Learn from my mistake (load balancing)

[mikeywith]

This is important for those who  have 3 phase wiring, but it's also important for "internal" load balancing to those who have a single phase set-up.

So yesterday I added 2 S9E (will make a review on those tomorrow there it is )to this small mining farm , went home and everything was working just fine , woke up and found "low-hashrate" notification from the pool, checked the gears and they were all offline.

I went there early in the morning and found this  



so how did this happen? where did I go wrong??

So the electric company installed this 80amp breaker and said the wire size will only handle 60-65amp on each phase, so that's more or less 9*S9s per phase or 28 S9s in total.

My mistake was that I "by mistake" missed up with the wiring colors because I ran out of wires when I was installing this location, I ended up plugging more miners on one of the phases  ," the burnt one" had already 10 gears on it , and I added 2 more S9E to it, and boom!! burned the shit of that Schneider breaker (the wire did handle that for couple hours , gotta give it that) and technically it should have tripped, but that shit didn't happen.

Anyhow, I called the electric company, and had them change it,  i could have done it myself but I don't have access to the main breaker so it would have been super risky to do so.



And I of course learned from my mistake, spent the whole day balancing those phases and so far everything seems to work just fine.

Now by all means, you should always hire an expert to do these kind of stuff, but there are cases where you have to do the wiring yourself, hope this bit of information will be of any use.

[1714079898]

1714079898

[NotFuzzyWarm]

.... Given that you said

So the electric company installed this 80amp breaker and said the wire size will only handle 60-65amp on each phase

WHY on earth would they even do the install??? NEC and no doubt local electric codes specifically forbids it for this very reason...

[philipma1957]

I will mention I was up in Clifton today.

We have three phase and we are having a low voltage issue.

I know you mention you have some low voltage protection gear in some of your installs.
I am not sure if this install is using any low voltage protection.
But if you balanced wrong and volts drop to say 190 or 185 many psu’s will attempt to continue to run.

So try and check if that spot has good voltage levels.

A 210 volt setup will do 12600 watts and take 60 amps

A 200 volt setup will do 12600 watts and take 63 amps

A 190 volt setup will do 12600 watts and take 66.3 amps

I am glad it was just a melted breaker.

[mikeywith]

I don't live in the U.S , life here is a lot  less complicated  

The electric company will follow the rules and codes all the way to the 11kv level, they don't play around with those, but once the wiring gets to 380v they usually work with what they have, so instead of installing a 50amp breaker they went ahead and used whatever was available which is the 80amp ( i paid for it by the way)

Phil , yes I do have voltage regulators at this location, so balancing the load was pretty accurately done.

[wndsnb]

I think the lesson to be learned here is just make sure the correct size breaker is installed. The same meltdown could have occurred if a power supply failed in the right way. The cost of a 50A breaker isn't much compared to the damage that could have occurred.

[mikeywith]

@wndsnb

Yup, wire size must be larger than what the breaker can handle, but honestly I think the breaker was bad, i don't understand how these breaker function, but common sense states that if the wire got way to hot to the extent that it melted, the breaker should have sensed that and did the exact thing it was made for "kill the power" but the response took way too long till the breaker went on fire.

[wndsnb]

@wndsnb

Yup, wire size must be larger than what the breaker can handle, but honestly I think the breaker was bad, i don't understand how these breaker function, but common sense states that if the wire got way to hot to the extent that it melted, the breaker should have sensed that and did the exact thing it was made for "kill the power" but the response took way too long till the breaker went on fire.

Yeah, but over time the overloaded wire can degrade and fail slowly, so the resistance at a failure point can keep increasing. With the same current draw and increasing resistance, the wire gets hotter and hotter. Eventually it can essentially turn into a heating element, and that could have cooked your breaker.

[mikeywith]

the wire gets hotter and hotter. Eventually it can essentially turn into a heating element

Honestly I always touch all the wires to check if they get hot or not, and usually they are just a bit warm during noon time, there are many factors that could cause these wires to heat and melt, the technician who came to change the breaker suspects that the wire was a bit loose , he said these wires need to be tightened every now and then because they get loose over time , not sure how accurate this piece of information is, but I took it into consideration and i will add that task to my to-do-list whenever I go there to dust off the gears.

[Philipma1957cellphone]

yeah they can loosen up. Also a bit of grease helps the contact not oxidize. We just did some maintenance on a 250kwatt inverter we greased it tightened it. Went to roof worked on panels two hours later tightened the contacts.

[jbillk]

This has nothing to do with load balancing. The issue was improper sized cables. The cables have to be rated for the installed breaker.

Doesn't matter if it was not balanced or not.  If it was too un-balanced, the breaker would have safely tripped, and no damage. You can safely run unbalanced loads as long as done to code and properly engineered.

[mikeywith]

Doesn't matter if it was not balanced or not.  

This is so wrong, unbalanced load leads to the same result, you can read about the distavtanges of having an unbalanced  3 phase system, one of those is the increase of the returned current on the neutral wire, which can eventually lead to a lot of troubles, you are stating the obvious , in fact the breaker should have tripped even if the wire size wasn't able to handle that much current flow.

This of course does not mean you are wrong by saying  "The cables have to be rated for the installed breaker." , but in a case like mine where i can't change the wire size neither the breaker, load balancing is the only thing I can do to fully utilize the power I have.

[philipma1957]

@ mikeywith and jbillk you are both right. leave it at that.

The english language  plus internet can lead to this apparently contradictory statement I just made..

I see and read both points  and both are correct.

As for 50 amp or 80 amp breaker vs correct wires.

code = 50 amp

but it is China

I grew up in New York City and in a lot of places or sections of NYC  work is done against code.

[mikeywith]

@ mikeywith and jbillk you are both right. leave it at that.

The english language  plus internet can lead to this apparently contradictory statement I just made..

Can't disagree, however these kind of discussions are supposedly good for everyone, it's a good way to learn , but first you must admit that you don't know everything and there is always something to learn from everyone, that is why I without a shame admitted that I am not any where near expert in the electric field, in fact not even close to average  

I grew up in New York City and in a lot of places or sections of NYC  work is done against code.

I didn't think that was possible in a state like New York , but now that you mentioned it,and since I do trust you I am feeling kind of relieved that these things happen else where and not only in the shit-hole I live in  

[NotFuzzyWarm]

Ok, to clear the issue: Most circuit breakers found in older homes and businesses are mainly thermally operated devices that rely on heating of a bimetallic thermal link to trip the breaker, the magnetic component of them is reserved for tripping under direct short circuits. Depending on their class they can pass varying percentages of over current - total and per-pole - for different amounts of time before tripping. A wire getting getting hot/burning due to wrong size WILL NOT trip the breaker as long as the current remains below the breakers trip point. Again, that is the whole point of codes requiring that ampacity of the wiring be matched to breaker size so even under worst-case conditions the breaker will trip before the wiring fails.

Typical class-C or class-D breakers will hold 100% load indefinitely, 125-150% load for several minutes and >200% load for several seconds to 10's of seconds but those ratings assume even loading across all poles. Unbalance the loads and the trip points get a bit higher with the pole running higher load being able to pass higher current w/o causing a trip because the lighter loaded poles are not helping to force a trip. Yes eventually an overloaded phase will force a trip, just at a higher than expected value. In any case that undersized wire will have ample time to cook before the breaker trips.

That said, these days in the US, Canada and many other countries most codes will require using AFCI breakers in at least some locations of a home. Reason is the previously mentioned issue of connections loosening. An AFCI not only looks for over current but also contains electronics that look for low-level, high-frequency signatures that any sort of arc produces. If a connection gets loose and there is even the tiniest bit of sparking, the AFCI trips, if a wire burns and starts to short out, AFCI trips before a standard breaker will trip.  ref https://en.wikipedia.org/wiki/Arc-fault_circuit_interrupter Wikipedia also has a nice graphic showing trip time vs current vs class https://en.m.wikipedia.org/wiki/File:Standard_Trip_Characteristic_of_a_Thermomagnetic_Circuit_Breaker.svg

[DaCryptoRaccoon]

Holy crap.

That could have ended very bad indeed.

[NotFuzzyWarm]

Oh, you mentioned neutral currents from an unbalanced load and taking another look at the 1st pic I see that only 1 wire is burnt telling me you are not pulling power from across the phases (2 wires would be burnt)  but instead pull from phase to neutral right? The pic also clearly shows that the breaker burnt from bottom-up meaning the burning wire under it was cause.

Do keep in mind that when the electric company said the wiring was only good for 60-65A they meant it. With any wiring when pulling max current continuously the wire WILL become rather warm. In fact alarmingly so to the touch. If the insulation is not rated for high temperatures to allow for that then danger is brewing. Since the breaker is 80A it is more than happy to provide it (and more) through that one pole as the wire cooks...

Now about the 2nd pic after repairs....
PLEASE PLEASE PLEASE AT LEAST put rubber grommets around the bare metal holes in the electrical box!!! You are just asking for more trouble there! Did the wire burn just from the box to breaker? If so it is because the insulation softened and sitting against a bare metal edge it then flowed out of the way... And please tell me that I do not see exposed copper on one of the heavy gauge lines on the far right feeding the box..

Sorry, having designed/built/repaired all manner of power systems and power electronics  from milli-watt to megawatt since the mid 1970's things like that make me cringe.

[mikeywith]

Oh, you mentioned neutral currents from an unbalanced load and taking another look at the 1st pic I see that only 1 wire is burnt telling me you are not pulling power from across the phases (2 wires would be burnt)  but instead pull from phase to neutral right? The pic also clearly shows that the breaker burnt from bottom-up meaning the burning wire under it was cause.

Not sure I quite understand the question, but here is the set up , I have 4 wires coming in , 1N and 3L , when you measure the voltage between two phases you get 380v, between any phase and neutral you get 220v, so I pull 220v from phase to neutral,i hope this answers your question !!

PLEASE PLEASE PLEASE AT LEAST put rubber grommets around the bare metal holes in the electrical box!!! You are just asking for more trouble there!

Thanks , I will ask them to do it, I am afraid to do it myself and then later on if any problem appears, they will blame me for putting the rubber grommets  

Did the wire burn just from the box to breaker? If so it is because the insulation softened and sitting against a bare metal edge it then flowed out of the way..

This makes perfect sense, I think this is exactly what happened.

And please tell me that I do not see exposed copper on one of the heavy gauge lines on the far right feeding the box..

lol , no that is not exposed copper, those guys don't do these things in  perfect manners, but not to that extent   , the copper-like color that appears in the image is like sponge pieces stuck on them,not sure how they got there.

Sorry, having designed/built/repaired all manner of power systems and power electronics  from milli-watt to megawatt since the mid 1970's things like that make me cringe.

I understand, and I can relate, my dad saw this shit and he said he wouldn't put a 5$ machine behind this set-up , but I really have no other option, and since I don't pay for power, I don't expect them to provide me top notch setup, as long as it works and it's not too bad, I am satisfied,

[philipma1957]

... I didn't think that was possible in a state like New York , but now that you mentioned it,and since I do trust you I am feeling kind of relieved that these things happen else where and not only in the shit-hole I live in  

I could tell you stories  about NYC  apartment living  when I was first married  but I will tell just two.

I was in Astoria, Queens  Just across the river from the UN building.  This leads to having a lot of diversity it is the most diverse zip code in the USA.

It was 1987  or 1988 long before BTC  personal pc's were still rare.  It was a hot night in August  and boom a blackout.  All of Queens Bronx and ½ of Manhatten shut down.  So  my wife and I said we just filled the refrigerator we will lose all our food. Since our stove was gas feed and worked I told my wife we can cook all the food. I open the refrigerator and it had power!!!   I said WTF  looked out my window and no light for miles.
 I went out side not a single light of any kind.  So I told my wife I have no idea what they did but we are good. I check it out when power came up.  I turned off all breakers in my small sub-panel and refrigerator worked! My meter for the bill read zero.
  So I knew I had a line that tapped into some source of power.  I opened the small receptacle and it was  10gauge not 12 or 14.  So I know I could pull more juice then the fridge.  I ran 1 air conditioner for free  from 1987/1988 to 1992 along with the fridge.  Good thing there was not any mining  it would have been tempting to max that line out.

Second story my friend did New York state taxes for the New York state government  he went on an audit of a fairly famous metal work artist.  Was looking at the  workshop and saw a door  asked the guy where does it go?  guy opens the door  walks in a 50 foot long tunnel  and goes into a 3000 square foot store room with 12 foot ceilings.   The metal work guy had access to an old hidden store room used to hid booze during the 1925-1936 prohibition of booze in the USA.

the room was not even in his building it was across the street!  lots of lights and power etc.  certainly not up to code.

[mikeywith]

Did you manage to know where the hell did that 10gauge wire come from?? that is a bit strange, it goes to show how fucked up the set-up is , but that was almost 30 ago, I am sure things are not as bad today , are they?

I can tell you strange stories about my country too, sadly nobody would believe it , I see it with my own eyes and I can hardly believe it.

Not too long ago, maybe around 2000-2002 we went to spend the summer in my hometown, there was an issue with the power meter , it was not reading , so dad calls in and they sent someone to fix it, after he was done, the meter was spinning backwards, the number of kwh was decreasing and not increasing, my dad only noticed that a while later, he called again and said there is still an issue but he didn't tell them what happened exactly, he was afraid that technician would be fired or something, so they sent the same guy again, and he was like , oh i must have missed up the wiring, and he came without any tools, he told my dad , listen just leave it be I will come tomorrow to fix it , he came 2 weeks later , not only we enjoyed free power for 2 weeks, we got to unload a good chunk of the bill   , despite power being too cheap to the extent that people don't bother about turning off their ACs before going out, it was really funny to watch the meter go the opposite direction for 2 weeks.

[philipma1957]

Well that was the mystery since it did not attach to any meter in the apartment building.

And it did not attach to the main transformer on the street.

NYC is pretty old not crazy old links Europe cities or some Chinese cities.

So it does have some hidden spots. We were a mile from a large con-Ed power plant maybe the wire tapped into an underground cable. I  will never know but I do wonder about it every once in a while since it was a pretty cool mystery and in my favor.😁