made a mistake

wellbuilt

Yes I have the tools for the mc4 cables all I need is the time now 
I’m trying to get back there next weekend but I my son is  Busy 
  Getting old sucks and I can’t  balance the panels on my head while”  unplugging them 
   I can’t really work buy my self In case I have some type of accident never now

BB.

I agree--It sounds like the panels should not have been damaged because of the low current with low sun angle.

However, that does beg the question of how the breaker got toasted if current was so low.

-Bill

Estragon

Low current, but even in low early light, voltage might be pretty high. 100ish vdc could arc (maybe "sizzle") even at lowish current, couldn't it?

Vic

BB Bill said,  "However, that does beg the question of how the breaker got toasted if current was so low".

BINGO !!

The MNEPV breakers are designed to handle currents at the Rating and voltage of the breaker for up to 10,000  5,000 trips.

Not having seen a pic of the exact damage to the breaker,   it is a bit difficult to know ...

The current flowing into that reversed string at the time of the event might have been different than that noted,  later.   Perhaps,   at the initial breaker closure,   the battery or loads need more current,   but by the time that wellbuilt was able to observe the CC power,   that that need had passed  ... 

It really does seem that at some point the current into that string must have been significantly higher than that represented by 50,  or 130 (or was it 150 Watts.

One might also wonder if the breaker terminals were correctly torqued,   but,   here too,   significant current flow would be needed to cause discoloration,   unless the connection/s were very loose at the terminals.

Vic

Vic

In doing some checking on the MidNite Solar Forum,  found the following from Robin (CEO & Founder of MidNite,  and OutBack):

"Both the panel mount and the din rail mount breakers must pass the 5000 times under full load. They also must pass some really bizzare short circuit tests. We had to pass about 2000 amps through the little CBI breakers at 165 volts 50 times before they would give us the 150VDC rating. Make sure they aren't hooked up backwards in a case like that though. It will fail on the very first time you open up the breaker.
Both breakers are very high quality. Use whatever suits your fancy. If anything ever breaks, just give us a call for a free replacement. That just doesn't happen very often. Maybe once a year.
Robin".

The above was from this Thread:
http://midniteftp.com/forum/index.php?topic=351.msg2020#msg2020

So  I was wrong about the number of rated cycles of both the MNEPV and MNEDC breakers.
That number of cycles is 5000 at full rated load   ...   sorry for the mis-statement.

FWIW,   Vic

Estragon

I'm curious/confused about Robins "hook up backwards"... "it will fail the very first time" comment. If the breaker is on the negative, does that make it "backwards".

BB.

Possibly.

One of the ways these DC breakers can be constructed is to put a permanent magnet next to the Arc chute. The arc current is blown into the arc chute.

Connect a DC breaker with reverse current flow, the arc may be sucked into the breaker assembly and cause damage and or sustained arcs.

I cannot say what happened to this breaker. Not my area of knowledge.

Bill

Vic

The breaker in question  --  MNEPV DIN Rail type  --  DO have permanent magnets inside,   evidenced by a weak attraction twix several breakers.

FWIW.   Vic

wellbuilt

Really , I had 2 strings of 3  panels powered up and I was Waiting for the FM80 to wake up 
 it starts the wake up at 50 watts between 730 and 800 . 
 I walked around back and turned on the first new string and pop  sizzle and I turned it off right away. 
 Went to check the out put of the panels And only had 60 watts.
 The sun was still very low behind the trees.

wellbuilt

The breaker was   Sizzling and I pushed it off with my finger It did not turn off 

Vic

wellbuilt said:

Really , I had 2 strings of 3  panels powered up and I was Waiting for the FM80 to wake up 
 it starts the wake up at 50 watts between 730 and 800 . 
 I walked around back and turned on the first new string and pop  sizzle and I turned it off right away. 
 Went to check the out put of the panels And only had 60 watts.
 The sun was still very low behind the trees 

v

wellbuilt,

OK,   most of us here,   were not at your location.   As almost always,   we all are trying to use the info provided,   and from our experiences to try to make some sense on what might have happened.

We almost ALWAYS want/need MORE info.   Your situation,  to me,  does not make a lot of sense   ...   that is all,   was not trying to be snarky.   It was not obvious where you were when you were switching breakers,  and  so on.

In addition,   with many Buck type MPPT CCs,  you do not want to see a short  between the PV input terminals.   This can toast the CC's FETs.   It is not clear (to me),   if some of this current that the breaker was experiencing might have been coming from the battery,   via the CC PV input terminals.   This would depend upon things ...   But you did not say that there was any issue with the CC.

There seem to still be some unknowns,   and probably this person should really stop trying to guess toooooooo   much.

FWIW,   Vic






 

wellbuilt

Thank for the in put Vic . 

bill von novak

wellbuilt said:

The breaker was   Sizzling and I pushed it off with my finger It did not turn off 

That's the hallmark of an arcing breaker.

Estragon

My thought also. The question was (I think) whether the panels were damaged, so it seems to me the next step would be to disconnect the mc4 connectors to the suspect panels and check the open circuit voltage of each.

Agree about getting old sucks, but it beats the alternative. I wouldn't balance the panels on my head doing this, but might rig some fall protection if on the roof on my own

wellbuilt

Ya it’s just killing me , not knowing how much trouble I caused my self . 
 I had to leave to head home and did not get a chance to check things out . 
 My son just runs up the ladder and hold the panel with his head and  makes the connections and screws it down .
  I can’t stand to work on a 9 pitch roof bad ankle I have to have help . 
 I found my meter so that should help . 

wellbuilt

I  guess I got lucky , my son did not notice one of the mc4 Connectors pulled out when he was tugging on the  connection . 
 It was a simple fix I changed out the burnt breaker fixed the plug and every thing is working fine. 
I did swap out the 3 Questionable panels for new ones , but before we took them down they were reading the same as the other strings. 
 It’s 930 and I’m coming up to 98% charge .