Lux/eg4 18k/12k. Got shocked while in standby.

[kennyb]

Tldr: lux12k, eg4 18k Carries ~200vdc on the grid lines in off-grid mode. Even in standby voltage is present. Be careful.

Not sure if this has been discussed before.

I was working on the grid splitter box pulling feeders to the outdoor disconnect (no grid here, but future proofing) I put the inverters in standby, turned pv off, and then checked the EPS terminals were off and no AC voltage present.

Went about my business and got a zap. Grabbed my tester, sure enough after checking, I found 60vdc on the grid terminals. So I re-enabled the the inverters and checked. ~200vdc live to ground/neutral.

I contacted lux and got a pdf in response saying that "this is normal, and not a shock hazard".

A couple things; I did get a shock, it wasn't my imagination. Voltage doesn't go to 0 under load - I have a constant 250w load and I've checked with a 2000w load. ~200vdc always present. My Inspector is going to raise hell about un-documented voltage sources being present on "dead" lines.

This is a hazard and should be documented in the manuals.

 

[Brucey]

Standby is not the same as total shutdown and all input power sources turned off.

 

[kennyb]

Standby is not the same as total shutdown and all input power sources turned off.

No grid connection. No input. No pv.

Regardless. There is an undocumented 200vdc present on the grid terminals when the inverters are in "off grid mode"

 

[timselectric]

Always remove all power sources before working on anything.

 

[Brucey]

No grid connection. No input. No pv.

Regardless. There is an undocumented 200vdc present on the grid terminals when the inverters are in "off grid mode"

The battery input was connected?

 

[wpns]

It’s been mentioned before (I measured 400Vdc? Maybe across L1-L2?) but it seemed to disappear with a 60W(?) incandescent bulb, so figured it wasn’t a hazard. Yours seems to act differently, but I’ve been meaning to put an ammeter on it.

 

[kennyb]

The battery input was connected?

When the shock occured yes. I'll be sure to kill the entire thing next time.

But I think this still misses the point. When operating in off-grid mode, and the inverter is enabled, the inverters have 200vdc present on the grid terminals.

 

[timselectric]

When set to "Off-grid mode" it should open the grid relay. There shouldn't be anything on those terminals, because they aren't connected to anything.

 

[kennyb]

When set to "Off-grid mode" it should open the grid relay. There shouldn't be anything on those terminals, because they aren't connected to anything.

I know. Which is why I wrote it's a hazard. There should have been nothing present on those lines. And yet there is.

I tested with microgrid on and off as well. It's present.

 

[wpns]

When set to "Off-grid mode" it should open the grid relay. There shouldn't be anything on those terminals, because they aren't connected to anything.

It appears to be part of the grid detection. I agree you shouldn't need that in off-grid mode, but engineering in the ability to disable it under certain circumstances opens up a whole can of worms and it's _SUPPOSED_ to be a high enough impedance to not present a shock hazard, though clearly not in at least one case. Wrong component values in one (run of) PCB(s)?

 

[kennyb]

It appears to be part of the grid detection. I agree you shouldn't need that in off-grid mode, but engineering in the ability to disable it under certain circumstances opens up a whole can of worms and it's _SUPPOSED_ to be a high enough impedance to not present a shock hazard, though clearly not in at least one case. Wrong component values in one (run of) PCB(s)?

From the pdf i attached, i gather it has to do with the neutral relay closing during off grid operation. Lux states that the caps are supposed to bring the voltage to 0 during a load, but that doesn't occur on mine for whatever reason. I'll put plaques on any access point. For now both ends are padlocked.

I just wanted to raise awareness.

 

[Quattrohead]

Thanks for raising awareness and reminding us all, anytime you are working in an electrical cabinet even if you know it is all turned off, confirm with a tester.
Kenny, it would be very interesting to connect a regular household bulb not led, to those terminals and see whether it lights up or whether your voltage disappears. It's either slight voltage leak to do with the grid detection circuit, or there's a small possibility you actually have a faulty component there somewhere.

 

[timselectric]

It appears to be part of the grid detection. I agree you shouldn't need that in off-grid mode, but engineering in the ability to disable it under certain circumstances opens up a whole can of worms and it's _SUPPOSED_ to be a high enough impedance to not present a shock hazard, though clearly not in at least one case. Wrong component values in one (run of) PCB(s)?

Makes sense, grid detection would still be connected to the port.

 

[rhino]

I just checked mine.. it also has 220V DC and I am in off grid mode.

 

[wpns]

I just checked mine.. it also has 220V DC and I am in off grid mode.

Can you easily put a lightbulb across it and/or measure the current?

 

[ksmithaz1]

This evening I shuffled me feets across the carpet. . . Ouch touching the metal on the lamp.

 

[Quattrohead]

That's another reason I moved to Florida, frightens the shit out of me now when it very occasionally happens during our cold spells.
Although there used to be something quite satisfying about tearing off your pullover and lighting the room up.

 

[ricardocello]

This evening I shuffled me feets across the carpet. . . Ouch touching the metal on the lamp.

10,000V! You’ve got to do something about that !

 

[Brucey]

That's another reason I moved to Florida, frightens the shit out of me now when it very occasionally happens during our cold spells.
Although there used to be something quite satisfying about tearing off your pullover and lighting the room up.

Jumper

 

[Brucey]

10,000V! You’ve got to do something about that !

Permanent flexible ground strap on ankle.

 

[timselectric]

Permanent flexible ground strap on ankle.

You probably meant that as a joke, but it is a thing.
I done some work at an alarm manufacturing company. Where they made glass breakage detection sensors. And each worker has a grounding wristband, at their station. Because a static discharge would destroy the sensor.

 

[Brucey]

You probably meant that as a joke, but it is a thing.
I done some work at an alarm manufacturing company. Where they made glass breakage detection sensors. And each worker has a grounding wristband, at their station. Because a static discharge would destroy the sensor.

Yeah I was joking, and I know about wristbands for assembly workstations. Never really got into it during my PC building days but I'd always leave the psu connected to the wall and ground myself on the chassis before installing a cpu/mem/gpu etc.

 

[ricardocello]

Yeah I was joking, and I know about wristbands for assembly workstations. Never really got into it during my PC building days but I'd always leave the psu connected to the wall and ground myself on the chassis before installing a cpu/mem/gpu etc.

I’ve been in labs with anti-static floors with copper tape running up to the outlet grounds.
And they make you wear a ground strap over your shoe with a lead that you tuck into your sock.
And there is a strap tester at the door when you enter, you have to pass the test with a beeper (like standing on a scale).
And there are rules for wrist straps at the benches.
And the lab safety person is also the local anti-static nazi.
And yet, you still hear the electrical engineers blame their latest board failure on ESD.

My labs: Install a humidifier in the winter, always wear straps the bench. Done.
Making a career out of ESD protection is one of my pet peeves.

 

[Brucey]

And yet, you still hear the electrical engineers blame their latest board failure on ESD.

Easy to be assigned as the patsy versus poor design

 

[Oldphile]

We had anti-static mats on our benches. Nobody used the straps. 20+ years, I never saw a failure due to static.