Easy way to find which Fluorescent fitting needs new ballast?

[topt]

2 separate square shaped areas recessed in the ceiling each with 4 fluorescent light fittings.

 

There is a humming noise from each area which I am presuming means the ballast of one or more fittings needs changing. How does one go about working out which fitting is the one (or several) that needs changing? I cannot seem to tell just by listening. 

[Crossy]

A faulty ballast may be getting hot but apart from listening there's not much else you can check.

 

If you take out the starters the associated ballasts shouldn't have any current and therefore shouldn't hum (turn off before removing the starter) so you could isolate the noisy one that way.

 

You could just replace all the ballasts with electronic ones, they're not that expensive now and are silent. They will also save on power and should extend the life of your tubes.

[sometimewoodworker]

9 hours ago, Crossy said:

You could just replace all the ballasts with electronic ones, they're not that expensive now and are silent. They will also save on power and should extend the life of your tubes.

Wouldn't it cost about the same to switch to LED tubes as to replace the ballasts?

[Crossy]

3 minutes ago, sometimewoodworker said:

Wouldn't it cost about the same to switch to LED tubes as to replace the ballasts?

Probably, electronic ballasts are probably price comparable, magnetic ballasts are so cheap they almost give them away.

 

Much depends upon his actual application, I'm assuming this is some kind of concealed "mood" lighting which relies on the fact that a tube emits light 360^o, some (cheaper) LED tubes tend to be one-sided (so they don't "waste" light by emitting upwards) these may not have the desired effect.

 

[mogandave]

Will not the one buzzing be hot to the touch?

[Crossy]

8 hours ago, mogandave said:

Will not the one buzzing be hot to the touch?

Always a good and easy first check, a shorted turn will make things get warm and often causes the core to buzz. But loose laminations (cheap ballast) will also buzz but won't necessarily get hotter than normal.

 

[mogandave]

Always a good and easy first check, a shorted turn will make things get warm and often causes the core to buzz. But loose laminations (cheap ballast) will also buzz but won't necessarily get hotter than normal.
 

Well to be sure, the buzzing ballast will be making more noise than the one not buzzing?

(just kidding)

Incidentally, why are they called “ballasts”?

[topt]

On 8/29/2018 at 2:41 PM, Crossy said:

Probably, electronic ballasts are probably price comparable, magnetic ballasts are so cheap they almost give them away.

 

Much depends upon his actual application, I'm assuming this is some kind of concealed "mood" lighting which relies on the fact that a tube emits light 360^o, some (cheaper) LED tubes tend to be one-sided (so they don't "waste" light by emitting upwards) these may not have the desired effect.

 

Thanks for that about some LED tubes as I was not aware.

Had a quick look yesterday and Home Pro ballasts 99 baht for Tosh and 125 for Phillips at the moment. Electronic (Thai brand?) started about 159 baht. 

 

The electrician I had quoted me 2,500 baht (not including cost of new fittings!) to replace the lot, wiring etc. I said I would think about it........?

[topt]

1 hour ago, mogandave said:

 

Well to be sure, the buzzing ballast will be making more noise than the one not buzzing?

(just kidding)

Incidentally, why are they called “ballasts”?

 

I am being lazy as the only ladder I have currently is a folded extendable which is a pain to set up and I would need to stick my head close to them all to work out which it is - probably most of them as I think they were installed well over 10 years ago.

[mogandave]

I am being lazy as the only ladder I have currently is a folded extendable which is a pain to set up and I would need to stick my head close to them all to work out which it is - probably most of them as I think they were installed well over 10 years ago.

If you have a rod, you can touch it to the fixture and put your ear to it...

(don’t do this standing barefoot on a wet floor...)

[cooked]

I got sick of this kind of stuff years ago and since I discovered LED lighting I have no mercy. It's in the bin with you boyo, no more messing with ballasts and starters, as soon as a problem develops.

[Crossy]

4 hours ago, mogandave said:

Incidentally, why are they called “ballasts”?

 

"Ballast" adds stability, think sailing vessel, loads of rocks (ballast) in the bottom to balance the sails.

 

In our case the ballast adds stability to an inherently unstable system.

 

Fluorescent tubes when cold have a very high resistance, so connect the regular mains supply and nothing happens, however once struck they have a very low resistance, so low that if left alone they go bang.

 

Our ballast serves two purposes, in the "on" state it limits the tube current to a safe level. In the off (ok starting) state it provides (in conjunction with the starter) the high-voltage pulse needed to strike the tube (the starter also supplies the heaters in the tube which lower the striking voltage).

 

[mogandave]

"Ballast" adds stability, think sailing vessel, loads of rocks (ballast) in the bottom to balance the sails.
 
In our case the ballast adds stability to an inherently unstable system.
 
Fluorescent tubes when cold have a very high resistance, so connect the regular mains supply and nothing happens, however once struck they have a very low resistance, so low that if left alone they go bang.
 
Our ballast serves two purposes, in the "on" state it limits the tube current to a safe level. In the off (ok starting) state it provides (in conjunction with the starter) the high-voltage pulse needed to strike the tube (the starter also supplies the heaters in the tube which lower the striking voltage).
 

Makes sense, thanks.

An the starter is something of a relay?

[Crossy]

10 minutes ago, mogandave said:

An the starter is something of a relay?

 

Pretty much, it's actually a bi-metallic contact combined with a neon type lamp, the lamp heats the bi-metal strip.

 

There's a pretty good explanation here http://www.edisontechcenter.org/Fluorescent.html

 

Or just watch their animation:-

 

 

 

[mogandave]

So how do fluorescents differ from neon?

[Crossy]

Just now, mogandave said:

So how do fluorescents differ from neon?

Neons contain neon gas which whilst easier to get going (no heater needed) glow in a nice red colour, not really suitable for lighting.

 

Fluorescent lights contain mercury (vapour once it heats up) which glows in the UV. A phosphor coating the inside of the ube glows white (or any other colour you want) under the influence of this UV.

 

[mogandave]

Neons contain neon gas which whilst easier to get going (no heater needed) glow in a nice red colour, not really suitable for lighting.
 
Fluorescent lights contain mercury (vapour once it heats up) which glows in the UV. A phosphor coating the inside of the ube glows white (or any other colour you want) under the influence of this UV.
 

So the neon starting easier facilities lighting around the bends?

If the neon glows red, how are the different colors done, coating the inside of the tube?

[Crossy]

17 minutes ago, mogandave said:

So the neon starting easier facilities lighting around the bends?
If the neon glows red, how are the different colors done, coating the inside of the tube?

 

OK, I over-simplified ?

 

"Neon" signs use a special high-voltage transformer (15 kV or so) which also acts as the limiting ballast.

 

It looks like this (that's a 9V battery for scale):-

 

 

The various colours come from different gases or mixtures of gases.

[mogandave]

OK, I over-simplified [emoji846]
 
"Neon" signs use a special high-voltage transformer (15 kV or so) which also acts as the limiting ballast.
 
It looks like this (that's a 9V battery for scale):-
 

 
The various colours come from different gases or mixtures of gases.

Cool, I used to have an old RCA Victor TV sigh..,thing worked forever