Just trying to sign off a nightmare job, and one or two little quibbles are still being raised by the owner.
One is that on occasions the mcb trips when switching lights off at the switch. Since I have not been there they are not too clear but it would appear that at the same time a bulb blows in one of 3 fittings they have in the lounge, with 5 arms each running 20W globe bulbs.
The wiring is all new and has been insulation tested. The switches are new and tightness checked (no dimmers). I've also specified Osram bulbs though I don't think all of them are changed yet.
The lights downstairs all run 5x40 W so 200W a light point, and potentially 5 all on at once, along with 4 36W flourescent fittings in kitchen/utility room and a 100W light in the portch, so it may be getting close to the trip rating for 6A.
Obviously is is inconvenient for this to keep happening, so I have a couple of options I'm considering.
Upgrade the MCB to a B10 (1.5mm cable laid in open in the loft so still protecting cable)
Upgrade the MCB to a C10 to avoid surges when a lamp blows causing a short surge.
I will probably also put the kitchen lights on the upstairs circuit so that they do not trip and the homeowner can see to flick the mcb back on.
I realise the issue with C type is meeting the Zs requirement, but as this is a TT installation none of the circuits meet the type B requirement either (Zs is ~22). The source of installation is protected by a type S 100ma rcd, and the db with this lighting circuit on has 30ma protection for all circuits.
I'm open to other advice - the light fittings in the lounge are the sort with 'petal' shades so get very hot with the globe lights in (I would have expected candle lights but apparently globe ones were specified). On inspection some of the SES terminals also show signs of pitting, suggesting that they were not firmly screwed in and perhaps arcing. One of these fittings in the past has ejected a blown bulb across the room, though I think that was down to cheap bulbs (and probably the fact that it was on a 16A circuit when I started the job).
Gavin
One is that on occasions the mcb trips when switching lights off at the switch. Since I have not been there they are not too clear but it would appear that at the same time a bulb blows in one of 3 fittings they have in the lounge, with 5 arms each running 20W globe bulbs.
The wiring is all new and has been insulation tested. The switches are new and tightness checked (no dimmers). I've also specified Osram bulbs though I don't think all of them are changed yet.
The lights downstairs all run 5x40 W so 200W a light point, and potentially 5 all on at once, along with 4 36W flourescent fittings in kitchen/utility room and a 100W light in the portch, so it may be getting close to the trip rating for 6A.
Obviously is is inconvenient for this to keep happening, so I have a couple of options I'm considering.
Upgrade the MCB to a B10 (1.5mm cable laid in open in the loft so still protecting cable)
Upgrade the MCB to a C10 to avoid surges when a lamp blows causing a short surge.
I will probably also put the kitchen lights on the upstairs circuit so that they do not trip and the homeowner can see to flick the mcb back on.
I realise the issue with C type is meeting the Zs requirement, but as this is a TT installation none of the circuits meet the type B requirement either (Zs is ~22). The source of installation is protected by a type S 100ma rcd, and the db with this lighting circuit on has 30ma protection for all circuits.
I'm open to other advice - the light fittings in the lounge are the sort with 'petal' shades so get very hot with the globe lights in (I would have expected candle lights but apparently globe ones were specified). On inspection some of the SES terminals also show signs of pitting, suggesting that they were not firmly screwed in and perhaps arcing. One of these fittings in the past has ejected a blown bulb across the room, though I think that was down to cheap bulbs (and probably the fact that it was on a 16A circuit when I started the job).
Gavin