DSA Posted January 29, 2004 Posted January 29, 2004 Sorry to perhaps ask a silly question, but I am looking into hiring a molefay blinder for our Rock Concert... Are they differend to rig than a 'normal' light eg Parcan - I have heard they have 2 plugs..the item in question is a 4 cell Molefay Blinder. Secondly (it seems silly to start a new thread), how long can a 15 A extension be, between the light and the dimmer, before there are 'problems' (2kW load). Thanks,David
SceneMaster Posted January 29, 2004 Posted January 29, 2004 How far were you thinking for the distance between the light and the dimmer for the 15amp load?
DSA Posted January 29, 2004 Author Posted January 29, 2004 Right, its a bit complicated really. I am going to hire in 2 wired bars or 4 parcans, with 4 floor cans taken from spare sockets on bars (those 15A TRS will be length about 10-15m each) - socapex off each bar round to FOH sockets (about 30m each bar), via a socapex spider, grelco and a TRS extension (5m) into socket. From there it is on our installation multicore to patch bay where it will be plugged into dimmer. Hope this is clear. That should be OK shouldnt it??? Cant have dimmer onstage as only 13A sockets, and want to use onstage plugs on the lx bars for other lights. Thought this would solve the prob. I suppose total length could be, at maximum (not knowing our installation length) 60-80m, per circuit of 2kW. Thanks,David
SceneMaster Posted January 29, 2004 Posted January 29, 2004 Should be ok. But check with other people as I am not a qualified Sparky. :blink: And I don't want to be held responsible for injury. Moderation, 19:13, 29/1/04 - two unnecessarily separate posts merged into one. Again.
ianl Posted January 29, 2004 Posted January 29, 2004 the 4 light molefay have 2 plugs with 2 lights on each plug (in series) each plug will draw aprox 6 amps so be careful about pairing them if you only have 10amp dimmers. as regards cable lengths ,as I understand it your 2 k load is 2 lots of 1k loads paired at the dimmer end of the cable so each long cable is only drawing 1k. therefore you should be fine with this. the max length of standard (1.5mm)socapex multicore running 2k on each of the 6 channels to comply with all the regulations ( heating, voltage drop, earth loop impedance, etc) is about 35 metres although you can get away with at least 50 metres without noticing much of a problem
SparkySteve Posted January 30, 2004 Posted January 30, 2004 running a 15a for 50metres give you a voltage drop of approx 0.30v and a resistance rating of .12... depending on type of cable etc. although not reccomended you could probably push 75m before noticeing anything... like I said though, not reccomended
MarcT Posted January 30, 2004 Posted January 30, 2004 Secondly (it seems silly to start a new thread), how long can a 15 A extension be, between the light and the dimmer, before there are 'problems' (2kW load). Since you asked, as a rule of thumb I use 30m as the maximum permissible length of 15A extension. The reasoning is below, though note that I'm not a qualified electrician. Thus I present this more as a basis for discussion: If you treat your extension cables as an "appliance" for the purpose of PAT testing (as is suggested), to pass an "earth bond" test at <0.1 Ohms (recommended by most PAT test manufacturers) limits the maximum length of cable due to the resistance of the earth conductor. Using the resistivity of copper at 20degC as 1.85x10^-8 Ohm m, and allowing 0.5 mOhms for the connections; the maximum length of a 1.5mm2 extension cable (ie standard 15A extension) turns out to be 7.3meters... This is obviously fairly useless. However, BS415 (which may have been superseeded - Brian might know) "Safety requirements for mains operated and related electronic apparatus for household and similar general use" allows for a protective earth resistance of < 0.5 Ohms. Thus, if your lanterns have <0.1 ohm earth bond (ie pass a PAT test with <0.1 Ohm earth bond limit), then you can use a limit of 0.4 Ohms for your extension cables. With the same assumptions as above this then gives a maximum 15A extension length of ~31m. In reality the resistance of the earth between the dimmers and the supply earth also needs to be taken into account, although this is likely to be a much thicker cable. So, what can you do? If you're hiring socapex, specify 2.5mm2 stuff (most is 1.5mm2) or use 2.5mm2 CEE17 16A extensions with the relevant adapters. For an earth resistance of <0.4 Ohms, you can have ~50m of 2.5mm2. Failing that, use some heavy mains extensions to put something like a betapack or ACT6 near where you need the channels - and just run DMX to it. If you are in any doubt, consult an electrical engineer who will be able to assess the installation and make recommendations as necessary. Hopefully some food for thought. Marc
Brian Posted January 30, 2004 Posted January 30, 2004 However, BS415 (which may have been superseeded - Brian might know) "Safety requirements for mains operated and related electronic apparatus for household and similar general use"Now BS EN 60065, same title
DSA Posted January 31, 2004 Author Posted January 31, 2004 So does the socapex multicore not matter about its length - just the 15A extensions??? - there wont be more than c.20m of 15A ext. before it goes into socapex... So will that be OK? Also will I encounter a problem with a 2.6kW blinder in one 10A dimmer channel? - the hire company said grelco the two plugs together and run it in the same way to the dimmer. They said that the always do it that way, and have never ever had a problem..... They are quite a reputable hire company so I take their word for it, but what do you think?? David
Rob Posted January 31, 2004 Posted January 31, 2004 Also will I encounter a problem with a 2.6kW blinder in one 10A dimmer channel? - the hire company said grelco the two plugs together and run it in the same way to the dimmer. They said that the always do it that way, and have never ever had a problem..... They are quite a reputable hire company so I take their word for it, but what do you think?? You might get away with it depending on the dimmers, but its unlikely and not worth the risk. A 10 amp dimmer will happily take 2.4Kw, 2.6Kw may well be pushing your luck.
timmath Posted January 31, 2004 Posted January 31, 2004 Also will I encounter a problem with a 2.6kW blinder in one 10A dimmer channel? - the hire company said grelco the two plugs together and run it in the same way to the dimmer. They said that the always do it that way, and have never ever had a problem..... It's been done like this for years, most 4 cell blinders only have one plug anyway. sometimes you get nuisance tripping - especially when you flash them hard. if you set your flash level to 90% then you should have no problems at all. If you have the circuits available then run each half of it separately for safety sake, if you get a fault then you will only lose half of the lamp, whereas if you get a fault midshow and they are grelcoed then you loose the whole fitting. So does the socapex multicore not matter about its length - just the 15A extensions??? yes technically the length does matter, but again people have been running cable far further than they should for years too - if the max lengths where adhered too most arena shows would be running on 6mm socca - which would prove weight prohibitive! - MMmmm just imagine a loom of 10 x 40m 6mm socca - I'd like to see the cable case! :( tim
robloxley Posted January 31, 2004 Posted January 31, 2004 It also depends what fuses you've got in the dimmer - if you've got standard (not F or FF) 10A fuses then you'll be able to pull well over 10A for a considerable time. You can look up fuse characteristics in reference texts and some in the IEE Regs. It would however be, at the least, bad practice to deliberately overload a dimmer channel.
DSA Posted January 31, 2004 Author Posted January 31, 2004 I should easily have the means and space to run it of 2 channels. So I think I will do that - just means another TRS extension from the hire company....I've already twisted his arm enough! OK, thanks. David P.S. Where whould they be rigged for best effect?? and are they hard to focus?
TomLyall Posted March 2, 2004 Posted March 2, 2004 you want to make sure you rig them as far downstage as possible really as having them behind the performers will ruin the effect (im assuming you want blinder not backlight). also running it off two channels allows for a little more fun, I guess you could do something interesting only flashing half alternately or something.. [edit] thinking about it... might look horriable, dunno, try it
Ike Posted March 3, 2004 Posted March 3, 2004 Last rock n roll type gig I did we had 12 of them, now THAT was fun
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