147 volts dc will not pass thru breaker (yes, breaker is on)

[Crowz]

+1
MC4's are designed expressly so you don't have to disassemble them

This is also why a commissioning step is very important; imagine if the connector was *mostly* working, just dropping say 30% of the voltage instead of all the voltage. In this case, you might not notice the problem, but if you had commissioned, you would have picked up that the current and voltage didn't match the expected values, and investigate.

Regarding the dielectric grease comment, you should probably only follow the manufacturer's installation procedures. None of the MC4's I've ever used require (or even allow) the addition of any sealant or insulator, but I will stand corrected if someone can point me to one.

And with MC4's, be wary of any internet "expert" that tells you to disassemble the connector and slide part of it onto the cable before crimping - I've never come across an MC4 manufacturer that teaches disassembly of the MC4 - this is a recipe for getting a seal pinched, water ingress, and connector failure.

I'm dying to see how this not having to disassemble them to to put the ends on for crimping works.

Lets use this video here so you can tell us what he did wrong when he "took it apart" to crimp the end. I know that most of the mc4 end will fight you tooth and nail shoving that end into it without unscrewing the part off the mc4 connector. I also know its a heck of allot easier to get the holder onto the cable before you crimp the end on it.

 

[Bluedog225]

+1
MC4's are designed expressly so you don't have to disassemble them

Right? They just burn off on their own. ?

 

[PVorBust]

I know that most of the mc4 end will fight you tooth and nail shoving that end into it without unscrewing the part off the mc4 connector.

Try buying better connectors.
If you need to pull every connector apart to get it on the cable, you are doing something wrong.

 

[400bird]

I'm dying to see how this not having to disassemble them to to put the ends on for crimping works.

Lets use this video here so you can tell us what he did wrong when he "took it apart" to crimp the end. I know that most of the mc4 end will fight you tooth and nail shoving that end into it without unscrewing the part off the mc4 connector. I also know its a heck of allot easier to get the holder onto the cable before you crimp the end on it.

I've used both Staubli genuine MC4 and Amphenol knockoff MC4. Both work the same way. Crimp terminal into wire, shove wire and terminal through assembled connector, tighten nut. No need to disassemble, I don't think there's any harm in disassembly, just wasted time.

In the video, I'd say he went "wrong" right where he removed the rear part and more importantly where he didn't use a tool to tighten the nut to get a good seal. There's a torque spec for the nut to get the seal properly compressed. I don't remember what it is, but more than hand tight.

I don't know how to link directly to a time stamp. Assembly starts at 6:51

 

[Crowz]

I've used both Staubli genuine MC4 and Amphenol knockoff MC4. Both work the same way. Crimp terminal into wire, shove wire and terminal through assembled connector, tighten nut. No need to disassemble, I don't think there's any harm in disassembly, just wasted time.

In the video, I'd say he went "wrong" right where he removed the rear part and more importantly where he didn't use a tool to tighten the nut to get a good seal. There's a torque spec for the nut to get the seal properly compressed. I don't remember what it is, but more than hand tight.

I don't know how to link directly to a time stamp. Assembly starts at 6:51

I tighten mine till the plastic tool "slips". I figured it was by design to give the right tightening spec

 

[ksmithaz1]

Very interesting about the voltage and breaker size. What is the source for this?

A google search for me turns up instructions on how to size a breaker for amps without mentioning how much to oversize for voltage.

Because circuit breakers/fuses trip based on current (amps) not voltage. The breaker must be rated at or below the voltage it is being used for. That being said if your voltage rating is drastically lower it may affect your trip curve a bit.

 

[Hedges]

Because circuit breakers/fuses trip based on current (amps) not voltage. The breaker must be rated at or below the voltage it is being used for. That being said if your voltage rating is drastically lower it may affect your trip curve a bit.

I hope that was a Freudian slip, or some alternative.

 

[ksmithaz1]

Regarding the dielectric grease comment, you should probably only follow the manufacturer's installation procedures. None of the MC4's I've ever used require (or even allow) the addition of any sealant or insulator, but I will stand corrected if someone can point me to one.

And with MC4's, be wary of any internet "expert" that tells you to disassemble the connector and slide part of it onto the cable before crimping - I've never come across an MC4 manufacturer that teaches disassembly of the MC4 - this is a recipe for getting a seal pinched, water ingress, and connector failure.

I used WD-40, YMMV. Kinda depends on if you want to get the f*cking thing apart later, tool or no tool. The lubricant would be for the O-ring that seals the male part of the plastic that is shrouding the female contact, where it slides into the female housing that shrouds the male contact so the ring does not disintegrate into goo and/or sieze the crap together. Silicon would probably be the best, my can was empty.

I bought a large box of Chinese knock-offs, that seem to be much better engineered than the junk on the CS panels that I had to cut-off and replace because I had to shatter the connector to get them loose, but hey! Any connector left out in this dust-pit place with it's wild rapid temperature swings, and extreme sun needs to have a little wider tolerance. I also note, I isolated 'spotty' panels, that were causing wide fluctuations of output on the used panel arrays I built, and in all but 1 case replacing the MC-4's corrected the issue.

 

[Hedges]

With 0V out of the breaker, could be open or dead short.
I was hoping to read 1V or 2V, a reverse-polarity protection diode.

Breakers usually have accessible terminals. Probe there to see if there is voltage in, to distinguish open connection from open breaker.
With PV disconnected, test continuity of breaker.

 

[ksmithaz1]

Original question around oversizing a breaker for voltage and why you don't see it anywhere.

Because circuit breakers/fuses trip based on current (amps) not voltage. The breaker must be rated at or below the voltage it is being used for. That being said if your voltage rating is drastically lower it may affect your trip curve a bit.

I hope that was a Freudian slip, or some alternative.

We were talking about DC breakers for a PV array? They do have a recommended range, but breakers and fuses trip generally based on current not voltage. That being said you should not exceed nor go below any voltage rating listed for a breaker, as they work a little differently than a fuse. A fuse doesn't generally give a crap, which is why they tend to be used for solar panels. A 500v/1A fuse will happily blow if you run 1.25A @ 12v thru it. Modern breakers will trip both thermally and magnetically, and an over-voltage condition usually comes with a corresponding over-current condition as the resistance/reluctance/impedance of the load does not change causing an exponential increase in current. If there is something there I have misunderstood please enlighten.

 

[ksmithaz1]

Original question around oversizing a breaker for voltage and why you don't see it anywhere.





We were talking about DC breakers for a PV array? They do have a recommended range, but breakers and fuses trip generally based on current not voltage. That being said you should not exceed nor go below any voltage rating listed for a breaker, as they work a little differently than a fuse. A fuse doesn't generally give a crap, which is why they tend to be used for solar panels. A 500v/1A fuse will happily blow if you run 1.25A @ 12v thru it. Modern breakers will trip both thermally and magnetically, and an over-voltage condition usually comes with a corresponding over-current condition as the resistance/reluctance/impedance of the load does not change causing an exponential increase in current. If there is something there I have misunderstood please enlighten.

S*T At or ABOVE. the voltage you are using. I'm an idiot.

 

[Hedges]

If there is something there I have misunderstood please enlighten.

The breaker must be rated at or below the voltage it is being used for.

I would say breaker must be rated at or above the voltage it is being used for.

We were talking about DC breakers for a PV array? They do have a recommended range, but breakers and fuses trip generally based on current not voltage. That being said you should not exceed nor go below any voltage rating listed for a breaker, as they work a little differently than a fuse.

Is there any reason why a 600V rated breaker would trip differently in a 36V circuit than in a 600V circuit?
I don't think it sees the circuit voltage (prior to tripping) except across its insulation to chassis.

But yes, I've noticed that a 600V rated Class T fuse has different characteristics from a 300V rated Class T fuse. Whatever they did to absorb the greater amount of energy affects its let-through and other characteristics, when blowing. And its characteristics of when it blows - longer element will have different thermal behavior, as heat is conducted out the ends.

I was looking at fuse curves, trying to coordinate a ~ 400A fuse with a 200A breaker such that if a bonded fault occurred the fuse would go first and protect breaker from destruction (they're rated for only one or two operations above a certain fault current level.)

So I would say a 600V fuse or breaker's behavior will be somewhat different from a 300V one (for circuits not exceeding rating of either).

 

[Hedges]

I used WD-40, YMMV. Kinda depends on if you want to get the f*cking thing apart later, tool or no tool. The lubricant would be for the O-ring that seals the male part of the plastic that is shrouding the female contact, where it slides into the female housing that shrouds the male contact so the ring does not disintegrate into goo and/or sieze the crap together. Silicon would probably be the best, my can was empty.

Lubricant and rubber compatibility (something all guys should be familiar with). There are many different materials.

I would be concerned WD-40 might dissolve seals.

I have a particular grease for use with seals on pool pump.

Silicone lubricants are also only for some seal materials. I was reviewing a recommendation for field maintenance, when the factory material wasn't readily available. Because the program had assigned its own part numbers, was more difficult to track down manufacturer data. But turned out to be a silicone lube being considered, and the device had silicone O-rings. Those were NOT compatible.

 

[ksmithaz1]

I would say breaker must be rated at or above the voltage it is being used for.

So would I if I didn't have my head up my ...

Is there any reason why a 600V rated breaker would trip differently in a 36V circuit than in a 600V circuit?
I don't think it sees the circuit voltage (prior to tripping) except across its insulation to chassis.

Perhaps not as much with a modern breaker, If it's a thermal trip it will take a longer to heat up, and at lower voltages there is a tendency for greater current loss at the source and sink, so technically it shouldn't, in practice it might change the curve slightly but it should trip as long as you are sinking the current. I was torn fuse/breaker, but I settled on the breaker because I can use it as a switch from time to time.

 

[Hedges]

Fuse, the element is going to be longer for higher voltage rating, changing its thermal characteristics.
Thermal-magnetic breaker, I think thermal element would be the same. Just pole spacing, arc chute, etc. would be different.

So maybe only fuses have characteristics changed when voltage rating is different. If packaged in the same body size (e.g. QO 3-pole breakers rated 277V/pole, vs. 2-pole "120/240V" which are only 120V unless explicitly higher.)

Then there are magnetic-hydraulic, which I didn't understand at first (what mechanism could give such a long delay). Turns out to be a spring-loaded core moving through silicone oil, which changes the magnetic coupling from coil to trip mechanism.

 

[ksmithaz1]

Lubricant and rubber compatibility (something all guys should be familiar with). There are many different materials.

I would be concerned WD-40 might dissolve seals.

I have a particular grease for use with seals on pool pump.

Silicone lubricants are also only for some seal materials. I was reviewing a recommendation for field maintenance, when the factory material wasn't readily available. Because the program had assigned its own part numbers, was more difficult to track down manufacturer data. But turned out to be a silicone lube being considered, and the device had silicone O-rings. Those were NOT compatible.

Scowl, yea, generally in my experience silicone lubricants are better for most cheap o-rings, but I find it interesting that a silicone based lubricant would not be suitable for a silicone O-ring. Plastics on cars are generally fairly tolerant of most oils, but the problem with alcohol based fuels comes to mind. A lot of the automotive seals around connectors went to an orange waffle stuff a while back. I'm guessing the chinese built MC-4 is not using anything esoteric, probably ABS with an off-the-shelf silicone o-ring. Maybe we should try KY Jelly?

 

[ksmithaz1]

My father owned a swimming pool company. We always used Vaseline on all the housing buckets and such. Been a long time, but I think we used it for the impeller shafts and the like as well. For some reasons customers didn't like to see black lithium grease all over everything at their pool.

 

[PVorBust]

I find it interesting that a silicone based lubricant would not be suitable for a silicone O-ring.

Same with sex toys - never use silicon lube on silicon rubber.

black o-rings are likely to be a nitrile rubber, while orange are probably a fluro-elasomer

Vaseline will destroy latex, but is ok on silicone.

You need to know your "rubber" before you pick your lube.

 

[Hedges]

That's what I said!

Lubricant and rubber compatibility (something all guys should be familiar with).

;^)

 

[Hedges]

(Did I say I bring to bear my experience from a wide range of disciplines?
I'm a "multi-disciplinary" engineer.)

 

[ksmithaz1]

Same with sex toys - never use silicon lube on silicon rubber.

black o-rings are likely to be a nitrile rubber, while orange are probably a fluro-elasomer

Vaseline will destroy latex, but is ok on silicone.

You need to know your "rubber" before you pick your lube.

Got it KY Jelly for, ...

 

[Whats_per_question]

I'm dying to see how this not having to disassemble them to to put the ends on for crimping works.

Lets use this video here so you can tell us what he did wrong when he "took it apart" to crimp the end. I know that most of the mc4 end will fight you tooth and nail shoving that end into it without unscrewing the part off the mc4 connector. I also know its a heck of allot easier to get the holder onto the cable before you crimp the end on it.

Hi @Crowz
There is a chance that the brand he used recommends disassembling the 'nut' end of the MC4, but i doubt that very much.
The correct way (according to every MC4 supplier i've ever used) is to crimp the metal part like he did, then simply push the metal part into the MC4 until you hear and feel the click, then pull back to ensure it has engaged. This is what the barbs are for - to allow the metal part to be inserted but not pulled out. If the correct way to fit was to disassemble, the barbs would instead be collars, and there would be a greater difference between the diameter of the metal connector part and the outer diameter of the collar.

I saw another user comment that "it probably doesn't hurt" - i disagree. There is a very real chance that you pinch the seal when trying to re-fit the back end of the MC4, leading to leakage, corrosion, and a failed connector, possibly a fire.

I don't know why anyone would argue against using the manufacturer's instructions just because "that's how i was taught" or "that's what i saw on the web" or any other reason?
Why would you risk a declined insurance claim when the correct installation method is faster, more reliable, and you don't risk dropping the 'nut' part or losing the sealing gland?

 

[PVorBust]

and you don't risk dropping the 'nut' part or losing the sealing gland?

I believe that is the key to the design - the less parts the installer has to juggle while trying not to fall off a roof, the better the chance the connector is assembled complete and correctly (it also removes the temptation to use a shell after loosing the gland).

 

[12VoltInstalls]

don't think there's any harm in disassembly, just wasted time

I had an issue with water ingress due to freeze/thaw where it would suck in the rubber compression ferrule that is supposed to be IP68 (or 67?) iirc
Took me a couple months to figure it out.
I replaced every MC4 with new ones but I squirted lexel inside before sliding the compression rubber into place. Then lexel’d over that before tightening the nut. Been a coupla years and no further problems. “Disassembly” takes seconds and I can guarantee no leaks. Never had the orings leak.

Lubricant and rubber compatibility (something all guys should be familiar with). There are many different materials

I’ve grown an affinity for the overpriced CRC dielectric. Vaseline crumbles over time as does cheap dielectric in my observations.
From the feel it is a silicone grease. Though I haven’t seen problems I have wondered about compatibility with the MC4 orings.

Do you have comments on this product?

 

[Hedges]

https://www.crcindustries.com/media/msdsen/msds_en-1003734.pdf

Polydimethylsiloxane - Wikipedia

en.wikipedia.org

I suppose the silica is to make it less runny.

"silicone polymer" so need to ensure O-rings are compatible with that.