Home |
Search |
Today's Posts |
|
UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
|
|||
|
|||
Consumer unit switch tripping despite RCD
Radial spur off of main consumer unit in garage. The spur feeds
exterior lighting via a dusk till dawn unit - 3 x 40 watt halogen lamps and 1 x 150 watt halogen security lamp. It was cheaper for me to buy an RCD plug than a separate RCD and fuse box so I simply plug the exterior lighting in to the radial spur using the RCD plug. When I first plugged in the circuit the consumer unit fuse tripped, but the RCD didn't cut out. I'm not sure I understand why, can anyone help? I thought the RCD would cut out before anything else and therefore protecting the main consumer unit. In attempt to find out the cause of the fuse trip on the consumer unit I checked every single connection on the dusk till dawn, junction boxes, and lamps, and they all looked fine. So I flicked the switch on the fuse and this time I heard a pop outside and again the fuse tripped. One of the lamps had popped - identifiable from a black ring on the brick around the lamp. Again I checked the connections in the junction box leading to that lamp and again also inside the lamp. They all are fine, but I noticed more carbon around the manufactured attachments where the cable runs in to the lamp unit. So I'm figuring the lamp is faulty. I'll be replacing this lamp unit and of course I do not leave the circuit on. But that said, strangely, I flicked the trip switch on the fuse in the consumer unit back to on and the circuit works fine now - not sure why either! So my questions are - 1. why didn't/doesn't the RCD trip before the fuse on the consumer unit 2. any ideas what the likely cause of the problem is with the lamp - just out of interest? Like I say I'll just get a replacement from B&Q anyway but just curious. |
#2
|
|||
|
|||
The RCD only protects against a fault to earth
What you had was a short circuit in a faulty lamp, this would not produce a fault to earth and therefore not operate the RCD. This fault would product a current sufficient to operate the fuse in the CU. Hope this helps -- Ellis Greensitt Supplychain(Doncaster) Ltd. www.supplychain.org.uk 01302 761205 : Tel 01302 761206 : Fax "Dundonald" wrote in message ups.com... Radial spur off of main consumer unit in garage. The spur feeds exterior lighting via a dusk till dawn unit - 3 x 40 watt halogen lamps and 1 x 150 watt halogen security lamp. It was cheaper for me to buy an RCD plug than a separate RCD and fuse box so I simply plug the exterior lighting in to the radial spur using the RCD plug. When I first plugged in the circuit the consumer unit fuse tripped, but the RCD didn't cut out. I'm not sure I understand why, can anyone help? I thought the RCD would cut out before anything else and therefore protecting the main consumer unit. In attempt to find out the cause of the fuse trip on the consumer unit I checked every single connection on the dusk till dawn, junction boxes, and lamps, and they all looked fine. So I flicked the switch on the fuse and this time I heard a pop outside and again the fuse tripped. One of the lamps had popped - identifiable from a black ring on the brick around the lamp. Again I checked the connections in the junction box leading to that lamp and again also inside the lamp. They all are fine, but I noticed more carbon around the manufactured attachments where the cable runs in to the lamp unit. So I'm figuring the lamp is faulty. I'll be replacing this lamp unit and of course I do not leave the circuit on. But that said, strangely, I flicked the trip switch on the fuse in the consumer unit back to on and the circuit works fine now - not sure why either! So my questions are - 1. why didn't/doesn't the RCD trip before the fuse on the consumer unit 2. any ideas what the likely cause of the problem is with the lamp - just out of interest? Like I say I'll just get a replacement from B&Q anyway but just curious. |
#3
|
|||
|
|||
On 5 Jun 2005 15:43:29 -0700, Dundonald wrote:
1. why didn't/doesn't the RCD trip before the fuse on the consumer unit An RCD does not provide any overload protection. It only trips if there is an inbalance in the current flowing in the live an neutral wires connected through it. If you have live/neutral short an RCD won't see that as a fault condition as 6kA if going and 6kA is coming back. -- Cheers Dave. pam is missing e-mail |
#4
|
|||
|
|||
In message , Ellis Greensitt
writes The RCD only protects against a fault to earth What you had was a short circuit in a faulty lamp, this would not produce a fault to earth and therefore not operate the RCD. This fault would product a current sufficient to operate the fuse in the CU. Hope this helps Look ellis this is how it works __________________________________________ [Post you are replying to with irrelevant bits snipped] [Your contribution] Sig sep Your sig - to which you can put a link to your site ___________________________________________ Hope this helps and hope you're able to take this simple concept onboard -- geoff |
#5
|
|||
|
|||
Look ellis this is how it works __________________________________________ [Post you are replying to with irrelevant bits snipped] [Your contribution] Sig sep Your sig - to which you can put a link to your site ___________________________________________ Hope this helps and hope you're able to take this simple concept onboard -- geoff Sorry Geoff, I had all the bits but in the wrong order. Outlook express puts the quoted portion at the end by default. Im new to this, thanks for putting me right. -- Ellis Greensitt Supplychain(Doncaster) Ltd. www.supplychain.org.uk 01302 761205 : Tel 01302 761206 : Fax |
#6
|
|||
|
|||
Dundonald wrote:
1. why didn't/doesn't the RCD trip before the fuse on the consumer unit As Ellis said, an RCD only detects faults to earth, most obviously L to E. If your wiring or lamp had an L-to-N short, that'll make the MCB pop, but the RCD will be happy as Larry, since just as much current - in this case, lots and oodles - is flowing out down the L as is coming back up the N. 2. any ideas what the likely cause of the problem is with the lamp - just out of interest? Like I say I'll just get a replacement from B&Q anyway but just curious. As mentioned above, a fault making the L shorted to N. Either a fault in the lamp, or - more likely, I'm afraid - you wired it up wrong (or ended up with bare L and N conductors touching when you sqaushed them back in place). The blackening of the brick, and the popping of the MCB, says you had quite a lot of electricity flowing for a short time. When big fault currents like this flow, they can 'clear' the fault by burning away the metal bits wot are touching where they shouldn't be - so explaining your 'well now it doesn't trip the MCB any more!' observation. HTH - Stefek |
#7
|
|||
|
|||
Ellis Greensitt wrote:
Sorry Geoff, I had all the bits but in the wrong order. Outlook express puts the quoted portion at the end by default. Im new to this, thanks for putting me right. Use this niffty little plug in for OE http://home.in.tum.de/~jain/software/oe-quotefix/ -- Mark Please replace invalid and invalid with gmx and net to reply |
#8
|
|||
|
|||
"Stefek Zaba" wrote in message
... Dundonald wrote: 1. why didn't/doesn't the RCD trip before the fuse on the consumer unit As Ellis said, an RCD only detects faults to earth, most obviously L to E. If your wiring or lamp had an L-to-N short, that'll make the MCB pop, but the RCD will be happy as Larry, since just as much current - in this case, lots and oodles - is flowing out down the L as is coming back up the N. 2. any ideas what the likely cause of the problem is with the lamp - just out of interest? Like I say I'll just get a replacement from B&Q anyway but just curious. As mentioned above, a fault making the L shorted to N. Either a fault in the lamp, or - more likely, I'm afraid - you wired it up wrong (or ended up with bare L and N conductors touching when you sqaushed them back in place). The blackening of the brick, and the popping of the MCB, says you had quite a lot of electricity flowing for a short time. When big fault currents like this flow, they can 'clear' the fault by burning away the metal bits wot are touching where they shouldn't be - so explaining your 'well now it doesn't trip the MCB any more!' observation. HTH - Stefek it does however raise the worrying question as to what would have happened to any insulation in the immediate vicinity of this self-righting extraneous-metal-bit-vapourising fault, though. -- Richard Sampson mail me at richard at olifant d-ot co do-t uk |
#9
|
|||
|
|||
Theres nowt wrong with top posting or interspersed posting. Top is
partcilarly good for a quick comment reply. The insistence on bottom posting is a convention from days now gone. Its side Ellis Greensitt wrote: posting you've Look ellis this is how it works got to watch for __________________________________________ ! [Post you are replying to with irrelevant bits snipped] |
#10
|
|||
|
|||
|
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
GE refrigerator warranty repair misery | Home Ownership | |||
3 way switch disaster (long but interesting) | Home Repair | |||
Earthing Conductor size (massive??) & new Consumer Unit | UK diy | |||
Ring mains and consumer unit | UK diy | |||
Secondary consumer unit | UK diy |