Lights and MCB's

Doofa · Posted: Sat Sep 08, 2007 3:02 pm Post Subject: Lights and MCB's

Hi,

I am finding that I am getting through a large amount of light bulbs, even high quality expensive ones that are advertised as 1500hr + lifespans are lasting sometimes hours or days. Whenever one of the bulbs goes, the MCB related to that ciruit (one for upstairs, one for downstairs ) trips, this happens everytime.

Do you think there is a fault in the wiring or is there anything I can do to maximise the life of the bulbs (apart from leaving them off!

)?

They are running off Hager 6A Type 2 M6 MCB's. There is no RCD that I can see.

Thanks.

GaryMo · Posted: Sat Sep 08, 2007 3:08 pm Post Subject:

It's a general characteristic.
A type B MCB will trip at between 3-5 x In, so for a B6 that'll be between 18 and 30A.
When a filament is ready to go for a split second there will be a surge in current will trip the MCB.
Depending on cable sizing and conditions you may be able to uprate your B6 MCB's to B10. This will probably solve the problem.
Another way would be to swap the B6's for C6's ( 5-10 x In), as long as the circuit can meet the lower maximum loop impedance figures.

breezer · Posted: Sat Sep 08, 2007 3:09 pm Post Subject:

the lamps you have brought are not good qaulity, since as you say the mcb tris.

good qaulity lamps have their own internal fuse

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davy_owen_88 · Posted: Sat Sep 08, 2007 3:09 pm Post Subject:

Are they the correct lamps for the fittings? Are they inserted correctly? Are the contacts of the light fittings corroded/worn so they have a high resistance and generate excessive heat? What type/brand of lamps and what type of fittings are you using (LV or ELV?)?

luminaire · Posted: Sat Sep 08, 2007 3:11 pm Post Subject:

What is the load on that circuit? Have you got anything else on that circuit apart from light bulbs?

What size bulbs are they, and do you have dimmers on there?

Doofa · Posted: Sat Sep 08, 2007 3:29 pm Post Subject:

Are they the correct lamps for the fittings? Yes
Are they inserted correctly? Yes
Are the contacts of the light fittings corroded/worn so they have a high resistance and generate excessive heat? No most are new.
What type/brand of lamps and what type of fittings are you using (LV or ELV?)There are various (no LV/ELV) all 240v between 40 and 100W.
What is the load on that circuit? Not sure what the exact load is but we havent added any additional light points
Have you got anything else on that circuit apart from light bulbs? No
What size bulbs are they, and do you have dimmers on there? betwenn 40W and 100W and yes we have a dimmer swicth in the sitting room but not upstairs

Steve · Posted: Sat Sep 08, 2007 5:18 pm Post Subject:

OK, I would suggest you measure the voltage on the circuit. If its below 240 volts, (which it should be - the absolute maximum is 250 volts but this is pushing it)

You say most of the fittings are new - Perhaps they were a fault batch.

JohnD · Posted: Sat Sep 08, 2007 5:23 pm Post Subject:

the other thing you can do is fit Compact Fluorescent Lamps (Energy Saving bulbs). These last much longer, use much less electricity, make the lamp fittings last longer as they run cooler, are tolerant of voltage fluctuations, and will not trip your MCB when they fail.

It will save you a lot of time up your stepladder too.