snellenr
Member
Maybe OP can branch the feed to the HPWC and run one leg to a small (1-2 circuit) panel w/ a 50 amp breaker that feeds the 14-50?
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Maybe OP can branch the feed to the HPWC and run one leg to a small (1-2 circuit) panel w/ a 50 amp breaker that feeds the 14-50?
You can use that 100 amp conductor as a feeder and place a small sub panel with a 50A breaker and a 100A breaker in it.
You do not have to include both in the load calculation if it is likely that the loads would not be used concurrently, you can just use 100A if the receptacle is considered backup to the HPWC. Just remember if you try to use both it'll likely trip the feeder breaker.
You say this, but my electrician says no, since there is no mechanism to stop both from being used at the same time and they are both 100% duty cycle loads.
I'd ask him for the code reference. That's why they're protected upstream by the 100 amp feeder breaker in the main panel.
225.39, "Rating of Disconnect", says "The feeder or branch-circuit disconneting means shall have a rating of not less than the calculated load to be supplied, determined in accordance with [...] Part III or IV of Article 220 for feeders". 225.39, A through D, give minimums, but they're all 100 amps or less.
So we look at art. 220, part III for the proper sizing of feeders. 220.40 says "the calculated load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied" - that's the sum of the calculated loads. 220.60, "noncoincident loads", says that "where it is unlikely that two or more noncoincident loads will be in use simultaneously, it shall be permissible to use only the largest load(s) that will be used at one time for calculating the total load of a feeder or service".
That's pretty clear. I have read some opinions from other electricians that suggest it shouldn't be done without some type of interlock to prevent it, but that's their own thought. The code expressly permits it in this case because it will be unlikely that you will use both at the same time. A simple sign above the receptacle will also serve to make it even more unlikely, "do not use at same time with wall connector".
DMC-Orangeville
Audi eTron & John Deere 5100E
....or wire in a transfer switch. One side of the panel at 100 amp, one side at 50 amp. I used a Siemens EQG6600D 12 circuit Generator transfer panel for mine.
It is when an EVSE is plugged into it. (Shrug) I ended up running a separate circuit for my 14-50. They're all on the same 200A panel that is dedicated for the garage.
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FlatSix911
Porsche 918 Hybrid
My HPWC install
125 Amp breaker in the main panel (outside) feeding sub panel inside the garage
100 Amp breakers dedicated to HPWC (Charge @ 80 Amp max)
50 Amp breakers dedicated to NEMA 14-50 (Standby for Mobile Connector if HPWC fails or stops working, this outlet is useful for lots of other things. But i always make sure i turn this breaker ON only when the HPWC 100 Amp breaker is OFF)
30 Amp breakers dedicated for Hybrid water heater (20 Amp max when used in full electric mode which i never do)
So in a nutshell i'm drawing 80+20 amps of current when the car is charging at night on 125 Amp
125 Amp breaker in the main panel (outside) feeding sub panel inside the garage
100 Amp breakers dedicated to HPWC (Charge @ 80 Amp max)
50 Amp breakers dedicated to NEMA 14-50 (Standby for Mobile Connector if HPWC fails or stops working, this outlet is useful for lots of other things. But i always make sure i turn this breaker ON only when the HPWC 100 Amp breaker is OFF)
30 Amp breakers dedicated for Hybrid water heater (20 Amp max when used in full electric mode which i never do)
So in a nutshell i'm drawing 80+20 amps of current when the car is charging at night on 125 Amp
From a code-compliant load standpoint, you're actually drawing the equivalent of 120A, 100A (80A continuous * 1.25) + 20A (20A intermittent). It's important to think of it that way.
Right,
Water heater after 11PM is generally not using any electricity, as the heat pump kicks in always to heat the water from ambient air which needs less than 5A.
I wish i had time and money to get another 200A of power to the house. These days new constructions in bay area are getting 400A of power for homes more than 3000 sqft.
Water heater after 11PM is generally not using any electricity, as the heat pump kicks in always to heat the water from ambient air which needs less than 5A.
I wish i had time and money to get another 200A of power to the house. These days new constructions in bay area are getting 400A of power for homes more than 3000 sqft.
I have a 1600 sq. ft. house in a mild climate, 2 occupants, no AC, no pool, and I am very glad I installed 200A service, replacing the original 100A service panel. It made it an easy matter to put in an HPWC and run it at 80A.
Even before I got the Model S, I had lights dimming due to the loads created by pool, hot tub, multiple refrigeration units, dual A/C units, etc., with 200A service on 2/0 AL service conductors (which NEC says is good to 135A) and a 10 kVA transformer. When I told the local power company operations chief that I was getting a Tesla, they came out and upgraded me to 400A service. They placed a 37.5 kVA transformer and pulled new 350 mcm compact conductor cable through the old conduit, using the old cables as the pull-rope. I told them to prepare my home for a day when we'd have 2 EV's as our primary vehicles, along with all the other demand I have.
A 37.5 kVA transformer is rated at 156A with PF=1, so there will be times we'll exceed the rating with Model S and Model X charging both at the same time plus other loads in the house. But, as I've noted before, the transformers can handle it - most of them can run at 200% of their rated capacity for quite a long time.
I'm in the midst of upgrading my home service from 400A to 600A. While the utility company is covering the bulk of the expense to run the new 750mcm cable, I'm paying my electrician to upgrade the termination equipment, grounding, and meters, as well as the boring under my driveway. Adding the MX as well as a pool did me in.
I'll end up with two HPWCs in the garage at 100/80A amp, and a 14-50 for our volt. My TOU window is only 4 hours long. If I didn't already have to upgrade the service because of the pool I would have reduced the charge rate on the HPWCs to 50/40A and gone off TOU rather than incur the upgrade costs.
There is going to be a market for an intelligent EVSE that can communicate with multiple units that work in conjunction with the EVs. Between the two (or more) units, it would be great if I could say use a combined max of X amps, and allow them to figure out the optimal charge rates across them based on the SOCs of the batteries and the length of the TOU ultra-low window. I should go patent this.. But I suspect Tesla already has.
I'll end up with two HPWCs in the garage at 100/80A amp, and a 14-50 for our volt. My TOU window is only 4 hours long. If I didn't already have to upgrade the service because of the pool I would have reduced the charge rate on the HPWCs to 50/40A and gone off TOU rather than incur the upgrade costs.
There is going to be a market for an intelligent EVSE that can communicate with multiple units that work in conjunction with the EVs. Between the two (or more) units, it would be great if I could say use a combined max of X amps, and allow them to figure out the optimal charge rates across them based on the SOCs of the batteries and the length of the TOU ultra-low window. I should go patent this.. But I suspect Tesla already has.
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mknox
Well-Known Member
I have a similar sized house. Gas heat but very hot/humid summers so significant a/c load for July and August. I also have electric hot water which I wish I could convert to gas, but it would take major work due to where the tank is in the house. Only a 100 amp service, but I did convert both my electric clothes dryer and range to gas so I have enough capacity for my HPWC at 50 amps.
Patent??? This is several lines of code at most. Hell, given the parts of the tesla API that are known, this could be done in a third-party app this afternoon.
There is also prior art - Evercharge uses this model. There are a few other companies who have developed charging solutions for multi-family housing as well. I wouldn't be surprised if Tesla puts something like this out there in the next couple of years as more and more households become 2+ EV households.
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