Yes, that's my point. Plugging in an EVSE because a breaker doesn't trip immediately with an overload is dangerous, to say the least.
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Idea for apartment dwellers: 'host' charging through window
- Thread starter Quothmar
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Yes, that's my point. Plugging in an EVSE because a breaker doesn't trip immediately with an overload is dangerous, to say the least.
Oilpan4 said:A good test would be if you can draw more than 150% amps over a breaker for more than 3 minutes it's probably bad, unless it's some old obsolete style of breaker, that may be normal for them and likely the reason they're obsolete.
Thanks -- I'll keep that in mind. I would feel bad about leaving a vacuum, a table saw, and a dehumidifier on for several hours, but if it's one time only, it should be for a good cause.
When you say it's 'dangerous', it makes me wonder how that should be defined. There is, obviously, the danger that gas fumes have on pedestrians and on the ozone layer, and then as you mention there's the danger of a fire if circuits are overloaded. What if the danger of a fire occurs with something like 0.001% probability? I don't know enough about electricity to calculate the figures, but I think some kind of cost-benefit analysis would weigh in.
My idea about host charging is something to help apartment complexes get on board with letting their residents charge their electric vehicles at home. Once they go to, say, about 5 or 6 electric vehicles, they could then install charging stations. Opposing it, there is the on-demand charging station idea, where as soon as one person buys an electric car the complex management must shortly thereafter install a charging station for that single owner. I don't disagree with this idea, but I can imagine homeowner associations everywhere pitching a fit over it.
If not by host charging, how would you say that we should get apartment complexes to make it practical for residents to own electric vehicles?
In regards to dangerous and electrical wiring anything that runs more than 80% of the continuous amp rating of the wire is potentially very dangerous.
For example a 16 amp evse should be ran on a 20 amp circuit that is wired with 12 gauge wire.
If a 16 amp evse is plugged into a 15 amp circuit ran on 14 gauge wire it may not trip breaker and the wire would become quite warm. When a 14 gauge wire is confined inside a fixed wall running 16 amps with cellulose blown in house insulation all around it it will become very hot and potential exceed 60 degrees Celsius, which is the temp rating of the insulation on about 97% of house wiring.
This is why the basic evse only draws 12 amps in the US. They are assuming you have 14 gauge wiring. A very safe assumption.
(A 14 gauge circuit can only handle 12 amps continuously)
According to the NEC "continuous" can mean anything from 20 minutes to 3 hours or more depending on the application. So charging an electric vehicle is on the absolute high end of what they call "continous".
Personally I have over breakered 6 gauge 60 amp and 4 gauge 125 amp circuits in my garage. They are for welders and plasma cutters but will work fine for a little 16 amp evse.
The problem with apartments and charging electric vehicles is the only dedicated circuits are going to be in the kitchen and bathroom.
If there are any outside receptacles they should be on their own circuit and have gfi, but they are not required to provide outside receptacles.
Chances are if you run an extension cord out the window is that cord is going to plugged into a room circuit that has up to a dozen other receptacles on it and who knows what else could be on that circuit plugged into one of those receptacles.
For example a 16 amp evse should be ran on a 20 amp circuit that is wired with 12 gauge wire.
If a 16 amp evse is plugged into a 15 amp circuit ran on 14 gauge wire it may not trip breaker and the wire would become quite warm. When a 14 gauge wire is confined inside a fixed wall running 16 amps with cellulose blown in house insulation all around it it will become very hot and potential exceed 60 degrees Celsius, which is the temp rating of the insulation on about 97% of house wiring.
This is why the basic evse only draws 12 amps in the US. They are assuming you have 14 gauge wiring. A very safe assumption.
(A 14 gauge circuit can only handle 12 amps continuously)
According to the NEC "continuous" can mean anything from 20 minutes to 3 hours or more depending on the application. So charging an electric vehicle is on the absolute high end of what they call "continous".
Personally I have over breakered 6 gauge 60 amp and 4 gauge 125 amp circuits in my garage. They are for welders and plasma cutters but will work fine for a little 16 amp evse.
The problem with apartments and charging electric vehicles is the only dedicated circuits are going to be in the kitchen and bathroom.
If there are any outside receptacles they should be on their own circuit and have gfi, but they are not required to provide outside receptacles.
Chances are if you run an extension cord out the window is that cord is going to plugged into a room circuit that has up to a dozen other receptacles on it and who knows what else could be on that circuit plugged into one of those receptacles.
WetEV
Well-known member
Quothmar said:If not by host charging, how would you say that we should get apartment complexes to make it practical for residents to own electric vehicles?
Installing EVSEs in the parking areas for residents only. L2 240V/208V, hourly limit, dual cord units would probably be best. One for every N units, with N being perhaps 5, more or less. 4 hour limit during the day, perhaps 8 hours or a bit more overnight.
Or in more expensive apartments, for a unit only, perhaps in a garage, perhaps with a separate rental agreement.
And/or charging at work.
A problem that will need to be solved once the percentage of EVs gets up to near 50%.
When you say it's 'dangerous', it makes me wonder how that should be defined. There is, obviously, the danger that gas fumes have on pedestrians and on the ozone layer, and then as you mention there's the danger of a fire if circuits are overloaded. What if the danger of a fire occurs with something like 0.001% probability? I don't know enough about electricity to calculate the figures, but I think some kind of cost-benefit analysis would weigh in.
Indeed. The likelihood of a fire in an overloaded circuit goes up over time, but can be high in Minute One if the wiring is old and/or in poor condition. This is NOT something you want to ignore or shrug off. Just running a circuit at 100% of capacity for many hours is risky. Running it over that is like smoking with a gas leak in the house and one window cracked open.
smkettner
Well-known member
As a landlord I would not allow extension cords (EV or otherwise) hanging out of windows or crossing common areas for more than a few days.
Yeah in my rental house I installed an L14-30 receptacle.
It's part of my personal charging network.
I did a test just to see what would happen. I took my 14 gauge 240v spot welder SJ cable extension cord and plugged in the 16 amp evse just to see what would happen.
For the first 20 minutes nothing seemed to happen the cord barely warmed up. But after an hour it was pretty warm, then after 2 hours it was hitting 125F according to my flir i7 camera.
If that 14 gauge wire had been inside a wall covered with insulation it would have gotten much hotter.
It's part of my personal charging network.
I did a test just to see what would happen. I took my 14 gauge 240v spot welder SJ cable extension cord and plugged in the 16 amp evse just to see what would happen.
For the first 20 minutes nothing seemed to happen the cord barely warmed up. But after an hour it was pretty warm, then after 2 hours it was hitting 125F according to my flir i7 camera.
If that 14 gauge wire had been inside a wall covered with insulation it would have gotten much hotter.
LeftieBiker said:Indeed. The likelihood of a fire in an overloaded circuit goes up over time, but can be high in Minute One if the wiring is old and/or in poor condition. This is NOT something you want to ignore or shrug off. Just running a circuit at 100% of capacity for many hours is risky. Running it over that is like smoking with a gas leak in the house and one window cracked open.
Are you suggesting it's a bad idea for an apartment-dweller with 14 gauge wire to trickle-charge even one car from a room circuit?
Quothmar said:LeftieBiker said:Indeed. The likelihood of a fire in an overloaded circuit goes up over time, but can be high in Minute One if the wiring is old and/or in poor condition. This is NOT something you want to ignore or shrug off. Just running a circuit at 100% of capacity for many hours is risky. Running it over that is like smoking with a gas leak in the house and one window cracked open.
Are you suggesting it's a bad idea for an apartment-dweller with 14 gauge wire to trickle-charge even one car from a room circuit?
That depends on the condition of the wiring and the size of the load. A typical 12 amp EVSE (charging cable or station) can safely charge on a 15 amp circuit with 14 gauge wires, IF there are no other significant loads, and IF there are no weak or worn connections. Worn or low quality outlets are a major source of problems like fires, so it's a good idea to use a new, commercial grade outlet.
The spring-loaded 'backstab' outlets are the dangerous ones. Leviton, IIRC, makes rear-connect outlets in which the internal clamps are tightened and held by the side screws instead of by a spring. So those are about as safe as the side connect outlets.
Oilpan4 said:Virtually no one wires up room outlets for continuous high amp use.
Oh and if some amateur wired the receptacles with the "back stab" method there will be a fire.
I just read about 'backstabbed' outlets, and they sound dangerous. But will there be a fire?
Much of these discussions surround the notion of what makes a wise decision, given that opposing decisions have alternate risks. In an earlier post, you gave some figures involving the risk that blown-in cellulose insulation would create a fire hazard: that 16 amps on 14-gauge wire running continuously could push the cellulose toward its temp rating of 60 degrees Celsius.
How do you arrive at these figures? Have you actually done thermal calculations with the physical properties of cellulose to determine the probability of a fire? I only took a few basic physics courses, but I would be interested to further research your claims.
The only reference I found to the temp ratings of various types of insulation are here:
https://www.engineeringtoolbox.com/insulation-temperatures-d_922.html
https://en.wikipedia.org/wiki/Insulation_system#cite_note-IEC60085-3
None of the ratings shown go as low as 60 degrees Celsius. I'm also reading that cellulose is treated with fire-retardant material, making it safer for use around electrical wires.
Somehow, I think you would have to arrive through thermal calculations at the probability of a fire, and incorporate that probability into a further calculation involving the probabilities of other expected outcomes and their relative magnitudes of favorability (air pollution, ozone damage). While favorability isn't as easily measured as the likelihood of a fire or of health hazards due to air pollution, I think some kind of cost-benefit analysis would have to weigh in before we could automatically dismiss home-charging on a room circuit as unwise.
Again, this is for one car. I did some research and found that the upper wattage limit for a 12-volt, 14-gauge wire is 2400 watts, which is well above the 1300 used by my EVSE. Although two cars charging at once would not work (1300 + 1300 = 2600 > 2400), I still like my idea of putting each charge port on a timer (say, 7:00 PM - 11:00 PM, 11:00 PM - 3:00 AM, 3:00 AM - 7:00 AM), to ensure that 1300 watts is never exceeded.
As a competitor to the idea of host charging, however, see below...
WetEV said:Quothmar said:If not by host charging, how would you say that we should get apartment complexes to make it practical for residents to own electric vehicles?
Installing EVSEs in the parking areas for residents only. L2 240V/208V, hourly limit, dual cord units would probably be best. One for every N units, with N being perhaps 5, more or less. 4 hour limit during the day, perhaps 8 hours or a bit more overnight.
Or in more expensive apartments, for a unit only, perhaps in a garage, perhaps with a separate rental agreement.
And/or charging at work.
A problem that will need to be solved once the percentage of EVs gets up to near 50%.
At first, I was skeptical that EVs could ever get up to 50% without allowing apartment-dwellers to charge their EVs at home. Oddly enough, I never bothered to do the research to see that roughly 3/4 of the United States population live in houses. I imagined that apartments were more 'compact' and that there would be more people living in them. But if more people live in houses, then putting more responsibility on house-owners to purchase electric vehicles, until EV-driving house-owners reach a certain percentage of the population, and then mandating that charging stations be installed at apartment complexes, could work.
So host charging would not be necessary to get the ball rolling for apartment complexes, though it may nevertheless be a viable supplementary strategy.
Few household wiring fires start inside the cables themselves. Instead, they usually start at the connections: connections at the outlet and inside the outlet, connections at the main service panel (rare) and connections at junction boxes in between. Junction and outlet and switch boxes were originally fire-suppression devices: by confining a connection fire inside a sealed steel box, the fire was smothered by exhausting the oxygen. Now, with plastic boxes in use, you'd better hope that fire gets smothered VERY quickly...
Quothmar said:Oilpan4 said:Virtually no one wires up room outlets for continuous high amp use.
Oh and if some amateur wired the receptacles with the "back stab" method there will be a fire.
I just read about 'backstabbed' outlets, and they sound dangerous. But will there be a fire?
Much of these discussions surround the notion of what makes a wise decision, given that opposing decisions have alternate risks. In an earlier post, you gave some figures involving the risk that blown-in cellulose insulation would create a fire hazard: that 16 amps on 14-gauge wire running continuously could push the cellulose toward its temp rating of 60 degrees Celsius.
How do you arrive at these figures? Have you actually done thermal calculations with the physical properties of cellulose to determine the probability of a fire? I only took a few basic physics courses, but I would be interested to further research your claims.
The only reference I found to the temp ratings of various types of insulation are here:
https://www.engineeringtoolbox.com/insulation-temperatures-d_922.html
https://en.wikipedia.org/wiki/Insulation_system#cite_note-IEC60085-3
None of the ratings shown go as low as 60 degrees Celsius. I'm also reading that cellulose is treated with fire-retardant material, making it safer for use around electrical wires.
Somehow, I think you would have to arrive through thermal calculations at the probability of a fire, and incorporate that probability into a further calculation involving the probabilities of other expected outcomes and their relative magnitudes of favorability (air pollution, ozone damage). While favorability isn't as easily measured as the likelihood of a fire or of health hazards due to air pollution, I think some kind of cost-benefit analysis would have to weigh in before we could automatically dismiss home-charging on a room circuit as unwise.
Again, this is for one car. I did some research and found that the upper wattage limit for a 12-volt, 14-gauge wire is 2400 watts, which is well above the 1300 used by my EVSE. Although two cars charging at once would not work (1300 + 1300 = 2600 > 2400), I still like my idea of putting each charge port on a timer (say, 7:00 PM - 11:00 PM, 11:00 PM - 3:00 AM, 3:00 AM - 7:00 AM), to ensure that 1300 watts is never exceeded.
As a competitor to the idea of host charging, however, see below...
WetEV said:Quothmar said:If not by host charging, how would you say that we should get apartment complexes to make it practical for residents to own electric vehicles?
Installing EVSEs in the parking areas for residents only. L2 240V/208V, hourly limit, dual cord units would probably be best. One for every N units, with N being perhaps 5, more or less. 4 hour limit during the day, perhaps 8 hours or a bit more overnight.
Or in more expensive apartments, for a unit only, perhaps in a garage, perhaps with a separate rental agreement.
And/or charging at work.
A problem that will need to be solved once the percentage of EVs gets up to near 50%.
At first, I was skeptical that EVs could ever get up to 50% without allowing apartment-dwellers to charge their EVs at home. Oddly enough, I never bothered to do the research to see that roughly 3/4 of the United States population live in houses. I imagined that apartments were more 'compact' and that there would be more people living in them. But if more people live in houses, then putting more responsibility on house-owners to purchase electric vehicles, until EV-driving house-owners reach a certain percentage of the population, and then mandating that charging stations be installed at apartment complexes, could work.
So host charging would not be necessary to get the ball rolling for apartment complexes, though it may nevertheless be a viable supplementary strategy.
NEC 625.29 states the evse shall be plugged into the receptacle and not be plugged into an extension cord.
NEC 210.17 states that a receptacle used for charging an electric vehicle shall not contain other receptacles. Each electric vehicle charger is to be on its own dedicated circuit.
NEC 240.4 requires a 15 amp breaker on a 14 gauge circuit.
If you plug a 16 amp load on a 15 amp breaker it may trip after 2 or 3 hours.
So the NEC answer to can I plug an extension cord into some random apartment receptacle that may be on a 15 circuit to charge an EV is no, no and no. Or just no and no.
Ignore NEC, test your smoke detectors for real and meet the fire department.
Any other questions?
LeftieBiker said:Few household wiring fires start inside the cables themselves. Instead, they usually start at the connections: connections at the outlet and inside the outlet, connections at the main service panel (rare) and connections at junction boxes in between. Junction and outlet and switch boxes were originally fire-suppression devices: by confining a connection fire inside a sealed steel box, the fire was smothered by exhausting the oxygen. Now, with plastic boxes in use, you'd better hope that fire gets smothered VERY quickly...
This is why I like and prefer to use metal boxes. Then I further insulate the out door receptacle boxes with a coating of construction foam over the inside portion, mostly to keep out bugs and dirt out of the walls and to shut down air circulation. But will also help smother and isolate a fire. The aerosol construction foam I use only burns if I hold a propane torch to it.
NEC 210.17 states that a receptacle used for charging an electric vehicle shall not contain other receptacles. Each electric vehicle charger is to be on its own dedicated circuit.
This isn't practical for 120 volt charging, and is generally ignored (except for not using more than one EVSE). Extension cord use is a grey area: I definitely see why it's prohibited, but a best-case setup, with high quality, heavy cord, good outlet, and no foot traffic over the cord, isn't very unsafe.
LeftieBiker said:NEC 210.17 states that a receptacle used for charging an electric vehicle shall not contain other receptacles. Each electric vehicle charger is to be on its own dedicated circuit.
This isn't practical for 120 volt charging, and is generally ignored (except for not using more than one EVSE). Extension cord use is a grey area: I definitely see why it's prohibited, but a best-case setup, with high quality, heavy cord, good outlet, and no foot traffic over the cord, isn't very unsafe.
I use an extension cord too sometimes.
Problem with most cords is even if they have heavy 12 gauge conductors the cheap thermoplastic moulded ends can burn up. I have smoked them just using them on a little 1.5hp air compressor.
My evse extension cords are all 240v 6-20 plugs and receptacles on each end. Since I can not go to the hard ware store and buy a 6-20 ended cord I made my own by putting commercial grade replacement ends on a 12 gauge STW cord. I would prefer sjoow cord but the STW was pretty much free.
If you live up north trust me, pay extra, you want the sjow or sjoow cord in the winter.
If your house is wired to code and you use an outside 120v receptacle, these individual outside receptacles should be in their own dedicated circuit, or at the very least all the outside ones should be on their own circuit (old code).
The EVSE we have outside the garage is a Toyota PIP unit, with the cord run through the wall and plugged in inside (and a plastic garment bag over the unit). The Nissan dual voltage cable is plugged into a short appliance extension cord, and then into an outlet, all inside the garage, so I can charge while the Leaf is inside. I've been wanting either a 240 volt circuit or at least a 20 amp dedicated 120 volt circuit for years, but it hasn't happened yet.
Oilpan4 said:NEC 625.29 states the evse shall be plugged into the receptacle and not be plugged into an extension cord.
NEC 210.17 states that a receptacle used for charging an electric vehicle shall not contain other receptacles. Each electric vehicle charger is to be on its own dedicated circuit.
NEC 240.4 requires a 15 amp breaker on a 14 gauge circuit.
If you plug a 16 amp load on a 15 amp breaker it may trip after 2 or 3 hours.
So the NEC answer to can I plug an extension cord into some random apartment receptacle that may be on a 15 circuit to charge an EV is no, no and no. Or just no and no.
Ignore NEC, test your smoke detectors for real and meet the fire department.
Any other questions?
So you're quoting the NEC now. That's fine, but now we're discussing American law and not physics. In your previous post, you had put forth an argument about the constitution of wall insulation materials, suggesting that if the wiring approached 60 degrees Celsius, it could start a fire. My question was whether you could supply a physical justification for this claim, deriving the probability of a fire from the known properties of cellulose insulation and from the laws of thermal physics.
If you're not into complex mathematical derivations, that's fine. I understand that this forum is not a physics course. But that is what you would need to justify any claim about the probability of a fire.
Although I use a JLong extension cord, the fact that it pulls only 1300 watts on a 120-volt outlet means that it only draws 1300 / 120 =~ 11 amperes, well below your example of a 16-amp load. And I did previously say that we were stipulating trickle-charging, and that we were putting the EVSEs on timers so that only one would be charging at a time.
Now obviously, we couldn't do this with 'some random receptacle' if we had reason to believe it was defective. But if you're going to argue that it's simply a bad idea, you would need to supply the physical derivations to obtain the probability of a fire, and use that probability in a weighted calculation of the favorability of alternative actions in respect of their possible outcomes. These outcomes include, on the one hand, smoggy streets and parking lots in urban cities (very annoying, and also high probability), and on the other, a fire (devastating, but possibly also very low probability).
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