I live in a condo. The main breaker is only 70A. Now what? [Resolved]

[eprosenx]

You are really overthinking this. One electrician already said you could add a 30a charging circuit.

Quick back-of-the-napkin load calc: 24A HVAC and another 20A for applicances (microwave, dishwasher, refrigerator, washer, dryer) brings you to 44A. Another 6A for lighting and other miscellaneous and you are at 50A - if everything is running at the same time. I think you would have a hard time generating a 50A load in your house if you tried.

Another way to look at it is your highest electric bill during the year - my guess is maybe 36kWh average per day. That would be a 15a average load.

Get an electrician to do real load calculation, and I'll bet you'll find you can add a 20A charging circuit to the existing panel without any issue.

If you want to upgrade your electric service and replace the panel that is fine - but why not use the money to upgrade your M3 instead?

Yes, this is a good callout.

If it can be determined that your panel is not one of the fire hazard ones and you can find a compatible tandem breaker for that AC spot and the load calculations allow for it, you could potentially put in a 20a 240v receptacle (assuming that was enough juice for your needs and desires). If those conditions are all true this would be a cost effective solution.

Even if the breaker panel is a hazard or you can’t find a tandem, you could swap that panel with a new one pretty inexpensively.

But otherwise, I probably would reconductor back to the main panel before I spend $$$ on the DCC unit.

I am dead curious to hear what you come up with in the end, so please do report back when it is all done!

 

[andy92782]

Yes, this is a good callout.

If it can be determined that your panel is not one of the fire hazard ones and you can find a compatible tandem breaker for that AC spot and the load calculations allow for it, you could potentially put in a 20a 240v receptacle (assuming that was enough juice for your needs and desires). If those conditions are all true this would be a cost effective solution.

I'm really hoping to squeeze as much juice out of this as possible. I'm shooting for a 14-30 - that's good for 22 miles of range per hour according to Tesla. My other concern are the EV charging guidelines released by my city that shows a 100A main breaker as being the smallest one they'll approve. They're already a little suspicious of the DCC (out of unfamiliarity), but if I can get a 100A main breaker retrofitted along with new wire in the conduit and a new panel then I'm optimistic they'll rubber stamp it.

Either way, I think those are my two best options at the moment. I got delivery of my car scheduled for a week from today so with any luck I can git 'er done before then!

 

[JTwo]

I thought I could live with the 120v outlet but it takes way too long to even top it off. I’m going with a NEMA 14-30 outlet. I was told I can’t run my stove and charge my car at the same I could trip a breaker. I already have my charging start at 9:30pm to take advantage of the lower rates at night. With the quicker charging from the 14-30, I’ll change my charge to start at 11:00pm when the chance of using my stove is slim and none.

 

[EdM3]

Nice first post. Out of curiosity, how did you find out about the DCC? From your electrician?

Long story, I requested permission to install a charger from the HOA that would have just been a straight connection into my meter in the electrical room to my parking space. They pushed back over concerns about the overall power capacity in the building. Did a bunch of research into all the shared charging systems and also found the DCC in an article on Electrek. Found the electrician off of the DCC website. As I said, overall was a pricey option but was the best solution in this case to satisfy everyone involved. And yes, long time lurker, first time poster

 

[eprosenx]

I'm really hoping to squeeze as much juice out of this as possible. I'm shooting for a 14-30 - that's good for 22 miles of range per hour according to Tesla. My other concern are the EV charging guidelines released by my city that shows a 100A main breaker as being the smallest one they'll approve. They're already a little suspicious of the DCC (out of unfamiliarity), but if I can get a 100A main breaker retrofitted along with new wire in the conduit and a new panel then I'm optimistic they'll rubber stamp it.

Either way, I think those are my two best options at the moment. I got delivery of my car scheduled for a week from today so with any luck I can git 'er done before then!

So assuming you can upgrade to a 100 or 125a main, if you do a 30a circuit your car will draw 24a. If you do a 40a or 50a circuit on a 14-50 receptacle and you use the UMC Gen 2 that comes with the car, then it will only pull 32a since that is where the UMC maxes out. Even if it is a 50a circuit the UMC can't make use of all the capacity. A UMC Gen 1 could, or other EVSE units could. (I basically never recommend a 40a circuit with a 14-50 receptacle)

There are a LOT of threads on this forum regarding the merits of a UMC vs. using a Wall Connector. I recommend reading through several of them. If you want to keep your UMC in your car at all times and want to have the most charging speed flexibility and you are not very price sensitive, then I might recommend a Wall Connector. In addition to giving you higher capacity than a UMC it also gives more granularity to settings of max charge rate. You could install on a 60a capable circuit but then crank it down to say only 30a (24a continuous) if it turned out that was all your service could handle.

 

[eprosenx]

Long story, I requested permission to install a charger from the HOA that would have just been a straight connection into my meter in the electrical room to my parking space. They pushed back over concerns about the overall power capacity in the building. Did a bunch of research into all the shared charging systems and also found the DCC in an article on Electrek. Found the electrician off of the DCC website. As I said, overall was a pricey option but was the best solution in this case to satisfy everyone involved. And yes, long time lurker, first time poster

So that is interesting. Were you originally wanting to upgrade your main breaker off the main switchgear and this is what had them concerned about overall capacity?

The ironic part is that even with the DCC unit you may still push up their overall load... If everyone did what you did they still likely would be overloaded.

Typically in a condo situation like that say they have 48 units each with a 60a feed. If you took that at face value that would need a 2,880 amp feed. The power company would laugh at them since never would all units be drawing max at once. So they oversubscribe. So maybe on a good day they put in a 1000a feed. So while the DCC unit may keep you below 60a at all times, if everyone started adding chargers they eventually would be a world of hurt anyway.

Basically all the HOA/Condo's are going to have to get smart about this stuff. Electric cars are coming, and faster than you think. There are a number of ways to solve for this, but one way or another it is going to involve someone spending money. I would rather throw money into adding capacity instead of expensive solutions to try to cap load (though both are viable and there is a place and time for both solutions).

P.S. I think the future is with EVSE's that can receive information from current monitors on the main electrical feed and can self pare back what the car is allowed to draw in order to stay under some limit. Things like this DCC unit are a hack with a very big lever to pull (on/off). Doing it at the EVSE is a lot more granular.

The whole multi-tenant thing makes it a total mess though. Managing a system with so many tenants would be hard. In some ways it begs for a standard J1772 solution that is centrally managed, though the tech is moving so quickly that I probably would not recommend a HOA invest in that.

 

[EdM3]

Were you originally wanting to upgrade your main breaker off the main switchgear and this is what had them concerned about overall capacity?

Sort if, it was more about the oversubscribing situation you described - the master panel capacity for the entire building is less than number of units times the stated capacity of the individual unit panels. The DCC mitigates the issue, doesn't eliminate it. Eventually if everyone wants to have EV charging, still need to either upgrade the capacity or use a central charge management system.

 

[Cosmacelf]

Sort if, it was more about the oversubscribing situation you described - the master panel capacity for the entire building is less than number of units times the stated capacity of the individual unit panels. The DCC mitigates the issue, doesn't eliminate it. Eventually if everyone wants to have EV charging, still need to either upgrade the capacity or use a central charge management system.

Yes, central charge management will be the eventual answer. But, jeez, it’ll take years before condos get to that point.

 

[andy92782]

There are a LOT of threads on this forum regarding the merits of a UMC vs. using a Wall Connector. I recommend reading through several of them. If you want to keep your UMC in your car at all times and want to have the most charging speed flexibility and you are not very price sensitive, then I might recommend a Wall Connector. In addition to giving you higher capacity than a UMC it also gives more granularity to settings of max charge rate. You could install on a 60a capable circuit but then crank it down to say only 30a (24a continuous) if it turned out that was all your service could handle.

I know this is a Tesla forum but I sort of have it in my head that if I install a wall mount charger, I’d like it to be a generic J1772 form factor rather than Tesla’s proprietary wall charger. The zjuice Box comes to mind. Gotta plan long term. Tesla’s on a hot streak right now but 5 years from now who knows what else might be on the market.

The alternative to a fixed charger is to stick with a simple 14-30 outlet. Probably cheaper that way anyway...

 

[Krash]

...generic J1772 form factor rather than Tesla’s proprietary wall charger...

Just buy a third party K1772 adapter for the Tesla HPWC.

 

[andy92782]

Basically all the HOA/Condo's are going to have to get smart about this stuff. Electric cars are coming, and faster than you think.

It’s probably gonna get worse before it gets better. I’ll use my own HOA as an example. The one “cool” board member already told me “I won’t be around when that becomes an issue.” Yeah, he’s a bit older. Essentially he has no interest in coming up with a long term solution. In his defense, the board has more pressing issues to deal with; my entire development is currently undergoing a 6 month long repainting project. There’s also ongoing stuff like termite repairs, etc. And nobody dares speak of a due increase, which is almost certain to happen if a large scale electrical infrastructure project is required.

The other thing is the utility itself. Twice in the past year the large transformer that feeds my neighborhood (250 units or so) went up in smoke on hot days. I guess that’s a whole ‘nother problem to worry about another day...

 

[Rocky_H]

You could install on a 60a capable circuit but then crank it down to say only 30a (24a continuous) if it turned out that was all your service could handle.

I've seen you mention this same recommendation over and over in different threads, and it seems like it doesn't comply with electric code at all. If the load calculation says you can only have a 30A circuit, isn't that defined by the breaker you put on it? I don't think you can do what you always suggest about putting in a 60 or 80 or 100A circuit, and then just "fake it" by turning down the appliance to act as a 30A device.

 

[eprosenx]

I've seen you mention this same recommendation over and over in different threads, and it seems like it doesn't comply with electric code at all. If the load calculation says you can only have a 30A circuit, isn't that defined by the breaker you put on it? I don't think you can do what you always suggest about putting in a 60 or 80 or 100A circuit, and then just "fake it" by turning down the appliance to act as a 30A device.

So my understanding of NEC load calculations is that they are based off the actual nameplate rating of the device you are connecting NOT the ampacity of the circuit breaker you put it on. Overcurrent protection and load calculations are separable concerns. A good example is electric motors - you often times have to have pretty big breakers for them to deal with the surge current at startup, but from a load calculation standpoint you calculate it based on steady state running load I believe.

My understanding (and please point out code references if you understand it differently) is that this holds true for both hard wired devices and devices that are plugged in. A good example would be a UMC Gen 2 device: It can only ever pull 32 amps continuous (so you calculate it as if it was 40 amps for load calc purposes). It does not matter if you put it on a 40a or a 50a circuit, it will only ever draw 32a. A UMC Gen 1 on the other hand would be able to draw 40a which would have to be calculated as 50a due to the continuous load thing again.

So the Wall Connector is an interesting beast. It can provide up to 80 amps (on a 100a circuit). If you took that at face value, you would have to do your load calculations assuming every Wall Connector was a 100a load. This obviously would not work for the vast majority of installs... So what is obvious to me is that by setting the rotary dial inside the unit, you are effectively changing the nameplate value of the device as it limits what the car can pull. That is the value you would then use for your NEC load calculations. So if you set it to 40a (continuous), then you calculate it as a 50 amp load.

Now it really does not matter what size of wire or circuit breaker the Wall Connector is on as long as they are both equal to or greater than (up to a limit of 100a) the ampacity you set the rotary dial to. The wall connector assembly and cord and the cars you are plugging it into are clearly rated to be able to handle up to 100a of fault current so I see no issue with using a larger circuit to power the Wall Connector than what you are artificially limiting the car to due to load calculation reasons.

Does that logic make sense? Let me know if you have read anything in the NEC that contradicts this line of thinking!

P.S. I will also call out that I absolutely do NOT agree with "just turning it down using the settings in the car" as a way of "faking" it. I do NOT think this would comply with code since it relies on unreliable humans to set it every time. The rotary dial however is difficult to get to and generally only modified by professionals. This would be akin to changing motor tap settings in your HVAC blower motor, etc...

 

[juliusa]

My understanding (and please point out code references if you understand it differently) is that this holds true for both hard wired devices and devices that are plugged in.

I think you are wrong. Putting in a 50A outlet even though you "say" you will only be using 32A is not good enough. What happens when you replace the UMC later and draw 40A? Or when the next tenant moves in and does not know about only drawing 32A?

Even it that were somehow code compliant, I would never do that.

 

[eprosenx]

I think you are wrong. Putting in a 50A outlet even though you "say" you will only be using 32A is not good enough. What happens when you replace the UMC later and draw 40A? Or when the next tenant moves in and does not know about only drawing 32A?

Even it that were somehow code compliant, I would never do that.

I agree with you in principle, but I believe I am correct NEC code wise.

Note that code wise these things go both ways. Sometimes the code requires you to vastly over represent something in the load calculations and other times like this you wonder if it is enough.

Another example of this in the code is convenience outlets around the house. The code has you calculate load based on number of square feet in the house. Nothing stops you from loading all the convenience outlets around the house to their absolute max breakered limit. This will exceed what was calculated.

Please quote code sections if you think I am incorrect - I would like to get to the ground truth here if I am wrong.

 

[juliusa]

I'm not an electrician. You can wire your 14-50 with lamp wire and duct tape for all I care.

 

[Rocky_H]

Does that logic make sense?

No, and in all of that explanation, I don't see you addressing my question at all. You're talking about the 32A UMC being represented as a 40A circuit, which is obvious. And you talked about motors surge current, but that is all precisely specified on the nameplate.

Here's the part I'm getting at. Let's say someone has a 70A main breaker for the total service of the entire house. You have been saying that if the wall connector is set to something like 20A internally, then it doesn't matter how big the breaker is--go ahead and put it on a 125A circuit breaker, even though the entire feed for the house is only 70A, and a load calculation would never allow a 125A circuit in there. You are saying the switch inside the wall connector of 20A is all that matters with respect to complying with the load calculation. I don't think that would be the case.

For my code reference, I don't know if I can locate this exactly, but it should follow the same "spirit of the law" as the NEC requirement that the rating of an outlet must be at least as high as the circuit breaker it is on. So you can't put a 6-50 outlet on a 70 or 80 or 100A breaker. I would think that same rule applies. NEC wants the breaker to cut off early, so it shouldn't have the breaker much higher than the device.

 

[eprosenx]

Here's the part I'm getting at. Let's say someone has a 70A main breaker for the total service of the entire house. You have been saying that if the wall connector is set to something like 20A internally, then it doesn't matter how big the breaker is--go ahead and put it on a 125A circuit breaker, even though the entire feed for the house is only 70A, and a load calculation would never allow a 125A circuit in there. You are saying the switch inside the wall connector of 20A is all that matters with respect to complying with the load calculation. I don't think that would be the case.

For my code reference, I don't know if I can locate this exactly, but it should follow the same "spirit of the law" as the NEC requirement that the rating of an outlet must be at least as high as the circuit breaker it is on. So you can't put a 6-50 outlet on a 70 or 80 or 100A breaker. I would think that same rule applies. NEC wants the breaker to cut off early, so it shouldn't have the breaker much higher than the device.

To clarify, I do not think I have suggested that someone install a branch circuit (for an EVSE) with a breaker that is larger than their overall service feed rating. While off the top of my head I don't know where in the code that this is banned, but it is not very intuitive. There would really never be a use case for doing this unless you were planning to upgrade the service/feeder soon that was the limiting factor.

I *have* however suggested that folks put a ridiculously large breaker (say 50a) on a new branch circuit (along with appropriately rated wire) for a Wall Connector even when lets say they only had a 70a main service feed. While you would never be allowed to operate it at 50a due to load calculations limiting you, it would be ready in case you upgraded that service to 100a or 125a, etc... Really the key is that I have in some cases recommended that folks wire the Wall Connector with wire and a breaker larger than the load calculations would allow today so that they have the flexibility to change its settings as factors change. Examples would be: 1. They convert their oven, range, furnace, water heater, or dryer to gas which frees up load capacity that could be re-allocated to the Wall Connector. 2. They upgrade the main service/feeder as mentioned. 3. Or, really the kicker is this one: 220.87 says you can throw out all the code calculations and look at *actual* load over the course of the year and use that to base your demands on. It is my belief that something like the "sense energy monitor" could allow you to make an argument that the mathematic load calculations were not representative and that you should be allowed to turn up your Wall Connector higher than the calcs would otherwise allow. If you did not pre-wire and pre-install a larger breaker to allow this, it would be a ton of expense to later increase capacity.

I also need to clarify that I have never suggested to put a Tesla Wall Connector on a circuit greater than 100a (and I never would) since this is what the unit is rated to. Specifically, the nameplate on the side of the unit says it takes 80a of input, but since it is a continuous load we have to provide wire of 100a ampacity along with the matching circuit breaker. The install instructions say to install it on a 100a circuit (or lower if you can't support 100a).

But to the meat of your question:
Load calculations of Branch Circuits, Feeders (subpanels), and Services are covered in Article 220. These are completely decoupled from "Overcurrent Protection" which is covered in Article 240. The size of the breaker has nothing to do with how we calculate load. They are separable concerns.

Article 220 is quite complex and it is unfortunate that it does not address EVSE's directly (even though it seems to have special language for just about everything else). From what I can tell, EVSE's fall under 220.14(A). (also note that Article 625 which covers EV charging says nothing about load calculations there)

So to me, this covers a NEMA 14-50 for EV charging with a UMC, or a hardwired Wall Connector.

I read that as a UMC Gen 1 is calculated as 40a, times 1.25 due to continuous load, so 50a. A UMC Gen 2 would be 32a times 1.25 so 40a. In both cases it would be on a 14-50, but for the UMC Gen 1 you would only be allowed to use it on a 50a rated circuit. A UMC Gen 2 would be allowed on either a 40a or a 50a rated circuit (still on the 14-50 receptacle).

But to finally answer your concern: I calculate the "load" of a Wall Connector based on what the rotary dial is set to. The only other option would be to do it based on the max nameplate value listed on the side of the device which is 80a (100a when factoring in continuous load). If you used that number basically nobody would be allowed to install a Wall Connector as it would fail load calculations.

Something that is interesting here is that unlike a motor where you can configure different tap points that might cause different loads, in the case of the EVSE you are having the EVSE send a signal to the car and then you are *trusting* that the car does not draw more than you told it that it is allowed to. The actual device doing the restriction is not the Wall Connector. Now it begs the question in say commercial EVSE's: Do they have current CT's and can they detect how much a car is actually drawing and cut it off if it breaks the "rules" (instructions) the EVSE gives it?

So assuming we can get on the same page about the rotary dial being the "nameplate value" of the load being served, the other question is one of overcurrent protection:

The Wall Connector is rated for up to a 100a circuit - its components and the wire to the vehicle (and presumably the vehicle itself) are all rated so that if there is a fault (short), enough current can flow in order to trip the 100a breaker. The danger would be if the Wall Connector had thin wires in it that might melt and catch fire before flowing enough current to trip the main breaker. But this is not the case since it is rated up to 80/100a.

Now of course you absolutely need to protect the wire from the breaker panel to the Wall Connector, so to do what I suggest of say installing a 50a circuit even if you crank the wall connector down to 24/30 amps, you would need to install at least 6 AWG copper NM cable as an example to match or exceed the 50a breaker rating.

Does that make sense? I think what I have been recommending is both safe and within NEC regulations (and provides the user future flexibility and investment protection if applied in the right situations).

 

[juliusa]

I believe the code issue is when doing a load calculation, an outlet used for EVSE is a continuous load at 80% of circuit capacity. Adding a 50a EVSE circuit to a 70a main panel will not pass load test. Well, maybe if you live in a tent.

 

[eprosenx]

I believe the code issue is when doing a load calculation, an outlet used for EVSE is a continuous load at 80% of circuit capacity. Adding a 50a EVSE circuit to a 70a main panel will not pass load test. Well, maybe if you live in a tent.

Please cite a code reference for this. I believe you are wrong. Everything I have read indicates it is based on the EVSE you intend to use on that receptacle, NOT the rating of the branch circuit feeding the receptacle.

I understand where you are coming from from a logical and practical standpoint, but I do not believe this is how the NEC code is written.