Burnt out connector block - best thing to do?

abd08

Hi all,

I was having some problems with one specific light 12v halogen light fitting. After investigating futher, I found the below:



I checked a few of the other fittings out and they were all clear. A quick search online pointed to potentially loose connections on the live, but these all seemed tight.

Finally, I replaced the plastic block with a bigger one (assuming higher rated) and left it exposed/hanging for a week. No scorching/marks seem to be appearing.

Options at this point seem to be:

1. Replace the charred connector block with a similar one and keep an eye on it for another week. Then install back into plastic housing and re-fit.

2. Keep the larger block, but then find new housing for it.

Can anyone suggest the right way to go here? I'm assuming the block won't char/melt just because it's covered, so am leaning towards option1.

Really don't like not knowing exactly why the original char/melt occurred. Parts from reputable supplier etc.

Thanks!!

jcb208

Sure it is not heat from the bulb due to poor air flow

[Deleted User]

Looks to me like it melted because the connection was loose. As long as the new one is tight and the connector is a suitable rating for the load it should be OK.

jcb208

jack_pott wrote: »

Looks to me like it melted because the connection was loose. As long as the new one is tight and the connector is a suitable rating for the load it should be OK.

apart from heat that's all it can be really

zax47

Poor connection=high resistance=higher current=heating/burning.

Replace it but make sure it's tight. A 12V bulb at 50W (50VA) draws more current than a 240V one! I must change one a week for folks (I'm a sparky), usually in kitchens, always melted connections..

abd08

Poor connection=high resistance=higher current=heating/burning

Thanks for all the replies - appreciate the simple explanation above - am one of those people who can't stand not knowing why/how something works!! :j

muckybutt

I never use pvc connector blocks on LV or Mains downlight fittings, I always swap them for porcelain connectors https://www.google.co.uk/#q=porcelain+connector+blocks&tbm=shop

abd08

That looks like a great idea - will definitely check them out. Assuming they're designed to fit into the same sized casings etc as the PVC stuff.

[Deleted User]

zax47 wrote: »

Poor connection=high resistance=higher current=heating/burning.

Poor connection=high resistance=slightly lower current

Total circuit resistance is the connection resistance plus appliance resistance. Since the appliance is much higher resistance than the connector, even when faulty, the current remains almost constant. The connector gets hot because the power it is dissipating increases as the resistance increases, not because of an increase in current:

P = I^2*R

The power goes up until the connector resistance equals the appliance resistance.

(I'm a sparky)

Remind me not to hire you.

cyclonebri1

zax47 wrote: »

Poor connection=high resistance=higher current=heating/burning.

Replace it but make sure it's tight. A 12V bulb at 50W (50VA) draws more current than a 240V one! I must change one a week for folks (I'm a sparky), usually in kitchens, always melted connections..

Spot on,:T, many 25watt bulbs get replaced with 50's, not good.

Any loose connection lifts ressistance , heat is a byproduct, thus the result shown.

And the other 1, failure to keep an open area within the insulation to allow the lamp to cool., most likely cause if this is a recent issue as my loft is firkin cold at the mo.;)

zax47

jack_pott wrote: »

Poor connection=high resistance=slightly lower current

Total circuit resistance is the connection resistance plus appliance resistance. Since the appliance is much higher resistance than the connector, even when faulty, the current remains almost constant. The connector gets hot because the power it is dissipating increases as the resistance increases, not because of an increase in current:

P = I^2*R

The power goes up until the connector resistance equals the appliance resistance.



Remind me not to hire you.

I've managed 30 years of a successful career without keyboard know-it-alls thanks. Power (inW)= VxA. If W is constant and V decreases then A increases.... :eek: