by ericmark »
Mon Mar 07, 2011 8:47 am
For a house with standard ceiling roses the maximum size of fuse or breaker is limited to 5/6 amp as that is maximum rating of the ceiling rose which acts as a junction box as well as holding lamp.
So 1380 watt is total for any lighting circuit. As standard 60W is considered normal for each ceiling rose so one could have 23 lights all switched on together without a problem. Most houses will not have this many so really one circuit will supply all lights.
Modern houses do tend to split the lights into two circuits to:-
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
But older houses often have just one circuit. In houses since 2008 likely also protected by a RCD.
Once the DIY takes over however then the loading can become silly. 14 x 40W = 2.4A which leaves 3.6A for rest of house. A few more alterations like a few silly 50mm spot lights and very quickly one is over the limit and the trip will open.
Dimmer units also have a limited current and are normally given in watts. The wattage does vary but 560W is rather high and many will not work with that load.
As to the periodic inspection and testing well that has nothing to do with Part P. The original installer will need to issue an Installation Certificate and that will be submitted and a completion certificate the latter being Part P will be issued. But anyone can do an inspection and test and all that is really required is that the insurance company have insured the guy with professional indemnity insurance. Normal insurance taken out by electricians may not cover giving an opinion, often it only covers work done. And the periodic inspection report is an opinion. The report is based on some testing and a lot of observations but it is impossible to remove floor boards etc. so it is not 100% and it is possible that many faults will be missed. Like a car MOT it is mainly about safety and if the system is safe then it will pass. However it is very rare for any system to pass. In most cases faults will be found and will be categorised as to how important normally given a number 1 to 4 with a "1" being very dangerous and recommending power being switched off until corrected and "4" a warning that if you want future work doing some modifications may be required.
I would be uneasy with a report listing no defects on any house built before 2008 as the rules changed in 2008 which means most houses will have items which don't comply.
As a rule of thumb I would not fit any lamp fitting needing more than 100W without checking the system first including ratings of dimmer switches. When I wanted more light I used discharge lighting which means using so called energy saving bulbs although don't really save energy during the winter months. But 14 x 8W would reduce the load a lot. However very few will work with dimmer switches and normal in rest of Europe where discharge lights have been used for years is the 1/3 to 2/3 split so either 1/3 of bulbs lit, or 2/3 of bulbs lit, or all bulbs lit which gives a good 3 stage lighting control.
If there is a centre bulb then using a single tungsten bulb in centre give immediate light while rest warm up.
