4' ( Fluorescent ) LED tube type B question... or comment

[The Cobbler]

I picked up 8-4' led tubes from habitat, type B . first time wiring these as previous ones were all powered from one end.
the diagram shows the pins at each end tied together ,s o I figured I only needed one wire per tombstone . . nope , lights didn't come on. so I jumped the tombstones and they came on.
just curious if only 1 pin is connected, or do they actually both have t be powered up? no big deal, just curious/

 

[dave*99]

This concept goes back to the type of tombstone used.. A shunted tombstone means both pins are tied together inside the tombstone. One wire to a shunted tombstone will drive both pins. Type B tubes work with these.

If you have non-shunted tombstones, the diagrams I have seen (and used) rely on your tying the 2 leads (hence 2 pins) together at each tombstone. Type B tubes work in this configuration as well.

To further complicate things, there are single ended and double ended type B tubes and corresponding wiring configurations.

LED Tube Retrofits: The Benefits and Types

Which LED tube retrofit should you choose to replace fluorescent lamps. Type A Plug n Play, Type B Ballast Bypass, Type A+B Hybrid, or Type C Remote Driver.

www.bulbsdepot.com

 

[Bert_]

It only needs one pin at each end. It is often marked in the end of the lamp.

Generally I just grab all wired from one end of the fixture and ties those to hot. All wires from the other end go to neutral.

 

[u2slow]

I've seen a few different types now with a multitude of acceptable pin/wiring configurations.

Best to follow the mfr's diagram as best you can. I often bench test/trial with alligator clip leads... to avoid extra dancing around on the ladder later.

 

[The Cobbler]

I understand there are different pin configurations, ( which , in my mind is crazy) but that's another story.
the bulbs in this case show the pins at each end shunted. so I wired the tombstones with one pin , but the lamps didn't light up. so I shunted the pins on the tombstones & they came on. I suspect only 1 pin on each end is connected to the LED even tho the instructions show both pins are joined .

 

[iron block]

just curious if only 1 pin is connected, or do they actually both have t be powered up? no big deal, just curious/

Yes, just one pin is connected in a double-ended tube. It's a safety measure in case a double-ended tube is installed in a single-ended fixture. Here is a sketch -- "Case 3" shows the potential problem.

You did the right thing by connecting both sides of the tombstone together. That ensures that no matter which of the two pins has the internal connection, you are sending it power.

 

[The Cobbler]

I often bench test/trial with alligator clip leads... to avoid extra dancing around on the ladder later.

good idea. this was supposed to be a fast repair to replace a bad ballast.

 

[cybrdyke]

Different manufacturers make them differently. There are those that connect both pins of the tube to the driver and those that only connect one pin to the driver. Had you rotated the tube 180 degrees, it would probably have lit, since the hot pin was now on the hot brass in the socket (although now the light is going up instead of down). Using both pins requires that the sockets are shunted, which is the norm these days.
Doing what you did, using one wire to a non-shunted socket, will work IF you use the correct side of the socket. If you choose incorrectly, it wont work. There's normally no way for you to know which pin is hot, other than trial and error. It's best to just jumper over to the other side of the socket and be done with it.
Good luck,
CD

 

[The Cobbler]

I get it, but there should be a standard . think of replacements down the road for an average homeowner

 

[rlitman]

I get it, but there should be a standard . think of replacements down the road for an average homeowner

Except the standard exists. The tombstone connectors are standardized around ballast connected bulbs. Once you do a ballast delete, you've broken the UL listing of the fixture and entered the realm of dragons.

 

[The Cobbler]

broken the UL listing of the fixture

no one is obviously concerned. still, there should be one standard for LED retrofit tubes

 

[cybrdyke]

I get it, but there should be a standard . think of replacements down the road for an average homeowner

Yeah, but 4' fluorescent lamps are a commercial product that occassionally get used in a home, so the average homeowner isn't taken into consideration.
CD

 

[The Cobbler]

so the average homeowner isn't taken into consideration.

ok, but in a lot of commercial ( smaller) I'm sure they aren't hiring electricians to replace bulbs either

 

[u2slow]

I get it, but there should be a standard . think of replacements down the road for an average homeowner

The locally sourced LED replacements I bought came with a "retrofit" decal to apply to the old fixture.

The Amazon ones I got did not.

Ballast labels always included a wiring diagram and listed required lamp types. So if you open the fixture to determine that, and find no ballast... well.... then it uses line voltage.