FRRYKidMentioning the electrical explosion reminded me of something that happened at my job.
That whole generator set installation was cursed.
All three units had "pusher" fans. The engines also had closed-loop low temperature aftercooling with a seperate heat exchanger for the aftercooling systems.
The building engineer had engine specification sheets for non-aftercooled engines with a much lower air flow through the exchangers. The inlet for air into the room was too small.
When we initially fired up the first engine, the door into the hallway was sucked shut with such force it ripped the frame out of the wall. When all three engines were running for the first time the negative pressure in the room caused the ceiling to collapse.
I don't miss working.
-Kevin
Living the dream.
Mentioning the electrical explosion reminded me of something that happened at my job. Not saying where, but the power to about half the building kept being thrown out. It had been remodeled at one point and new circuts were put in as part of that remodel. The old part of the building kept tripping while the new part was fine. Turns out that the heating systems in old part were trying to start all at the same time which overloaded a breaker hence shutting power off. Quick solution was to make sure that each heating unit would turn on at a different temperature so that they wouldn't turn on at the same time.
OK, tomorrow after doing a little more carpentry, I will be wiring a kitchen island for two outlets, a wine frig and a microwave.
Time for bed.
Sheldon
ATLANTIC CENTRAL480 volts is nothing, how about 2400 volt, 3 phase, 700 HP variable speed sewage pumps controlled by PLC's and liquid rheostats? That's what I what I was doing in 1981, replacing cabinets full of control relays with those then new fangled Programable Logic Controllers from Cutler Hammer and Allen Bradley.
I was on-site at the newest hospital down here when they did the full-load generator transfer test.
Two transfer switches exploded and caught the electrical room on fire. When a safety breaker attempted to open, it caused an arc-flash that triggered a second series of explosions.
I had to trip the manual shut-downs on three 60 liter 1.2 megawatt generator sets. That was the most terrified I have ever been.
The entire disaster was because of a miscalculation by an electrical engineer. The correctly rated transfer switches were each 6 inches wider than the ones that were installed, and they would not fit on the equipment pad.
It was an incredible mess-up that took months to resolve.
When you have seen the aftermath of an electrical failure, it gives you all kinds of respect for those vibrating electrons.
OK, to be clear about one more thing.
A normal sub panel in a structure needs a ground wire back to the main panel and the neutral in the sub panel must NOT be bonded to the panel can/ground, and the ground wires from the branch circuits in the sub panel need a separate ground bar, they cannot go on the neutral bar.
It is my understanding that the code now allows outbuilding to be wired this way - my code book is not handy, still packed from the move, not something I get into every day.
OvermodLook at how the schematic is drawn. My comment is based on that.
Ground and Neutral are bonded together in the main service box, as is typical down here.
York1If the outbuilding is connected to the main house with a ground wire back to the main service entrance, then a separate ground should not be used. If the outbuilding is connected using only a hot and neutral, then the sub panel should be grounded.
I don't like ground loops but the alternative here is to run neutral back to wherever the red and black wires started and connect to neutral for that box, and that is what I would have done. And I would not have bridged ground to neutral in that scenario either.
The diagram he provided shows no alternative but a good ground, deep enough that any stray current stays 'enough' below ground... and I don't like it.
I'm not even fond of powerline grounds in a populated neighborhood if not given proper conductivity...
SeeYou190 ATLANTIC CENTRAL but still brings into question how is it wired in the outbuilding and what are they using it for? Because you don't want 30 amps on a regular receptacle. There is a sub panel. I know there is a 240 volt outlet for a welder, a 120 volt 20 amp outlet for an air compressor, and additional breakers for outlets and lighting. I don't know the exacts, I did not like it. Honestly, I do not like any residential wiring. After working with industrial 3 phase 480 volt for decades, residential wiring is just plain scary. -Kevin
ATLANTIC CENTRAL but still brings into question how is it wired in the outbuilding and what are they using it for? Because you don't want 30 amps on a regular receptacle.
There is a sub panel. I know there is a 240 volt outlet for a welder, a 120 volt 20 amp outlet for an air compressor, and additional breakers for outlets and lighting.
I don't know the exacts, I did not like it.
Honestly, I do not like any residential wiring. After working with industrial 3 phase 480 volt for decades, residential wiring is just plain scary.
It's the same, but with one less phase. with 480, phase to neutral is 277 volts, and you have three legs that can share a neutral.
Or, step it down to 120/208 for lighting and outlets in an office building.
I got bit by 208 once......... knocked me off a six foot ladder and burned a hole in my finger.
I did industrial and commercial wiring for decades, schools, factories, water treatment plants, steel mills, and much more.
480 volts is nothing, how about 2400 volt, 3 phase, 700 HP variable speed sewage pumps controlled by PLC's and liquid rheostats? That's what I what I was doing in 1981, replacing cabinets full of control relays with those then new fangled Programable Logic Controllers from Cutler Hammer and Allen Bradley.
Those guys are in for trouble when the air compressor and the welder try to run at the same time.....
And yes about the neutral (white wire), the two 120 volt circuits can share the white wire in this case.
BUT, there really should be a single pole 15 or 20 amp breaker in the outbuilding for each 120 volt circuit in this case.
A little more about the neutral - when the power comes in your house, there are only three wires, lets call them black, red and white.
Red to black = 240 volts
Red to white = 120 volts
Black to white = 120 volts
Alternating current, the electrons don't "flow", they vibrate, changing direction 60 times a second in this case.
When you plug a two pole breaker into a panel you are automaticly connecting to red on one terminal and black on the other, the taps in the panel alternate that way.
The white wire is grounded to earth, at the power company, all along its way to you, and at your main panel. Kind of like the frame of a car with its grounded DC system.
While the red wire virbates in one direction, the black wire vibrates in the other. and then they switch.
So if the load on your black wire, is exactly equal to the load on your red wire, the white wire electrons stand still, and your lights still light up.
I wish I had some pictures, but I just don't have the computer skills to do that quickly.
So any two pole breaker curcuit with a neutral can provide 240 volts or two separate 120 volt circuits.
Ground wires are a separate story we will skip for now.....
SeeYou190 ATLANTIC CENTRAL Kevin are you sure about the wire gauge? For a 60A breaker it should be much larger, #6. But the connections are correct and the neutral needs only be the same size as the hot wires. The two hot phases are out of phase to each other, that is how you get both 240 volts and 120 volts from the three wires. Yes, I am sure it was wired with #10 wire. This was a case of two idiots not knowing what they were doing, I suggested to call a real electrician, and then I left. The shed was built without power, then after the inspections were done, someone decided to run power to it. I think YouTube videos were involved. Let me see if I understand this correctly. When using a 240 volt breaker (2 slots), you would use a 30 amp breaker and #10/3 wire. Then at the sub panel, you would get 30 amps EACH on the two 120 volt legs. Is that right? -Kevin
ATLANTIC CENTRAL Kevin are you sure about the wire gauge? For a 60A breaker it should be much larger, #6. But the connections are correct and the neutral needs only be the same size as the hot wires. The two hot phases are out of phase to each other, that is how you get both 240 volts and 120 volts from the three wires.
Yes, I am sure it was wired with #10 wire.
This was a case of two idiots not knowing what they were doing, I suggested to call a real electrician, and then I left.
The shed was built without power, then after the inspections were done, someone decided to run power to it. I think YouTube videos were involved.
Let me see if I understand this correctly. When using a 240 volt breaker (2 slots), you would use a 30 amp breaker and #10/3 wire. Then at the sub panel, you would get 30 amps EACH on the two 120 volt legs. Is that right?
Yes, or you could have 30 amps at 240 volts for an air compressor, etc.
30 amps at 240 volts makes little sense for a small outbuilding - unless, you run it into a small four breaker panel and and get four 15 or even four 20 amp, 120 volt circuits.
Remember, the "amperage" of the breakers in the panel can add up to more than the size of the feeder/main breaker. Feeders are sized based on actual demand load, not on the nominal value of the circuit breaker.
So if you had four circuits, are you likely to use all four at full capacity at any one minute? No.
The question really is, what are they going to power in this outbuilding?
But as wired, a short circuit will melt that #10 in half way before that 2P 60A breaker trips - and that is bad.
Yes, replacing the 2P 60A with a 2P 30A would make it safe, but still brings into question how is it wired in the outbuilding and what are they using it for? Because you don't want 30 amps on a regular receptacle.
ATLANTIC CENTRALKevin are you sure about the wire gauge? For a 60A breaker it should be much larger, #6. But the connections are correct and the neutral needs only be the same size as the hot wires. The two hot phases are out of phase to each other, that is how you get both 240 volts and 120 volts from the three wires.
ATLANTIC CENTRALBut if thats all the power that was needed a 12/3+G could have provided two 20A circuits using two 1P-20A breakers or a 2P-20A breaker depending on how your friendly inspector interprets the code.
Let me see if I understand this correctly. When using a 240 volt breaker (2 slots), you would use a 30 amp breaker and #10/3 wire. Then at the sub panel, you would get 30 amps EACH on the two 120 volt legs. The single #10 white wire is used on both legs. Is that right?
It sounds to me like replacing the 60A breaker with a 30A breaker would be an easy solution. Is this correct?
NittanyLionTesla chargers require something like a 60 amp circuit.
I won't be getting a Tesla. There are some electric trucks coming to the market soon, and the Colorado is getting old. The next truck very well could be an electric.
York1 I'm going to qualify what I earlier posted. If you have a ground wire to the main panel and you ground the outbuilding's sub panel, then the sub panel's neutral should not be bonded to the the panel or the ground. The rules were changed in 2008, and you can find different ways of wiring outbuildings, depending on when the building was wired.
I'm going to qualify what I earlier posted. If you have a ground wire to the main panel and you ground the outbuilding's sub panel, then the sub panel's neutral should not be bonded to the the panel or the ground.
The rules were changed in 2008, and you can find different ways of wiring outbuildings, depending on when the building was wired.
Agreed.
York1 John
Pruitt NittanyLion As our inspector told us when we bought our place, "200 amp main panel, that's all you're really going to need, unless you buy a Tesla." You need a new inspector - someone who knows what he's talking about.
NittanyLion As our inspector told us when we bought our place, "200 amp main panel, that's all you're really going to need, unless you buy a Tesla."
You need a new inspector - someone who knows what he's talking about.
I largely assumed he was speaking in generalities, not actual specifics. A "good enough for now, not so much if you want to do a lot of stuff later." We don't have a whole lot of excess spaces on the panel. Although I later figured out that we might, because I have two breakers that don't seem to control anything. The previous owners did a lot of stuff that they had a vague idea of what they were doing, but not a particular good idea of what they were doing. My favorite quirk is the breaker labeled "Pinball Machine."
Anyhow, I'm glad to know that I can have my subpanel put in where I want to it (which does meet the code requirement for working space around it). I'd much rather run my four basement circuits into their own panel than work with the existing circuits.
York1 If the sub panel is connected to the main panel with a ground wire, then the sub panel should not have a separate ground rod of its own in the ground. It is dangerous to do so. It doesn't matter if it's in a separate building. Once the system is grounded through the main panel, introducing a second ground makes a possible dangerous route for current if a defective appliance is connected somewhere in the system. In the same manner, washing machines used to have a ground wire connected to water pipe. Now, with washing machines using three-prong plugs which include the ground, there should never be a ground wire from the machine to a pipe. Overmod 1) if this is an 'outbuilding' shouldn't there be a honkin' ground rod right there where white and ground are bridged? Really deep and perhaps tested in different weathers to make sure it is properly connected for 'telluric currents' as it were? If the outbuilding is connected to the main house with a ground wire back to the main service entrance, then a separate ground should not be used. If the outbuilding is connected using only a hot and neutral, then the sub panel should be grounded.
If the sub panel is connected to the main panel with a ground wire, then the sub panel should not have a separate ground rod of its own in the ground. It is dangerous to do so. It doesn't matter if it's in a separate building. Once the system is grounded through the main panel, introducing a second ground makes a possible dangerous route for current if a defective appliance is connected somewhere in the system.
In the same manner, washing machines used to have a ground wire connected to water pipe. Now, with washing machines using three-prong plugs which include the ground, there should never be a ground wire from the machine to a pipe.
Overmod 1) if this is an 'outbuilding' shouldn't there be a honkin' ground rod right there where white and ground are bridged? Really deep and perhaps tested in different weathers to make sure it is properly connected for 'telluric currents' as it were?
If the outbuilding is connected to the main house with a ground wire back to the main service entrance, then a separate ground should not be used.
If the outbuilding is connected using only a hot and neutral, then the sub panel should be grounded.
Yes, one or the other, not both.
Different jurisdictions have different interpretations as to when a separate derived service and ground rod is required.
Overmod1) if this is an 'outbuilding' shouldn't there be a honkin' ground rod right there where white and ground are bridged? Really deep and perhaps tested in different weathers to make sure it is properly connected for 'telluric currents' as it were?
NittanyLionTesla chargers require something like a 60 amp circuit. Once you work out the load and everything, there's a pretty good chance that you need an upgrade.
Mine is on a 100A breaker, since it's configured for full capacity - the 19.2kW I mentioned earlier. But it could have been configured for as low as 32 amps, or 7.7kW, which would only require a 40A breaker.
The current 48A max charge rate of the newer wall connectors would require the 60A breaker you mentioned, but they too can be configured for lower maximum charge rate (12A output is the lowest), which will reduce the required breaker size.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
NittanyLionAs our inspector told us when we bought our place, "200 amp main panel, that's all you're really going to need, unless you buy a Tesla."
I own a Tesla, which can charge at a maximum of 240V and 80A (19.2kW), and have a 200A service. Never been a problem, even in the summer with A/C running and other appliances also.
And the newer Teslas are more limited in their home charging, allowing only 48A at 240V (11.5kW).
Overmod 1) if this is an 'outbuilding' shouldn't there be a honkin' ground rod right there where white and ground are bridged? Really deep and perhaps tested in different weathers to make sure it is properly connected for 'telluric currents' as it were? 2) is the 'sub panel' wired simply with two outlets, wired red to white and black to white respectively? Because even with a 30A breaker I don't see that limiting one side to 15A before it trips, and that could cause trouble in the outlet structure and contacts if 'only' residential cheap grade outlets were used for a price. If that is a sub panel, I'd have two breakers for the outlet branches in there, each sized 'sensibly' (e.g. 20A if you are going to plug 'outdoor power equipment) in to use) and wire the outlets to them accordingly. That is no different from house wiring using a master 240V breaker and 120V branch breakers, where the latter correctly trip on overload regardless of 240V phase... Then he keeps his 60A breaker, spends the money to 'replace' it on the two new 15A 120V breakers, and has safe capacity to add two more branches to the sub panel if he wants them.
1) if this is an 'outbuilding' shouldn't there be a honkin' ground rod right there where white and ground are bridged? Really deep and perhaps tested in different weathers to make sure it is properly connected for 'telluric currents' as it were?
2) is the 'sub panel' wired simply with two outlets, wired red to white and black to white respectively? Because even with a 30A breaker I don't see that limiting one side to 15A before it trips, and that could cause trouble in the outlet structure and contacts if 'only' residential cheap grade outlets were used for a price.
If that is a sub panel, I'd have two breakers for the outlet branches in there, each sized 'sensibly' (e.g. 20A if you are going to plug 'outdoor power equipment) in to use) and wire the outlets to them accordingly. That is no different from house wiring using a master 240V breaker and 120V branch breakers, where the latter correctly trip on overload regardless of 240V phase...
Then he keeps his 60A breaker, spends the money to 'replace' it on the two new 15A 120V breakers, and has safe capacity to add two more branches to the sub panel if he wants them.
Yes, as a sparate building it should have a ground rod, but that is a minor issue. The 2P 60A breaker provides 60 amps at 240 volts, the wire size is too small - period.
No matter what it is connected to, the #10 wire is not protected.
Yes one might assume it is feeding a small panel of just 2 or 4 breakers. But if thats all the power that was needed a 12/3+G could have provided two 20A circuits using two 1P-20A breakers or a 2P-20A breaker depending on how your friendly inspector interprets the code.
NittanyLion I suppose I'll throw this out there too, since I'm in the process of refinishing my basement to turn it into a den and train room. I do want to have a subpanel installed and I'm smart enough to know when I'm out of my depth, so that's something I'll call in the professionals for. One of the things that's sort of got me perplexed is the grounding electrode. Does this influence the actual location of my subpanel? I've got a spot picked out where I'd like to go, but don't know how that, or if, the grounding provisions might make me have to change my plans.
I suppose I'll throw this out there too, since I'm in the process of refinishing my basement to turn it into a den and train room. I do want to have a subpanel installed and I'm smart enough to know when I'm out of my depth, so that's something I'll call in the professionals for.
One of the things that's sort of got me perplexed is the grounding electrode. Does this influence the actual location of my subpanel? I've got a spot picked out where I'd like to go, but don't know how that, or if, the grounding provisions might make me have to change my plans.
The sub panel does not get its own ground rod. It needs a ground wire separate from the neutral back to the main panel. Like Kevins drawing above.
In your main panel the neutral is bonded to the panel can and the ground conections, but in the sub panel the neutral must remain separate from the ground connections.
So your sub panel can go anywhere.
SeeYou190 As long as we are discussing wiring... My friend in Golden Gate Estates had an aoutbuilding built and electricity run to it. The diagram shows how it is wired, and it looks wrong to me. I understand the 60 amp breaker divides up the flow into two circuits, but is each limited to 30 amps? If not, wouldn't the 10 gauge wire be too small? Also, should the white (neutral) wire be larger than the other two since it is the return for both circuits and could have 60 amps current flow? Should there be a parallel 10 gauge white wire. Or, since the white and green both connect to the ground bar is this OK? What about the ground, should it be isolated since it is a seperate sub panel? Or, is this OK, and I just don't fully understand residential wiring? -Kevin
As long as we are discussing wiring...
My friend in Golden Gate Estates had an aoutbuilding built and electricity run to it.
The diagram shows how it is wired, and it looks wrong to me. I understand the 60 amp breaker divides up the flow into two circuits, but is each limited to 30 amps? If not, wouldn't the 10 gauge wire be too small?
Also, should the white (neutral) wire be larger than the other two since it is the return for both circuits and could have 60 amps current flow? Should there be a parallel 10 gauge white wire. Or, since the white and green both connect to the ground bar is this OK?
What about the ground, should it be isolated since it is a seperate sub panel?
Or, is this OK, and I just don't fully understand residential wiring?
Kevin are you sure about the wire gauge? For a 60A breaker it should be much larger, #6.
But the connections are correct and the neutral needs only be the same size as the hot wires. The two hot phases are out of phase to each other, that is how you get both 240 volts and 120 volts from the three wires.
Hot to hot is 240 volts, either hot to neutral is 120 volts.
The load on the neutral will never exceed the the highest load on one hot phase. The current flow on the neutral caused by "black" is canceled out by the opposite current flow on "red".
As I explained above, two 120 volt circuits can share a neutral as long as each is on a different hot.
Sounds like somebody set that outbuilding up for a 30 amp breaker, and then up sized the breaker after the fact. Not good.
NittanyLion Tesla chargers require something like a 60 amp circuit. Once you work out the load and everything, there's a pretty good chance that you need an upgrade.
Tesla chargers require something like a 60 amp circuit. Once you work out the load and everything, there's a pretty good chance that you need an upgrade.
I can tell you that based on what I know about Kevins house, even if his panel is full, he is only using about 60 or 70 amps.
He can add a sub panel and charge a Tesla with no worries.
NittanyLion "200 amp main panel, that's all you're really going to need, unless you buy a Tesla."
What... we are considering an electric car.
ATLANTIC CENTRAL Again, 200 amps is plenty for most houses, it is all about proper distribution.
Again, 200 amps is plenty for most houses, it is all about proper distribution.
As our inspector told us when we bought our place, "200 amp main panel, that's all you're really going to need, unless you buy a Tesla."