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[Debbie Dunkley]

Happy New Year Everyone - I hope your start to 2023 has been a good one!

I have a question:

I always daisy chain power to my truss lights but I just added one more and I'd like to make sure I have this right. Am I restricted only by power draw of all fixtures added together and cord gauge?? They are all very low draw.

I have 8 (multi) fixtures total ( 4 per side) and I feed each side separately so 3 are daisy changed from the first fixture each side.

Fixtures...
1) .64A
2) .4A
3) .18A
4) .33A

[Brian Jojade]

When you daisy chain, you also need to know how much current each fixture can support.  While they may have powercons, that doesn't mean they can support 15 amps internally.

Some lights have their fuse on the passthrough. Others just use thin cable with no fuse on the passthrough.

But, at the current draw you have listed, you're at under 2 amps.  Even the worst of the worst should be able to handle that.  A 24 gauge wire is rated at 3 amps, for reference.

[Erik Jerde]

Most fixtures with pass through power usually list in their specs the max number of fixtures supported in a chain.  You can use that info to work back what the recommended max current draw through one fixture would be.

[Debbie Dunkley]

I can find 3 of the fixtures maximums in their respective manuals. However, the 2 ADJ fixtures indicate they have to be daisy chained to the exact same fixture. All mine are different.
1) ADJ = 13 max - 'must' be same type.
2) Chauvet = 11 max - no restrictions
3) ADJ = 30 max - 'must' be same type
4) Unknown brand. no info.

[Erik Jerde]

I can find 3 of the fixtures maximums in their respective manuals. However, the 2 ADJ fixtures indicate they have to be daisy chained to the exact same fixture. All mine are different.
1) ADJ = 13 max - 'must' be same type.
2) Chauvet = 11 max - no restrictions
3) ADJ = 30 max - 'must' be same type
4) Unknown brand. no info.

They only give the must be same type thing because that way they're in a better position when someone does something stupid like putting a coffee maker on the end of the chain and starting a fire.  Power is power, the fixture won't care what's plugged into it as long as you don't exceed it's ability to pass through power.

Doing the math you get the following for max load through a given fixture:
1) 7.68A
2) 4A
3) 5.2A

That's by taking the max fixtures in a chain, remove one (because the we're finding the load that is passed through) and then multiply.  For the first this is (13-1)*.64A.

Once you look past the CYA lawyer stuff it's like most power stuff where you just have to do the math.  It's entirely possible that with staggered startup you could run more on a chain but they need to be careful of stuff like inrush current when you power up a whole chain at once.  I'd just go with what you can deduce from the manual.

[Debbie Dunkley]

They only give the must be same type thing because that way they're in a better position when someone does something stupid like putting a coffee maker on the end of the chain and starting a fire.  Power is power, the fixture won't care what's plugged into it as long as you don't exceed it's ability to pass through power.

Doing the math you get the following for max load through a given fixture:
1) 7.68A
2) 4A
3) 5.2A

That's by taking the max fixtures in a chain, remove one (because the we're finding the load that is passed through) and then multiply.  For the first this is (13-1)*.64A.

Once you look past the CYA lawyer stuff it's like most power stuff where you just have to do the math.  It's entirely possible that with staggered startup you could run more on a chain but they need to be careful of stuff like inrush current when you power up a whole chain at once.  I'd just go with what you can deduce from the manual.

Cool - thanks Erik. Makes sense. I am no where near the max then so should be good to go!!
'

[Brian Jojade]

Cool - thanks Erik. Makes sense. I am no where near the max then so should be good to go!!
'

With LED lights, it's awesome that you can pass power through. With my first LED cans, I actually modded them and added edison plugs on the back, wondering why nobody offered that as an option at the time.  With the stock 18 gauge power cables, you could string lots of lights together with no issue.

[Debbie Dunkley]

With LED lights, it's awesome that you can pass power through. With my first LED cans, I actually modded them and added edison plugs on the back, wondering why nobody offered that as an option at the time.  With the stock 18 gauge power cables, you could string lots of lights together with no issue.

Yes, it makes wiring trussing so much easier…

[Dave Garoutte]

Yes, it makes wiring trussing so much easier…

And you can get shorter and longer IEC cords to use exactly your needs, even cleaner on standard setups.

[Debbie Dunkley]

And you can get shorter and longer IEC cords to use exactly your needs, even cleaner on standard setups.

Yes I try to keep them neat by customizing lengths. I usually make them to size if I cant find what I want stock.

[Mike Karseboom]

In my experience with LED lighting GFCI tripping has been more of a concern rather than total amperage draw.  As already mentioned, unless you are using big power hungry fixtures, large movers, or maybe a hazer, you can typically daisy chain 8 or more and still be well under current draw / wiring capacity limits.


On the other hand, it seems each fixture and each "loop" has the potential for some miniscule, but not zero, current leakage that may affect a GFCI breaker.  Long power/dmx runs on bigger stages, cord connections on the ground, and any moisture can exacerbate the problem. 


In addition to lighting you may be energizing main speakers/amps, 4-6 powered monitors, as well as mixer, wifi, artnet converters, tablet chargers, etc from a limited number of separate outlets.  Then there is muso power for their amps, keys, laptops, phone chargers, etc. But muso/stage power always gets its own circuit in my book so any problems they introduce is isolated.


While the total current draw may be reasonable for each power outlet, and each fixture or device may be functioning properly on its own, the cumulative effect of too many devices on one circuit may be enough to trip a GFCI breaker.


I don't know the science behind this and probably could not prove anything but have had a handful of real life experiences where GFCI outlets have tripped just due to too many attached devices.  The solution has been careful re-distribution of the devices across the available outlets with attention to device count rather than current draw.  Reconfiguring wiring runs to be as short and direct as possible has also helped.


Those GFCI devices can be sensitive and  do age and become more sensitive, especially the outdoor ones. Something to keep in the back  of your  mind when wiring up a bigger show.

[Stephen Swaffer]

There have been a number of discussions of GFCI functions on the Power and grounding forum.  The gist of it is is that UL allows a certain amount of leakage to ground for a device to be listed-but the total leakage to ground is the sum of the leakage of all devices in the chain.  Given that the threshold for a GFCI is only a few milliamps, it doesn't take many devices to have "acceptable" leakage to add up to a problem for a GFCI.

I would think it a good idea to test on a GFCI with maybe 50% more fixtures than you intend to use to make sure you have a bit of leakage "headroom".

[ProSoundWeb Community]