Hi All,
Wonder if anyone could throw some light on this one (forgive the pun)-
Was called out to sort problem with landing light which blows the bulb when switched on.. mcbs not tripping and lighting is not on an rcd protection.
visited and looked at switches, both 2-way 2 gang coupled with the hall switches (which work fine) - nothing obvious there altho I noticed each wire had a voltage indication using a probe. Also no earthing at the switches - it is an old house with some of the cabling in rubber sheath.
Looked at the ceiling rose - feed in, another loop out both in pvc and the switch wire in the rubber. closer inspection reveraled the wire insulation on the switch wires had gone brittle and cracked off, with bare wires for about 50mm. aha, problem found thinks I and promptly repaired the wiring and fitted a new rose and 2-way landing switch for good measure - however, I was still getting a "live" indication on the switch wires; upon measuring it was 22 volts to earth with no discernable difference with switching .
Client was quite happy for me to disconnect the 2 way wiring and just use the landing switch for the landing light which all works well..
Question 1 - why was bulb blowing? my understanding is that overvoltage will blow the bulb, but 230 + 22v would this be a possibility?
Question 2 - where was the 22 v coming from on the 2-way wiring, both ends of each wire was disconnected!!
The Zs measured 18ohms at the rose but couldnt determine what earthing type it was as the earth wire came up separately from under the floor, presume either tns or tt. also the whole lighting seemed to be on the one circuit, even tho there were 2 other 6A mcbs.
Wonder if anyone could throw some light on this one (forgive the pun)-
Was called out to sort problem with landing light which blows the bulb when switched on.. mcbs not tripping and lighting is not on an rcd protection.
visited and looked at switches, both 2-way 2 gang coupled with the hall switches (which work fine) - nothing obvious there altho I noticed each wire had a voltage indication using a probe. Also no earthing at the switches - it is an old house with some of the cabling in rubber sheath.
Looked at the ceiling rose - feed in, another loop out both in pvc and the switch wire in the rubber. closer inspection reveraled the wire insulation on the switch wires had gone brittle and cracked off, with bare wires for about 50mm. aha, problem found thinks I and promptly repaired the wiring and fitted a new rose and 2-way landing switch for good measure - however, I was still getting a "live" indication on the switch wires; upon measuring it was 22 volts to earth with no discernable difference with switching .
Client was quite happy for me to disconnect the 2 way wiring and just use the landing switch for the landing light which all works well..
Question 1 - why was bulb blowing? my understanding is that overvoltage will blow the bulb, but 230 + 22v would this be a possibility?
Question 2 - where was the 22 v coming from on the 2-way wiring, both ends of each wire was disconnected!!
The Zs measured 18ohms at the rose but couldnt determine what earthing type it was as the earth wire came up separately from under the floor, presume either tns or tt. also the whole lighting seemed to be on the one circuit, even tho there were 2 other 6A mcbs.
