Kitchen Plinth Lighting ... Replacing bulbs ... Is it safe?

[azibux1]

Hi,

I have some kitchen plinth lighting that I installed about 3 years ago

The lights are round sealed units, drill a hole in the plinth, push them through and connect them up to the junction box supplied (they just plug in) ... I'm sure you know the ones?

Anyway each light has 3 LEDs and a resistor in

Recently they have started to fail, they flicker for a bit before stopping working completely

I had one spare so I replaced a faulty one, but now one has died and another is flickering

I took apart one of them and connected a standard 501 wedge bulb from a car sidelight (12V and 5W I think) to the end of the wire ... It worked but as it was a standard bulb it drew too much power and all the other LEDs on the circuit went dim

I have ordered an LED version of the 501 bulb which will draw less power ... I just wanted to check would it be safe to use?

With the 501 bulb I tried it worked (other than dimming all the rest of the lights due to the current draw) and it didn't make anything pop

So will it be safe to replace the dead lights with?

I will check the rating on the plug for the plinth lights tomorrow but they are low voltage ones as the plug is quite large (like they usually are when they turn down the voltage for DAB radios etc)

Obviously if this is dangerous I'd rather replace the whole plinth light kit for a new one for £30 ... Just thought if I can safely replace each bulb with one of the LED 501 car bulbs for £1 a light then I might as well.

http://www.ebay.co.uk/itm/181070798318?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648

These are the bulbs I've ordered

Thanks!

 

[Robin0577]

We'd need to know the exact rating and type of the transformer/driver unit to answer this one properly.

Dedicated LED sets often use constant current power supplies, whereas LED replacements for tungsten bulbs are designed to accommodate the existing constant voltage supply for the standard tungsten bulb.

 

[azibux1]

We'd need to know the exact rating and type of the transformer/driver unit to answer this one properly.

Dedicated LED sets often use constant current power supplies, whereas LED replacements for tungsten bulbs are designed to accommodate the existing constant voltage supply for the standard tungsten bulb.

Alright thanks ... So a picture of the plug/transformer would help?

I'll get one tomorrow

 

[azibux1]

Hi,

Here's a pic of the adapter

http://i.imgur.com/e058nc7.jpeg

I did test the LED car bulb today quickly and it worked without dimming any of the other lights...

Just wanted to make sure here it was safe to use for a long period of time (I've temporarily disconnected it)

So what do you think?

 

[Robin0577]

I'd say that looks like a simple transformer supply, not a constant current one. So, provided the total current requirement of your bulbs doesn't exceed the 250mA it claims it can supply then there should be no problem.

 

[azibux1]

I'd say that looks like a simple transformer supply, not a constant current one. So, provided the total current requirement of your bulbs doesn't exceed the 250mA it claims it can supply then there should be no problem.

Thanks for confirming

Should be fine then as this kit is suitable to run 10 plinth lights ... And I only have 9 plugged in

The original lights have 3 LEDs and this bulb I've bought has 5 but that shouldn't make that much difference as they hardly use any power anyway, right?

 

[Robin0577]

Well....

The ebay ad says "less than 1 watt" which isn't very helpful.

Taking the worst case and assuming 1 whole watt then 1w @12v = 83mA, so 9 of them would be 750mA which is 3 times the rating of your transformer so if you replaced them all with those it would overheat and (hopefully) cut out. replacing just one might not be an issue, it depends how much current the existing ones use.

You either need to find out exactly how much current your new lamps and your old lamps use and add up the total, or find some that use less than 25mA each, so you know for sure that you can run 10 of them.

We are, as you say talking about "hardly any power" at less than a watt each but the trouble is, the people who made the original set knew this and used a transformer that can produce "hardly any power", in this case 3 watts total, to suit!

The transformer label does claim that it has a thermal fuse that operates at 130C so the of it getting dangerously hot is quite low but in a unit like that I'd expect it to be the "once only" non replaceable type so you may find that it works for a period of time and then just stops forever.....

 

[azibux1]

Well....

The ebay ad says "less than 1 watt" which isn't very helpful.

Taking the worst case and assuming 1 whole watt then 1w @12v = 83mA, so 9 of them would be 750mA which is 3 times the rating of your transformer so if you replaced them all with those it would overheat and (hopefully) cut out. replacing just one might not be an issue, it depends how much current the existing ones use.

You either need to find out exactly how much current your new lamps and your old lamps use and add up the total, or find some that use less than 25mA each, so you know for sure that you can run 10 of them.

We are, as you say talking about "hardly any power" at less than a watt each but the trouble is, the people who made the original set knew this and used a transformer that can produce "hardly any power", in this case 3 watts total, to suit!

The transformer label does claim that it has a thermal fuse that operates at 130C so the of it getting dangerously hot is quite low but in a unit like that I'd expect it to be the "once only" non replaceable type so you may find that it works for a period of time and then just stops forever.....

Thanks for the detailed reply

If you do 250mA divided by 10 (as it is suitable to run 10 lights) that's 25mA per light (unlikely, but worse case scenario like you said)

So as I have 8 original lights = 200mA

Plus one x 83mA for the LED bulb I've added in place of the 9th light ... Takes it up to 283mA

Like you say it will most likely be under 250mA in real life as I doubt they made the transformer with such a small boundary ... But probably not worth risking it over £30

Might just let a couple more blow and then replace the whole set

Question about the original issue ... As they are flickering, then stopping working completely a little while after that ... Do you think the LEDs are reaching their life span or the resistor is burning out?

Also any way of checking how many mA the current lights are using? or not really?