Twin fluorescent - problems

[Taylortwocities]

I have been called out to an office today.

They have four fluorescent light fittings. Each has two 58W tubes
Three of the fittings have only one half working.

Swopping tubes and starters means its not the usual suspects.

After a lot of looking it would seem that these fittings are wired as lead/lag. this means that there are two ballasts and two starters but that one of the tubes if fed thru a series 4.7uF capacitor.
In all three cases its the half with the series capacitor that doesnt work.

I have a thought that some how the caps have died - maybe they got Meggered at some time.

I could just short out the cap as its only there to provide a reduced flicker.

Is this a valid way forward, or is there something else that i should think about?

Cheers, medears..

 

[Wooshzz99]

It has been done in the past. You could fit new capacitors BUT in my opinion it is probably the control ballast not the capacitor.

 

[333rocky333]

Both chokes are usually the same so thru crimping the two cap wires together would test the fitting.

If you done this it would be no worse than modern switch start twin fittings most of which do not have that capaciter.

unless strobing could be hazordous i cannot see a problem.

If you do change the caps though you will proberly find they are 400 volt rated and not standard voltage.

 

[RF Lighting]

Yep, it will run without the capacitor.

Can be done if a cheap fix is required. It is normal to have a capacitor across the supply. AFAIK it is for smoothing the supply to reduce flicker.

 

[Taylortwocities]

Thanks guys. Its just an office, so no hazards from strobe effect.

I'll try jumpering out the cap on one fitting and get replacements if it works out OK.
The caps are 440V 4.7µF so could have been zapped by something.

I will report back...

 

[333rocky333]

Dont think you could zapp it as it is in series with the choke. and there is no neutral connected.

The power factor correction one is the one across the supply.

It is usually due to the current usually about 0.37 amps constatly passing through it , just breaks it down eventually.

It is quite common with older 8ft single fittings which commonly used this method to strike up the lamp.