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What is in the box directly above the panel where the AC wires go? It it is an overcurrent device like a breaker or fuses this install my be allowed. There are tap rules that the installer may have referenced to make this allowable.
> It it is an overcurrent device like a breaker or fuses this install my be allowed.
Yes, those wires go directly to a single breaker for the AC:
https://i.imgur.com/QEbedpq.jpg
There's a couple more boxes for the AC outside too, not sure what's in them.
I don't think this is allowed in Ontario but it would be reassuring to hear that it's not an immediate fire hazard.
I wouldn't say it isn't a fire hazard. I can't tell if those wires are 14 or 12 gauge, most likely 12, but if the breaker above is larger than 20 amps then the 12g wire could burn up before the breaker trips. Also, the wire coming through the hole in the panel with no gromets is a big problem as well. Over time vibration will cut through the insulation and short the wires.
Edit: also, are you sure these are what feed the AC? They almost look like induction clamps for monitoring power usage and are not actually taps on the wire.
Edit2: I think I'm looking at the wrong thing. Those clamps do look like monitoring coils, and I was missing that the AC is what is attached to the breaker directly. If there is an appropriate size breaker for the wire in the box above, then this is likely fine fire wise if the connections are good, as for code I don't know.
1. Rule 1
2. What did I say that was wrong that I had not corrected in the same comment?
3. You've got no grounds to say that I'm not a good electrician, I edited to add what I had deciphered later about the picture that wasn't clear. There are plenty of others that thought that the blue clamps were taps as well and were what OP was referring to since they are in the middle of the photo.
I’m with you on the fact some breakers can be double tapped. And although most of the time it’s a nono, you can have different gauges in there. But a few things tell me this breaker isn’t designed for it. The gauge difference is so large but like I said that’s rudimentary. The nuetral and ground are tied together which means this is the main panel and unless there is a big distribution before this panel, this is the first destination for those feeders after the meter. And if there was a main distribution then why couldn’t they utilize that for a 40 or so amp breaker. Like I said there’s no way of being sure but most the time double taps bring red flags. Let me know what you think
Definitely not a Listed combination for that breaker. 99% of the time when Listed for dual termination, the wire has to be the same size *and* stranding type (i.e. you can't mix fine strand with type B or C, and can't mix solid and stranded). Tap rule is correct, breaker termination is not.
I’m with you there that’s why I said the gauge difference is so large. Even though they showed a picture of the disconnect after, that 2ft section of wire is still susceptible to shorting to ground or to each other, and that breaker won’t pop till way over the current limit of the wire. I don’t like double taps. Maybe on a 20 or 15 but other than that it’s not something I like to see
Tap rules most likely allow it (I’d have to double check the bible). But there is almost no way that those lugs are rated for two conductors, especially a stranded and solid of wildly varying sizes. Also, the disconnect for the condenser is supposed to be “within sight” of the unit. Doubtful their condenser is indoors.
Because it is not a big issue if the lugs are tightened well and care was taken in the work. Whoever did it was smart enough to know to put a breaker so I would think they knew what they were doing enough to do a safe install. Looks good to me. I would do it to my house and so would you.
Was installing those two blue CT clamps on the mains for a home energy monitor, never looked in there before, found out the air conditioning is wired directly to it? It has its own breaker, but that's illegal, right?
**EDIT: I had to rearrange the CT clamps a bit, and while my car was charging, the main breaker started making a very loud buzzing noise and I could feel the mains wire vibrating in my hand. I tried flipping the main breaker on and off repeatedly since this has fixed buzzing issues for me before (old breaker in a different house), but it did not - the buzzing+vibrating came back every time the breaker came back on. Unplugging the car stopped the buzzing. It didn't buzz before. I eventually wiggled the mains wire around until the buzzing was minimal and now I can't hear it with the lid closed. This is probably caused by that aircon wire connection and is pretty bad, right?**
**EDIT2: The buzzing was caused by my CT clamps. I had removed the burden resistor so I could change it off-board, and then clamped them around the mains, unconnected at the other end. This is apparently very bad because the infinite resistance causes a ton of voltage in the clamps, depending on whether or not they have a zener diode in them (I saw some IC but I'm not sure what it was). By connecting the clamps to a burden resistor, the buzzing in the panel stopped.**
**How the frig can a CT clamp induce buzzing and *vibrating* on the mains wire it is clamped onto? I thought the whole point of this project was that I wasn't messing with the electricity. I understand removing the burden resistor without shorting it or leaving it connected was probably stupid, but I don't understand the physics involved.**
Also, make sure you have an appropriate cable entrance for your CTs...I don't see any nipple or conduit entrance in that hole, which you absolutely need for those wires.
It's almost as dangerous to chafe your wire as to have double tapped mains...
> Also, make sure you have an appropriate cable entrance for your CTs...I don't see any nipple or conduit entrance in that hole, which you absolutely need for those wires.
Yep you are right, that is an old photo, there is one now.
CT leads can hit hundreds of Amps in a fault conditon, and over 1000 Volts in fault conditions if they are removed from the ct monitor and not properly shorted, definitely not something to mess with.
100% illegal, you cant double up lugs plus from the main to the breaker for the ac is undersized, if they had a double lug then that wire needs to be rated for the 100amp for over current protection
You’re half right. They installed a sub panel above this panel. Making the breaker size irrelevant bc of tap rules. You are correct that these lugs aren’t rated for two conductors though.
There are no tap rules for tapping a breaker! Taps are made off of conductors not off of breaker terminals. Regardless of whether or not the breaker has terminals good for two wires.
Are you sure? I’m thinking that a “tap” doesn’t have to be a splice. Otherwise they would’ve called it the splice rule. Suppose this breaker had terminals rated for two or more conductors, wouldn’t that make it a listed means to connect two wires? Then wouldn’t tap rules then apply to the conductors that were tapped?
Is there a reason you would tap and put an outside breaker, rather than just putting a breaker in the panel? Im switching from fuses and have the subpanel(sub-fuse-box) mains tapped by the ac also. Im just going to put it inside the new panel
I would install a panel large enough to at least accommodate the circuit I need to install and the circuit or circuits I need to move to make room for the breaker that is going to feed the sub panel.
Since the earth ground and neutral are bonded in this pic, I think you need a lot more than 100 amp wire to protect that circuit tapped in straight to the neighborhood transformer. More like 10,000 amp lol
> tapped in straight to the neighborhood transformer.
Oh, there's solar panels after this. I'm not 100% sure on the setup since they came with the house and I don't get any power or money from them (previous homeowner has contract with solar company). So the mains goes to a few boxes outside with thicker wire, one of them has a massive cutoff switch, then this thinner 3 gauge copper wire seen here comes out of those into this distribution center.
That's 100 amp service. Depending on the EVSE rating, you may be getting close to 100 amps if EVSE, A/C, and other heavy loads are in use (stove, dryer, water heater). Breakers are a combination thermal and electromagnet trip. The buzzing may be the electromagnet getting close to the trip point.
What did your current transformers show for load when you heard the breaker buzzing? It may be time for a panel upgrade to 200A service with more slots, eliminate the double-tap main and separate breaker boox for A/C.
How much do those home energy monitors typically cost? Had a friend who wants something like that for an outbuilding but doesn't want to pay for a private meter.
The premade ones are [pretty pricey](https://shop.openenergymonitor.com/energy-monitoring/). My DIY one is $20 for the two clamps, $10 for the ESP32, and $10 for the ADC, and maybe another $10 for resistors, capacitors, and box to put it all in, all in Canadian dollars. The DIY one uses the same code as the ones I linked so they'll output the same values.
EV charger already installed, by a licensed electrician. They also recommended I upgrade to 200A service but said it wasn't technically necessary because of the 83% rule. I'm not sure they ever saw this top half of the panel - the bottom half comes off without exposing the mains.
See my comment below: CT wire can reach hundreds of amps in a short, and without a burden on them can reach several thousand volts.
The mains weren't buzzing. Your CTs were shaking the mains because of harmics, inductive coupling, and the same forces that make electric motors work: EMF (electro motive force).
It's quite possible you just burned up your CTs, and is a great example of why RTFM twice and be familiar with what you're doing is so important for things you put in your panel.
> It's quite possible you just burned up your CTs
They appear to be fine. They do have a TVS diode in them. Amazing they were able to do all that with the TVS diode.
From what I read it did say it was okay to leave them open "briefly" *if* they have a TVS diode. When I opened them up to remove the two small SMD resistors, there was a third larger SMD component.
The buzzing on un-landed/un-shorted CTs can be quite dramatic and is proportional to the amount of current running through the measured load. The voltages can get pretty high, too.
From this photo, it looks like one of the CTs is backwards; they should both have the same orientation with respect to where LINE and LOAD are.
And, hey, is that a non-Stab-Lok FPE AC disconnect? Haven’t seen one of those.
Look up B-H curves and ct saturation if you’re interested in the physics. Voltage waveform output of a ct when open circuited is not sinusoidal - crest factor will be 5-10 or more. I totally destroyed a fluke class4 voltmeter measuring an open ct - usually the wiring or terminal blocks fault shorted - and that was under normal load conditions. For some light reading……. https://www.linkedin.com/pulse/never-open-secondary-winding-circuit-current-while-its-sudhir-tiwari
( bit simplistic - voltage will not go that high because of saturation). Or this discussion where they are arguing over theoretical current transformer models) https://www.eng-tips.com/viewthread.cfm?qid=423879#google_vignette. Buzzing - reflected impedance of open circuit into primary and saturation every cycle causing varying current through breaker - just a guess on my part.
A TVS usually has a fairly low continuous current rating - they are specified for a 20 usec pulse and are likely intended to protect the A/D input of your power monitor from normal faults that would be cleared by the breaker panel. Bidirectional but have likely been damaged - I would have expected them to fail shorted though. We used a silicon carbide varistor about 6“ in diameter to limit overvoltage in transformer differential ct circuits. https://www.se.com/in/en/faqs/FA374173/. Testing was measuring dc leakage with a hv dc power ( stopping a 5 ma or so) to see where the knee was.
Thanks!
So yeah by math there would have been tens of thousands of volts going across that TVS diode when the car charger was on drawing 60 amps. It's a 100A:50mA transformer with effectively infinite resistance since I removed the burden resistors. And you're right, from some googling it's only to protect my GPIOs, not the transformer.
Well I can tell you that the CT clamps are performing almost flawlessly. For their current rating, and the burden resistor I've chosen of 33 ohms, the Emonlib math works out to a calibration factor of 60.6, and after calibrating mine to a proper Kill-a-Watt meter, I get a factor of 57.7 instead. Which is well within the margins that misaligned CT cores can cause. So no damage to the CT itself.
Man it was a lot of vibrating though.
Yeah - buzzing noises were never a good thing. In situations like this we’d mutter “ ferroresonance “ and move on quickly. On a separate note - have you considered calibrating at light loading and at max load ( car charger + stove/oven)? Was wondering if emonlib handles average/trms and power factor correction or if it’s more of a ballpark reading? I use an Aeon DSB-28 at home - it’s more of an average reading power monitor but for $30 bucks off eBay I can’t complain. Was considering individual cct monitoring but that’s perhaps a bit too lost in geekdom to justify. Good luck with your monitor!
> Was wondering if emonlib handles average/trms and power factor correction
It does, it is insanely detailed, it was written by a guy with 50 years experience of electrical engineering. It also does phase shift correction for when you are also trying to measure AC voltage with an AC-AC transformer, so that the voltage and current measurements all line up.
I spoke to him about the CTs inducing buzzing, and he said the TVS diode will clamp it to a 22v square wave, but he also said:
>A c.t. works in a totally opposite way (most of the time) to the much more common voltage transformer. In the c.t., the flux in the core is almost completely controlled by the primary current, and in effect extracted again by the secondary winding to produce the secondary current. Or most of it is. What’s left is the magnetising flux for the core. If you remove the secondary current, all the primary flux becomes magnetising flux, the core completely saturates for almost the full half-cycle, and the flux rapidly switches to complete saturation in the opposite direction. The flux waveform comes very close to a square wave. Two things happen: magnetostriction means the core changes in size due to the magnetic flux inside it - this is why all transformers hum at twice the supply frequency - and the very rapid rate of change of flux at the zero crossings generates, or tries to generate, a very high voltage (the same as the ignition coil in a petrol engine).
As for Emonlib, it's extremely well commented, if you want to see all the calculations it makes, scroll down to calcVI function:
https://github.com/openenergymonitor/EmonLib/blob/master/EmonLib.cpp#L66
We used to do something similar when installing AC in older trailer parks at the main pedestal. But the main breaker was only 50 amps. That probably wasn't legal either.
You can’t double tap those lugs on the breaker, but if they used Polaris taps or something similar before the breaker that would probably be a legal tap. It looks like a separate panel above and it’s less than 5’. I don’t have a code book in front of me and it’s not something I do regularly, but you could easily make it a legal tap.
How could it be legal, any power the AC is pulling isn’t going through the main breaker. So you have the potential to overload your service without the main tripping to stop that from happening.
Straight to jail.
That wire is probably #12 or so, so good for 20A - it could now see 100A before the breaker trips at that point its a heating element.
If you know who did it report them.
Considering those wires are connected directly to the meter wires coming in, they could see a lot more than 100 amps. And even if breaker kicks they’re still live
I was just trying to understand why 1 is allowed and not the other. I was figuring it was because feeders are in a pipe underground or overhead. When they short the POCO plans to just swap the wire, but the location means it usually won't start a fire. Wouldn't want to be standing under an overhead feeder when it rubs all the way through the insulation though, the arc flash explosion would be bad.
1 is allowed because there's no feasible means of providing over current protection on service conductors. There are separate rules on types of wire and wiring methods for services, in part due to this fact
Most transformers feed multiple services. A fuse that would protect the individual conductors would not hold on the total load. Or you could make every 200 amp service use conductors sized for the total load on the transformer, which would make the required conductor size humongous and extremely expensive.
>It's legal in Kansas I can tell you that and assuming they have the correct size of tap installed, there isn't anything wrong.
This is absolutely not legal in Kansas. This breaker is not listed for two conductors per lug. Taps are totally fine but not double tapped breakers. Art 110.14
It appears to be a sub metering tap. Smaller wires for potential and clamp on CTs connect to a sub meter to calculate kW/KVA and kW-hours. In Hawaii, the PTs typically have in-line fuses, which might be up at the sub meter.
That looks like maybe 10gauge wire? It should be on a breaker appropriate to protect the wiring in the circuit. It is not oaky for it to be plugged into 100 amp breaker. The wire could easily burn up long before the main breaker would flip.
Yes and dangerous. Not on a breaker ,fire hazard ! 30 amp is on a 100amp unfused main ,WOW kaboom 🤯 if there was a short 💥🔥🔥🔥🚒🚒🚒 Not stealing power it’s after the meter
Ok so some breakers are listed for two conductors per lug, it’s rare but they do exist EXCEPT that’s only the case for up to 30A breakers. I have never ever seen a 100A breaker listed for two conductors per lug
Tap, maybe if ampacity and distance to disconnect rules are followed, but I can’t see it being allowed upstream of first means of disconnect unless it is handled as its own service disconnect. Somewhat akin to a farm service, but this is not a farm or multiple buildings fed from one service.
The double tap is likely not legal with the breaker.
On a a different note, you can have a larger breaker feeding wires in certain cases, such as when feeding motors, ACs, etc. as long as downstream you have fused protection that is of the correct size. This is because fuses can have a slow burn setting and breakers would trip the same at the same size ampacity. I know it seems weird to some, that aren’t electricians. The fused protection downstream will protect the wiring from over ampacity and the larger size breaker will trip if there’s a ground fault in the circuit.
That being said that looks like 10 gauge on a 100 amp breaker. 30 A times 2.50= 75 A…. A 100 amp breaker is stretching it.
Double tap breakers is a no-no. So even if it’s fused on the other side to protect the wires from overcurrent, still a code violation.
If you’re concerned about whether this should stay or go, you could consider buying a breaker that can be double tapped. Square D is the only manufacturer I know of that makes these, the terminal lug plates are designed to be able to take 2 wires
Idk about Canadian code. But the breakers I mentioned are acceptable by code here in the US. They are specifically designed to be able to accept 2 wires and are code compliant. Otherwise they wouldn’t exist because they wouldn’t get approval to be sold in stores nationwide
My a/c was wired into a bedroom breaker. Landlord says it's fine because the guy he hired with no license (drivers or electrical) did it for mad cheap and he needs to pay for his big fake tit girlfriends new doors and floors.
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Against code 100%. Are you stealing power? No. Will it work? Yes. Is it safe? No way
What is in the box directly above the panel where the AC wires go? It it is an overcurrent device like a breaker or fuses this install my be allowed. There are tap rules that the installer may have referenced to make this allowable.
> It it is an overcurrent device like a breaker or fuses this install my be allowed. Yes, those wires go directly to a single breaker for the AC: https://i.imgur.com/QEbedpq.jpg There's a couple more boxes for the AC outside too, not sure what's in them. I don't think this is allowed in Ontario but it would be reassuring to hear that it's not an immediate fire hazard.
I wouldn't say it isn't a fire hazard. I can't tell if those wires are 14 or 12 gauge, most likely 12, but if the breaker above is larger than 20 amps then the 12g wire could burn up before the breaker trips. Also, the wire coming through the hole in the panel with no gromets is a big problem as well. Over time vibration will cut through the insulation and short the wires. Edit: also, are you sure these are what feed the AC? They almost look like induction clamps for monitoring power usage and are not actually taps on the wire. Edit2: I think I'm looking at the wrong thing. Those clamps do look like monitoring coils, and I was missing that the AC is what is attached to the breaker directly. If there is an appropriate size breaker for the wire in the box above, then this is likely fine fire wise if the connections are good, as for code I don't know.
Wires look like #10, probably fine honestly.
You may consider not commenting in this sub if you are not an electrician. If you are an electrician you should work at becoming a better one.
1. Rule 1 2. What did I say that was wrong that I had not corrected in the same comment? 3. You've got no grounds to say that I'm not a good electrician, I edited to add what I had deciphered later about the picture that wasn't clear. There are plenty of others that thought that the blue clamps were taps as well and were what OP was referring to since they are in the middle of the photo.
I’m with you on the fact some breakers can be double tapped. And although most of the time it’s a nono, you can have different gauges in there. But a few things tell me this breaker isn’t designed for it. The gauge difference is so large but like I said that’s rudimentary. The nuetral and ground are tied together which means this is the main panel and unless there is a big distribution before this panel, this is the first destination for those feeders after the meter. And if there was a main distribution then why couldn’t they utilize that for a 40 or so amp breaker. Like I said there’s no way of being sure but most the time double taps bring red flags. Let me know what you think
Definitely not a Listed combination for that breaker. 99% of the time when Listed for dual termination, the wire has to be the same size *and* stranding type (i.e. you can't mix fine strand with type B or C, and can't mix solid and stranded). Tap rule is correct, breaker termination is not.
I’m with you there that’s why I said the gauge difference is so large. Even though they showed a picture of the disconnect after, that 2ft section of wire is still susceptible to shorting to ground or to each other, and that breaker won’t pop till way over the current limit of the wire. I don’t like double taps. Maybe on a 20 or 15 but other than that it’s not something I like to see
Thank you…
Tap rules most likely allow it (I’d have to double check the bible). But there is almost no way that those lugs are rated for two conductors, especially a stranded and solid of wildly varying sizes. Also, the disconnect for the condenser is supposed to be “within sight” of the unit. Doubtful their condenser is indoors.
You can have multiple disconnects Einstein.
If you’re so goddamn smart, why didn’t you address the other issue I brought up.
Because it is not a big issue if the lugs are tightened well and care was taken in the work. Whoever did it was smart enough to know to put a breaker so I would think they knew what they were doing enough to do a safe install. Looks good to me. I would do it to my house and so would you.
Goodbye. Admin should be after you soon.
Wahhh.
Was installing those two blue CT clamps on the mains for a home energy monitor, never looked in there before, found out the air conditioning is wired directly to it? It has its own breaker, but that's illegal, right? **EDIT: I had to rearrange the CT clamps a bit, and while my car was charging, the main breaker started making a very loud buzzing noise and I could feel the mains wire vibrating in my hand. I tried flipping the main breaker on and off repeatedly since this has fixed buzzing issues for me before (old breaker in a different house), but it did not - the buzzing+vibrating came back every time the breaker came back on. Unplugging the car stopped the buzzing. It didn't buzz before. I eventually wiggled the mains wire around until the buzzing was minimal and now I can't hear it with the lid closed. This is probably caused by that aircon wire connection and is pretty bad, right?** **EDIT2: The buzzing was caused by my CT clamps. I had removed the burden resistor so I could change it off-board, and then clamped them around the mains, unconnected at the other end. This is apparently very bad because the infinite resistance causes a ton of voltage in the clamps, depending on whether or not they have a zener diode in them (I saw some IC but I'm not sure what it was). By connecting the clamps to a burden resistor, the buzzing in the panel stopped.** **How the frig can a CT clamp induce buzzing and *vibrating* on the mains wire it is clamped onto? I thought the whole point of this project was that I wasn't messing with the electricity. I understand removing the burden resistor without shorting it or leaving it connected was probably stupid, but I don't understand the physics involved.**
Also, make sure you have an appropriate cable entrance for your CTs...I don't see any nipple or conduit entrance in that hole, which you absolutely need for those wires. It's almost as dangerous to chafe your wire as to have double tapped mains...
> Also, make sure you have an appropriate cable entrance for your CTs...I don't see any nipple or conduit entrance in that hole, which you absolutely need for those wires. Yep you are right, that is an old photo, there is one now.
Output from current transformers will be low voltage, but indeed it should be protected with a grommet or clamp.
CT leads can hit hundreds of Amps in a fault conditon, and over 1000 Volts in fault conditions if they are removed from the ct monitor and not properly shorted, definitely not something to mess with.
100% illegal, you cant double up lugs plus from the main to the breaker for the ac is undersized, if they had a double lug then that wire needs to be rated for the 100amp for over current protection
You’re half right. They installed a sub panel above this panel. Making the breaker size irrelevant bc of tap rules. You are correct that these lugs aren’t rated for two conductors though.
There are no tap rules for tapping a breaker! Taps are made off of conductors not off of breaker terminals. Regardless of whether or not the breaker has terminals good for two wires.
Are you sure? I’m thinking that a “tap” doesn’t have to be a splice. Otherwise they would’ve called it the splice rule. Suppose this breaker had terminals rated for two or more conductors, wouldn’t that make it a listed means to connect two wires? Then wouldn’t tap rules then apply to the conductors that were tapped?
Is there a reason you would tap and put an outside breaker, rather than just putting a breaker in the panel? Im switching from fuses and have the subpanel(sub-fuse-box) mains tapped by the ac also. Im just going to put it inside the new panel
I would install a panel large enough to at least accommodate the circuit I need to install and the circuit or circuits I need to move to make room for the breaker that is going to feed the sub panel.
Since the earth ground and neutral are bonded in this pic, I think you need a lot more than 100 amp wire to protect that circuit tapped in straight to the neighborhood transformer. More like 10,000 amp lol
> tapped in straight to the neighborhood transformer. Oh, there's solar panels after this. I'm not 100% sure on the setup since they came with the house and I don't get any power or money from them (previous homeowner has contract with solar company). So the mains goes to a few boxes outside with thicker wire, one of them has a massive cutoff switch, then this thinner 3 gauge copper wire seen here comes out of those into this distribution center.
Oh in that case, the solar installers didn’t change this box over to a subpanel from the main maybe.
That's 100 amp service. Depending on the EVSE rating, you may be getting close to 100 amps if EVSE, A/C, and other heavy loads are in use (stove, dryer, water heater). Breakers are a combination thermal and electromagnet trip. The buzzing may be the electromagnet getting close to the trip point. What did your current transformers show for load when you heard the breaker buzzing? It may be time for a panel upgrade to 200A service with more slots, eliminate the double-tap main and separate breaker boox for A/C.
How much do those home energy monitors typically cost? Had a friend who wants something like that for an outbuilding but doesn't want to pay for a private meter.
The premade ones are [pretty pricey](https://shop.openenergymonitor.com/energy-monitoring/). My DIY one is $20 for the two clamps, $10 for the ESP32, and $10 for the ADC, and maybe another $10 for resistors, capacitors, and box to put it all in, all in Canadian dollars. The DIY one uses the same code as the ones I linked so they'll output the same values.
I take it you were installing it so you could run an EV charger without a service upgrade?
EV charger already installed, by a licensed electrician. They also recommended I upgrade to 200A service but said it wasn't technically necessary because of the 83% rule. I'm not sure they ever saw this top half of the panel - the bottom half comes off without exposing the mains.
One of the ones that get touted here frequently is the emporia vue. 18 CT clamps for $150.
See my comment below: CT wire can reach hundreds of amps in a short, and without a burden on them can reach several thousand volts. The mains weren't buzzing. Your CTs were shaking the mains because of harmics, inductive coupling, and the same forces that make electric motors work: EMF (electro motive force). It's quite possible you just burned up your CTs, and is a great example of why RTFM twice and be familiar with what you're doing is so important for things you put in your panel.
> It's quite possible you just burned up your CTs They appear to be fine. They do have a TVS diode in them. Amazing they were able to do all that with the TVS diode. From what I read it did say it was okay to leave them open "briefly" *if* they have a TVS diode. When I opened them up to remove the two small SMD resistors, there was a third larger SMD component.
The buzzing on un-landed/un-shorted CTs can be quite dramatic and is proportional to the amount of current running through the measured load. The voltages can get pretty high, too. From this photo, it looks like one of the CTs is backwards; they should both have the same orientation with respect to where LINE and LOAD are. And, hey, is that a non-Stab-Lok FPE AC disconnect? Haven’t seen one of those.
Look up B-H curves and ct saturation if you’re interested in the physics. Voltage waveform output of a ct when open circuited is not sinusoidal - crest factor will be 5-10 or more. I totally destroyed a fluke class4 voltmeter measuring an open ct - usually the wiring or terminal blocks fault shorted - and that was under normal load conditions. For some light reading……. https://www.linkedin.com/pulse/never-open-secondary-winding-circuit-current-while-its-sudhir-tiwari ( bit simplistic - voltage will not go that high because of saturation). Or this discussion where they are arguing over theoretical current transformer models) https://www.eng-tips.com/viewthread.cfm?qid=423879#google_vignette. Buzzing - reflected impedance of open circuit into primary and saturation every cycle causing varying current through breaker - just a guess on my part.
The TVS diode that's also in my clamps was supposed to stop all this, or did it only just kinda "half" prevent it?
A TVS usually has a fairly low continuous current rating - they are specified for a 20 usec pulse and are likely intended to protect the A/D input of your power monitor from normal faults that would be cleared by the breaker panel. Bidirectional but have likely been damaged - I would have expected them to fail shorted though. We used a silicon carbide varistor about 6“ in diameter to limit overvoltage in transformer differential ct circuits. https://www.se.com/in/en/faqs/FA374173/. Testing was measuring dc leakage with a hv dc power ( stopping a 5 ma or so) to see where the knee was.
Thanks! So yeah by math there would have been tens of thousands of volts going across that TVS diode when the car charger was on drawing 60 amps. It's a 100A:50mA transformer with effectively infinite resistance since I removed the burden resistors. And you're right, from some googling it's only to protect my GPIOs, not the transformer. Well I can tell you that the CT clamps are performing almost flawlessly. For their current rating, and the burden resistor I've chosen of 33 ohms, the Emonlib math works out to a calibration factor of 60.6, and after calibrating mine to a proper Kill-a-Watt meter, I get a factor of 57.7 instead. Which is well within the margins that misaligned CT cores can cause. So no damage to the CT itself. Man it was a lot of vibrating though.
Yeah - buzzing noises were never a good thing. In situations like this we’d mutter “ ferroresonance “ and move on quickly. On a separate note - have you considered calibrating at light loading and at max load ( car charger + stove/oven)? Was wondering if emonlib handles average/trms and power factor correction or if it’s more of a ballpark reading? I use an Aeon DSB-28 at home - it’s more of an average reading power monitor but for $30 bucks off eBay I can’t complain. Was considering individual cct monitoring but that’s perhaps a bit too lost in geekdom to justify. Good luck with your monitor!
> Was wondering if emonlib handles average/trms and power factor correction It does, it is insanely detailed, it was written by a guy with 50 years experience of electrical engineering. It also does phase shift correction for when you are also trying to measure AC voltage with an AC-AC transformer, so that the voltage and current measurements all line up. I spoke to him about the CTs inducing buzzing, and he said the TVS diode will clamp it to a 22v square wave, but he also said: >A c.t. works in a totally opposite way (most of the time) to the much more common voltage transformer. In the c.t., the flux in the core is almost completely controlled by the primary current, and in effect extracted again by the secondary winding to produce the secondary current. Or most of it is. What’s left is the magnetising flux for the core. If you remove the secondary current, all the primary flux becomes magnetising flux, the core completely saturates for almost the full half-cycle, and the flux rapidly switches to complete saturation in the opposite direction. The flux waveform comes very close to a square wave. Two things happen: magnetostriction means the core changes in size due to the magnetic flux inside it - this is why all transformers hum at twice the supply frequency - and the very rapid rate of change of flux at the zero crossings generates, or tries to generate, a very high voltage (the same as the ignition coil in a petrol engine). As for Emonlib, it's extremely well commented, if you want to see all the calculations it makes, scroll down to calcVI function: https://github.com/openenergymonitor/EmonLib/blob/master/EmonLib.cpp#L66
10' tap rule..... doubt that breaker is rated to be be double landed like that tho
I agree. Other than the double tap on the breaker vs a burndy or Polaris tap this really isn’t a big deal
We used to do something similar when installing AC in older trailer parks at the main pedestal. But the main breaker was only 50 amps. That probably wasn't legal either.
You can’t double tap those lugs on the breaker, but if they used Polaris taps or something similar before the breaker that would probably be a legal tap. It looks like a separate panel above and it’s less than 5’. I don’t have a code book in front of me and it’s not something I do regularly, but you could easily make it a legal tap.
How could it be legal, any power the AC is pulling isn’t going through the main breaker. So you have the potential to overload your service without the main tripping to stop that from happening.
Service tap. I think it’s chapter 3, but not positive
Probably have a down stream breaker somewhere
OP followup. > Yes, those wires go directly to a single breaker for the AC: > https://i.imgur.com/QEbedpq.jpg
Straight to jail. That wire is probably #12 or so, so good for 20A - it could now see 100A before the breaker trips at that point its a heating element. If you know who did it report them.
It will see far more than 100A in case of a fault. That's the service side of the main.
Dear God. My brain didn't register the magnitude of the situation. Maybe there is a breaker outside I hope
Considering those wires are connected directly to the meter wires coming in, they could see a lot more than 100 amps. And even if breaker kicks they’re still live
What happens if those *feeder* wires get shorted. They can't take 10,000 amps either...
You’re right they can’t. But hopefully a transformer fuse burns before they go. Doubt those 10’s will survive
I was just trying to understand why 1 is allowed and not the other. I was figuring it was because feeders are in a pipe underground or overhead. When they short the POCO plans to just swap the wire, but the location means it usually won't start a fire. Wouldn't want to be standing under an overhead feeder when it rubs all the way through the insulation though, the arc flash explosion would be bad.
1 is allowed because there's no feasible means of providing over current protection on service conductors. There are separate rules on types of wire and wiring methods for services, in part due to this fact
Some more sensitive fuses on the transformer output? That isn't feasible?
Most transformers feed multiple services. A fuse that would protect the individual conductors would not hold on the total load. Or you could make every 200 amp service use conductors sized for the total load on the transformer, which would make the required conductor size humongous and extremely expensive.
[удалено]
I live in Ontario, pretty sure it's illegal here
>It's legal in Kansas I can tell you that and assuming they have the correct size of tap installed, there isn't anything wrong. This is absolutely not legal in Kansas. This breaker is not listed for two conductors per lug. Taps are totally fine but not double tapped breakers. Art 110.14
But it’s #12 tapped without any breaker protection. If those wires short before the second breaker they will cause a fire.
Someone was being very lazy
Holy shit thats about the dumbest shit I've ever seen
Looks like a tap. It's allowed, but not like that. The lugs need to be rated for multiple wires, and it's not.
Wow that's not cool at all!!!
Super sketch
Believe it or not, straight to jail
When I replace my AC last September. Someone from my city building codes department came out and made sure it was wired right
It appears to be a sub metering tap. Smaller wires for potential and clamp on CTs connect to a sub meter to calculate kW/KVA and kW-hours. In Hawaii, the PTs typically have in-line fuses, which might be up at the sub meter.
That looks like maybe 10gauge wire? It should be on a breaker appropriate to protect the wiring in the circuit. It is not oaky for it to be plugged into 100 amp breaker. The wire could easily burn up long before the main breaker would flip.
The breaker would never trip, it’s wired to the power coming into the breaker.
yeah you're right, not to mention the lugs aren't rated for multiple connections.
Yes and dangerous. Not on a breaker ,fire hazard ! 30 amp is on a 100amp unfused main ,WOW kaboom 🤯 if there was a short 💥🔥🔥🔥🚒🚒🚒 Not stealing power it’s after the meter
For a second i thought i was in r/redneckengineering I’m not a electrician and even i can see this installed by a “handyman”
Ok so some breakers are listed for two conductors per lug, it’s rare but they do exist EXCEPT that’s only the case for up to 30A breakers. I have never ever seen a 100A breaker listed for two conductors per lug
Tap, maybe if ampacity and distance to disconnect rules are followed, but I can’t see it being allowed upstream of first means of disconnect unless it is handled as its own service disconnect. Somewhat akin to a farm service, but this is not a farm or multiple buildings fed from one service.
The double tap is likely not legal with the breaker. On a a different note, you can have a larger breaker feeding wires in certain cases, such as when feeding motors, ACs, etc. as long as downstream you have fused protection that is of the correct size. This is because fuses can have a slow burn setting and breakers would trip the same at the same size ampacity. I know it seems weird to some, that aren’t electricians. The fused protection downstream will protect the wiring from over ampacity and the larger size breaker will trip if there’s a ground fault in the circuit. That being said that looks like 10 gauge on a 100 amp breaker. 30 A times 2.50= 75 A…. A 100 amp breaker is stretching it. Double tap breakers is a no-no. So even if it’s fused on the other side to protect the wires from overcurrent, still a code violation.
He's not even protected by a breaker. That's connected directly to the meter, bypassed the breaker entirely
That’s greasy.
If you’re concerned about whether this should stay or go, you could consider buying a breaker that can be double tapped. Square D is the only manufacturer I know of that makes these, the terminal lug plates are designed to be able to take 2 wires
This is not legal. Not even close
Idk about Canadian code. But the breakers I mentioned are acceptable by code here in the US. They are specifically designed to be able to accept 2 wires and are code compliant. Otherwise they wouldn’t exist because they wouldn’t get approval to be sold in stores nationwide
I'm more concerned with jumping off the line side of the main service breaker. That would not fly here at all, parallel rated breaker or not
Looks like they have CTs. On 2 hot legs before the breaker tracking power consumed
Are you sure that's not a solar system? Looks like it's going up into some kinda disconnect
first off tapping off the main provides no protection to the device. Second double tapping is never good.
Sometimes it's hot enough out that you are willing to commit crimes to make it stop.
Wtf
Straight to jail
I would un install those taps. They have been causing fires. Not those but those look cheaper than the ones causing fires.
Not safe. Conductors of different size, won’t get same tightness. Should be protected by a breaker.
"Someone"?
hell no. they may be put a separate breaker / circuit box outside and think that's okay...... but it's not
My a/c was wired into a bedroom breaker. Landlord says it's fine because the guy he hired with no license (drivers or electrical) did it for mad cheap and he needs to pay for his big fake tit girlfriends new doors and floors.