vbm Posted January 16, 2009 Share Posted January 16, 2009 Hi Blue Roomerinos... I have acquired, amongst a batch of lighting odds & sods, some 28V 600W Par 64 ACL type bubbles. If I was to use a standard 240V 500W lamp of any description in series as a dummy load, could I plug these into a regular 10 Amp dimmer channel? This would, I assume, give me a total load of 1100W at 268V. Obviously, the supply into the dimmer is usually only 240V, give or take a few volts. Will it go "pop"? Thanks, vbm. [edited for bad maths! Then edited again 'cos I was right the first time...] Link to comment Share on other sites More sharing options...
Robin D Posted January 16, 2009 Share Posted January 16, 2009 Put simply - No. If you put the 'dummy load' in parallel, you would still be delivering 240v to a 28v unit. If you put it in series, you'd have a mismatched chain so the precise result is unpredictable but likely to result in one or both units mimicking the big bang. Theoretically you could connect 8 or 9 in series but then you would be drawing around 20 amps on a single channel! Just don't go there. It's potentially lethal. Robin Link to comment Share on other sites More sharing options...
church Posted January 16, 2009 Share Posted January 16, 2009 If you just plug the ACL into one outlet on the dimmer and the 240V PAR64 into the other outlet on the dimmer,the dimmer it will burn out the ACL lamp and possibly pop the breaker or blow the fuse on the dimmer. All this does is put the two lamps in parallel not series which is what you had assumed in your post. If you rewire the fixtures so that the ACL lamp is in series with the 240V PAR 64 you will get both lamps turn on but will be at reduced brightness which defeats the purpose of using an ACL. To use ACLs you need eight or nine in series depending on the voltage at your venuies. If you use 8 and the voltage is 240V to 250V then you will shorten the already very short life of the ACLs. You may or may not be able to live with this. However I would recommend that if you are wanting to use ACLs you get them already wired for 240V from a rental shop because doing this incorrectly as with all electrical work is potentially dangerous if you are not 100% certain about what you are doing. Link to comment Share on other sites More sharing options...
vbm Posted January 16, 2009 Author Share Posted January 16, 2009 Hi chaps- Thanks very much... I understood the parallel/series bit, I'd never planned to put the lamps in parallel with anything else, but I'd forgotten about the reduced brightness thing with differently-voltage-rated lamps in series. As I'm unlikely to be purchasing any 20A dimmers in the near future, I think I'll just bung them in the bulb recycling box and stick to my regular ACL bars... vbm. Link to comment Share on other sites More sharing options...
adam2 Posted January 16, 2009 Share Posted January 16, 2009 These are quite expensive lamps and may be saleable if you have no use, worth trying an ad in the Blue Room? Link to comment Share on other sites More sharing options...
vbm Posted January 16, 2009 Author Share Posted January 16, 2009 Beat you to it! http://www.blue-room.org.uk/index.php?showtopic=31439 Link to comment Share on other sites More sharing options...
Oovis Posted January 16, 2009 Share Posted January 16, 2009 If you rewire the fixtures so that the ACL lamp is in series with the 240V PAR 64 you will get both lamps turn on but will be at reduced brightness which defeats the purpose of using an ACL.But you'd still be over driving the 28V lamp as you'd have (nominally) 115V across the ACL and 115V across the PAR lamp. Link to comment Share on other sites More sharing options...
JDP Posted January 16, 2009 Share Posted January 16, 2009 Martin, what dimmers do you run?? I may have an alternative idea :) Link to comment Share on other sites More sharing options...
adam2 Posted January 16, 2009 Share Posted January 16, 2009 If you rewire the fixtures so that the ACL lamp is in series with the 240V PAR 64 you will get both lamps turn on but will be at reduced brightness which defeats the purpose of using an ACL.But you'd still be over driving the 28V lamp as you'd have (nominally) 115V across the ACL and 115V across the PAR lamp. No you would not, running lamps in series is more complex than than that. In example given , the 240 volt lamp would receive virtually full voltage, and the ACL allmost nothing, certainly not enough to make it glow even dimly. For lamps to run correctly in series, they must all have the same operating current, and the total of the lamp voltages must equall the supply voltage. For example if you had a non standard 360 volt supply, then you could in theory run in series a 120 volt 100 watt lamp and a 240 volt 200 watt lamp, both would in theory receive the correct voltage and work normally.In practice it does not allways work very well because the lamps may not be closely matched for operating current. If the 120 volt lamp was actually 96 watts, and the 240 volt one was in fact 205 watts, then the 120 volt lamp would be badly over run. In practice series operation should use only lamps of the same voltage, not just the same current, and preferably from the same manufacturer (lamps from different firms may vary a few % in actuall wattage despite being of the same nominal wattage) Drifting somewhat O/T, years ago, major lamp suppliers stocked 110 volt 60 watt GLS lamps "specially designed for series burning, accuratly manufactured as regards current"Anyone know what for ? Link to comment Share on other sites More sharing options...
j_b Posted January 16, 2009 Share Posted January 16, 2009 Series burning lamps were often used with motors. If the motor stalled, the lamp would glow brighter, if the motor was turning freely, the lamp would be dim, or out. If you apply ohms law (ok, lamps are non ohmic, but it'll show roughlt what's going to happen) The 28V lamp has an on resistance of about 1.3 ohms.the 240V lamp has an on resistance of about 115 ohms. Thus, wired in series, the 240V lamp would pretty much glow at normal brightness, and the 28V lamp would see about 2.6W, and thus barely glow, let alone do it's thing, thus rendering the exercise pretty useless. Kev Link to comment Share on other sites More sharing options...
daifuse Posted January 16, 2009 Share Posted January 16, 2009 Just a thought - these could be aircraft landing light bubbles! I can't remember what the wattage was but many moons ago in an aircraft spares store there were quite a few of these. Some of the bigger heavy bombers (WW11) had these for night landing use.I can remember using the reflectors for photographic work. :) Dave Link to comment Share on other sites More sharing options...
Bryson Posted January 16, 2009 Share Posted January 16, 2009 Yes, ACLs are Aircraft Landing lights. They're the same thing.... Link to comment Share on other sites More sharing options...
johnhuson Posted January 16, 2009 Share Posted January 16, 2009 In practice series operation should use only lamps of the same voltage, not just the same current, and preferably from the same manufacturer (lamps from different firms may vary a few % in actuall wattage despite being of the same nominal wattage)Whilst technically correct, in practice I've had success on many occasions with a single 4-lamp ACL bar (running 28v 250w rather than 600w lamps being discussed) with a 110v 1000w par lamp in series as a load lamp and never had any problems. Link to comment Share on other sites More sharing options...
vbm Posted January 16, 2009 Author Share Posted January 16, 2009 In practice series operation should use only lamps of the same voltage, not just the same current, and preferably from the same manufacturer (lamps from different firms may vary a few % in actuall wattage despite being of the same nominal wattage)Whilst technically correct, in practice I've had success on many occasions with a single 4-lamp ACL bar (running 28v 250w rather than 600w lamps being discussed) with a 110v 1000w par lamp in series as a load lamp and never had any problems. Indeed... Link to comment Share on other sites More sharing options...
boatman Posted January 16, 2009 Share Posted January 16, 2009 [..Whilst technically correct, in practice I've had success on many occasions with a single 4-lamp ACL bar (running 28v 250w rather than 600w lamps being discussed) with a 110v 1000w par lamp in series as a load lamp and never had any problems. If you do the maths on that combination, you'll see why it works. Four off 28V @ 250W in series is equivalant to a 112V @ 1000W, which a close enough match to 110V @ 1000W to balance OK. Probably just a tad overloaded at 240V though. Link to comment Share on other sites More sharing options...
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