Is it safe to change fluorescent lamps when the unit is live

[staithes14]

I'm talking about the circular tubes in a round ceiling unit. Cutting the power means darkness in the room as both lights are on the same switch so I've simply removed the dead lamp and put a new one in. There seems to be virtually no chance of coming into contact with anything live, but someone has pointed out that I should always cut the power and that I wouldn't be allowed to do this at work.

What's the risk? Is there one? Is my friend right? Would I be breaching regs if I did this at work?

 

[PrenticeBoyofDerry]

Providing you cannot come in to contact with live conductive parts, there should be no issue hear.
Ideally you would at least open the switch and in darkened areas, have a secondary means of lighting (torch, plugged in lamp etc...).

But safer to work with light rather than without.

 

[danechip]

I am no electrician. But I usually change these with the power on as it can be a bugger know knowing if they are connected right. Not as simple as popping in a simple lamp as trying to connect both ends at the same time. I did get a belt off a starter once though.

 

[ericmark]

In theory you should not change tubes with the power on. It could blow a HF ballast and with some early tubes there was an earthing strip down length of lamp which could cause problems.

However where one is sure there are no HF ballast fitted and wearing light gloves I have changed tubes live. But I have also installed lighting track and

these ceiling roses to enable lights to be locally isolated in order to change one tube without turning off all lights.

Since near impossible to identify if a HF ballast is fitted unless one can see the starter I would not send anyone to change tubes live even though I may do it myself. Specially in my own house when I know no one is looking.

 

[staithes14]

OK thanks, that's reassuring. I have no idea if there's a ballast. The light fittings are pretty new I think, less than 2 years old.

 

[ericmark]

There will be a ballast it's which type that is important. The cheap one is a coil of wire around a laminated iron like a transformer it has two jobs one is to increase the strike voltage helped by the starter and two reduce the current once started. They make the lamp very voltage critical too high and power use goes way up and too low they stop working.

The new HF ballast uses a high frequency hence called HF stopping the stroboscopic effect, it also corrects for voltage and since it controls the power so well tubes last longer and are often brighter. These never have starters.

Although most of the old ballasts do have started not all have them.

The new HF ballast can fail due to not changing a faulty tube since tubes last a lot longer there is normally a change date where tubes are changed even if still working. Although the tube is the same the heaters are not normally used with HF type.

The strike voltage can be very high with HF and I would not want to chance getting a 1000 volt belt while up steps. It is this high voltage which causes the HF unit to be damaged when the load (tube) is removed. There should be a safety shut down to save the unit but it don't always work.

Unless your certain they are not HF units I would not change live.

 

[danechip]

See, I can still learn something every day. Cheers eric (and mark ) ?

 

[Iggifer]

I always change them live

 

[EFLImpudence]

I always change them live

Then you're not the Messiah either, then.

 

[securespark]

Hmmm. He's a very, very, not the Messiah.

 

[333rocky333]

Your more at risk changing circular lamps live than changing a tube as there is 240 volt between Two pins/wires less than 25mm apart

In either case its best to turn off and use temporary lighting if needbe.

 

[Iggifer]

I was told by a spark I was working with a while ago of a guy he knew who had changed a 5ft tube live, and to locate one end of the tube into the holder, held onto the two pins the other end. For some reason he was surprised he got a bit of tingle!

The majority of tubular lamp holders don't make the circuit until you rotate the lamp 45 degrees so I can't say it's really ever bothered me that much.

I was working with another spark and there was a blown cap in a 4x2ft fitting and he just cut it off and put the wires into a terminal block with the fitting live.

Now that's just silly.

 

[securespark]

Must confess, when I was ill-educated, I have done that, but never got a shock.

Surely, there's no "connection" between the two pairs of pins until both pairs are connected to their respective lampholders?

 

[Iggifer]

I guess it depends which pins you're touching and which contacts you push it into when you're doing it.

I don't think you'd feel anything off a ballast as the starter wouldn't strike but I'm not sure about a HF fitting. Not about to go try!

 

[333rocky333]

The majority of tubular lamp holders don't make the circuit until you rotate the lamp 45 degrees

90 degrees