On Sat, 21 Apr 2018 13:41:49 +0100, Dave Plowman (News) wrote:

In article ,
Harry Bloomfield wrote:
58w fluorescent on a PIR, with mag-ballast in a utility room.

The tube finally refused to strike up last week, so I installed a
replacement tube, all back to normal now, but I am wondering whether to
adapt it to LED tube or fit an E-ballast. It is a room we often walk in
or out of with hands full, so I replaced the switch with an occupancy
switch (PIR). Once triggered, it remains lit for maybe ten minutes and
maybe comes on three to five times a day - so economy is not a high
priority, so much as tube life. It has gone through maybe three tubes,
in around 20 years.

A decent electronic ballast will not only give longer tube life, but
faster start up too.

Not true with the T8 tubes and microprocessor controlled HF ballasts
compared to the ancient Quickstart ballasts used with the, now sadly,
obsolete T12 tubes (250ms versus the 900ms of the electronic ballast).

I guess the T8 tubes need a hell of a lot more Baby like care over their
startup phase than their more rugged T12 ancestors which lasted two or
three times longer on a Quickstart ballast than with a simple switch
start one, typical of most domestic kitchen lighting.


I am not keen to replace the complete fitting, but I have a small stock
of 3.5w BC LED's. I could perhaps cheaply DIY adapt the fitting, with
4x BC lamp holders.

Despite the claims for long life, I'm not convinced replacement LED
bulbs with built in electronics do all last the claimed life except
under lab conditions.

The problem is that for a given LPW lamp design, their cooling
requirements become ever more demanding with higher lumen ratings. They
can't shed their waste heat at 200 odd degrees C like an incandescent
can, it's more like an 80 deg C limit tops. The higher lumens output
lamps of any given LPW generation are likely to overheat if fitted in a
less than fully ventilated fitting designed to cope with 100/150W
incandescent lamps.

The older 81LPW lamps were usually ok up to 810Lm in most open shades
any higher lumens output lamps of this generation needed really good
ventilation to avoid death by overheating. Today's 125LPW 1500Lm "100W
incandescent equivalent" BC light bulb as sold by Home Bargains and other
retail outlets can now be safely used in standard luminaires that were
previously unsuitable for the earlier generation of LED lamps.

My interest in LPW improvements is less to do with electricity savings
and more to do with lamp savings in locations that are crying out for a
decent 100 or 150 watt incandescent's worth of lighting power. At the
moment, with those 125LPW lamps, we seem to be at the stage where we can
now fit a "100W incandescent equivalent" in a standard fitting with
little fear of premature failure.

--
Johnny B Good