Dc mini breaker confusion

[fromport]

Does that say negative 203 volts?

it does and that why it goes to zero when he connects things.

*ouch* I hope the input of your inverter survived

 

[Mannfamilywoodworks]

it does and that why it goes to zero when he connects things.

*ouch* I hope the input of your inverter survived

All is well ?

 

[Hedges]

Funny you say this.
I didn’t think to test the breaker in the “on”position and the “off” position at first.
After you said this I decided to test it.

it still allows 50ish volts to go through it?
Why is this?
It’s a breaker I got off Amazon.

That 50V may be backfed from your inverter. People have reported getting shocked from PV input terminals with no PV connected.
You could test with breaker isolated from inverter.
Or, with battery and any AC sources isolated from inverter.

 

[Hedges]

Positive side

Edithoto didn’t load

Negative side

Regarding your wire splicing methods ...

Unless those are grease-filled wire nuts, they may deteriorate with moisture.
Uh, does your inverter have AFCI? I think you may be needing that.

What I do is run conduit to a junction box. Cut a 1m MC cable in half, use as pigtails coming out of the box.
They can go through a compression gland, or bottom of the box to be drip-proof.

 

[Mannfamilywoodworks]

Regarding your wire splicing methods ...

Unless those are grease-filled wire nuts, they may deteriorate with moisture.
Uh, does your inverter have AFCI? I think you may be needing that.

What I do is run conduit to a junction box. Cut a 1m MC cable in half, use as pigtails coming out of the box.
They can go through a compression gland, or bottom of the box to be drip-proof.

I purchased a mc4 kit and a bunch of connectors I was planning on using those!
I just did this for testing purposes temporarily

 

[Mannfamilywoodworks]

That 50V may be backfed from your inverter. People have reported getting shocked from PV input terminals with no PV connected.
You could test with breaker isolated from inverter.
Or, with battery and any AC sources isolated from inverter.

Ahhh I didn’t think about that. Okay that makes more sense

 

[BradCagle]

it still allows 50ish volts to go through it?
Why is this?

Your charge controller has large capacitors on the PV input. They can stay charged even after you disconnect PV. This is probably what you're reading.

 

[BradCagle]

That 50V may be backfed from your inverter. People have reported getting shocked from PV input terminals with no PV connected.

I think it's the input caps of the charge controller holding voltage. Probably the same for the shock reports you're seeing.

 

[Vigo]

That 50V may be backfed from your inverter. People have reported getting shocked from PV input terminals with no PV connected.

Can't recall the thread but @RCinFLA explained some of that recently. Maybe he'll link to it or charitably do it again.

It's a good piece of safety info to spread around!

 

[Hedges]

Of course caps can hold voltage. I watch mine discharge, relatively fast. I think that is designed in as a safety feature.
Off-brands maybe not.

I think the guy who described getting a shock said he had not yet connected PV for the first time. It was a higher voltage system.

SMA Support sent me info on a firmware update for Sunny TriPower, which included:
"New function discharges the DC side in case of a rapid shutdown"
That probably is a faster discharge (like 30 seconds) than just disconnecting. Instructions say wait 20 minutes, but I'm impatient so I test.

 

[Hedges]

I purchased a mc4 kit and a bunch of connectors I was planning on using those!
I just did this for testing purposes temporarily

I've avoided having to do crimp terminations as much as possible. Still don't have proper tool for MC4, tried to use a Harbor Freight hydraulic hex crimper.
Mostly, I buy ready-made MC wire (MC3 or MC4) and cut in half.
I bought a lot of surplus junction boxes, which has kept me supplied in pigtails for all the test setups I put together (wires into switchboxes, to connect ammeter or short/connect load. Reconfigurable wiring on the garage floor before installing inverter.)

I did install some MC3 on ends of PV panel wires that had been cut. It would help to have correct size contact for the wire gauge, and correct size boot for the insulation. I used wire lube but it was still tough. Someone told me soften them in hot water, will try that next time.

I think originally MC4 was MC4 was MC4. Following the Walmart disasters, now the mated pair is only UL listed if the specific brands being used together have been tested and received UL listing together. Brand A may be listed with brand B, Brand B may be with brand C, but Brand A is not UL listed with brand C and is a fire hazard. Data sheet for your panels will declare which brands it can be mated with. i.e., you have the opportunity to not use that MC kit (unless it is the right brand/model), if you want to go by the book and be as safe as possible.

 

[Prince Of Darkness]

Many MPPT CCs use Synchronous Rectifiers, which are located between the battery, and the PV input. through some of the circuitry, like the buck inductor, etc. These rectifiers often have a small effective resistance between the PV inputs and the battery -- often around 10-ish K Ohm of R. This fairly high resistance can cause a voltage to appear on the PV terminals, if there is little leakage current, in that PV input circuit.

This voltage is usually present when the PV input disconnect is open, for those CCs with sync rectifiers.

IMO, POD 'Luke'

 

[Prince Of Darkness]

I should have heartily agreed with @Vigo, that, @RCinFLA has an amazing depth and breadth of knowledge about many RE, and general topics, and a very clear way of explaining fairly complex things ... Thanks, RC!

POD

 

[Mannfamilywoodworks]

I've avoided having to do crimp terminations as much as possible. Still don't have proper tool for MC4, tried to use a Harbor Freight hydraulic hex crimper.
Mostly, I buy ready-made MC wire (MC3 or MC4) and cut in half.
I bought a lot of surplus junction boxes, which has kept me supplied in pigtails for all the test setups I put together (wires into switchboxes, to connect ammeter or short/connect load. Reconfigurable wiring on the garage floor before installing inverter.)

I did install some MC3 on ends of PV panel wires that had been cut. It would help to have correct size contact for the wire gauge, and correct size boot for the insulation. I used wire lube but it was still tough. Someone told me soften them in hot water, will try that next time.

I think originally MC4 was MC4 was MC4. Following the Walmart disasters, now the mated pair is only UL listed if the specific brands being used together have been tested and received UL listing together. Brand A may be listed with brand B, Brand B may be with brand C, but Brand A is not UL listed with brand C and is a fire hazard. Data sheet for your panels will declare which brands it can be mated with. i.e., you have the opportunity to not use that MC kit (unless it is the right brand/model), if you want to go by the book and be as safe as possible.

Wow that’s really good to know and to be aware of.
I’m going to go up to my
Panels now and take a picture of the specifications sheet.
Hopefully I can use these mc4 kits as I hoped lol it was a whole 30ish dollars spent.

 

[Mannfamilywoodworks]

Your charge controller has large capacitors on the PV input. They can stay charged even after you disconnect PV. This is probably what you're reading.

My system has been off for three days while I was away working. These capacitors should be fully drained of power after 72 hours? Is that correct?
I’m going to take a reading now and see what I get.

 

[Mannfamilywoodworks]

After several days of the system being off.
I can verify the breaker is working properly.
I have 150ish volts coming into the breaker.
0v leaving the other end of the breaker.
This is what I was trying to accomplish the whole time.
I want to be able to stop power going into my unit at any given time.
The 50v I was reading previously was backfed from the growatt itself.

 

[BradCagle]

Of course caps can hold voltage. I watch mine discharge, relatively fast. I think that is designed in as a safety feature.
Off-brands maybe not.

Yeah a good designed should have a 5k or 10k resistor across the cap terminals to drain them when powered off.
But that is probably too much of an expense in many controllers

 

[Mannfamilywoodworks]

Yeah a good designed should have a 5k or 10k resistor across the cap terminals to drain them when powered off.
But that is probably too much of an expense in many controllers

I’m guessing I don’t get that or I do lol?

 

[Vigo]

If your voltage 'drained' somehow or another, you don't have anything to worry about other than to remember that just because you've flipped the breaker off doesn't mean there is instantly 0 volts on the other side. You either need to measure and wait until it drops to a safe level before touching it, or just come back later. It would help to measure the voltage 'rate of change' at least once just so you can ballpark how long you have to leave it alone before it drops to a low enough voltage to stop worrying about it.

And check both AC and DC volts to be safe. Arguably 50v DC is already unlikely to hurt you, but i still avoid touching it and there is a thread going on elsewhere where someone recently recounted some slight nerve damage in a finger gotten from a ~48v system. But there could be AC volts on there too, so just check both, establish a rough timeline of how long you need to let it 'drain' until you're comfortable touching it, and then use that info for all future occasions that you have to work on it. And preferably still verify with a meter anyway, because everything works the way it usually does, until it doesn't. ?

 

[Hedges]

Transformerless grid-tie inverters are capable of coupling AC onto the PV wires.
They are supposed to disconnect when not operating, but that is just transistors, and relays controlled by electronics. Not something you should trust your life to, so disconnect AC sources.

When transformerless GT PV inverter is connected to split-phase (e.g. 120/240V), no AC is seen. When connected to single phase (e.g. 277V or 230V L to N), or two legs of 3-phase (e.g. 208V), the PV wires will have a fairly constant DC between them, but will move with AC relatively to ground/neutral.

 

[Mannfamilywoodworks]

If your voltage 'drained' somehow or another, you don't have anything to worry about other than to remember that just because you've flipped the breaker off doesn't mean there is instantly 0 volts on the other side. You either need to measure and wait until it drops to a safe level before touching it, or just come back later. It would help to measure the voltage 'rate of change' at least once just so you can ballpark how long you have to leave it alone before it drops to a low enough voltage to stop worrying about it.

And check both AC and DC volts to be safe. Arguably 50v DC is already unlikely to hurt you, but i still avoid touching it and there is a thread going on elsewhere where someone recently recounted some slight nerve damage in a finger gotten from a ~48v system. But there could be AC volts on there too, so just check both, establish a rough timeline of how long you need to let it 'drain' until you're comfortable touching it, and then use that info for all future occasions that you have to work on it. And preferably still verify with a meter anyway, because everything works the way it usually does, until it doesn't. ?

That’s actually a great test and idea. I’m going to test that next time I power down the system. Thankyou very much.

 

[12VoltInstalls]

Positive side

Edithoto didn’t load

You need a much better weatherproof connection than wire nuts in tape. Actually not much better. You need a good weatherproof connection.

 

[12VoltInstalls]

Hopefully I can use these mc4 kits as I hoped lol it was a whole 30ish dollars spent.

Depends on the brand.

I personally proved the cheapies leak water and corrode inside with multiple replacements.

One cheapie brand that worked for me (over a year later and no failures) was Bouge RV. I bought a gazillion pairs and changed every one. Because I also proved mixing ‘brands’ also leak and the cheap brands have even been ferrous (magnet proves it).

Use a proper ‘B’ crimper and you’ll be fine.

Still don't have proper tool for MC4,

That really surprised me!

 

[wiseacre]

One cheapie brand that worked for me (over a year later and no failures) was Bouge RV. I bought a gazillion pairs and changed every one. Because I also proved mixing ‘brands’ also leak and the cheap brands have even been ferrous (magnet proves it).

As I did. The key is to keep all connectors the same brand and check them at least yearly.
Although MC4 connectors are supposed to be compatible I've found them not to be.
It might have taken a year but after seeing PV production drop I opened up the connectors and all the "mismatched" MC4s (original panel connectors to Bouge RV) had corroded to some extent, some pretty badly.

 

[Hedges]

Use a proper ‘B’ crimper and you’ll be fine.

(Still don't have proper tool for MC4)

That really surprised me!

Actually, I've never crimped an MC4. I bought a batch of MC3, because someone had cut all the connectors off a lot of panels.
It was from my experience with them that I said, "Make sure pins are correct size for the wire, and boots correct size for insulation.)

All the rest of my MC connections, whether 3 or 4, are either with pre-made extension cables or with pre-made cables I cut in half to make pigtails coming out of boxes. So I'm subject to component and assembly quality of whoever made them. I was working on stuff before it was figured out that MC4 doesn't mate to all MC4 reliably, and UL Listing required tested pairs of brands, and PV panel labels reflected that.

I preferred MC3. Nice machined pins. MC4 looks like the cheapest rolled sheetmetal contacts possible, suitable for Molex connectors inside an appliance. I think quality contacts would be something like hardened and tempered beryllium copper. But even those sometimes aren't manufactured correctly, as figured out from field failures. Contacts have a spec for range (tolerance) of pin sizes they accept, and how much they spring back.

I may yet experience overheated or corroded MC connectors, but hasn't happened so far. Relatively mild weather here. In a place like my mountain property where everything rusts, could be different.

I have ratchet crimper with many other die types, and Harbor Freight hydraulic for larger cables. Need to get a ferrule crimper.

It might have taken a year but after seeing PV production drop I opened up the connectors and all the "mismatched" MC4s (original panel connectors to Bouge RV) had corroded to some extent, some pretty badly.

Maybe dielectric grease between boot and insulation, and mating surface of boots, is the thing to do.

But certainly don't want ferrous contacts, and drop in production must mean severe heating of connectors (or else some strings completely open).