Dimming Lights Mystery

[Grant]

I have a problem with lighting on the ground floor of a retail premesis.

The lighting which is a mixture of 240V recessed flourescent down lights and low voltage 12V 50 Watt Down lights.

The lights, especially the flourescent, seem to dim for no reason, some days they are fine others they are not. One possible suggestion by manufacturers is that there is an air flow over the flourescents which cools the tubes and affects performance, however the problem still occurs on sunny calm days. It also seems to affect other 240V 150 Watt pendant type lights also on the ground floor.

All circuits are fed through a consumer unit fitted with MCB’s via light switches. The maximum cable length is 20M of 1mm/2 drawing 3 Amps across separate circuits. Lighting on the first floor of the premesis with the same mixture of lights remains unnaffected.

Anybody have any ideas as to what could be causing this?

Thanks in advance for your help.

 

[breezer]

sorry but as its a commercial premises, you must call an electrician. if you touch it and place catches fire (heaven forbid) insurance will not pay out because it was not done by qualified sparks, and you may get sued

 

[Grant]

I appreciate where you are coming from but I AM an electrician and have been for 35 years, Im JIB approved and I installed the lighting myself.

This thing has really got me scratching my head though!

 

[securespark]

The air flow theory is supported by the fact that this phenomenon is not occuring on the first floor.

However, you say the dichroics also dim?

Have you looked to voltage fluctuations just to rule that out?

Are the pendant lights ceiling roses?If so, they are only rated to a maximum of T1, 60W or T2, 100W.

 

[andy]

sorry but as its a commercial premises, you must call an electrician. if you touch it and place catches fire (heaven forbid) insurance will not pay out because it was not done by qualified sparks, and you may get sued

always jumping 2 'get an electrician'

 

[Grant]

Securespark,

I have ruled out voltage fluctuations, have tested at lights 240V is present.

The pendant lights are suspended from ceiling roses, but the the pendants are manufacturers fittings.

By dechroics do you mean the low voltage halogen lights? If so they do appear to dim yes.

I could perhaps put some insulation in the ceiling to stop airflow over the lights.

I am baffled why some days lights are perfectly normal and for no reason on others they appear dim.

Would you think it is possible that there is a resistance in the circuit somewhere?

 

[ban-all-sheds]

Would you think it is possible that there is a resistance in the circuit somewhere?

If a resistance somewhere was causing the lamps to dim then it would be because the voltage was dropping, and you've ruled that out.

Are both floors on the same circuit? Same phase?

Have you measured the voltage with a true-RMS meter? It's pretty farfetched, but I wonder if you aren't actually getting 240V RMS for some reason.

It might also be interesting to stick a power analyser or phase angle meter on there.

 

[Damocles]

Really can't believe its a draft. Where does the power come from before it gets to the lighting CU? Is there a heavy load somewhere else? Have you had it rigged up to carefully check voltage on different days when this is/ is not happening?

 

[breezer]

always jumping 2 'get an electrician'

you have to bear in mind this IS a DIY forum

grant did not say in his post that he is an electrician, so how are we to know he is? (we do now)
as has been mentioned several times before on this forum, electricians make things look easy to do, quite often not all the relevant informaton is forthcoming (as this example shows)

it also depends on the persons ability, some posts on here the person asking has no idea what so ever, it is better safe than sorry