Wiring query

[mcc1979ian]

Morning folks, hope everyone’s well, 

a while back I posted about some wiring I was about to attempt, Iv got everything wired in but Iv melted a wire on my led bar, looking at my diagrams do we think Iv maybe gone too thin on cable. I used 11 amp cable from fuse to switch and back to relay plus from fuse to relay on most circuits. Panicked my baby was gona go up in flames when the smoke started but got the feed pulled straight away. 
 

Iv numbered everything so that I know where all my cables go, just have a funny feeling Iv scrimped on cable. I’d attach this to my original post but for some reason I can’t find that one

[Maverik]

It would be useful if you highlighted which wire you have a problem with on the original wiring diagram - I had a quick look through your old post but it wasn't so clear.

 

From what I understand, you've used 11amp rated wiring for the Relay switching system for your LED light bar?

To activate a 12v relay it only usually uses max 0.5amp to switch them so 11amp wire should be fine.

If this is the situation then you've got a problem.

 

Also these ultra bright LED's can pull some Amps - what light bar have you got

 

Ok on looking at your photo, have you fused the switch circuits as well as the relay supply circuits?

[Maverik]

 

 

[FridgeFreezer]

Looking back at your post on the light bar it suggests it's a 300W one, which would be 25A at 12v if the spec isn't massively lying like they all do... which would want 3mm² in thinwall cable and ~4mm² in regular. (calculator here)

I'd also ask if the cable is stuff sold by grown-ups or random copper-coloured aluminium junk sold on eBay from the far east... there's a lot of fake cable out there. There's also a lot of fake fuses...

If you've used 11A cable you should at absolute most be running a 10A fuse for the circuit, but given the way real-world fuses & cables behave, 7.5A would be about the max I'd be trusting it with. My general rule is >50% over-spec on the wire, so if something's drawing more than about 5A I'll step it up to the 1mm / 16A rated stuff.

I'll also mention that on my installs I've taken to fitting a MIDI fuse at the battery feed end, 50-100A are available, based on whatever the expected total load is going to be, that way if the big feeder cable should short on anything it is at least protected from making a small problem into a very big one.

Oh and next time buy a few different colours of wire, it makes life so much easier!

[mcc1979ian]

6 hours ago, Maverik said:

It would be useful if you highlighted which wire you have a problem with on the original wiring diagram - I had a quick look through your old post but it wasn't so clear.

 

From what I understand, you've used 11amp rated wiring for the Relay switching system for your LED light bar?

To activate a 12v relay it only usually uses max 0.5amp to switch them so 11amp wire should be fine.

If this is the situation then you've got a problem.

 

Also these ultra bright LED's can pull some Amps - what light bar have you got

 

Ok on looking at your photo, have you fused the switch circuits as well as the relay supply circuits?

Hi, aye I fused both circuits, could that be my issue?

[mcc1979ian]

4 hours ago, FridgeFreezer said:

Looking back at your post on the light bar it suggests it's a 300W one, which would be 25A at 12v if the spec isn't massively lying like they all do... which would want 3mm² in thinwall cable and ~4mm² in regular. (calculator here)

I'd also ask if the cable is stuff sold by grown-ups or random copper-coloured aluminium junk sold on eBay from the far east... there's a lot of fake cable out there. There's also a lot of fake fuses...

If you've used 11A cable you should at absolute most be running a 10A fuse for the circuit, but given the way real-world fuses & cables behave, 7.5A would be about the max I'd be trusting it with. My general rule is >50% over-spec on the wire, so if something's drawing more than about 5A I'll step it up to the 1mm / 16A rated stuff.

I'll also mention that on my installs I've taken to fitting a MIDI fuse at the battery feed end, 50-100A are available, based on whatever the expected total load is going to be, that way if the big feeder cable should short on anything it is at least protected from making a small problem into a very big one.

Oh and next time buy a few different colours of wire, it makes life so much easier!

All the wiring came from an auto cable supply company. Buying large reels seemed an easy option at the time but thinking about it if I was to do it again I’d defo use a selection of colours

[mcc1979ian]

[mcc1979ian]

Basically the led bar blows fuses, dash cam, attwood fan, volt gauge and small strobes but Iv a feeling whatever cable melted has took out the rest,

Hopefully this weekend I’ll pull the loom out and see for sure

[mcc1979ian]

[mcc1979ian]

6 hours ago, Maverik said:

It would be useful if you highlighted which wire you have a problem with on the original wiring diagram - I had a quick look through your old post but it wasn't so clear.

 

From what I understand, you've used 11amp rated wiring for the Relay switching system for your LED light bar?

To activate a 12v relay it only usually uses max 0.5amp to switch them so 11amp wire should be fine.

If this is the situation then you've got a problem.

 

Also these ultra bright LED's can pull some Amps - what light bar have you got

 

Ok on looking at your photo, have you fused the switch circuits as well as the relay supply circuits?

Sorry meant to say all my switching and 12v supplies to relay are 11 amp throughout. So same fuse used from fuse to switch and fuse to relay, plus 11amp from switch to relay 

[FridgeFreezer]

OK from the various descriptions you've posted I'm totally confused about what on earth you've managed to do... if you weren't at the opposite end of the country I'd suggest dragging the truck round to my workshop for a poke about!

Also @Daan/mods/admin can someone rotate the pictures? Or maybe even look for an upgrade/plugin to the forum that allows pictures to be rotated after upload? Or maybe bribe one of the developer types that hang round here to write a little tweak

[Maverik]

On 12/1/2023 at 2:51 PM, mcc1979ian said:

Sorry meant to say all my switching and 12v supplies to relay are 11 amp throughout. So same fuse used from fuse to switch and fuse to relay, plus 11amp from switch to relay 

Just looking at your photo and from what you've described, I'd say the wires you've used to the "powered" side of the relay is too small, so everything going to Pin 30 on the relays should be the same thickness as leaving the relay on Pin 87 - your photo looks like it shows thicker wiring leaving Pin 87.

 

What Amp rated wire have you used leaving Pin 87 going to your lights etc?

 

[geoffbeaumont]

2 hours ago, FridgeFreezer said:

Also @Daan/mods/admin can someone rotate the pictures? Or maybe even look for an upgrade/plugin to the forum that allows pictures to be rotated after upload? Or maybe bribe one of the developer types that hang round here to write a little tweak

There're long running issues with iOS image uploads, as when iOS converts the image to a JPG to upload it, it strips out the meta-data that records which way the phone was held when the photo was taken, so they can't be automatically rotated. Don't know if anyone has ever added a button to Invision Community to allow easy manual fixing - doesn't look like Invision have every been inclined to, and this issue has been running for years.

[FridgeFreezer]

56 minutes ago, geoffbeaumont said:

Don't know if anyone has ever added a button to Invision Community to allow easy manual fixing - doesn't look like Invision have every been inclined to, and this issue has been running for years.

At the risk of wandering off-topic I've done a few little scripts like that for my own personal website gallery, it's ridiculously easy with ImageMagick which is often installed by default or easily enabled.

 

On whatever Ian has done with his wiring I'll have to wait till this evening to get the crayons out and draw a diagram.

[mcc1979ian]

9 hours ago, Maverik said:

Just looking at your photo and from what you've described, I'd say the wires you've used to the "powered" side of the relay is too small, so everything going to Pin 30 on the relays should be the same thickness as leaving the relay on Pin 87 - your photo looks like it shows thicker wiring leaving Pin 87.

 

What Amp rated wire have you used leaving Pin 87 going to your lights etc?

 

39amp to LED bar, think I used 25amp to front spots but I know Iv used 11amp from fuse to switch and back to relay pin 86 and same for fuse to pin 87

[mcc1979ian]

Sorry meant fuse to pin 30 not 87🤦🏻

[FridgeFreezer]

11 hours ago, mcc1979ian said:

39amp to LED bar, think I used 25amp to front spots but I know Iv used 11amp from fuse to switch and back to relay pin 86 and same for fuse to pin 87

So:

Pins 85 + 86 are the relay coil and need bu&&er all power to operate, less than an amp. So wiring that part can use any old cable and might go something like: fused live feed --> switch --> Relay pin 85 --> Relay pin 86 --> GND

Pins 30 + 87 are the power side and carry the full device power, so both need appropriate wire size and the circuit needs to be fused correctly.

It sounds like you might've run 11amp cable from fuse to pin 30 which is not going to work if the circuit draws more than 10A / is fused above 10A.

[mcc1979ian]

22 hours ago, FridgeFreezer said:

So:

Pins 85 + 86 are the relay coil and need bu&&er all power to operate, less than an amp. So wiring that part can use any old cable and might go something like: fused live feed --> switch --> Relay pin 85 --> Relay pin 86 --> GND

Pins 30 + 87 are the power side and carry the full device power, so both need appropriate wire size and the circuit needs to be fused correctly.

It sounds like you might've run 11amp cable from fuse to pin 30 which is not going to work if the circuit draws more than 10A / is fused above 10A.

Ah, think that could be my issue. Would I be better also running a seperate fuse for the supply to pin 30 from the fuse I run to the switch?

[FridgeFreezer]

2 hours ago, mcc1979ian said:

Ah, think that could be my issue. Would I be better also running a seperate fuse for the supply to pin 30 from the fuse I run to the switch?

It depends a little how you want stuff to work but I'd say "yes".

The switch-to-coil side can be super low power, I have a single low-fused (<3A) permanent live and ignition-switched live that can be picked up for any switches I want to supply, they don't need their own fuse per switch.

The "high power" side (fuse to relay P30 to P87 to device being powered) you absolutely need the right size fuse for the load and wire that's rated ABOVE the rating of the fuse.

As I said, I tend to stop up a wire size if I get much above 50% of the wire's rated capacity as you not only need to allow for how slow fuses can be but also the voltage drop that you'll get down a skinnier wire as the load goes up - at 10A you're dropping about volt on a 5m run of 11A cable, which also means that cable is acting as a 10W heater.

[mcc1979ian]

56 minutes ago, FridgeFreezer said:

It depends a little how you want stuff to work but I'd say "yes".

The switch-to-coil side can be super low power, I have a single low-fused (<3A) permanent live and ignition-switched live that can be picked up for any switches I want to supply, they don't need their own fuse per switch.

The "high power" side (fuse to relay P30 to P87 to device being powered) you absolutely need the right size fuse for the load and wire that's rated ABOVE the rating of the fuse.

As I said, I tend to stop up a wire size if I get much above 50% of the wire's rated capacity as you not only need to allow for how slow fuses can be but also the voltage drop that you'll get down a skinnier wire as the load goes up - at 10A you're dropping about volt on a 5m run of 11A cable, which also means that cable is acting as a 10W heater.

Spot on, thankyou, I’m learning a lot from this post

 

Much Appreciated 🙏

[mcc1979ian]

Ok so Iv redrawn a plan for the led bar

300watt so 25amp fuse or would you step up to 30amp?

30amp cable from fuse to pin 30 or should I look at heavier cable?

11amp cable to pin 85 for earth

30amp cable from pin 87 to led or should I go heavier?

11amp from switch to pin 86

should I fuse before or after switch running a seperate supply from the fuse board running pin 30?

[FridgeFreezer]

That's better!

A 30A fuse for a 25A load is not unreasonable but you always want higher rated cable than the fuse - Bussman's data sheet has some good info, key point is a fuse will not be guaranteed to blow at 110% current, could take 2 minutes to blow at 135% of its rated current, and 5 seconds at 200% rated current! And that's if it's a good quality fuse not a random Chinese one. I'd be stepping up a wire size by default.

58 minutes ago, mcc1979ian said:

should I fuse before or after switch running a seperate supply from the fuse board running pin 30?

Generally you want the fuse as close to the battery end as practical, that way it's protecting the most stuff. Obviously there's practical limits to that.

[mcc1979ian]

2 hours ago, FridgeFreezer said:

That's better!

A 30A fuse for a 25A load is not unreasonable but you always want higher rated cable than the fuse - Bussman's data sheet has some good info, key point is a fuse will not be guaranteed to blow at 110% current, could take 2 minutes to blow at 135% of its rated current, and 5 seconds at 200% rated current! And that's if it's a good quality fuse not a random Chinese one. I'd be stepping up a wire size by default.

Generally you want the fuse as close to the battery end as practical, that way it's protecting the most stuff. Obviously there's practical limits to that.

Cheers, Iv run a main cable from battery to fuse box through a 150amp mega fuse. Would it be worth another main run to a fuse box near the switches to fuse the switch side of things too?

[FridgeFreezer]

Not sure exactly what you're proposing, as I said the switches collectively are using naff all power to energise relay coils so you don't really need a bank of individually fused feeds per switch.

[mcc1979ian]

Cool 🙏 Thankyou