LED Strip Lighting Installation - Some Specific Queries

[john watts]

All seems well on the installation side and products but..

A couple of things I would add are,
Yes the power supply is open terminal and designed for a locked racking system. So if it is installed in a home you would need a cover / vented box, enclosure you can google transformer enclosure for led drivers as their are some ready available.
You would be better off buying an enclosed power supply which are again readily available and cheaper combined to both options + always look for 5 year warranty with the power supplies, like the Meanwell brands etc as if your LEDs last 10 years but your power supply only lasts one then it's a nitghtmare to keep swapping them.

RF can work from within a stud wall , ceiling etc etc, I have seen this many times and if the controller / receiver are of good quality they can still work up to 20m away from each other even behind a wall.
The only thing I would recommend there is I would always advise to have access to all items. As if you permanently plaster the receivers in, if it comes to a fault (which sods law always happens when no access) you will be in a lot of hassle.

You can get larger control systems out there, eg, one power supply, one receiver to run all 15m (ish) LED strip, but that's another question entirely.

Anything else , please ask away

 

[john watts]

All seems well on the installation side and products but..

A couple of things I would add are,
Yes the power supply is open terminal and designed for a locked racking system. So if it is installed in a home you would need a cover / vented box, enclosure you can google transformer enclosure for led drivers as their are some ready available.
You would be better off buying an enclosed power supply which are again readily available and cheaper combined to both options + always look for 5 year warranty with the power supplies, like the Meanwell brands etc as if your LEDs last 10 years but your power supply only lasts one then it's a nitghtmare to keep swapping them.

RF can work from within a stud wall , ceiling etc etc, I have seen this many times and if the controller / receiver are of good quality they can still work up to 20m away from each other even behind a wall.
The only thing I would recommend there is I would always advise to have access to all items. As if you permanently plaster the receivers in, if it comes to a fault (which sods law always happens when no access) you will be in a lot of hassle.

You can get larger control systems out there, eg, one power supply, one receiver to run all 15m (ish) LED strip, but that's another question entirely.

Anything else , please ask away

 

[shaun1]

As mentioned above, you would be better going with 24v, or using 2 smaller 12v PSUs. 20A is quite a large current on the 12v side, and the strip cannot safely handle this current. So you would need to add fuses for each strip.

The loft is probably the most suitable location for accessability, although remember that it will get very warm up there in the summer, which could cause the PSUs to overheat/reduce their lifespan.

 

[john watts]

Im not sure what you mean by saying the 20amp is not safe on the 12v side?
The only thing to make sure when using a 20amp power supply is that you use the correct thickness cable, eg.1.5mm or whatever thickness it must be (you can check using and online calulator).
There are many power supplies that are rated higher than 20amp.
The 20amp at 12v is a 240w power supply which are very standard and widely accessable. The LED strip draws the power from the power supply not the other way round. So if you have 50w of LED strip on a 240w power supply the LED strip will draw the 50w from the power supply. Therefore not a constant 240w. Maybe i'm misunderstanding something? But ive never heard any of our electrician customers add fuses to LED strips for this very standard project requirement.

 

[shaun1]

Im not sure what you mean by saying the 20amp is not safe on the 12v side?
The only thing to make sure when using a 20amp power supply is that you use the correct thickness cable, eg.1.5mm or whatever thickness it must be (you can check using and online calulator).
There are many power supplies that are rated higher than 20amp.
The 20amp at 12v is a 240w power supply which are very standard and widely accessable. The LED strip draws the power from the power supply not the other way round. So if you have 50w of LED strip on a 240w power supply the LED strip will draw the 50w from the power supply. Therefore not a constant 240w. Maybe i'm misunderstanding something? But ive never heard any of our electrician customers add fuses to LED strips for this very standard project requirement.

The problem with having such a large power supply is if you get a short on the strip. The PCB tracks are nowhere near the 2.5mm you would probably need to safely carry that current. And due to the resistance of those tracks, a short wont always allow a high enough fault current to trigger the power supply overcurrent protection. So you could end up with 15A flowing through the strip, which can heat it enough to cause a fire. Also, its not easy to attach a cable that thick to the strip, so people tend to wire in in much thinner cable.

 

[john watts]

The problem with having such a large power supply is if you get a short on the strip. The PCB tracks are nowhere near the 2.5mm you would probably need to safely carry that current. And due to the resistance of those tracks, a short wont always allow a high enough fault current to trigger the power supply overcurrent protection. So you could end up with 15A flowing through the strip, which can heat it enough to cause a fire. Also, its not easy to attach a cable that thick to the strip, so people tend to wire in in much thinner cable.

I have to disagree. As mentioned before all 20amps are not being forced from the power supply to the strip. The strip is drawing what power it needs from the power supply. So if this strip is only 3amps it draws that from the power supply. If the strip has a short circuit it will react the same on any power supply.
It you have 3amps worth of strip on a 3amp or 20amp power supply it doesn't affect the strip it just draws the 3amps.
The main thing that maybe you are thinking is that the whole 20amps is going to one strip, this wouldnt be the case, as how the stips would be wired is in parralel, so 4 x say 5amp strips wired into one receiver and one 20amp power supply.

 

[shaun1]

I have to disagree. As mentioned before all 20amps are not being forced from the power supply to the strip. The strip is drawing what power it needs from the power supply. So if this strip is only 3amps it draws that from the power supply. If the strip has a short circuit it will react the same on any power supply.
It you have 3amps worth of strip on a 3amp or 20amp power supply it doesn't affect the strip it just draws the 3amps.
The main thing that maybe you are thinking is that the whole 20amps is going to one strip, this wouldnt be the case, as how the stips would be wired is in parralel, so 4 x say 5amp strips wired into one receiver and one 20amp power supply.

The strips would only draw 3amps under normal conditions, but a short circuit would behave in the same way as on any circuit, causing the resistance of the circuit to decrease and the current to increase.

Its exactly the same as a lighting circuit in your house. You could supply it from a 400A fuse and it would only draw an amp or 2 at most. But you need an OCPD to protect against a fault.

 

[davesparks]

Im not sure what you mean by saying the 20amp is not safe on the 12v side?
So if you have 50w of LED strip on a 240w power supply the LED strip will draw the 50w from the power supply. Therefore not a constant 240w. Maybe i'm misunderstanding something? But ive never heard any of our electrician customers add fuses to LED strips for this very standard project requirement.

An unused supply with the capacity to deliver 20A is dangerous as it can deliver more current than an LED strip can safely handle.
If a short circuit were to occur at the far end of the strip then this could allow 20A to flow through the strip which is likely only designed to have around 3A flow through it, this prevents a risk of fire.
Not fusing LED loads fed from power supplies of this size is madness and very bad practice.

 

[john watts]

An unused supply with the capacity to deliver 20A is dangerous as it can deliver more current than an LED strip can safely handle.
If a short circuit were to occur at the far end of the strip then this could allow 20A to flow through the strip which is likely only designed to have around 3A flow through it, this prevents a risk of fire.
Not fusing LED loads fed from power supplies of this size is madness and very bad practice.

Thanks for the replies,
How about your thoughts on the project in the thread which is the actual common use.
So for example,
A 20amp power supply to power 4 x 5 amp led strip lengths ( 4 strips wired in parralel). Are you saying if one of the 5amp strips had a short circuit it would be receiving 20amps even though 15 amps are being used by the the other strips?

 

[James]

Thanks for the replies,
How about your thoughts on the project in the thread which is the actual common use.
So for example,
A 20amp power supply to power 4 x 5 amp led strip lengths ( 4 strips wired in parralel). Are you saying if one of the 5amp strips had a short circuit it would be receiving 20amps even though 15 amps are being used by the the other strips?

It would probably use close to 20A
A short will have a low resistance compared to the other loads and draw far more current

 

[john watts]

It would probably use close to 20A
A short will have a low resistance compared to the other loads and draw far more current

Just looking into this and the power supplies we have used have short circuit protection. Maybe this is why ive never heard of this being an issue
See image:

 

[davesparks]

Thanks for the replies,
How about your thoughts on the project in the thread which is the actual common use.
So for example,
A 20amp power supply to power 4 x 5 amp led strip lengths ( 4 strips wired in parralel). Are you saying if one of the 5amp strips had a short circuit it would be receiving 20amps even though 15 amps are being used by the the other strips?

It all depends on exactly how the power supply behaves in this situation, the resistance of the fault etc etc.
This is obviously very simplified and assuming the power supply has an output limited/fixed at 20A, but the majority of the 20A will flow via the fault in accordance with the bahaviour of resistances in parallel. Some current will continue to flow via the other loads, but most will flow through the fault.
I've installed a lot of LED strip and use one driver per strip or fuse each strip.
If I'm feeding multiple LED loads from one driver I usually fit it in a rittal box with fused din terminals to feed each load.

 

[davesparks]

Just looking into this and the power supplies we have used have short circuit protection. Maybe this is why ive never heard of this being an issue
See image:View attachment 49902

That will only work if the short is a dead short, if the fault has some impedance the result will still be fire.
A elv supply such of this should be treated the same as at any other voltage as far as the provision of ocpds appropriate to the load is concerned.

 

[James]

Just looking into this and the power supplies we have used have short circuit protection. Maybe this is why ive never heard of this being an issue
See image:View attachment 49902

It doesn’t state how it deals with over current or short circuit protection.
I.e. is it current limiting and reducing the voltage to cap at 20A
Or a shutdown of psu until power cycled?
Or another method?

If it is capable of providing 20A then every part of the circuit after that point needs to be able to deal with carrying 20A without overheating.

 

[shaun1]

As far as I know these PSUs just turn off their output if the load goes over 20 amps. A short at the end of a strip wont always exceed that current and so the PSU may well be seeing a load of 18 amps for example, which wont activate its protection. Someone made a youtube video where they measured the resistance of a 5m length of strip and the potential short circuit current if you shorted the end furthest from the PSU. This demonstrated on most strips that a high enough current to cause oveeheating/fire could be drawn, but not high enough to trip the PSU. I cant remember the exact values they used.

If, as in your example, you are running 4 strips from one 20A power supply, you can feed each one via a 5A fuse to protect them.