non-maintained lamp failure

Hi,

Some time ago, I took the advice of many here and installed an Eterna non-maintained 8w fluorescent lamp above my CU. It is under the stairs and there is no window, so it allows me to see to reset the RCD if it trips.

When similar lighting was installed at work. We were told to test them by running off the battery for one hour once each month. Once every six months, we were supposed to run them for three hours.

Looking at the Eterna booklet, it says the three hour test should be annual, not six monthly. It says every six months to test for one hour and every month to test for no longer then 45 minutes. What does "no longer than 45 minutes" really mean: does it mean 45 minutes or something less? We were told at work that switching them on and off again was not a sufficient test of the batteries, hence the requirement to run them for so long. The Eterna instructions seem to contradict that. Perhaps different manufacturers have different recommendations?

I must confess I have never done routine tests on the one at home. Does anyone else?

The reason I ask is that mine appears to have failed. The other day we had a power cut and the light came on. I was outside, so it did not bother me too much and I never paid attention to the time. Some (unknown) time later, I noticed the light had gone out but the power was not back on. At the time, I just thought the battery had run flat but now I think back, I am not sure that three hours had passed.

There is an LED that shines when the unit is powered and I thought I was imagining it but when the power came back on, at night when the house was dark, it seemed brighter than before. SWMBO agreed. The next day, so at least 24 hours later, I switched off the MCB to make the light come on. It did not. I have checked the fuses and they are fine. So does this mean the battery has died?

The battery pack says April 2010 and says to replace in 2014, so we are not there yet and I would not say it has had heavy use. It is an Eterna brand, I was hoping a known name might have been more reliable than a no name brand.

Is the LED a red herring or is it brighter because of an increased voltage or current, possibly due to the battery no longer charging?

TIA

Reply to
Fred
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Yes, but not as often as I should - probably once every 3 years.

The ones I have were removed from an office ~10 years ago, because the batteries were 4 years old and no one seems to bother replacing the batteries - they just replace the whole thing.

They still work fine. They're 3 hours rated and still do 3 hours.

These use industrial high temp NiCds, and they're expensive to buy. Actually, cheapest way to buy them is to buy an emergency light! Replacement batteries cost more than a new light.

Some of these lights use a single cell, some use multiple cells. NiCds don't like being reverse changed, and that can happen when a multi-cell pack is fully discharged, so if you have multi-cell batteries, I would avoid running them until the light goes out. For single cell batteries, this isn't a problem, as it can't get reverse charged by another stronger cell in the pack.

Doesn't sound like symptoms of dead battery pack to me. That usually shows up as the lamp not staying on for long, or never coming fully on in the first place, but you usually see some light, at least initially even if not for long.

I haven't looked inside a modern emergency light, but I would hope they have improved technology versus these ones with NiCds and inverters. There certainly are LED based ones. I would hope there are better battery and power management designs now too. The NiCd ones are simple, and charge the NiCds at high current so the lights are ready to operate again quickly, but have no intelligence to reduce the charging current when they're charged, and the charging circuit is just a dropper resistor which gets very hot, so they aren't energy efficient.

Reply to
Andrew Gabriel

First silly question: Have you checked the battery? They usually unplug so = it shouldn't be difficult to try with a suitable bulb.

Second silly question -- have you checked the tube? I ask because I've had = trouble with one of the ones in our church hall. First, it went dim and bla= ck for several inches at one end, even though it's non-maintained, only run= s when on test (weekly, for 20 mins, while I'm setting other things up for = Sunday), and they don't use the filament. I had trouble getting a replaceme= nt tube to strike, but it worked after a trying several and a bit of fiddli= ng -- perhaps a bad/slightly corroded contact as it's over a lobby door to = the street.

Otherwise, if yours ran and then stopped, perhaps the electronics has died.

Personally, I wouldn't bother with a mains emergency light above a CU. They= take 5W or more even when the lamp's out. I'd just use a wall-mounting LED= from a pound shop. You should be able to find its switch in the dark.

Chris

Reply to
chrisj.doran%proemail.co.uk

I think I'd have had it apart by now and done some tests on the charging circuit and the battery to find ot. could be something as simple as a bad connection.

Brian

Reply to
Brian Gaff

Thanks. I suspect that people swap the whole thing because, like you said in your post, it can be cheaper to buy a new light than just the batteries. Of course, buy buying new lights means there is no market for replacement batteries, so the price for the batteries remains high, so we are trapped in a circle!

This one looks like two D cells.

The lamp did come on when I had the power cut. It's only on subsequent tests that it has not lit.

How do the fluorescent ones work? If they contain two D cells, do they use an inverter to increase this to 240v? Is there a reason they do this rather than use a low(er) voltage tube and drop the mains down (for maintained lamps)?

I don't think LED bulkheads were about when I purchased mine. I don't like the look of light fittings with hundred of LEDs in (exterior lights etc) but I guess that's because I am used to single bulb fittings. Perhaps I will get used to these in time and I should not be so fussy about a non maintained bulkhead!

Are there any plans to phase out tubes and force the LED ones on to us? I can see the LEDs will have advantages to companies in that they will not have to pay for replacement tubes or for a man to climb a ladder to change one.

If the LED ones use a lower current, I wonder whether they remain on for longer in a power cut?

TIA

Reply to
Fred

Yes, but not to 240V, but to the tube voltage. Off-load it may be a few hundred volts, but when the tube conducts, it will be in the 30-50V range if running the tube at full power. (Many run the tubes at reduced power, which will be a higher tube voltage.)

They have to work from both mains and battery. Some had completely separate control gear for the two cases, whereas others had a battery inverter to drive the tube, and a low voltage supply derived from the mains to do so when mains is present. Part of the problem is that cheap battery inverters don't give very long tube life, which doesn't matter for occasional emergency use, but does matter for a maintained one.

The EU lighting industry will inevitably try to push this, because they make more money out of more expensive LEDs. This is what drives lighting legislation nowadays, because much legislative process is driven by industry to improve their profits and there is no consumer representation involved. This process is universal in the UK too.

LEDs and their driver circuitry die too. In emergency lighting, it's the rechargable batteries which actually limit the life.

LEDs are easily more efficient than the short fluorescent tubes used in emergency lights. Larger tubes are much more efficient, and then you have to buy much more expensive LEDs to match the efficiency.

Reply to
Andrew Gabriel

on 04/11/2012, Fred supposed :

There is really no need for you to do any tests, apart from for your own peace of mind that it will work when needed. A ten minute test once per year would probably do that.

Commercially - lights need a 3 hour test once per annum, with a one hour test at six months and a brief test of function once per month.

Reply to
Harry Bloomfield

Andrew Gabriel explained :

They also tended to output a chopped DC, which because it was polarised it tended to blacken one end of the tube. Swapping the tube over end for end regularly helped reduce the effects.

Reply to
Harry Bloomfield

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