LED GU10 - equivalent wattage?

[Tim Streater]

I'm looking at LED GU10s from CPC. They give the actual wattage of the device (e.g. 2W or 3W), but how does that compare in terms of light output to say a 35W tungsten GU10?

[Paul D Smith]

Not tried GU10s but I have a 12V, 1W outside to light the doorway. It's bright enough for what I want but is rather blue/grey in output and very directional. Also nowhere near as bright as the 50W it replaced; if I were doing it I'll would probably put in 3 or 4 of them (I didn't install the original 50W).

BTW, I found that the regular halogen 12V transformer would not drive the LEDs - there are special transformers for that job.

[David Hearn]

I believe the best way to compare lights now is their lumen output, and I believe this information must be supplied on the packaging etc. Therefore you just need to find the lumens for a 35W GU10 and the lumens for the LED GU10 you're looking at. I believe lumen output can very a lot with LED/CFLs (so check the specific bulb you're buying), whereas I expect the old style tungsten etc bulbs were more consistent with watts to lumens (so less important to match the existing 35W bulb to find the right output).

D

[Mark]

Beware of these bulbs. I had several (all quite expensive) and only one lasted more than two years.

[Tim Streater]

Ummm.

[Dave Liquorice]

Agreed but be aware of beam widths etc. A bulb with a 15 degree beam width may have the same lumen number as a bulb with a 50 degree beam width. The latter will percieved to be have far more light output than the former. LEDs tend to have tight beam widths...

It's been there for a very long time but it's only very recently that it has moved from the small print on the bottom with the other technical informamtion (volts, base, etc) to having marketing value and thus far more prominent.

[Adam Funk]

How did they fail? I'm under the impression LEDs themselves (as long as they are used correctly) don't generally wear out.

[Mark]

One starting flashing off/on and the others simply stopped lighting up completely.

As they were quite expensive they would have had to have lasted at least 4 (IIRC) years to save me money, as the retailer claimed.

[Martin Brown]

It is the "used correctly" bit that is tricky to do. Getting rid of the small amount of waste thermal heat they generate is distinctly non-trivial in the form factor that typical incandescent lights occupy. The step down DC power supply also has capacitors that tend to die too.

Properly designed LED fixtures have thermal management to spread heat away along a metal heatsink and prevent the junction going over temperature. Some of the latest high brightness LEDs will still cook the phosphor and epoxy near the emitter even when properly used.

All high power LEDs come with a warning that operating them at full power without a heatsink will substantially shorten operating life.

[Mike Barnes]

Martin Brown :

That could explain why the LED floodlight I've just bought is larger and heavier than its halogen predecessor.

[Martin Brown]

Very likely. Halogen and filament bulbs in general don't mind being in a pretty hot environment. Incidentally which sort is it?

I am eyeing up some of the Stairville models for our village hall as I expect that the lower maintenance will help. I have in mind ones that will double as self contained sound to light for discos as well as for coloured stage lighting (manual for now DMX controlled later).

eg LED PAR 56 or LED PAR 64. I have no experience of either.

[Richard]

A number of work colleagues have bought these GU10 without any issues.

& trusted I thought......

Unfortunately, of those I bought several failed within a year:(

Retailer exchanged the first 3 which failed within 3 months.

After several months, five more had failed and the retailer would not answer my e-mails:(

I believe they failed because I used them in fire rated GU10 down lighter fittings. Fitting is a metal cylinder which encloses the GU10 lamp and has several holes at the top for ventilation.

Colleagues who did not have problems installed them in open back GU10 fittings.

Mine failed in the same way as Marks - flashing on & off.

These GU10 lights have 3 LEDs in series and I found that the failed lights each had an LED which would "jump" from a forward voltage of 3'ish volts to over 9 volts in the "off" state.

I repaired all the lights using:

still working two months later - will see how they go.

Richard

[Mike Barnes]

a 150W halogen. Light output is acceptable but it's too directional for my taste. With 12 LEDs they could have spread the light out a bit by pointing them in slightly different directions, but they didn't.

[Adam Funk]

[Mark]

A heatsink for the whole enclosure or just for the individual LEDs. The GU10 bulbs are sold as a complete package and I haven't tried to dissassemble them.

[Martin Brown]

That is really the problem you are replacing something that will work happily with its outer glass envelope mad hot with something that really needs to get rid of any and all heat generated.

It doesn't help that some halogen enclosures are rather well insulated to protect their surroundings. So even if the GU10 bulb gets the heat away from the emitting junction if there is nowhere for it to go aftr that then the whole assembly gets a bit too warm for its own good.

Really you need fittings designed from the outset to take LEDs and provide them with appropriate thermal management.

[Dave Plowman (News)]

Exactly the same applies to CFLs. It would make much more sense to have a custom designed fitting with the power supply separate from the actual lamp. Same as traditional fluorescents. What makes it worse is most are used in pendant fittings, so any heat goes straight to where it does most harm.

[ARWadsworth]

IMHO the GU10 LEDs are a pile of s**te with a short lifespan and crap illuminance.

I fitted over 300 this week and 20 are going to be sent back to the wholesalers because they failed to last a week. There will be another 20 going back next month when they start flashing.

[Martin Brown]

Sounds like you have a big enough sample there to get at least plausible statistics on infant mortaility and longer term failures. So DOA 0.6% Week old flashers ? % and First month fails would be interesting numbers if you feel like posting them.

If they are as bad as you imply then you will have a job for life replacing them. Part of their problem is they don't like being hot and they are often being retrofitted into enclosures that are typically well insulated to protect the ceiling from mad hot quartz halogen bulbs.

[Adam Funk]

Since you seem like a nice guy (I haven't been talking your apprentices), I assume you're installing these because some fool insisted on them & not in order to guarantee repeat business on repairs.

;-)