I did a brief search and did not find updated info in the FAQ about the Model X and the 48 amp charger. What CB size, proper wire size, and receptacle should be used to get full power to the on board charger in this case? Will the Tesla UPC draw 48 amps or just 40? Thanks to anyone who can give any facts on this situation.
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FAQ: Home Tesla charging infrastructure Q&A
- Thread starter FlasherZ
- Start date
Cottonwood
Roadster#433, Model S#S37
You will need an HPWC to get the full 48 Amps of charging. To meet code and avoid tripping the breaker, the breaker has to be 125% or more of the continuous load, or the load has to be no more than 80% of the breaker rating (same numbers, different view). That means that you need a 60 Amp circuit for 48 Amp charging.
The problem is that the currently offered version of the HPWC does not have a DIP switch setting for a 60 Amp Breaker, 48 Amp Charging. Until Tesla offers a 60/48 option, you will have to put in an 80 Amp circuit that can support up to 64 Amp charging (80/64) with appropriately sized wire. The HPWC will then offer 64 Amps of charging to the Tesla and your Model X will use all it can, or 48 Amps.
See page 16 of https://www.teslamotors.com/sites/default/files/pdfs/tesla-wall-connector-installation-80A-12A.pdf for reference.
Hopefully, with the 48 and 72 Amp charging choices offered for the Model X, Tesla will soon offer HPWC's with 90/72 and 60/48 Amp choices. If you can find an old HPWC, those units had 60/48 Amp choices.
fwgmills
Member
Ok, what I heard you just say was, "On come on, how hard is the derpy derp blargelldy gibbit phurdun blah blah zerby derp something" :wink:
If you really need 60/48 Amp charging due to panel limitations or something, a Clipper Creek HCS-60 would be a good choice. However, at $899 it's more expensive than a HPWC and you would have to use the J-plug adapter all the time.
dgpcolorado
high altitude member
Had my 14-50 outlet installed today — by swapping out the previous L6-20 outlet — for a reasonable $125. My question: I've seen some discussion that the UMC units can have some problems and some need replacing. Should I limit charging to 32 amps? Run 40 amps for the first year, in case the UMC breaks, then dial it back to 32 amps? Or just ignore it as nothing to worry about?
Actual speed of home charging is of little consequence; I plan to just charge to 50% for local driving and only up that when about a make a long trip. Also, both of my more distant local destinations have public charge stations that I use so that people in this remote area can see them getting used.
Actual speed of home charging is of little consequence; I plan to just charge to 50% for local driving and only up that when about a make a long trip. Also, both of my more distant local destinations have public charge stations that I use so that people in this remote area can see them getting used.
I don't believe you should worry about it. My UMC was replaced due to the melting plug problem in the early days, but since then has been rock solid.
Presumably you had a wire swap too along with moving from a 20-amp receptacle to a 50-amp one.
Most people haven't had any problems with the UMC at 40A since the adapter was changed. I've charged every night for almost 3 years at 40A without any problems.
dgpcolorado
high altitude member
Yes, I had him upgrade the wire to 6 AWG, which also required a conduit change from 1/2 inch to 3/4 inch. That 6 gauge wire is thick stuff! (Over the last four years I put 6901 kWh in my LEAF, all of it from sunpower.)...Presumably you had a wire swap too along with moving from a 20-amp receptacle to a 50-amp one.
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diamond.g
Active Member
I have a question about charging in a house 'protected' by a whole home generator. Is it okay to have a WC sitting behind the generator? It is a 20kW unit, if that matters.
I think it depends upon what current setting your WC is configured at.
You can have the wall connector behind the generator, provided the whole-home generator is installed properly with relation to grounding/bonding. If your WC configuration is set at 100A and the car begins to charge while the generator is running, though, you're going to use the entire rated capacity of the generator just trying to serve the car's load. If the A/C units and/or refrigerator/freezer kick on while this is happening, it could trip the circuit breaker on the generator and leave you completely dark at some random time (defeating the generator's purpose).
I have a 25 kW genset protecting my home. In my case, both wall connectors are on the grid-only panel and are not behind the generator. Should we have a longer-term outage, my plan is to use 120V charging on the UMC (since it's likely that many other businesses will be out of power) -or- in case of emergency, I will rewire the circuit. The probability I will need to do that last step, though, is probably close to 0.01%.
diamond.g
Active Member
Thanks! I'll keep that in mind. My plan was to go with a 60A fuse for 48A charging, but this is assuming the 3 will come with a 48A charger like the S & X.
You'll have to figure the highest realistic coincidental load you might see in case of power failure. When asked to look at it, I generally start with anything that may automatically run (especially if no one's home): A/C units, heat pumps, & blowers; refrigerators and freezers; car charging; automatic coffee makers (if you like your Keurig to stay hot), etc. Then add a factor on top of it for other smaller loads like computers and other phantom/vampire draw - I usually start with 10A (2400W). If you know the generator's running you can take steps on discretionary loads (like cooking appliances), so I don't really count those in the absolute minimum.
So 48A (car charging) + 28A (A/C compressor) + 5A (blower) + 5A (fridge 10A @ 120V) + 10A overhead = 96A. That's already 23 kW, and doesn't even include the continuous load headroom that you need to have, so it will exceed your generator's capacity. I've run mine at more than 100% for a short period of time, but I don't recommend that as it can burn out your windings and shorten the life of your generator. That's why I made the decision not to put a wall connector behind the generator and instead leave an option to plug in a UMC via 120V (or even just install a NEMA 5-20 or 6-15 or something on the generator panel to give you slightly faster charging if required).
In addition, as you run closer to 100% load it's more likely that your generator will deliver dirtier power for electronics. At a certain threshold, the Tesla chargers will pause charging or even give up.
diamond.g
Active Member
So would the electrician need to install an additional panel off the mains but before the transfer panel in order to remove the car load from the generator?
diamond.g
Active Member
Your generator's transfer switch might have load shedding capability. Lots of the bigger ones do. When the load on the generator gets too big it drops a selected load, like water heater or AC or maybe even EVSE. Your electrician should be able to help you.
diamond.g
Active Member
Yeah the biggest module seemed to be 50A though. Great for a 14-50, not so much for a 60A load.
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