Which fluorescent tube do I need?

HappyHippyDad · Aug 24, 2022

Apologies for starting a new thread with this question. I tagged it on to the end of my other thread, but I fear it may get missed, hence reposting...

I need to replace a fluorescent tube in this light fitting (see pic below). It is difficult to see with the reflective material, but there are x2 fluorescent tubes.

I have already made the mistake of putting in a physically identical tube which didn't work (at least physically identical to look at) but I realise now that there are different pin designations on these tubes. The tubes that I need say CLL 55W/840 but I cannot find these on the net. I 'think' this is the equivalent to '2G11' but I am not sure?

I am unsure what markings/model number I should be buying, perhaps as above '2G11'?
The markings on the tube that does work are seen in the picture below

The markings on the tube that does not work are in the picture below.

buzzlightyear · Aug 24, 2022

HappyHippyDad said:
The tubes that I need say CLL 55W/840 but I cannot find these on the net.

blt direct

davesparks · Aug 24, 2022

2G11 is the type of lampholder.

I thought PLL and CLL were interchangeable and just different brands of the same lamp.

Is there a known good lamp you could use to check the control gear is OK? Maybe a working lamp from another fitting?

HappyHippyDad · Aug 24, 2022

davesparks said:
2G11 is the type of lampholder.

I thought PLL and CLL were interchangeable and just different brands of the same lamp.

Is there a known good lamp you could use to check the control gear is OK? Maybe a working lamp from another fitting?

I have used a known good lamp and the fitting works, hence why I know it's not the ballast. I have also used a known 'working' lamp (last picture in my OP) taken from a 1200 x 300 fitting and it doesn't work in the 600 x 300 unit even though physically they are identical to look at. .

Also, when I put the working lamp from the (twin) 600 x 300 fitting into the 1200 x 300 fitting both lamps don't work in the 1200 x 300 fitting, leading me to think there must be fifferent pin designations in the lamps themselves.

Well if 2G11 is just the lamp holder then I'm stuck! I cant find CLL anywhere!

westward10 · Aug 24, 2022

2G11 is the lamp base configuration not the tube type.

loz2754 · Aug 24, 2022

Obvious perhaps, but the wattage of the lamp needs to match the wattage of the ballast.

Moley · Aug 24, 2022

Are these the ones?
HERE

Moley · Aug 24, 2022

Pah, pressed send before I finished typing. Anhway, try contacting them and ask about availability BUT as far as I know any pl-l lamp should work.

HappyHippyDad · Aug 24, 2022

loz2754 said:
Obvious perhaps, but the wattage of the lamp needs to match the wattage of the ballast.

Good point, but as in the picture the one that doesn't work (even though its a working lamp) is still a 55W

westward10 · Aug 24, 2022

Are you putting two tubes in that you have proven to be functional.

HappyHippyDad · Aug 24, 2022

westward10 said:
Are you putting two tubes in that you have proven to be functional.

To be honest Westward I'm confused about what I've done now

.
Will both lamps stop working if one is duff?
I think I'll go back.... again.

loz2754 · Aug 24, 2022

HappyHippyDad said:
To be honest Westward I'm confused about what I've done now .
Will both lamps stop working if one is duff?
I think I'll go back.... again.

Quote possibly yes. It's common to find one ballast feeds 2 lamps, and both have to work or none of them do.
Similar to the use of series starters in the 2 foot fluorescent fittings.

HappyHippyDad · Aug 24, 2022

loz2754 said:
Quote possibly yes. It's common to find one ballast feeds 2 lamps, and both have to work or none of them do.
Similar to the use of series starters in the 2 foot fluorescent fittings.

In that case, I'm wondering if I got the lamps mixed up and that's what's confusing me.

From all the replies it seems that all the lamps are the same and there isn't actually any difference in pin configurations.

westward10 · Aug 24, 2022

No there isn't take the tubes from a fitting which functions and try them in the fitting which currently doesn't.

davesparks · Aug 24, 2022

HappyHippyDad said:
To be honest Westward I'm confused about what I've done now .
Will both lamps stop working if one is duff?
I think I'll go back.... again.

Yes, it confused me the first time I encountered it, the tubes are often connected in series so removing one will break the circuit.

But if you think about it it makes sense, the ballast is there to control the flow of current so, much like LEDs on a constant current driver, the load would need to be connected in series to control the current through them.
If the lamps were in parallel on the same ballast then removing one lamp would result in twice the running current flowing through the lamp that is left which would certainly cause some damage.