Anyone familiar with NEC (USA electric code) that can do a load calculation ? - Page 1
Forum section: electronics / projects

author: free_electron
author_rank: Super Contributor
timestamp: October 18, 2013, 03:54:53 am
content: Here is my problem.I want to install an additional breaker in my fusebox. There is room to do this.I would either need :- a NEMA 14-50 circuit ( 40 amp on a 50 amp breaker or a 40 amp breaker if that is legal. they tell me 50 amp breaker for this ) This is typically called an RV hookup.- a NEMA 14-30 circuit (30 amp breaker ) this is called a Dryer hookup.so these are 240 volt circuits.My feed line is 100 AMP 240 volts using ALCAN 1 AWG XLPE XHHW2 cable. this cable is rated for 110 amp at 90 degree C.The mains fuse is 100 AMP . NEITHER main fuse NOR cable can be upgraded. That avenue has been explored and it can't be done. (this is a condo , the mains fuse is on the common breaker panel, the cable between main breaker and my fusebox runs through 7 properties and under the concrete slab. you can't pull another cable as the incoming load from the street can't handle it either.So we need to work with that. 100 AMP 240 volt.i measured my real power consumption ( AC running, washer , dryer (gas) , dishwasher , oven on and i end up at 54 amps.so drawing an additional 30 amps is not a problem , even 40 is not a problem ( i can live with a 30 amp circuit but woudl prefer 40 if possible )NEC requires , in order for a permit to add a breaker and outlet that a load calculation is done. There is two methods. both are a bit convoluted and i can't really work it out. using the alternate method and using the real power consumption of my appliances i end up 100 VA short of the allowed 24000 (23900) so it should work from a NEC perspective.I'm wondering if there is someone here that has experience with electrical installation and doing this kind of calculation.I need to have a guarantee that i can get the permit signed off...no permit means .. no car ..Here is the underlying story :i'm thinking of buying a Tesla... a 40 amp circuit can charge it in 9 hours (even though it is a 50 amp circuit the car will not draw more than 40 amp as that is the limit of its on board charger circuit) . A 30 amp circuit can charge it in 11 hours. Both are acceptable as i have a supercharger i can use on the way home. The car detects what circuit it is on (they cave a device in the endpiece for the cable that tells the max power draw allowed . if i plug in the nema 14-30 endpiece the car dials down to 28 amp load automatically )My dryer is gas , so is the cooking in the kitchen. Heating is also purely on gas.Again , from a pure technical perspective : no problem . i am not using my oven at night. only Airco could kick in and about 10 ampere of vampire loads ( clockradio , computer in standby, refrigerator , nightlights , no dishwashers no washer or dryers. the car would only charge between 10 PM and 6 AM , or , at daytime when i know i can't run the oven in the kitchen because the car is charging.My commute and daily driving is max 40 miles so 2 hours of charge tops that off. Only on weekends when i do a longer trip would i need a 6 to 8 hour charge to keep the battery full, but on the way home i can stop for 15 minutes at a supercharger and blast it half full... so i'd be charging max 4 to 5 hours at home. So i can run 260 miles a day without problems in the weekends.there is alternate routes i have been thinking about but i don't know if they are possible (permit wise and NEC wise):I have a 30 amp 240 circuit feeding the oven in the kitchen. i use that oven maybe 3 or 4 times a year. Converting to gas is NOT an option. This is an in-wall oven single height and nobody makes an in-wall gas ovens. I'd have to break out half the kitchen counter and cabinets to convert to a range ( oven and cooktop in one) and that is not something i am willing to do. It's a solid granite countertop.... plus the cost of a range ... no go. And my current cooktop and oven are barely 2 years old.But .. is it ALLOWED (according to code ) to install a second plug on the 30 amp breaker ? ( i know if i run oven and car it will pop the breaker. i would not be splicing the existing cable. it would simpy be inserting an extra cable in the existing breaker. One cable leaves ot oven , one leaves to plug right underneath fusebox. In Belgium you can have as many load points per breaker as you want. it's up to you to make sure you don't go over... i don't know if this is the case in the US.if that is not possible, code wise : Can a manual mechanical switch be installed on the breaker (double pole , dual throw ) so i can switch or CAR , or Oven ?Anyone know the answer or knows someone who can give me the answer ?This has been bugging me for weeks. nobody seems to know a definitive answer on this one...Even the city is confused... According to ordnance , for an electrical vehicle charger you need xyz , but the Tesla does not use a charger ! there is no wall mounted unit. According to law a charger for an electrical vehicle needs to be permanently wired into the fusebox and yo need to submit plan where you will install it.But a tesla doesnt have a charger ! It only has an extention cord ( there is no intelligence in the cord ) that plugs in the car on one end ,and plugs in a standard wall socket on the other end. That wall socket can be a 110 volt 20 amp , 240 volt 30 amp or 240 volt 40 amp outlet. The tesla eats anything you throw at it. So it doesn't fall under that category ...The people at tesla told me : just have a dryer outlet or Rv outlet installed. that's it. you don't need to muck about with EV charging permits. For all purposes the car is a dryer or an RV. (worst case it is a 110 volt 15 amp but that takes 60 hours + to charge. that is not feasable)

author: superUnknown
author_rank: Regular Contributor
timestamp: October 19, 2013, 06:50:06 pm
content: I've done this to run VFDs in the garage. Simplest is to install 50amp 2pole breaker install a short run to a stove outlet in the garage. Plug in aux. equipment as needed. Make sure it's done correctly, tidy, properly sized and omit the permitting. The plug was installed on the original permit at the time the house was wired. "Field rev. not in the record? Weird cause wiring got inspected and approved."OR...Hire an electrician.

author: IanB
author_rank: Super Contributor
timestamp: October 19, 2013, 08:03:48 pm
content: This probably doesn't work for you or you would have mentioned it. But my dryer hookup (in the garage) has options for either gas or electric appliances. Since I have a gas dryer I have an unused electric dryer socket sitting in the wall above the dryer. Since you mention that you have a gas dryer, do you not have the same situation? I think 90% of people run electric dryers so an electric dryer socket should be standard in almost all homes.

author: JohnnyGringo
author_rank: Regular Contributor
timestamp: October 19, 2013, 08:50:59 pm
content: First of all, theNEMANEC is only the starting point for Code Regulations. Each state has their own, most just adoptNEMANEC as a base and add to it for the local environment (i.e. earth quake prone regions, hospitals, etc..) and then Counties and Cities get to add their own regulations on top of that.For load calculations start as Section 200http://www.brunswickcountync.gov/Portals/0/bcfiles/Building_Codes/bldinsp_2006_NC_Code_Handbook.pdfNorth Carolina has the strictest code of all states, and indeed was the first state to ever adopt Electrical/Building codes. I graduated from a 2 year Electrician's Program at Durham Community College. And have worked primarily in retrofitting electrical systems.In NC, you can work on your own property (with permits, in the county), but generally not within city limits. You can extend any circuit, but you cannot add a circuit to the service. For new circuits, you can do all the wiring, but a electrician must do the final hookup.Now, with a condo, I'd expect local ordinances would prohibit you from modifying your electrical system without an electrician, for the protection of all the other residents. Can you imagine the liability issues if you screwed-the-pooch and burned down not only your own condo, but several others nearby? Sure would make some lawyers somewhere very happy.You're spending $40k for a new car, don't be cheap, spend another 1K to get it done by an electrician.

author: free_electron
author_rank: Super Contributor
timestamp: October 19, 2013, 10:09:42 pm
content: i had asked multiple elctricians and they all assured me it was 'no problem' , here is a quote.however, i had done the calculation myself and it IS a problem. but the electricians dont want to listen. as soon as i asked : this needs to be done with PERMIt and SIGNED off , none of em called back ... eveyine scrambles from this problem...I went to the City code enforcement and had I had the calculation done by the city inspector and city electrician. It turns out my load is 88.1 ampere on a 100 amp circuit so i can not add a 30 amp circuit. end of line.However, i have an existing 30 amp breaker on 240 volt feeding the oven. Installing a 2 way switch is legally a no-go. So i took the decision : the oven will be replaced by a gas oven. The oven is old anyway and the only remaining original appliance when i bought the condo 3 years ago. A licensed electrician has been hired that will disconnect the existing wiring , run 2 feet of appropriate cable and install a NEMA 14-30 outlet.Since no breakers or load are added (oven out , which was a 6.8 Kilowatt beast, car in) the inspector signed off.Both oven and car charger are , legally , considered a permanent load ( anything that can run more than 3 hours nonstop is considered permanent ). so there no problem either.A nema 14-50 would be impossible. Even though the car will never draw more than 37 ampere on such a circuit ( limit of the on board EMU ) on a Nema 14-30 the car will limit to 24 ampere charge. the car detects what circuit it is on and adapts appropriately.you can feed it from a NEMA 50 NEMA 30 NEMA20 (all 240 circuits) or a regular 110. The adapter tip has a device in it that lets the on-board charger know what it has to do.This was never a technical problem. i don't run ovens and washers at night when the car would be charging. It was purely a permit issue.And yes, because this is a condo it is mandatory to get the permit signed. If something were to happen it protects me.The electrician quoted me 170 + material ( some wire and the outlet ) + 50$ for the permit.Not a problem.And that car ain't exactly 40K either... (Tesla P85) so insurance wise i want to be in the safe zone.

author: JohnnyGringo
author_rank: Regular Contributor
timestamp: October 19, 2013, 10:19:55 pm
content: Outstanding!Most *shade tree-weekend* electricians run and hide when you ask about permits, and if they tell you that one is not needed, or that it will double the cost of the job, avoid them like the evil shadows in the night.Legit electricians generally hate doing retros and avoid it like the plague, unless there is no new constructions going on. Usually, just not enough money in it for them.I'm glad that you found someone to do it for you (cheaply, and with permits). Kudos for doing it correctly.How much is a new electric car these days?

author: free_electron
author_rank: Super Contributor
timestamp: October 19, 2013, 10:40:20 pm
content: Quote from: JohnnyGringo on October 19, 2013, 10:19:55 pmThis is a general contractor that ha experience with this kind of stuff. he was recommended by the car maker. they know what they are doing.Cost of the car .. i'm afraid to tell... but hey, i'm single... still cheaper than getting a girlfriend.And the P85 isn't exactly what you think an electric car is ... 0 to 60 in 4.2 seconds.. eat my ion trail...and 300 miles range.. Some guy last week managed to pull 412 miles out of a single charge ... And a team of students in the netherlands at some university that is involved in solar races did some optimisation calculations and measurements. they went even further by driving it at peak efficiency...http://cleantechnica.com/2013/09/04/tesla-model-s-driven-388-miles-on-one-charge/

author: JohnnyGringo
author_rank: Regular Contributor
timestamp: October 19, 2013, 11:12:25 pm
content: WoW! That's a beast. Hope you end up getting one !

author: c4757p
author_rank: Super Contributor
timestamp: October 19, 2013, 11:15:34 pm
content: Normally, the more digital stuff it has in it, the less I like it... but this is the first time in ages I've come this close to salivating over a car...

author: free_electron
author_rank: Super Contributor
timestamp: October 19, 2013, 11:20:42 pm
content: Main control panel runs on an nVidia Tegra-3 , the dashboard runs on a Tegra-2...It has 43 microcontrollers distributed throughout the car. all talking on a proprietary bus.i test drove it 3 times so far. it is incredible. Forget it is electric , just look at how it works and how it interfaces with the humans. this is car 3.0...Watch the 'new owner video' ...http://www.teslamotors.com/models/walkthroughThe other carmakers are scrambling to catch up...I saw the model X last (coming next year) week at the opening of the new store in Palo Alto. They whipped it up another notch ...I am not a car buff. i have had a Volksawgen golf and a chrysler so far. I don;t care about Ferrari' and BMW's and Mercs. I don't drool over porsches and Lambos and Maseratis.But this thing.. this is as far removed from a car as possibly can be. It is whisper quiet, smooth , noiseless and vibrationless. The seats are very comfortable. the cabin is large. You have this enormous trunk + the 'Frunk'. And its got all the intelligence that you wish normal cars would have. Normal cars have all this electronics but nothing is integrated or works together. This thing ? approach home and the GPS detects you are home and send the command to open the garage door. Walk away from the car and it locks itself and goes to sleep. approach it , doorhandles come out , open door, sit down , displays turn on. hold brake , put in forward of reverse and off you go. There are no buttons, no keys ,no levers, no knobs. just a little scale model of the car in your pocket.If there are multiple drivers assigned the car remembers all your preferences. put it in reverse, mirrors fold down , rear camera goes on. Listen to streming audio from sources like SLacker , or regegular radio , play music from Flashdrive or through bluetooth from smartphone.Plus it accelerates like a bat out of hell, set on fire, with a cruisemissile up its ass..

author: c4757p
author_rank: Super Contributor
timestamp: October 19, 2013, 11:42:18 pm
content: There are some weird design choices. That remote control is complicated... and I do not like one bit that the emergency brake is electronic. That should be fully mechanical so I can stop myself no matter what has gone wrong in the car. The charge port is weird - they have an adapter to fit to a public charging station. Why can't they just use that connector for the whole thing?One reason I'm not too amused by the LCD stuff - how easy is it to, for example, control the heater while the car is in motion? Traditional control designs put a surface underneath controls, so that you can rest your hand there to help position your finger to press the control, while the car is moving and vibrating. The seem to have replaced all that with a little up/down button on the wheel - but I don't really want to have to read a menu on the instrument panel while I'm moving down the road! I don't even have to look over to set those controls on my car.

author: free_electron
author_rank: Super Contributor
timestamp: October 20, 2013, 03:04:05 am
content: Nope. You THINK it is complicated. until you have used it !here is how you misunderstood the remote control. You do not need to use the remote. you keep that thing in your pocket. approach the car , doorhandles extend , open door get in. car powers up. No need to press a single button.Walk away : car shuts down and locks itself.To open the 'Frunk' double click the nose on the remote.To open Trunk : double click tail on remote.change your mind : single click and it closes again.the open/close button is the third one . if you have the tech package you don;t need that one. ( walkup ) everyone gets the tech package.in that case double click is open. single is close. hold down and all windows go down.on cars with a single button for open and close have you wondered : did i lock it or unlock it ? i have ! i had a renault with a remote . there is only one button. press it it locks, press again it unlocks.my current car remote has 4 buttons. one to unlock the trunk , one to lock the car , one to unlock the car. plus a panic buttonin case of the tesla you would had to have 6 buttons: one to open trunk one to close trunk (remember the tail is motorized !), one to open frunk , one to open car, one to close car , one to roll down all windows...Now ? the remote has 3 . 3 to be used for people that dont use the tech package , or two if you have the tech package. Genius !And if you have the tech package you will most likely never press the one for the trunk because , as you walk up to the car the button on the trunk becomes active. push that and it lifts.push again and it lowers.How you misunderstood the charge port :To begin : the problem with the charge port is that there are 2 worldwide standards. Yes two ! and they are incompatible with each other. One is called CHAdeMO the other J1771. Both are gigantic big and bulky connectors.Both rely on charger electronics on the wall. there is no charger in those cars. it sits on the wall. And both standard can only handle a relative small current . enough to trickele a 14KWH battery full in 10 hours... . Here comes Tesla with a 85KWH pack. And they want to fill it half in 22 minutes. YIKES ! that is 10 times the current the 'standard'connectors can handle ! )So due to Tesla's charging and battery technology and their design goals these were not usable. Fortunately both standard have a mode where you can say : just give me power , i will regulate it myself.Tesla wants to sell their car worldwide. so they designed their on-board charger to eat anything. Have 110 volt ? will charge. Have 220 volt ( europe ? ) will charge !. Have 240 ( US) ? will charge. Have a supercharger ? ( their own technology which is 400 volts DC at 320 ampere ) will charge !So now you have a problem. you would need to install 5 bulky connectorsone chademoone j1771your own proprietary one for superchargingone that is compatible with a NEMA 240 volt outletone that is compatible with 110 volt.and for europe you'd have to bolt on a standard and a high current one. ( you are now at 7 ! )Plus the car has the option of having double chargers to talk to an 240 volt 80 amp station you can get on your wall as well.. which would be yet anothe rconnector... that makes 8 !half the tail of the car would be filled with charging ports.So what did they do ? They design a universal 'Tesla' connector. that can handle the tremendous current of the supercharger , and has a 3 wire control port. And they give you 2 things :- a cable- a little J1771 to 'Tesla' adapter.and soon there will be the chademo adapter as wellon the road you carry the J1771. 99% of the installed public charging ports in the us and europe are J1771. Chademo is APAC ( asia pacific)So drive up to a public charger , click on the adapter and off you go.Drive up to a supercharger and you dont need anything. the supercharger has a permanent cable with tesla connector installed.Come home : take your tesla cable of its hook and plug it in the charge port. done.Depending on what circuit you have at home you will click either the 110 volt , the 30 amp or the 40 amp tip (or 20 20 amp or 220 40 amp tip for europe)on the other end of the cable and plug that in the appropriate outlet in your house. you never remove that cable from its outlet. there is a big relay in the wall-plugged end that de-energises the cable when not plugged in the car so the long cable is powerless unless it is plugged in. safety first !Tesla owners never remove their cable from the home. it stays home , plugged in to the wall outlet, no matter what type.The only instance you want to take your cable on the road is if you are going for a weekend somewhere and want to have a 'backup' . trow the cable and its adapter tips in the trunk and you can charge the car from whatever possible outlet you can find. going to the middle of the woods to visit your weekend retreat cabin at lake tahoe where all you can find is a standard 110 volt plug ? Yes, you can charge the car (you cant even get to lake tahoe, or anywhere else that is not work-home commute, in any other electric car.. they don't have the range) . Going to a place that has an RV outlet ? you can charge. going to where there is a J1771 : you can charge it. and you can still stop long the way at one of the superchargers as well.That is the reason why they did it.All other cars are restricted to a J1771. If you can't find one where you are and you need juice : you are stuck ! that is a catastrophic design failure !The tesla ? it eats anything you throw at it ! all with 1 small connector on the car ! (and a little adapter for j1771) and a tesla branded extension cord with end pieces. That charge cable is 20 feet long so you can reach anything.Plus the car connector is capable of voltages and currents far beyond that of what can be done with both existing standards. both existing standard were designed for commuter cars. So essentially they are half-arsed attempts. they are designed from the perspective that electric cars will only be a fraction of the total cars on the road. Tesla designed theirs from the perspective : lets make a car that can eliminate gasoline cars. By allowing ultra fast charging and removing 'range anxiety' (the anxiety you feel when, in an electric car, you see the battery depleting and start looking for a J1771 ... and can't immediateley find one... and have to keep driving to find one .... thus even more increasing anxiety.. will i find one in time ? )The tesla does not have a range anxiety problem. you can plug it in whatever power source you find, and it has 4 times,or more, the range of any other electric car out there to begin with ( Leaf is 75 miles... Tesla gets 300 miles easy , and if you watch it over 400 ! )Tesla designs the cars from a different persepctive.Other car makers add electric to an existing portfolio of Gasoline and diesel cars. electric is only 1 model out of many others.Tesla only makes electric cars. So they have to make not only much better , they have to give it more capability and technology other car makers haven't even thought of for their regular cars, to be able to compete.As for the emergency brake :you misunderstand that one too mr Bond !To begin : you still have standard 4 wheel disc brakes. Those are purely mechanical and have ABS ! but most tesla drivers never touch that pedal. you learn very quickly hoe the regenerative braking works and you play the throttle ( and yes the brake lights will turn on when you use regenerative braking. as soon as regeneration begins the on board charge control computer turn on the brake lights )In a normal car you have a handbrake lever. the tesla doesn't have that. It does have a handbrake ( engage rear disc brakes only , just like in a regular car ). to engage handbrake : push the Park button when the car is at a stop. pressing park takes the car out of drive mode and locks the parking brake.Now , when driving , pressing that button doesn't do anything. unless you press it longer than an instance :then they engage the parking brakes. So this is essentially the same as you pulling your handbrake while driving. That is what tesla calls an emergency brake.normal powerup sequence for the car:walk up ,handles extend and seats and mirros and radio and all the other crap adjusts to your presets by the time you are close enough to grab the handle to open the door, and sit down. Car is powered up.put foot on normal brake pedal. push the control lever into forward or reverse. this disengages parking brake as well. step on accelerator and go.to shutdown. : press the park button , open door, get out , close door . walk away.it doesnt get any simpler than that. no mucking with keys, handbrakes, parking pedals, parking release levers shifting from park to neutral to reverse to neutral to forward. none of that old style crap. its 2014 almost. can we make it a little more intelligent ? or do we want to keep using controls that were designed 150 years ago ? the only 150 year old control i=on the Tesla is the streering wheel and Elon has set out to kill that one off in 3 years from now by having self driving cars ... he just hired a team of more than 30 people to design the controller for it ...watch out future , here we come !

author: c4757p
author_rank: Super Contributor
timestamp: October 20, 2013, 03:29:16 am
content: Hmm... OK, I get what you're saying about the remote. The guy in the video made it sound complicated... but he seems to be unusually skilled at that...Quote from: free_electron on October 20, 2013, 03:04:05 amA single button is idiotic anyway... every car I've seen has a separate lock and unlock button. If Renault calls that a sensible idea, I can only imagine what the rest of the car is like...And I see your point about the charge port.QuoteThe way the regenerative braking works is cool. But that's not an emergency brake! An emergency brake should work even if the car's electrical system shits itself... the one in my car pulls a cable straight back to the rear wheels, where there are secondary drum brakes actuated by that cable. The only thing that could stop it from working is if the cable sticks, and I use it for parking as well, so I know it won't.QuoteThe automated startup sequence is interesting. I don't much care for that kind of automation, myself, but I can see the attraction. I'll admit some bias - I'm the sole driver of my car, so there's never anything to adjust. My "startup sequence" is this: key in the ignition as I slide into the seat, twist it to 'start' as I put my belt on, hands on the controls, pull away! It's basically one fluid motion. But back when I was learning to drive and sharing my mom's car, I bet she'd have killed for a car that fixes the mirrors after I've moved them...

author: SeanB
author_rank: Super Contributor
timestamp: October 20, 2013, 06:06:02 am
content: You still have the regular hydraulic brakes which work even if the electrics have multiple failures and die. You lose ABS and regen, but those will work in any case so long as the car is mostly in one piece.