How hot is to hot? Combiner box

[42OhmsPA]

Thought it was a poor connection, not the case, same temps after a new wire.
Noticed it yesterday.

 

[Supervstech]

Any significant heat spot is a point needing attention.
The fact it is 130 on that screw, but nowhere else on the circuit says to me the device has a bad connection, not a bad wire

 

[42OhmsPA]

I'm going to skip the fuse holder and go straight to the breaker for piece of mind until I get better fuse holders.

This was the wire I replaced.

https://diysolarforum.com/attachments/img_20240225_101620-jpg.198269/

 

[Supervstech]

I'm going to skip the fuse holder and go straight to the breaker for piece of mind until I get better fuse holders.

This was the wire I replaced.

https://diysolarforum.com/attachments/img_20240225_101620-jpg.198269/

Wire looks fine, the connection in thw holder must be bad.

 

[42OhmsPA]

It was still over 90F after sitting for over 5 minutes.
Direct to the breaker now, 40A Chitaxi.

 

[400bird]

Copper conductors both heat and electricity, so a bad connection or bad fuse holder will cause the wire to get hot.

Did you try loosening and retorquing the clamp screw? If so, I'd pop open the fuse holder to see what's inside.

 

[42OhmsPA]

One thing to note is I did split the holder apart, it was 3p. That shouldn't have had any impact at all since it was just a pin holding them together, nothing to do with the wire connection.

 

[42OhmsPA]

Copper conductors both heat and electricity, so a bad connection or bad fuse holder will cause the wire to get hot.

Did you try loosening and retorquing the clamp screw? If so, I'd pop open the fuse holder to see what's inside.

Yes, no difference before and after replacing the wire as well.

I was having issues blowing 20A fuses a few days / weeks back but figured that was because I was running ~22A through them. I used a 25A I ordered the other day and figured I'd check temps after the recent fire thread...
Everything with the holder appeared fine.

I'll get some Midnite holders on order and see if they make a difference.

 

[400bird]

Why are the spec on the front (32a @ 690vac) vs the side (30a @ 750vac)?

Is that fuse holder rated for DC? It probably doesn't matter it's just a fuse holder, the fuse is the important part.

Pics of the inside?

What current was the constant current running through it and the fuse rating?

 

[400bird]

Yes, no difference before and after replacing the wire as well.

I was having issues blowing 20A fuses a few days / weeks back but figured that was because I was running ~22A through them. I used a 25A I ordered the other day and figured I'd check temps after the recent fire thread...
Everything with the holder appeared fine.

I'll get some Midnite holders on order and see if they make a difference.

I see you posted the answer to my current question just as I was asking it.

22 amps continuous throughout a 25 amp fuse, is likely the problem. A fuse is a resistor and creates heat to melt and blow.

Normal recommendation is to run a fuse at a max of 80% continuous. Stepping up the fuse to 30 amp would be the minimum to meet that spec.

Was the other holder doing the same current?

 

[TomC4306]

I had a similar issue at the breaker.
Was getting hot enough to trip it .
I THOUGHT I was able to 'torque' the screw down with just a screwdriver in my hand but went ahead and put a bit holder and bit on my torque wrench.
More than half a turn later, the issue iwas fixed.

 

[TomC4306]

I also removed the big diodes with heat sinks in my combiner because they produce a lot of heat in a sealed box.
Swapped in a bus bar.

 

[42OhmsPA]

Why are the spec on the front (32a @ 690vac) vs the side (30a @ 750vac)?

That's a good question.

Is that fuse holder rated for DC? It probably doesn't matter it's just a fuse holder, the fuse is the important part.

According to the Amazon listing, yes.

Pics of the inside?

Can't get much without breaking it open.

What current was the constant current running through it and the fuse rating?

I see you found it.

I see you posted the answer to my current question just as I was asking it.

22 amps continuous throughout a 25 amp fuse, is likely the problem. A fuse is a resistor and creates heat to melt and blow.

Normal recommendation is to run a fuse at a max of 80% continuous. Stepping up the fuse to 30 amp would be the minimum to meet that spec.

Was the other holder doing the same current?

No. The other strings (roofs) are running around 340V 9A at peak conditions but are combined after the fuse.
The ground mount fuse in question is paralleled at the array.

 

[42OhmsPA]

I had a similar issue at the breaker.
Was getting hot enough to trip it .
I THOUGHT I was able to 'torque' the screw down with just a screwdriver in my hand but went ahead and put a bit holder and bit on my torque wrench.
More than half a turn later, the issue iwas fixed.

I'm confident they are tight enough.
If I go any tighter I'll break something.
I could see the plastic flexing when tightening...
I was able to get another ¹/⁵ a turn on the other connections that aren't getting hot.

 

[42OhmsPA]

I'll order some 30A fuses to go with the midnite holders.

 

[HalfBaked]

I'll order some 30A fuses to go with the midnite holders.

Were you able to resolve this? I just got a thermal cam and so far only seeing hot temps in the combo box. Mostly around the diodes in the middle, 156f. (99f ambient) This doesn't feel good.
I saw where @TomC420 said he replaced his diodes with a bus bar. Is this my best move?

 

[seneysolar]

I'll order some 30A fuses to go with the midnite holders.

Just curious, have you tried running it without the ferrules?

 

[42OhmsPA]

Were you able to resolve this? I just got a thermal cam and so far only seeing hot temps in the combo box. Mostly around the diodes in the middle, 156f. (99f ambient) This doesn't feel good.
I saw where @TomC420 said he replaced his diodes with a bus bar. Is this my best move?

I never did install the midnite holder and 30A fuses, temps were fine using the breaker.
I definitely will be installing the holder when I add my 2nd ground mount.
I'm really not sure on the diodes, I didn't notice anything really hot when I checked the panels.

Just curious, have you tried running it without the ferrules?

I can't remember, don't think so.

 

[robbob2112]

Your picture of the ferrule looked like it wasn't full and was flattened verse hex crimped.

Not full is a bad connection. I wonder if this was your problem back then.

I will assume the flattened verse hex is from torquing down the breaker.

I have a post in my answer thread in my sig line about ferrules.

 

[42OhmsPA]

Thanks, I'll check it out.

It is a square crimper not a hex and they were definitely squished from torquing down.

One was using PV wire with thick strands the other was marine rated with fine strands. I think it was full, I'll see if I still have those whips in my junk bin.
I leave a ~1/"4 of wire sticking out of the end of the ferrule, crimp, spin, crimp again then trim off the excess sticking out. Not sure if that's correct but it made sense in my mind.

 

[robbob2112]

No harm but no need if the ferrules are full and good quality. And like a lot of things 99% of ferrules of amazon are junk. To thin, metric wire sizes, to short, etc.

Ferrules should be totally full or you have the wrong size.

 

[ThaiTaffy]

Are they tinned copper ferrules or chepo Chinese stainless steel?

 

[TomC4306]

Were you able to resolve this? I just got a thermal cam and so far only seeing hot temps in the combo box. Mostly around the diodes in the middle, 156f. (99f ambient) This doesn't feel good.
I saw where @TomC420 said he replaced his diodes with a bus bar. Is this my best move?

Fixed the nuisance CB trips due to heat in the box.
Was tripping every day last summer. Hasn't tripped once since this change.