G9 LED: heat a problem?

[F]

I have a new ceiling light to install. It comes with 28W (the maximum
rating of the fitting), 370 lumens, G9 lamps but I would prefer to use
LEDs that are at least as bright.

As the LEDs will be 5W or 6W, I assume that heat won't be an issue?

Any potential problems I might have missed?

--
F

[F]

And can anyone recommend a source of decent 400+ lumens G9s?

--
F

[Martin Bonner]

Well clearly if you stick a 6W LED in a fitting that is good for 28W, the
fitting isn't going to have a problem with heat.

The only problem is whether the LED will have a problem (they *really*
don't like getting hot).

[Martin Brown]

On 09/12/2015 20:03, F wrote:

> I have a new ceiling light to install. It comes with 28W (the maximum
> rating of the fitting), 370 lumens, G9 lamps but I would prefer to use
> LEDs that are at least as bright.
>
> As the LEDs will be 5W or 6W, I assume that heat won't be an issue?

It won't cause any problems for the enclosure designed to withstand the
fierce radiative heat of quartz halogen lamps.

But it might shorten the working lifetime of the LED bulbs considerably
if their working temperature is close to 100C. Capacitors boil dry after
a while.

>
> Any potential problems I might have missed?
>


--

Regards,
Martin Brown

[Roger Mills]

Going off at a slight tangent, some lampshades are rated for 60 watt
tungsten or 11 watt (I think) energy saving bulbs. I can understand that
they might overheat if you put a larger conventional bulb in them, but
why the hell should they mind having a higher capacity energy saving
bulb? Has someone just quoted a bulb with (alleged) equivalent light
output without thinking logically about it?
--
Cheers,
Roger
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[F]

On 10/12/2015 13:23, Martin Bonner wrote:

> On Wednesday, 9 December 2015 21:03:46 UTC+1, F wrote:
>> I have a new ceiling light to install. It comes with 28W (the maximum
>> rating of the fitting), 370 lumens, G9 lamps but I would prefer to use
>> LEDs that are at least as bright.
>>
>> As the LEDs will be 5W or 6W, I assume that heat won't be an issue?
>>
>> Any potential problems I might have missed?
>
>
> Well clearly if you stick a 6W LED in a fitting that is good for 28W, the
> fitting isn't going to have a problem with heat.

Thanks. That's what I expected, though was concerned that the G9 might
have some localised hot spot where all of the 6W(!) (7W as it turns out)
might be concentrated.

> The only problem is whether the LED will have a problem (they *really*
> don't like getting hot).

The 'shade' has plenty of large holes in it.

--
F

[Martin Brown]

Probably, at least for open lampshades with free air flow.

However, the glass globe ceiling mounted ones will rapidly kill a same
nominal output CFL/LED bulb by cooking its control electronics once the
temperature gets close to boiling point for the capacitor electrolyte.

Glass shade and an incandescent bulb are quite happy getting pretty hot.

It is still hard to get any energy saving lamps with the same light
output as 150W and 200W incandescent lamps for a sensible price.

Industrial grade ones are available but not very pretty.

--
Regards,
Martin Brown

[Johnny B Good]

The problem isn't so much about the rating for the luminaire (in
particular the bulb holder itself - plastic or ceramic) so much as it is
about the maximum temperature the lamp can tolerate within the confines
of said luminaire.

A tungsten filament lamp typically converts more than 95% of the input
energy to 'waste heat' (infra-red and convected/conducted 'waste heat')
and is designed to cope with the relatively high temperatures produced
(circa 200 deg C). The luminaire's rating is based on these temperatures
(60W for a plastic bulb holder, 100 to 150 W for a ceramic one - 100W
rating being the limit due to other materials used by the luminaire and
its level of ventillation).

CFLs and LEDs both use electronic ballast circuits built into the lamp
base which have much lower temperature limits (silicon devices max out at
150 deg C and high temperature electrolytic caps at 105 or so deg C).

Since the silicon devices aren't perfect lossless switching devices,
they generate additional heat which requires their immediate environment
to be a few tens of degrees lower than their maximum ratings in order for
the heat to be conducted/convected away.

Whilst good quality electrolytic capacitors don't normally generate much
waste heat in a properly designed circuit, these too need to be operated
in an environment several degrees lower than their maximum rating (the
lower the better since this extends their lifetime hours rating
significantly beyond the typical ten to twenty thousand hours at max
rated temperature).

I haven't seen any 'environmental temperature' ratings mentioned as part
of the specification of these CFL and LEDs. No doubt the manufacturers do
have such limits in the 'spec sheet', they just don't bother 'troubling
the end consumer' with such pesky details. CFLs have a definite 'optimum
temperature range' for the actual fluorescent tubes themselves (50 to 60
deg - significantly higher than the 30 to 40 deg for conventional linear
tubes).

Allowing for the required temperature gradients between the electronic
components used by the lamp ballast circuitry confined to the lamp base
and thermal contact to the luminaire acting as a 'heatsink', I'd be very
much surprised to see an environmental temperature limit much above 70
deg for the lamp base of an LED lamp, considerably lower than the 150 to
200 deg for a tungsten filament lamp.

Rather conveniently, the 11W or so LED/CFL equivalent of a "60W"
tungsten lamp offers enough temperature reduction in most cases
sufficient to allow the use of such "60W Equivalents" in a 60W rated
luminaire without undue overheating risk. Unfortunately, this is often an
unknown parameter as far as most luminaires are concerned (no temperature
versus wattage figures being readily available - it's down to the end
user to take test measurements if they want to determine this all too
critical factor in regard of the effect on LED lamp life).

I'm facing a similar conundrum with an external "60W rated" porch
luminare I recently fitted over our front door as a stop gap to tide me
over the period between now and the appearance of 200Lm per watt security
lamps finally appearing in the stores (the lousy 90Lm per watt lamps are
about to be obsoleted any time soon - yet another 12 to 24 months later
than Cree and Philips were promising would appear some 18 to 24 months
later nearly 24 months back with their 300Lm per watt laboratory samples).

I'm trialling a 20W CFL in the new porch light which replaces an
original porch light I fitted some 30 years back but which failed and was
sidelined by a 500W halogen security light over twenty years ago. I
fitted the security light quite high up to give better coverage and less
light spill. Unfortunately, whenever I need to change a burnt out lamp or
even replace the whole unit (I'm on my third one this time round), I need
to set up a three piece ladder to gain access and the novelty of 'working
at height' has worn rather thin.

I'm determined that the next security light will be a 200lm/W 25W LED
that will last me out for the remainder of my days, hence the 'temporary
porch light' to silence the XYL's moaning about trying to park up on our
drive in darkness.

The CFL is, as you could predict, rather slow in ramping up to full
brightness at this time of the year (about 5 minutes run up time).
Nevertheless, it does seem to reach full brightness.

Since it's only twenty watts, the protracted run up period can be
sidelined by leaving it switched on until bedtime. The fact that it seems
to be surviving 6 to 8 hour sessions ok suggests that I might be ok with
a modern 15W LED, especially if it's a 200 Lm/w type rather than an 81 to
90 Lm/w type typically on today's shop shelves (even less 'waste heat' to
be dissipated - the main benefit rather than just the higher lamp
efficacy).

The *real* benefit of the later 200 and 300 Lm/W LEDs isn't the
reduction of lighting energy costs compared to the 67Lm/W of CFL and 80
to 90 Lm/W of today's LED, it's the reduction of waste heat that has to
be handled by our existing luminaires.

The simplest way to demonstrate this benefit is to assume the
replacement of a "60W 810 Lm" 10W 810 Lm LED (in reality, a 75W 240v lamp
- 60W is the American 120v 750 hour rated 810 Lm standard) with a 2000Lm
10W LED. For the same input wattage you get over a doubling in light
output meaning even less of the input energy showing up as non-productive
waste heat in the luminaire.

The former 10W 810 Lm is emitting about 1.5W as useful light[1] leaving
8.5 watts to heat the lamp and the luminaire, just doubling up the lamp's
efficacy means 3 watts goes to useful radiation in the case of a 10W 1620
Lm LED lamp, leaving only 7 watts as heat for the same 10 watt input
power. If all you need is an 810Lm 5W lamp then the waste heat drops from
8.5 watts down to 3.5 watts.

The next generation of LED lamps will make a lot of existing light
fittings (luminaires), that aren't suited to the current generation of
LEDs, entirely adequate to the new task in hand, neatly avoiding any need
to upgrade them for use with the currently available LED lamps.

[1] This figure is just a best 'guestimate' I've used to provide example
figures to demonstrate the effect of improved luminous efficacy on
luminaire (and hence lamp) temperature.

--
Johnny B Good

[PeterC]

On Fri, 11 Dec 2015 14:07:47 GMT, Johnny B Good wrote:

> The CFL is, as you could predict, rather slow in ramping up to full
> brightness at this time of the year (about 5 minutes run up time).
> Nevertheless, it does seem to reach full brightness.

Perhaps a bit late now for your purpose, but a CFL floodlight that I got
from Aldidl about 3 years ago (they are in store every so often) and put on
my neighbour's back wall does come on to full brightness almost immediately.
It's 23W, fixed, about 4000K at a guess. Aimed well down so that it doesn't
'spray' all over the place.

As for LED type, I'd use the twin-head sort here as they're more 'aimable' -
2x5W, say 450 - 500lm each, would do for my requirement.
--
Peter.
The gods will stay away
whilst religions hold sway

[Johnny B Good]

I plan on eventually replacing the 20W 810lm CFL with a suitable 360 deg
radiation pattern 15W LED lamp[1]. The porch light fitting I bought from
Toolstation ( Code 12199 Victorian Style Lantern Black 60W ES) as shown
on this web page:

<http://www.toolstation.com/shop/Lighting/d220/Exterior+Lights/sd2663>

is basically just a stopgap remedy until I can replace the halogen
security light with a modern 200lm/w 25W LED version in another year or
two's time which, like its predecessor, will render said porch light
redundant. I chose the 'cap down burning' version simply to minimise the
heating effect on the lamp base electronics. Unfortunately, this
conflicts with the typical 270 deg radiation pattern of most of the
cheaper LED lamp types making my choice of lamp a little more critical
than usual.

The fitting is only 'ventilated' by four small 'breathing holes' in the
base designed to prevent moisture accumulation so it's a bit of a heat
trap, relying essentially on conduction to pass the heat from the
internal air to the exterior environment via the glass panels and
metalwork of the fitting, not the most sympathetic of designs as far as
LED lamps are concerned.

The original porch light was fitted first, followed by the 500W halogen
security light. When that porch light finally fell to bits a few years
afterwards, there didn't seem much point in replacing it so I just
removed the 'dangly bits' to make it safe, leaving the twin core flex
dangling, ready for the 'replacement' (having isolated it from the
lighting circuit connection to make it electrically safe).

At the time, I wasn't expecting it to remain a "Feature" for the next
two decades but that was how it was until just a few weeks ago. The white
cable was only used as a 'draw string' to pull the end of the 1.5mm FT&E
it had been crimped onto (I'd left a few metres of extra slack under the
bathroom floor boards for just an occasion as this).

Not being made from cheap mild steel, I expect the new porch light to
last a lot longer than its predecessor did so once I've got the new
security light sorted, it's main use will be simply to provide a
'decorative back up' to mitigate any future problems that might arise
with the security light. At least as a 'Decorative Feature' it's a
significant improvement over the previous one of a 'dangling length of
white flexible cable'. :-)

[1] I reckon a modern 15W 200lm/w LED lamp will produce no more than half
the waste heat of the existing 20W CFL so ought to be able to run cool
enough to realise its full life expectancy whilst providing a 3 to 4 fold
increase in light output raising the porch light's current efficacy from
'barely adequate' to 'nicely adequate'.

For the time being, 'barely adequate' is a damn sight better than 'no
light at all' so it suffices until modern LED prices drop out of the
stratosphere in a year or three's time. Hopefully, it will be relegated
to 'decorative back up' status a year or two before then.

--
Johnny B Good