Type of Ballast

[john4703]

I want to replace some fluorescent D shape lamps with LEDs.

Lyco sell two types, one for electronic ballasts and one for magnetic ballasts.

GE 12.5W White LED 4 Pin 2D Bulb for Electronic Ballasts or

GE 12.5W White LED 4 Pin 2D Bulb for Magnetic Ballasts

How do I work out which ballast is in the existing fittings? They are more than 15 years old if that helps.

 

[flameport]

More than 15 years old probably means magnetic.
A magnetic ballast is a heavy solid metal item, the electronic equivalent is a lightweight plastic box.

A complete new LED fitting would be a better option than those LED replacement efforts.

 

[john4703]

More than 15 years old probably means magnetic.
A magnetic ballast is a heavy solid metal item, the electronic equivalent is a lightweight plastic box.

A complete new LED fitting would be a better option than those LED replacement efforts.

Thanks flameport, that makes it easier. I agree new fittings would be better but there are 25 of them in the entrance, hallway and toilets in a church and the cost of replacing them all is too much. Replacing them as tubes fail is a slower and cheaper option. I intend fitting a few PIR sensors so the lights are not left on and LEDs have the advantage of instant start.

 

[333rocky333]

Going by the lamps your looking at its likely your replacing 4 pin 2D 28 watt lamps, if so the old existing 4 pin lamps if they had MAGNETIC chokes there would be a starter evident in the fitting, though often out of sight behind the backplate and likely this would have been evident by a slight delay and flicker on and off when initially turned on.
Electronic ballast fittings would need NO starter and have no flicker start and just a slight delay on start.
We do care homes and find similar replacement led lamps unstable, and find it more economical to replace with ROBUS Golf led fittings as and when they go.
Other makes do ones with a Pir fitted
Bear in mind some may be emergency versions and Led retrofit lamps may not be an option

 

[john4703]

Going by the lamps your looking at its likely your replacing 4 pin 2D 28 watt lamps, if so the old existing 4 pin lamps if they had MAGNETIC chokes there would be a starter evident in the fitting, though often out of sight behind the backplate and likely this would have been evident by a slight delay and flicker on and off when initially turned on.
Electronic ballast fittings would need NO starter and have no flicker start and just a slight delay on start.
We do care homes and find similar replacement led lamps unstable, and find it more economical to replace with ROBUS Golf led fittings as and when they go.
Other makes do ones with a Pir fitted
Bear in mind some may be emergency versions and Led retrofit lamps may not be an option

Thanks 333rocky333 I'd not seen fittings as cheap as those Robus ones. I want something that lasts and if the LED replacements are not 100% reliable I'll change the fittings a few at a time.
The emergency lighting is totally separate, there was none until few units were fitted a couple of years ago.

 

[ericmark]

28W 2D 4pin fluorescent fitting = approx 2050 lumen approx £2.50 ex vat.
12.5W 2D LED replacement = approx 1500 lumen approx £12.50 ex vat.
The 12.5W LED is not in any way equivalent to 28W fluorescent.

For HF electronic fittings it is unlikely there will be any gain, they have around same life and although it states 120 lumen per watt rather than 73 lumen per watt that is only if you remove the ballast. Not sure how it gets around the problem with versions for the electronic ballast, but with the magnet ballast the ballast becomes a resistor as of course it also does with the fluorescent tube, the ballast reduced voltage after start to around 70 volt with fluorescent since with LED it does not use as much likely around 140 volt so the tube will used 12.5/140 = 0.09 amp at 230 volt 0.09 x 230 = 20.5 watt, only with ballast removed will it be really 12.5 watt. Easy to show this is case, ballast gets warm that heat comes from somewhere.

So in real terms this means around 73 lumen per watt for LED so yes exactly the same as fluorescent, only reason it saves energy it is dimmer.

 

[winston1]

The ballast does not become a resistor. It remains mostly inductive. That being the case you total wattage calculation is a bit high. But yes the principal is there.

 

[JohnW2]

.... with the magnet ballast the ballast becomes a resistor as of course it also does with the fluorescent tube, the ballast reduced voltage after start to around 70 volt with fluorescent since with LED it does not use as much likely around 140 volt so the tube will used 12.5/140 = 0.09 amp at 230 volt 0.09 x 230 = 20.5 watt, only with ballast removed will it be really 12.5 watt. Easy to show this is case, ballast gets warm that heat comes from somewhere.

As has been said, it does not 'become a resistor'. It remains as much of an inductor as it is at any time, with either type of tube, and I think you may not have taken that into account in your calculation.....

.... is not a problem with your calculation that, because the ballast remains highly inductive, the PF of the ballast+tube (LED or fluorescent) will be much lower than unity (and much lower than with the ballast removed)? In other words, if one assumes your 140V across the LED tube, hence ~0.09 A, then that current through the ballast+tube would amount to about 20.5 VA (not 20.5 W) at 230V, but the power in Watts would be much lower than that - i.e. much closer to the power with ballast removed.

Easy to show this is case, ballast gets warm that heat comes from somewhere.

If the ballast were a perfect inductor (zero resistance), there would obviously be no heating of the ballast ('lost' energy - or, at least, energy used to heat the environment). It is the resistance of an 'imperfect' ballast that leads to the heating and 'lost' energy, and the magnitude of that heating/'lost' energy will depend upon the current going through it which, with either type of tube, will be dependent on the overall VA of the ballast+tube (at 230V or whatever).

Kind Regards, John

 

[ericmark]

OK I over simplified, however 1500 lumen does not equal 2050 lumen so the LED tube is not equivalent to the Fluorescent tube. Multiply by 25 and that is a lot of light lost. The 16W 2D is 1050 lumen if the area could have been lit with reduced lumen then the 16W would have been fitted.

With the CFL designed to fit in a bulb holder then no problems using LED is far better than the CFL, however with the larger fluorescent units the gain in minimal. I swapped a 65W tube in my kitchen, mainly as can't buy 65W tubes any more and need to swap ballast to use 58W tubes, but the 28W LED gives out far less light, 2800 lumen compared with 5400 lumen it is much darker, OK with kitchen likely it was brighter in the first place to what was required, but with 2D it is unlikely the lamps were over sized, if it did not need 2050 lumen they would have used 16W so it will be dimmer, and for a church one has to consider health and safety it would need a new risk assessment to reduce the light output to show there was no danger as a result.