Light bulbs blow after few hours

[DonnyO]

Light bulbs only last a few hours before they blow. Applies to all fittings on the lighting circuit, both standard 240v and low voltage. Checked all the obvious items like correct voltage and damaged fittings. Property was built in 1930s and cabling is pvc with fuses rather than circuit breakers.

Any ideas on what to check?

Thanks

 

[ericmark]

Two main causes are:-
1) Over voltage.
2) Two many switching cycles.
The latter will include bad connections and the switching off and on may be that quick you can't see it.
However where a switched mode power supply is used this would normally remove the effect of the rapid switching problem. Some discharge lamps and some extra low voltage (12v) lighting systems use the switch mode method which takes the AC supply converts to DC feeds a capacitor and then back to AC at a high frequency hence with fluorescent units often called HF.
These units will also take a wider range of voltages and in some cases can go from 100 to 300 volts this will vary unit to unit.
The best cure is to find bad connection of course but if you have transformers on your "Low Voltage" (I expect you mean extra low voltage as 230v is low voltage) changing these to inverters may help. Also some compact fluorescent lamps have switched mode circuits built in so using energy saving lamps may also help. Unfortunately the type of control gear used within CFL is not advertised so it is a little hit and miss. I will guess those with high hours guarantee will be of switch mode type.

 

[Space cat]

If you have a meter, check your supply voltage. For the 'low voltage' bulbs, if your transformers are real ones - that is two coils of wire on an iron core - excessive mains voltage going in will give you excessive voltage out. If they're the more usual electronic type then ericmark is correct. Most will accept a wide range of input voltages while still giving the correct output. This leads to ---

Cause number three is poor quality bulbs.

PS: If you have a real transformer, check that it is the right power rating for the bulbs. If you underload a transformer,you will get more voltage out than you expect.

 

[ericmark]

Space cat is correct about real (only contains a transformer) transformer and the electronic (switch mode still has a transformer but works on high frequency) and sometimes there are clues on the device. i.e. Electronic written on it is likely switch mode.

For the Electrician it is easy the switch mode type are a lot lighter than the plain transformer type but it is something I have never put on a set of scales so can't really tell you what weight to look for.

Some of the Energy meters designed to see how much power you are using do measure max voltage but it is very hard to monitor for spikes.

I don't like dimming switches but these do seem to prolong the life of standard bulbs. However they should never be used with quartz halogen bulbs as the way the quartz halogen works it life will be shortened by reducing the voltage. All to do with active material being reflected off the very hot quartz.

Bulb quality is not so easy either as bulbs made in UK are designed for 240v and those made in rest of Europe are 220 or 230v. In theory they should all be 230v. One quick fix is to buy rough service bulbs. Not as bright but are likely to last longer.

However although there are all these ways to get around the problem it would be better to find the cause. Bad connections get hot and can be a fire risk so I would be looking for real cause. May even be in the supply. Again a ring and a complaint may cause them to send out an electrician to check supply side of things.