LED driver

[simonw247]

i have my electrician installing some LED strip uplighting this week. It has a 100W transformer which is quite chunky -150mm long X 50mm X 30mm. I'd like to hide this behind a false wall.

Does anyone know if this is possible or will there be issues with heat dissipation?

If this is an issue and it can't be hidden, is my only option to mount this remote from the strip and run the cables to the strips (at 12v DC) and if so, will there be significant power loss over a 5m cable run?

 

[winston1]

i have my electrician installing some LED strip uplighting this week. It has a 100W transformer which is quite chunky -150mm long X 50mm X 30mm. I'd like to hide this behind a false wall.

Does anyone know if this is possible or will there be issues with heat dissipation?

If this is an issue and it can't be hidden, is my only option to mount this remote from the strip and run the cables to the strips (at 12v DC) and if so, will there be significant power loss over a 5m cable run?

Well that depends on the size of the cable you choose. Bell wire will have a lot more loss than 10mm2 for instance.

 

[bernardgreen]

First of all that is 99% certain to be a Switch Mode Power Suppy ( or electronic transformer ) and not a true ( magnetic ) transformer. A 100 watt transformer would be considerable larger.

An SMPS will get warm so it should have free air flow around it. They fail quite often ( especially the cheap imports ) so access to replace is a good idea.

The use of a 5 metre lead may cause the SMPS to become unstable ( many are limited to 0.5 metre ( or less ) between SMPS and the LED lamps. Long leads will also radiate radio frequency noise which can affect radios and wireless equipment in the vicinty of the leads.

 

[ericmark]

If a true driver not a simple power supply any volt drop will be auto compensated for it controls current rather than volts. If not a true driver but a simple voltage regulated power supply then there must be a driver built into the lights, this could be a chip using pulse width modulation if so it will compensate for volt drop or a simple resistor in which case it will not.

The method the unit uses to regulate will also effect what heat needs dissipating, using a bi-polar transistor and varying the base current to adjust volts will produce a lot of heat, but using a switch mode or pulse width modulated method the heat will be a lot less. The problem is of course the units don't publish how much heat they generate, and having had to work out heat sink sizes in University I understand why. The only real way is to test it or measure it. If the LED's use 20W and the power supply uses 22W then there is 2W given out in heat. Now in my beer brewing fridge 5W is enough to raise the temperature for 5°C to 20°C so in an insulated wall it will be much more of a temperature rise. I am not sure what temperature the device can run at but likely at 40°C and above the life of the electrolytic capacitors will be reduced and you will get an early failure.

Now 100W at 12V = 8.3A so with 2.5mm cable the volt drop should not be that bad, but as to what volt drop is acceptable is anyone's guess as we don't know how it is regulated. Also a 100W seems rather a lot, my kitchen extension has 24W LED, my living room 30W LED so either very inefficient LED's or you will need sun glasses.

 

[ericmark]

The use of a 5 metre lead may cause the SMPS to become unstable ( many are limited to 0.5 metre ( or less ) between SMPS and the LED lamps. Long leads will also radiate radio frequency noise which can affect radios and wireless equipment in the vicinty of the leads.

I know many AC power supplies use a high frequency so have a limit of 0.2 meters cable length. But unaware of any problems with a DC supply? I know some DC power supplies are three wire pos, neg, and sensing, and will auto compensate for volt drop. Problem is here we are guessing.

 

[ban-all-sheds]

They fail quite often ( especially the cheap imports ) so access to replace is a good idea.

And whilst I wouldn't say "quite often", cheap imports are known to catch fire often enough for me to be wary of walling them up.

 

[securespark]

Well that depends on the size of the cable you choose. Bell wire will have a lot more loss than 10mm2 for instance.

First of all that is 99% certain to be a Switch Mode Power Suppy ( or electronic transformer ) and not a true ( magnetic ) transformer.

SHIIIIIIII!!!

Is this opposites day?

First of all that is 99% certain to be a Switch Mode Power Suppy ( or electronic transformer ) and not a true ( magnetic ) transformer.

Well that depends on the size of the cable you choose. Bell wire will have a lot more loss than 10mm2 for instance.

No, it can't be.....

They fail quite often ( especially the cheap imports ) so access to replace is a good idea.

And whilst I wouldn't say "quite often", cheap imports are known to catch fire often enough for me to be wary of walling them up.

 

[Iggifer]

I know, Winston missed the chance to correct a member of the public on the use of the word transformer. He must be ill, someone call him a doctor

 

[bernardgreen]

He must be ill, someone call him a doctor

No..... something else. All explained here

"Self-transformation" an essay by Bhikkhu Bodhi

http://www.accesstoinsight.org/lib/authors/bodhi/bps-essay_16.html

 

[Iggifer]

FAR too deep for a monday evening!

 

[stillp]

i have my electrician installing some LED strip uplighting this week. It has a 100W transformer which is quite chunky -150mm long X 50mm X 30mm. I'd like to hide this behind a false wall.

Does anyone know if this is possible or will there be issues with heat dissipation?

If this is an issue and it can't be hidden, is my only option to mount this remote from the strip and run the cables to the strips (at 12v DC) and if so, will there be significant power loss over a 5m cable run?

Well that depends on the size of the cable you choose. Bell wire will have a lot more loss than 10mm2 for instance.

I know, Winston missed the chance to correct a member of the public on the use of the word transformer. He must be ill, someone call him a doctor

All right, who are you and what have you done with Winston?

 

[Taylortwocities]

It was me. I did warn him…

Untitled

• Taylortwocities
• 21 Mar 2014
• 1

 

[ericmark]

What is assessable? I know when we has a problem with a shower had to cut a hole in the wall of next door room to gain assess around a foot square but we could access it with a pad saw. When working on building of Sizewell 'B' saw equipment arrive and once in position a wall was built but a good sledge hammer would allow future removal and the was access doors you just could not fit the equipment through them.

I am old school I think fitted using a screw is assessable and with a nail not assessable but packing cases use nails. It is really a risk assessment, what is the likely hood I need assess and how often. At one time the EICR was every 10 years and there was no requirement to access item in the loft space if no hatch provided. Now it seems even if slates need removing loft spaces should be inspected. And the time has reduced to 5 years.

I don't live in Scotland so not law where I live, but I do wonder how one "PAT tests" fixed equipment? OK we should call it the "Inspection and testing of in service electrical equipment" and take a standard lamp easy enough to plug it in to the tester and press the buttons. But to assess every power supply for lighting and test would not be easy as many even if you do have access used maintenance free connectors.

As to washing machine, are we to stand there with the machine watching as it goes through a full cycle? Other wise likely we have not tested the pump or other items within the machine which are activated intermittently. Same applies for a freezer need to test the defrost so likely would take 8 hours to test. All well and good when not legal requirement we just inspected, but as yet not seen a PAT tester that you plug in like an energy meter and return the next day to see the readings.

 

[ban-all-sheds]

What is assessable?

That which can be assessed.

 

[ericmark]

Battles about Chattels, it is all about landlord's and tenant's fixtures, and who owns them. However the court cases refer to how attached and some have resulted in items not belonging to who you would think. There was a case where two mortgages were taken out one on the land the other on the machinery. But because the machine could not operate unless attached to the building then the court found that the land mortgage included the machinery. Being a fixture or chattel is rather important in the case "British Economical Lamp Company (Ltd) v Empire Mile End (Ltd) and another" it was found that the light fittings were not part of the electrical installation in the flat. On the other hand Scott LJ seems to state the reverse.

It would seem fixtures and fittings the term fittings has no legal status.

How this all relates to inspection and testing not so sure, it would seem that a built in kitchen has been found to be both a fixture and chattel by different courts so as to if tested by person doing the installation testing or the appliance testing is also rather open. Clearly when the same person does both then not a problem but I have been employed to "PAT" test and testing the hand drier bolted to the wall or the overhead projector in the ceiling was clearly going to be a problem. The idea of £1 per item and needing either two electricians, or step ladders to test them does not hang well.

So we get the PAT tester saying not portable, and the installation tester saying not a fixture. The ESC seems to include items in the installation testing like wires trailing through doors which personally I feel has nothing to do with installation if not fixed under 28 lbs and has a plug I would say it is chattel and is done by the PAT tester.

The law also seems to consider if it can be done DIY it is chattel and fixtures would normally need some one paid to do that line of work. In real terms some 25 years ago I fitted a metal box in the loft with a HF ballast and batteries to work a ceiling fluorescent and I have never opened the box again. Not even sure where the key is.