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Shocking reminder to install ferrule, then install wire, one-at-a-time.

thomBangor

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Joined
Jun 5, 2024
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Bangor, ME
I've never used ferrules before, and it threw off my wire-safety game. Forgot to go one-at-a-time (leaving the other wire covered in insulation).

I went to slip the pv wires through the aio frame and connected the 200 pv volts thru my forearm.

A good rule of thumb might be: you're doing it wrong if you can see more than one ferrule at a time.
Another good rule of thumb might be: wait until the wire is already installed right up to the last connection point before you install the ferrule.

Wondering if anybody else has a good rule of thumb?

1727956644663.png

edit: I should have been more explicit: I assume that anyone working with their wires live has the ends capped with wirenuts. So, remember that once you have a ferrule installed, your wirenut insulation is no longer possible. Factor that into your safety plans.
 
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I disconnect one of the MC4 connections on the string (PV is turned off at inverter/panel covered/not under load) before messing with the PV wires. And I check voltage on the AIO's PV connections before doing anything with those wires to make sure I disconnected the right string and/or that I am working on the right set of string connections at the inverter. One of my PV strings is around 400V, so not to be messed around with.
 
Ya I might even go further and not do that kind of work live.
I do hot work from time to time, but I try to avoid it.
When I do it and there is no option I wear type O gloves .
( I wear them all the time for testing too...., Snicker.... I am supposed to..... Listen wear proper PPE sometimes you can cut a corner and sometimes you cant but if your at risk of a serious shock or burn get some gloves and gauntlets .)
Keep your sleeves tucked in.


1727961349205.jpeg

I imagine the US navy also has boiler suits like this...
I don't know I have never seen them in surplus before.
But the Canadian and UK navies used to issue these to sailors.
Specially treated cotton that was flash rated to self extinguish if you were set a lite.
You can buy them very cheap because they expire, but even expired washed out flash suit is much better than nothing.
Before my employer began issue arc flash suits and clothing thats what I bought.
 
Even my one old ground mount array that was installed 20 years ago I go out and manually flip the breaker in the combiner box off before working on anything related to the system. Why were you working on live wires? Don't think the issue was the ferrules ;)
 
Why were you working on live wires?
Yep. Only way to avoid working with live wires in initial installation is to wire up before serial connection, disconnect an MC4 (assuming you didn't follow Prowse's advice to barrel crimp), or work in the dark. Even if you install a disconnect before the aio, your wires will be live when installing to the disconnect. In my case, the PV disconnect prior to the inverter is integrated onto the aio (EG4 6000xp); so technically I was wiring up the pv disconnect when this happened.

I don't work with live AC, but will work with live DC, if I have the wires capped with wirenuts. That is why I describe the ferrules as throwing me off. I needed to keep my wirenuts attached until the very last step, and then remove one, install ferrule, install into disconnect.
 
I should have been more explicit: I assume that anyone working with their wires live has the ends capped with wirenuts. Exposed high voltage DC conductors are great at arcing, and also known as a welding machine. So, remember that once you have a ferrule installed, your wirenut insulation is no longer possible. Factor that into your safety plans.
 
Some things have to be done live or they can’t be done at all
But some things that are done live probably could be done more safely with propper PPE and planning

Where I work there are several jobs that are not being done at all
I have offered to do them if the bosses would approve a hot work permit for me.

The longer it goes they are not done the more it’s going to cost when the machines fail.
 
TiGo RSD is your friend

Don't trust electronics with your life.

"Isolator", a UL rated disconnect that has 1" gap between conductors.

I turn off circuit, probing before/after to confirm by voltage change it was the right one.
Turn off DC disconnect (on some of my inverters, to isolate capacitors)
Unplug MC3 or MC4 at array
Lift touch-safe fuse holders if in circuit.
Probe to confirm zero volts.

(That's when I don't do something stupid and shock myself.)

or work in the dark.

Don't rely on darkness, certainly not opaque cover; doesn't take much to make voltage.

MC4 connectors are great for isolating. Confirm zero current first.
If you've decided to make hard connections for reliability, you'll need some way to work safely.

Some things have to be done live or they can’t be done at all
But some things that are done live probably could be done more safely with propper PPE and planning

PG&E of course does live service drops all the time.

The companies and labs I've worked for do live work almost never.

(An example of when it is appropriate is keeping fans powered for negative pressure in a facility that processes plutonium. But I think better planning, redundant fans, could address that.)
 
Don't trust electronics with your life.

"Isolator", a UL rated disconnect that has 1" gap between conductors.

I turn off circuit, probing before/after to confirm by voltage change it was the right one.
Turn off DC disconnect (on some of my inverters, to isolate capacitors)
Unplug MC3 or MC4 at array
Lift touch-safe fuse holders if in circuit.
Probe to confirm zero volts.

(That's when I don't do something stupid and shock myself.)



Don't rely on darkness, certainly not opaque cover; doesn't take much to make voltage.

MC4 connectors are great for isolating. Confirm zero current first.
If you've decided to make hard connections for reliability, you'll need some way to work safely.



PG&E of course does live service drops all the time.

The companies and labs I've worked for do live work almost never.

(An example of when it is appropriate is keeping fans powered for negative pressure in a facility that processes plutonium. But I think better planning, redundant fans, co
Well, next time i need to work on my plutonium powered reactor, i will be sure to keep that in mind, otherwise, i will just disconnect an MC4 and work at night.
I have an Iranian friend and he keeps his plutonium safely rolled up in a sock under a mattress
 
I first flip the on-inverter PV isolator, disconnect the MC-4s, flip the PV breaker (I added before the AIO), and only work at night.

I still wear gloves, and treat it like it's live anyway.

I always treat firearms like there's one in the chamber, too.
 
I connect my panels to a combiner, and in that combiner cabinet I have an isolation switch.

I wouldn't be doing anything on the system without isolating the battery (from both the controller charger, and the load! People miss that if the battery is connected to the charger, it will come back up that cable if you make a mistake) and the PV.

I even put up a checklist next to the whole setup so that it's clear what needs to be isolated, and what to do in an emergency.
 
I connect my panels to a combiner, and in that combiner cabinet I have an isolation switch.

I wouldn't be doing anything on the system without isolating the battery (from both the controller charger, and the load! People miss that if the battery is connected to the charger, it will come back up that cable if you make a mistake) and the PV.

I even put up a checklist next to the whole setup so that it's clear what needs to be isolated, and what to do in an emergency.
How about putting up a copy of your checklist ! I love checklists
 
Yep. Only way to avoid working with live wires in initial installation is to wire up before serial connection, disconnect an MC4 (assuming you didn't follow Prowse's advice to barrel crimp), or work in the dark. Even if you install a disconnect before the aio, your wires will be live when installing to the disconnect. In my case, the PV disconnect prior to the inverter is integrated onto the aio (EG4 6000xp); so technically I was wiring up the pv disconnect when this happened.

I don't work with live AC, but will work with live DC, if I have the wires capped with wirenuts. That is why I describe the ferrules as throwing me off. I needed to keep my wirenuts attached until the very last step, and then remove one, install ferrule, install into disconnect.
Why would you work with live DC if not with live AC? For the same voltage and enough amperage, DC is more dangerous. My theory is that most people's DC experience is with low voltage (and limited amperage). Thus the attitude. Is this why?
 
AC can be more dangerous, just a split second to disrupt heart rhythm.
vs. DC, needed time to deliver enough power to cause damage.

I've read that for AC, it depends on timing of the shock, so may be a roll of the dice.
I've been bit by both and don't recommend either.
 
Even with a breaker off or disconnect MC4, I would cover a panel or two in the string with a blanket. I know this can be difficult with some setups but its much easier on the gear. I always cover a panel when I'm disconnecting or connecting my solar string and all my strings are low volts/power.

I don't run that high voltage non-sense on any of my strings

Glad you lived to tell another day.
 
AC can be more dangerous, just a split second to disrupt heart rhythm.
vs. DC, needed time to deliver enough power to cause damage.

I've read that for AC, it depends on timing of the shock, so may be a roll of the dice.
I've been bit by both and don't recommend either.
They both hurt
Both cook tissues from the inside

But you can feel the difference
One a shaking spastic pain
One is burning clenching pain

Both kill equally well
 
AC can be more dangerous, just a split second to disrupt heart rhythm.
vs. DC, needed time to deliver enough power to cause damage.

I've read that for AC, it depends on timing of the shock, so may be a roll of the dice.
I've been bit by both and don't recommend either.
DC also disrupts your heart - just in a different way.

"Both AC and DC can disrupt the normal rhythm of the heart and evoke ventricular fibrillation"

People like my father, who worked as an engineer on fork trucks and the like (large DC lead-acid banks), kept a 2x4 and a friend handy. It's to remove your hands from whatever you're holding when you accidentally short the battery or chassis.

"Based on these thresholds, a touch voltage of 50 V AC or 120 V DC should not be exceeded in healthy adults to avoid a life-threatening situation"

"found that low-voltage DC caused unconsciousness (n = 11, 2.2%) or shock (n = 24, 4.8%) less often than low-voltage AC (n = 808, 7.3% and n = 598, 8.7%, respectively), but burns were more frequently documented"

People die from DC just the same way as from AC:

(Source of the above quotes)
 

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