear in mind LED lights run at very low current rates so if you are replacing, say tungsten with LED then you would be OK most likely.

I agree about scotchlocks but I thought motor manufacturers and constructors avoided soldering joints wherever possible because they can fail due to vibrations. Crimped joints are favoured but the Wago connectors are well made and easier to use.

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[CamperJack]

Thanks to all for the replies.

The better way than scotch locks is to splice into the wires and solder then insulate, that way you have a much lower resistant connection and safer. Scotchlocks eventually have corrosion at the join which is a very small piece of copper alloy, probably brass, pinching the internally wiring, great for a temporary job but not a permanent job. All my wiring in my van has been by soldered spliced joints ie remove the insulation for a short length, separate the internal wire strands into two, push through the gap the new wire, solder that up then insulate with insulation tape ensuring it is well past the exposed wires.
Yes you do have to do it for both positive and negative wires. As to whether you can have all on at the same time depends on the circuit fuse or trip as to the loa possible but bear in mind LED lights run at very low current rates so if you are replacing, say tungsten with LED then you would be OK most likely.

In terms of amp rating etc, I'm using 6mm wire because I have it and its not much more expensive then 4mm. The 6mm wire I have is rated at 56 amps. The rating of the reading lamps are 3W (or 0.25A at 12V). There are 4 so max 1A. The puck lights are 0.4A each. I want 5, so that will be 2A. Total amps for lights is 3A. I may add strip lights or more puck lights to the underside of the high level kitchen cabinets. But I haven't built them yet!

What I propose is to partition the lights into two systems - front and back. For the front three puck lights and the under kitchen lights on one system, going out from and returning to the 12v fuse / negative box. And another system for the back of the van / above the bed - 4 reading lamps and two puck lights.

I would like to be able to switch on the lamps individually. In addition to be able to switch on either the back puck lights or the front or both at the same time.

The piccy below is a little diagram I made up, which might better illustrate what I plan.

What I really want to know is if I tap into the wire running to the last puck light to power the reading lamps will the reading lamps be able to come on if the puck lights are switched off?

 

[CamperJack]

I agree about scotchlocks but I thought motor manufacturers and constructors avoided soldering joints wherever possible because they can fail due to vibrations. Crimped joints are favoured but the Wago connectors are well made and easier to use.

I thought similar about wago. They rattle about and disconnect so are not recommended in auto industry. Might be wrong. (Likely).

 

[CamperJack]

To keep it simple, you want to access a light cable that is always live and splice off that to your new lamp, as long as that has it's own switch it will operate independently.

If the puck lights are controlled by a switch is the +tive to them still live when the puck lights are switched off?

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[CamperJack]

Diagram updated to show location of puck light switches.

 

[St3v3]

eh?

If the puck lights don't have power, and the reading lights are fed from them, then the reading lights won't have power.

 

[CamperJack]

eh?

If the puck lights don't have power, and the reading lights are fed from them, then the reading lights won't have power.

The puck lights will be powered by connecting them to the fuse box. They will be wired in parallel.

The thing I do not understand though is if I can connect into that line for the lamps and expect to be able to turn the lamps on if the pucks are off. Will turning the pucks off mean it is impossible to get power out of that line to the pucks for the lamps?

Sorry if the answer is blindingly obvious.

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[St3v3]

. Will turning the pucks off mean it is impossible to get power out of that line to the pucks for the lamps?

Sorry if the answer is blindingly obvious.

Yes it would mean that. Think about the switch as a valve in a water pipe if it helps. Switch off = valve closed, which means no water in any of the pipes after the valve (switch)

I think you need someone else to wire this up for you! Please tell me you're not doing any mains wiring or gas install...

 

[Pausim]

I thought similar about wago. They rattle about and disconnect so are not recommended in auto industry. Might be wrong. (Likely).

Not heard that before. Generally thought safe because of low insertion force and high retention force. Possibly some cheap copies about that are not so well manufactured.

 

[CamperJack]

Yes it would mean that. Think about the switch as a valve in a water pipe if it helps. Switch off = valve closed, which means no water in any of the pipes after the valve (switch)

I think you're misunderstanding me because I'm explaining myself badly. What if you spliced into the wire after the fuse box supply but before the puck light's switch? That way the wire would not be broken before it got to the puck.

Or would it just be easier to have the pucks on one system and the reading lights on another?

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[Ian Bosman]

I agree about scotchlocks but I thought motor manufacturers and constructors avoided soldering joints wherever possible because they can fail due to vibrations. Crimped joints are favoured but the Wago connectors are well made and easier to use.

The point is you achieve a mechanical, non soldered joint, first then solder it assuring that you have used the correct heat and it has penetrated into the wires and the joint is thus being made permanent

 

[Phill D]

the way you have the switch wired to the pucks when that positive is broken ( switched off ) there is no power to any of the others

 

[St3v3]

I think you're misunderstanding me because I'm explaining myself badly. What if you spliced into the wire after the fuse box supply but before the puck light's switch?

That would be fine, but it's not what you've drawn.

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