How many amps are you going with for your Model 3 home charging circuit?

[rdturner0]

40amp is plenty. I have invested in hpwc and 80amp wiring thinking that I'll make it future-proof while keeping the old box and dialling down hpwc for now. Guess what, it's been 5 years and I never needed more. Now with Model 3 joining the family might need to add another 40 amp HPWC and upgrade the house to 200 amp.

Yep, should be enough. More worried about when I add the second PHEV or EV, but that likely won't be for 7-10 years.

I've got 12 hours of off peak time electricity available, and usually at least 9 of those where the car is at home, so I expect that maybe once every few years I might have a ''wish it would charge faster" moment.

 

[rdturner0]

since I had to add a circuit to the garage, and the labor was the same, went with the full 60 amp breaker in a sub-panel. (Just a few extra dollars for heavier gauge wire.)

Mine's all properly wired for 60A too (including cut off) (and I might just have a breaker lying around here somewhere...), but it would not have passed inspection (solely due to load calculation). I suppose I could have lied to the inspector about the load calculation, but that just doesn't seem right...and he could have asked to see the calculation (or done it himself).

 

[ksumnole]

Your numbers should be very similar to mine, so very surprised you aren't considered over. With the chargers and the home area, you would only have about 9000 watts remaining of the 38400 watts allowable on a standard 200 A service.

So 9000 watts for stove, pool pump, central heating, AC, hot water and dryer isn't typically anywhere near sufficient if all electric.

So assuming you have gas heating, gas dryer, gas hot water and a gas stove, you might just be marginal.

Do you know if a load calculation was done when your chargers were installed?

If you want to run one yourself, here's an easy to use calculator: CEC Electrician Calculators

(I'm mostly bummed because I'm (officially) capped at 40A total load for car chargers. Just don't know how others are 'getting away' with more.)

My load calc is about 180 amps. This is of course rating the 80 amps of charging (32 EVSE + 48 HPWC) as continuous loads.

For the load calculation, since these are not continuous loads, you are actually able to load a 200 amp breaker up to 200 amps. The 80% rule does not apply as it does to branch circuits. So I believe you are incorrect in saying you only have 38400 watts...you actually have access to all 48000 watts of the 200 amp breaker.

It appears that you ecalc.ca website agrees with this.

Someone please correct me if I am wrong.

 

[rdturner0]

My load calc is about 180 amps. This is of course rating the 80 amps of charging (32 EVSE + 48 HPWC) as continuous loads.

For the load calculation, since these are not continuous loads, you are actually able to load a 200 amp breaker up to 200 amps. The 80% rule does not apply as it does to branch circuits. So I believe you are incorrect in saying you only have 38400 watts...you actually have access to all 48000 watts of the 200 amp breaker.

It appears that you ecalc.ca website agrees with this.

Someone please correct me if I am wrong.

So I went and re-read the whole of section 8 of the CEC 2015 (the section about load calculations), and I think you are correct about being allowed to push up to the 200 A limit. What it says is that "the minimum ampacity of service or feeder must be the greater of ... ", where the "of" is the total given by the calculations. I was dead convinced that it was 80% of the total. I did lots of reading over a few weeks, maybe I got confused by it all. Also, one of the electricians that visited for a quote also felt I was over with a 60A circuit for the charger as well (I didn't see his load calculation data though).

However, what isn't clear to me is how that applies to the main breaker for the house. Is that still restricted to 80% or not? Section 8-104 suggests that you can have up to 100% of the rating if the breaker is marked for continuous operation at 100% of the device rating, but if only rated for 80% continuous, then it would obviously be limited to 80%. So there might be some restrictions related to the over-current protection device at the whole house level beyond that of the service size.

I really should have asked the inspector when he was here today...just to get clarification. I'll try asking an electrician I know and see what he says.


Relevant sections of the 2015 CEC code for reference:

8-104 Maximum circuit loading (see Appendix B)
(1) The ampere rating of a consumer’s service, feeder, or branch circuit shall be the ampere rating of the overcurrent device protecting the circuit or the ampacity of the conductors, whichever is less.
(2) The calculated load in a circuit shall not exceed the ampere rating of the circuit.
(3) The calculated load in a consumer’s service, feeder, or branch circuit shall be considered a continuous load unless it can be shown that in normal operation it will not persist for

(a) a total of more than 1 h in any two-hour period if the load does not exceed 225 A; or
(b) a total of more than 3 h in any six-hour period if the load exceeds 225 A.​

(4) A load of a cyclic or intermittent nature shall be classified as continuous unless it meets the requirements of Subrule (3).
(5) Where a fused switch or circuit breaker is marked for continuous operation at 100% of the ampere rating of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed

(a) 100% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 2 or 4; or
(b) 85% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3.​

(6) Where a fused switch or circuit breaker is marked for continuous operation at 80% of the ampere rating of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed

(a) 80% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 2 or 4; or
(b) 70% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3.​

(7) If other derating factors are applied to reduce the conductor ampacity, the conductor size shall be the
greater of that so determined or that determined by Subrule (5) or (6).
(8) Notwithstanding the requirements of Rule 4-004(1)(d) and (2)(d), the ampacity of the underground
conductors shall not exceed in any case those determined by Subrules (5)(b) and (6)(b) of this Rule.

8-110 Determination of areas
The living area designated in Rules 8-200 and 8-202 shall be determined from inside dimensions and include the sum of

(a) 100% of the area on the ground floor;
(b) 100% of any area used for living purposes on the upper floor; and
(c) 75% of the basement area.​

8-200 Single dwellings (see Appendices B and I)
(1) The minimum ampacity of service or feeder conductors supplying a single dwelling shall be based on the greater of Item (a) or (b):

(a) (i) a basic load of 5000 W for the first 90 m2 of living area (see Rule 8-110); plus

(ii) an additional 1000 W for each 90 m2 or portion thereof in excess of 90 m2; plus
(iii) any electric space-heating loads provided for with demand factors as permitted in Section 62
plus any air-conditioning loads with a demand factor of 100%, subject to Rule 8-106(4); plus
(iv) any electric range load provided for as follows: 6000 W for a single range plus 40% of any
amount by which the rating of the range exceeds 12 kW; plus
(v) any electric tankless water heaters or electric water heaters for steamers, swimming pools, hot tubs, or spas with a demand factor of 100%; plus
(vi) any electric vehicle supply equipment loads with a demand factor of 100%; plus
(vii) any loads provided for in addition to those outlined in Items (i) to (vi) at 25% of the rating of each load with a rating in excess of 1500 W if an electric range has been provided for, or 100% of the rating of each load with a rating in excess of 1500 W up to a total of 6000 W, plus 25% of the load in excess of 6000 W if an electric range has not been provided for; or​

(b) (i) 100 A where the floor area, exclusive of basement floor area, is 80 m2 or more; or

(ii) 60 A where the floor area, exclusive of basement floor area, is less than 80 m2.​

(2) The minimum ampacity of service or feeder conductors from a main service supplying two or more dwelling units of row housing shall be based on

(a) Subrule (1), excluding any electric space-heating loads and any air-conditioning loads, with application of demand factors to the loads as required by Rule 8-202(3)(a)(i) to (v); plus
(b) the requirements of Rule 8-202(3)(b), (c), (d), and (e).​

(3) Notwithstanding Rule 86-302, the total load calculated in accordance with either Subrule (1) or (2) shall not be considered to be a continuous load for application of Rule 8-104.

 

[ksumnole]

So I went and re-read the whole of section 8 of the CEC 2015 (the section about load calculations), and I think you are correct about being allowed to push up to the 200 A limit. What it says is that "the minimum ampacity of service or feeder must be the greater of ... ", where the "of" is the total given by the calculations. I was dead convinced that it was 80% of the total. I did lots of reading over a few weeks, maybe I got confused by it all. Also, one of the electricians that visited for a quote also felt I was over with a 60A circuit for the charger as well (I didn't see his load calculation data though).

However, what isn't clear to me is how that applies to the main breaker for the house. Is that still restricted to 80% or not? Section 8-104 suggests that you can have up to 100% of the rating if the breaker is marked for continuous operation at 100% of the device rating, but if only rated for 80% continuous, then it would obviously be limited to 80%. So there might be some restrictions related to the over-current protection device at the whole house level beyond that of the service size.

I really should have asked the inspector when he was here today...just to get clarification. I'll try asking an electrician I know and see what he says.


Relevant sections of the 2015 CEC code for reference:

8-104 Maximum circuit loading (see Appendix B)
(1) The ampere rating of a consumer’s service, feeder, or branch circuit shall be the ampere rating of the overcurrent device protecting the circuit or the ampacity of the conductors, whichever is less.
(2) The calculated load in a circuit shall not exceed the ampere rating of the circuit.
(3) The calculated load in a consumer’s service, feeder, or branch circuit shall be considered a continuous load unless it can be shown that in normal operation it will not persist for

(a) a total of more than 1 h in any two-hour period if the load does not exceed 225 A; or
(b) a total of more than 3 h in any six-hour period if the load exceeds 225 A.​

(4) A load of a cyclic or intermittent nature shall be classified as continuous unless it meets the requirements of Subrule (3).
(5) Where a fused switch or circuit breaker is marked for continuous operation at 100% of the ampere rating of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed

(a) 100% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 2 or 4; or
(b) 85% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3.​

(6) Where a fused switch or circuit breaker is marked for continuous operation at 80% of the ampere rating of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed

(a) 80% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 2 or 4; or
(b) 70% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3.​

(7) If other derating factors are applied to reduce the conductor ampacity, the conductor size shall be the
greater of that so determined or that determined by Subrule (5) or (6).
(8) Notwithstanding the requirements of Rule 4-004(1)(d) and (2)(d), the ampacity of the underground
conductors shall not exceed in any case those determined by Subrules (5)(b) and (6)(b) of this Rule.

8-110 Determination of areas
The living area designated in Rules 8-200 and 8-202 shall be determined from inside dimensions and include the sum of

(a) 100% of the area on the ground floor;
(b) 100% of any area used for living purposes on the upper floor; and
(c) 75% of the basement area.​

8-200 Single dwellings (see Appendices B and I)
(1) The minimum ampacity of service or feeder conductors supplying a single dwelling shall be based on the greater of Item (a) or (b):

(a) (i) a basic load of 5000 W for the first 90 m2 of living area (see Rule 8-110); plus

(ii) an additional 1000 W for each 90 m2 or portion thereof in excess of 90 m2; plus
(iii) any electric space-heating loads provided for with demand factors as permitted in Section 62
plus any air-conditioning loads with a demand factor of 100%, subject to Rule 8-106(4); plus
(iv) any electric range load provided for as follows: 6000 W for a single range plus 40% of any
amount by which the rating of the range exceeds 12 kW; plus
(v) any electric tankless water heaters or electric water heaters for steamers, swimming pools, hot tubs, or spas with a demand factor of 100%; plus
(vi) any electric vehicle supply equipment loads with a demand factor of 100%; plus
(vii) any loads provided for in addition to those outlined in Items (i) to (vi) at 25% of the rating of each load with a rating in excess of 1500 W if an electric range has been provided for, or 100% of the rating of each load with a rating in excess of 1500 W up to a total of 6000 W, plus 25% of the load in excess of 6000 W if an electric range has not been provided for; or​

(b) (i) 100 A where the floor area, exclusive of basement floor area, is 80 m2 or more; or

(ii) 60 A where the floor area, exclusive of basement floor area, is less than 80 m2.​

(2) The minimum ampacity of service or feeder conductors from a main service supplying two or more dwelling units of row housing shall be based on

(a) Subrule (1), excluding any electric space-heating loads and any air-conditioning loads, with application of demand factors to the loads as required by Rule 8-202(3)(a)(i) to (v); plus
(b) the requirements of Rule 8-202(3)(b), (c), (d), and (e).​

(3) Notwithstanding Rule 86-302, the total load calculated in accordance with either Subrule (1) or (2) shall not be considered to be a continuous load for application of Rule 8-104.

Right, you zeroed in on it.
I didn't go re-read all that before hand but it lines up with what I remember.
Here is my load calculation. As I said, I am just squeaking in under the allowed load. I am sure if I really wanted, I could pull my hourly meter data and show that my load is nowhere near this and that adding a 48A charger is not going to get me even close to my 200 amps, considering I have a very energy efficient house.

I am still waiting for my inspection, so we will see how it goes, but I think I am OK.

Basic Load for 372m2: 10000 W
Range: 6000 W
Air Conditioning: 5736 W
Clothes Dryer: 1560 W
Electric Vehicle Charging: 22080 W (I included my pool pump in here as a continuous load)
Total Demand Power: 45376 W
Calculated Ampacity: 189 ABreaker Panel Size: 200A
Circuit Breaker Rating: 200A
Minimum Conductor Size: #3/0 AWG Copper or #4/0 AWG Aluminum



Here is a good article describing this: Residential Load Calculations | IAEI Magazine

 

[rdturner0]

Right, you zeroed in on it.
I didn't go re-read all that before hand but it lines up with what I remember.
Here is my load calculation. As I said, I am just squeaking in under the allowed load. I am sure if I really wanted, I could pull my hourly meter data and show that my load is nowhere near this and that adding a 48A charger is not going to get me even close to my 200 amps, considering I have a very energy efficient house.

I am still waiting for my inspection, so we will see how it goes, but I think I am OK.

Basic Load for 372m2: 10000 W
Range: 6000 W
Air Conditioning: 5736 W
Clothes Dryer: 1560 W
Electric Vehicle Charging: 22080 W (I included my pool pump in here as a continuous load)
Total Demand Power: 45376 W
Calculated Ampacity: 189 ABreaker Panel Size: 200A
Circuit Breaker Rating: 200A
Minimum Conductor Size: #3/0 AWG Copper or #4/0 AWG Aluminum

Load calc makes sense to me (you're AC is more efficient, and you have slightly less "basic load" than I do.

Assuming you are correct about being able to push up to 100%, then it sounds like you should be fine. (Obviously over if limited to 80%).

Do follow up after the inspection, especially if they discuss load calculation...

 

[rdturner0]

Right, you zeroed in on it.
Here is a good article describing this: Residential Load Calculations | IAEI Magazine

That article very clearly suggests you can push the limit of the breaker on the main panel to 100% -- so, I can go (legitimately) swap my 50A breaker for the 60A one I seem to have here on a shelf and dial the HPWC back up the 48A.

It's a good explanation for folks too... well sourced.

 

[Lloyd]

Voted 60 amps for two cars

 

[roblab]

I only want to ask, "Why?" What's the push for another 8 amps of charge?

I guess if you're leaving at midnight you might want to have it complete, but my S and 3 both charge at 24 amps and are full every morning. If I put two 50 amp circuits in my box, it seems as if I might have my 100 amp box full, might have to turn off about eight other circuits, but since they both charge just fine, why the need to push them to a limit?

I just don't get it. You're asleep. It's not like you're in a hurry. It's like I need the app to send a notification, complete with vibration and loud notification sound so I can quick go unplug it at 2AM. It doesn't work that way.

 

[ksumnole]

I only want to ask, "Why?" What's the push for another 8 amps of charge?

I guess if you're leaving at midnight you might want to have it complete, but my S and 3 both charge at 24 amps and are full every morning. If I put two 50 amp circuits in my box, it seems as if I might have my 100 amp box full, might have to turn off about eight other circuits, but since they both charge just fine, why the need to push them to a limit?

I just don't get it. You're asleep. It's not like you're in a hurry. It's like I need the app to send a notification, complete with vibration and loud notification sound so I can quick go unplug it at 2AM. It doesn't work that way.

The simple answer is.....because I can.

 

[sauce]

I've opted for a future-proof setup with a 100A breaker and HPWC dialed up to 80A, though the 90D has a 48A charger but that will allow to hook up a second HPWC when the Model 3 arrives home in more or less 2 years from now.

 

[rdturner0]

I only want to ask, "Why?" What's the push for another 8 amps of charge?

I guess if you're leaving at midnight you might want to have it complete, but my S and 3 both charge at 24 amps and are full every morning. If I put two 50 amp circuits in my box, it seems as if I might have my 100 amp box full, might have to turn off about eight other circuits, but since they both charge just fine, why the need to push them to a limit?

I just don't get it. You're asleep. It's not like you're in a hurry. It's like I need the app to send a notification, complete with vibration and loud notification sound so I can quick go unplug it at 2AM. It doesn't work that way.

Yeah, it doesn't actually matter that much for the car for me (other than just trying to max out what I can just in case that one time I might need it in 10 years) -- I've got other things I want to load into the house in addition to the second EV/PHEV at a later date -- I'm more worried about total load of everything...

 

[Darthbenji]

I’ve got 100amp service and have an induction stove, AC, electric hot water tank, electric dryer and a pool pump. 1700 sq feet. Will I need to upgrade to 200 amp? What’s the max amp charging I can do if not?

 

[Canuck]

40amp is plenty.

That's probably true with a 3 especially since it only goes up to 48 amps. But I often go to my cabin in the morning, cut the grass and do other things, then come home. Without being able to charge at 80 amps, I couldn't do that in my S. It will be interesting to see how that goes with the 3 at 48 amps. I wish it could charge at 80 amps too -- that would sure be great. I don't know why Tesla has gone backwards on the charging. You can still buy a HPWC that puts out 80 amps but you can't buy a new Tesla that can use all of that.

 

[03DSG]

I only want to ask, "Why?" What's the push for another 8 amps of charge?

I guess if you're leaving at midnight you might want to have it complete, but my S and 3 both charge at 24 amps and are full every morning. If I put two 50 amp circuits in my box, it seems as if I might have my 100 amp box full, might have to turn off about eight other circuits, but since they both charge just fine, why the need to push them to a limit?

I just don't get it. You're asleep. It's not like you're in a hurry. It's like I need the app to send a notification, complete with vibration and loud notification sound so I can quick go unplug it at 2AM. It doesn't work that way.

For me it’s really just one of those things that doesn’t have to make practical sense. The cars got an onboard 48 amp charger. I want the infrastructure at home to be able to utilize the charger’s designed capacity. In fact I may never need to charge at 48 amps. Normally I probably won’t. But I want the ability.
OK. I’ll admit it. The Tesla WC is just so much cooler looking than a 14-50

 

[darkenergy]

We'll share using the Tesla SAE J1772 adapter that comes with the portable Tesla EVSE. Does anyone know why the Canada Tesla online store doesn't carry those? I would like to get a spare.

I've spoken with a couple of people on the support line about Canadian availability of both the J1772 adapter and the clip in sun shade. In each case they deflected the question to someone else; so I haven't received an answer. Not ideal, but I assume that it's just that they are overloaded with bigger fish to fry.

 

[rdturner0]

I’ve got 100amp service and have an induction stove, AC, electric hot water tank, electric dryer and a pool pump. 1700 sq feet. Will I need to upgrade to 200 amp? What’s the max amp charging I can do if not?

Very likely.

Here's a load calculator you can evaluate your required service size for different charger sizes:
CEC Electrician Calculators

(You need to use 240V or 120V when calculating load based on the maximum current draw of the appliances.)

Also, go back and read this whole thread for more details and other links.

 

[1Step2NoGas]

I've spoken with a couple of people on the support line about Canadian availability of both the J1772 adapter and the clip in sun shade. In each case they deflected the question to someone else; so I haven't received an answer. Not ideal, but I assume that it's just that they are overloaded with bigger fish to fry.

That helps to put it into perspective. I suppose the accessories will follow the demand after the cars have been successfully delivered.

Thanks.

 

[sauce]

That's probably true with a 3 especially since it only goes up to 48 amps. But I often go to my cabin in the morning, cut the grass and do other things, then come home. Without being able to charge at 80 amps, I couldn't do that in my S. It will be interesting to see how that goes with the 3 at 48 amps. I wish it could charge at 80 amps too -- that would sure be great. I don't know why Tesla has gone backwards on the charging. You can still buy a HPWC that puts out 80 amps but you can't buy a new Tesla that can use all of that.

I'd like to discuss that. When I ordered my car last year, Tesla had discontinued the 72A option for the 90D and made it standard on the 100D.

Upon ordering last year I had set out the condition sine qua non of ordering my 90D with the 72A on-board charger. It could be retrofitted at the SC, however as I insisted a little much about this, the MTL Ferrier store manager contacted me and talked me out of it, even if I considered it a necessity, being that I travel upwards of 80,000km/yr with sometimes crazy travelling schedules. He reasoned: ''With the supercharger infrastructure, are you really going to get into situations where you wished you had 72A capacity at home? On the contrary, you might end up wishing you hadn't wasted 3k with that piece of equipment.'' Needless to say, he has a point where sufficient SC coverage beats any AC charge station as far as charging speed goes, which is the case around my home.

So I decided to trust him on that, after all I had no experience with EVs at all.

Here are 3 observations I have about this question ever since then:

1. In 50,000km+ driven so far, I haven't encountered that situation where I needed to charge at 72A
2. When I had a loaner 100D that did charge at 72A, I felt it was useless
3. I did get into that rare situation a few weeks ago when, upon arriving from Chester, PA after an 800km trip that day, I had to drop my luggage home, turn the car around and get it ready to depart immediately to NYC where close friends had encountered an emergency (their father died of a stroke while visiting Time Square) and even then, after having charged fully at DIX30 before arriving home, plugged in while I prepped the car for road trip 2 and back out on the road an hour later, I was able to drop my kids off in Laval and then head to Plattsburg SC where I was in dire need of a nap before resuming driving again. So even then, a 72A charger wasn't required.

Now I look at the Model 3 with its 75kWh battery, or even the short range version which I plan on buying and I don't see a need for anything more than 40A as it will require the same time frame for charging as my current 90D, and that is with the LR version. The SR version will do fine with the remaining 32A available from my 100A breaker/80A HPWC combo when the 90D is charging and will still be charging as quickly as the 90D side by side.

 

[Canuck]

In 50,000km+ driven so far, I haven't encountered that situation where I needed to charge at 72A

And that's fine -- and it's likely true for most people -- but not for me. I need 80 amps often and also on occasion. For instance, last summer my wife and I went to visit our daughter in Kelowna from our cabin in Tulameen (two hours over a significant mountain pass) . She had her BMW at our cabin but we took the Tesla, of course, to visit our daughter. When we got back, my wife realized her car keys were missing and they were at my daughters, it was late, and we just got back. My wife had to drive home the next day so we had to immediately go back to Kelowna. We couldn't drive her BMW of course and the Tesla had a low battery. At 80 amps we waited half the time to get enough range to get to the Kelowna supercharger. That's huge when you just want to get to bed.

Plus, if you like to travel and stay at hotels with 80 amp destination HPWCs (of which there are lots now) you can arrive with a low battery, get enough of charge while dropping off the luggage and having a shower for a night on the town, then charge fully overnight and skip the supercharger stop altogether. 40 or 48 amps just doesn't cut it for that type of stuff and when you're travelling the less time waiting while charging the better, especially if you have to drive out of your way to get to the supercharger.

The large frunk and 80 amp chargers are two things that make it really hard for me part with my classic. The peace of mind it brings is huge since when you need it, you usually really need it.