I finally got round to replacing the three 12V MR16 bathroom lights.
Annoyingly, the cut-outs weren't the same diameter as I had thought. The
originals were about 78mm with a bezel of 105mm, the new ones 73mm with
a bezel of 85mm. Luckily I had a decent supply of filler...

What was interesting was the 12V electrics. I had thought all the bulbs
were 20W, as that was printed on the one that blew. But there were two
20W and one 35W bulb. These were run from a Ring 12V AC 65VA
transformer. So it was being overrun (75W load in total). There was "130
deg C" printed on it (seems remarkably high to me). It was partially
potted, and the potting material had cracked in a couple of places.

The wiring was odd, too. The lights were piggy-backed in parallel - 20W
- 20W -35W. The first two had multistranded "speaker" type cable.
Looked to me 5A rating at best. The second 20W lamp had more cable for
the 35W lamp - but it was 1mm T/E!

The new GU10 IP65s look much better.

--

Jeff

Sounds like a bit of a bodge. The problem is of course what exactly is
overrunning a bulb if you are using AC? It all depends on whether the
voltage rating they say was RMS or peak.
Why have one higher wattage. I'd have thought that might look a little
odd.
Brian

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"Jeff Layman" wrote in message
...
I finally got round to replacing the three 12V MR16 bathroom lights.
Annoyingly, the cut-outs weren't the same diameter as I had thought. The
originals were about 78mm with a bezel of 105mm, the new ones 73mm with a
bezel of 85mm. Luckily I had a decent supply of filler...

What was interesting was the 12V electrics. I had thought all the bulbs
were 20W, as that was printed on the one that blew. But there were two 20W
and one 35W bulb. These were run from a Ring 12V AC 65VA transformer. So
it was being overrun (75W load in total). There was "130 deg C" printed on
it (seems remarkably high to me). It was partially potted, and the potting
material had cracked in a couple of places.

The wiring was odd, too. The lights were piggy-backed in parallel - 20W -
20W -35W. The first two had multistranded "speaker" type cable. Looked to
me 5A rating at best. The second 20W lamp had more cable for the 35W
lamp - but it was 1mm T/E!

The new GU10 IP65s look much better.

--

Jeff

The 35W one was the one over the basin. Perhaps it was originally a 20W
bulb but wasn't bright enough for shaving, but nobody bothered to check
if the increased current could be supplied by the transformer.

The bulbs were all a bit yellowish anyway. They were probably at least
10 years old and had been used for an average of an hour every day, so
well above the usual life expectancy.

--

Jeff


On 15/02/19 08:59, Brian Gaff wrote:
Sounds like a bit of a bodge. The problem is of course what exactly is
overrunning a bulb if you are using AC? It all depends on whether the
voltage rating they say was RMS or peak.
Why have one higher wattage. I'd have thought that might look a little
odd.
Brian

On 15/02/2019 08:59, Brian Gaff wrote:

Why have one higher wattage. I'd have thought that might look a little
odd.

Possibly not by design. One bulb blows and the householder in the past
just gets one that fits.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

alan_m wrote in
:

On 15/02/2019 08:59, Brian Gaff wrote:

Why have one higher wattage. I'd have thought that might look a
little
odd.

Possibly not by design. One bulb blows and the householder in the
past just gets one that fits.



Always see confused people liooking at lamps in the supermarkets.

On Fri, 15 Feb 2019 08:27:52 +0000, Jeff Layman wrote:

I finally got round to replacing the three 12V MR16 bathroom lights.
Annoyingly, the cut-outs weren't the same diameter as I had thought. The
originals were about 78mm with a bezel of 105mm, the new ones 73mm with
a bezel of 85mm. Luckily I had a decent supply of filler...

What was interesting was the 12V electrics. I had thought all the bulbs
were 20W, as that was printed on the one that blew. But there were two
20W and one 35W bulb. These were run from a Ring 12V AC 65VA
transformer. So it was being overrun (75W load in total). There was "130
deg C" printed on it (seems remarkably high to me). It was partially
potted, and the potting material had cracked in a couple of places.

The wiring was odd, too. The lights were piggy-backed in parallel - 20W
- 20W -35W. The first two had multistranded "speaker" type cable.
Looked to me 5A rating at best. The second 20W lamp had more cable for
the 35W lamp - but it was 1mm T/E!

The new GU10 IP65s look much better.

The few LEDs that I've bothered to measure seem to have a PF of about 0.5 -
if yours are like that then the VA is around 100!
Just tried a 12W 1500 lm LED: PF is 0.51.
--
Peter.
The gods will stay away
whilst religions hold sway

On 15/02/19 17:16, PeterC wrote:
On Fri, 15 Feb 2019 08:27:52 +0000, Jeff Layman wrote:

I finally got round to replacing the three 12V MR16 bathroom lights.
Annoyingly, the cut-outs weren't the same diameter as I had thought. The
originals were about 78mm with a bezel of 105mm, the new ones 73mm with
a bezel of 85mm. Luckily I had a decent supply of filler...

What was interesting was the 12V electrics. I had thought all the bulbs
were 20W, as that was printed on the one that blew. But there were two
20W and one 35W bulb. These were run from a Ring 12V AC 65VA
transformer. So it was being overrun (75W load in total). There was "130
deg C" printed on it (seems remarkably high to me). It was partially
potted, and the potting material had cracked in a couple of places.

The wiring was odd, too. The lights were piggy-backed in parallel - 20W
- 20W -35W. The first two had multistranded "speaker" type cable.
Looked to me 5A rating at best. The second 20W lamp had more cable for
the 35W lamp - but it was 1mm T/E!

The new GU10 IP65s look much better.

The few LEDs that I've bothered to measure seem to have a PF of about 0.5 -
if yours are like that then the VA is around 100!
Just tried a 12W 1500 lm LED: PF is 0.51.

The old 12v bulbs were halogen. The new GU10 bulbs are 5W mains leds.

--

Jeff

On Fri, 15 Feb 2019 19:02:53 +0000, Jeff Layman wrote:

On 15/02/19 17:16, PeterC wrote:
On Fri, 15 Feb 2019 08:27:52 +0000, Jeff Layman wrote:

I finally got round to replacing the three 12V MR16 bathroom lights.
Annoyingly, the cut-outs weren't the same diameter as I had thought. The
originals were about 78mm with a bezel of 105mm, the new ones 73mm with
a bezel of 85mm. Luckily I had a decent supply of filler...

What was interesting was the 12V electrics. I had thought all the bulbs
were 20W, as that was printed on the one that blew. But there were two
20W and one 35W bulb. These were run from a Ring 12V AC 65VA
transformer. So it was being overrun (75W load in total). There was "130
deg C" printed on it (seems remarkably high to me). It was partially
potted, and the potting material had cracked in a couple of places.

The wiring was odd, too. The lights were piggy-backed in parallel - 20W
- 20W -35W. The first two had multistranded "speaker" type cable.
Looked to me 5A rating at best. The second 20W lamp had more cable for
the 35W lamp - but it was 1mm T/E!

The new GU10 IP65s look much better.

The few LEDs that I've bothered to measure seem to have a PF of about 0.5 -
if yours are like that then the VA is around 100!
Just tried a 12W 1500 lm LED: PF is 0.51.

The old 12v bulbs were halogen. The new GU10 bulbs are 5W mains leds.

Ah, yes - if I hadn't been in the pub I would have realised that 75W of LED
was a bit OTT!
--
Peter.
The gods will stay away
whilst religions hold sway