At 50A why would one chose an HPWC over an UMC? Especially if one intends to wire a plug?
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FAQ: Home Tesla charging infrastructure Q&A
- Thread starter FlasherZ
- Start date
At 50A why would one chose an HPWC over an UMC? Especially if one intends to wire a plug?
Heavier-duty and longer cable (25 ft vs 18 ft), price difference of only $100 ($650 vs. $750), potential to expand to higher currents if desired later or when moving, etc.
HankLloydRight
No Roads
mknox
Well-Known Member
Yeah. I've been toying with the idea of a second UMC so I can keep one in the car, but for $100 more, the HPWC makes sense. Since I already have the NEMA 14-50, wiring a plug to it would simplify things a bit.
snort
Member
Using different UMC adapters to control current
I've been reading the various articles on adapters for the UMC, from FlasherZ, CosmacElf and others and have been thinking about it a lot...my dad has a 100 amp Zinsco panel from 1962 and a NEMA 10-30 dryer plug, which he's never used (gas dryer). Inconveniently, it's 26 feet from where I'll need to put the left rear corner of my model S. Optimal, obviously, would be to replace the panel with one that doesn't weld itself open when it fails, and put a 14-50 near the door, but he's resisting. I've even offered to pay for it. (He's a retired rocket scientist and I can't snow him about this stuff...) So I've been thinking about extensions and adapters.
The common approach is to make a single 14-50 extension and dial the charge rate down at the car. But such an extension, even just the 8 foot one I need, is a gigantic, heavy thing. a 10-30 extension is much smaller. so I got the parts to make a 10 foot extension...and thought about it for a while.
tesla currently sells 4 adapters: 5-15 (12A), 5-20 (16A), 10-30 (24A) and 14-50 (40A). Cosmac points out that correctly polarized, the 120V 5-20 will do the right thing even if you connect it to a 240V NEMA 6-20. this suggests a good idea. So I have made myself a set of adapters: a 12/16A group, which use 12AWG and have a 5-15R or 5-20R on the end. A 24A group, which have a L6-30R on the end using 10AWG, and a 40A group, with a 14-50R and 6AWG. I used the L6-30 because there's no cord-mount 10-30R. I have a single 10-30R to L6-30P.
the point of this is that if I build these adapters correctly, I cannot do the wrong thing and ask the car to draw more that the wire is rated for. The adapter does the right thing. Moreover, most of the extension cords and adapter/pigtails are quite a bit smaller than the counterparts I'd need for standardizing on 14-50. I'll leave the big stuff at home unless I'm pretty sure I'm going to use it.
And in fact, in my experiments, I discovered that the 12AWG 6-20 is a bit of a sweet spot: I was charging at 12MPH over a 9 foot 12AWG wire + the 18 foot UMC. (the 6-20R, which I'd put in for a table saw, is about 20 feet of wire from my panel and was delivering 241V to the car...) This cord is small enough I'm comfortable carrying it in my UMC adapter bag all the time. by providing a 5-20P to 6-20R, I can use it as a 5-20 extension, too.
comments? I'd like to convince Tesla to make an L6-30P to UMC adapter, which would let me dispose of the kludgey wall mount 10-30R I've put on a piece of 10/3 SOOW. I'll have to be careful with this thing. cord mount receptacles are designed to be stepped on and such, which this is not. (I've even thought about building one of ABS pipe and RTV....UL would probably freak out...)
I've been reading the various articles on adapters for the UMC, from FlasherZ, CosmacElf and others and have been thinking about it a lot...my dad has a 100 amp Zinsco panel from 1962 and a NEMA 10-30 dryer plug, which he's never used (gas dryer). Inconveniently, it's 26 feet from where I'll need to put the left rear corner of my model S. Optimal, obviously, would be to replace the panel with one that doesn't weld itself open when it fails, and put a 14-50 near the door, but he's resisting. I've even offered to pay for it. (He's a retired rocket scientist and I can't snow him about this stuff...) So I've been thinking about extensions and adapters.
The common approach is to make a single 14-50 extension and dial the charge rate down at the car. But such an extension, even just the 8 foot one I need, is a gigantic, heavy thing. a 10-30 extension is much smaller. so I got the parts to make a 10 foot extension...and thought about it for a while.
tesla currently sells 4 adapters: 5-15 (12A), 5-20 (16A), 10-30 (24A) and 14-50 (40A). Cosmac points out that correctly polarized, the 120V 5-20 will do the right thing even if you connect it to a 240V NEMA 6-20. this suggests a good idea. So I have made myself a set of adapters: a 12/16A group, which use 12AWG and have a 5-15R or 5-20R on the end. A 24A group, which have a L6-30R on the end using 10AWG, and a 40A group, with a 14-50R and 6AWG. I used the L6-30 because there's no cord-mount 10-30R. I have a single 10-30R to L6-30P.
the point of this is that if I build these adapters correctly, I cannot do the wrong thing and ask the car to draw more that the wire is rated for. The adapter does the right thing. Moreover, most of the extension cords and adapter/pigtails are quite a bit smaller than the counterparts I'd need for standardizing on 14-50. I'll leave the big stuff at home unless I'm pretty sure I'm going to use it.
And in fact, in my experiments, I discovered that the 12AWG 6-20 is a bit of a sweet spot: I was charging at 12MPH over a 9 foot 12AWG wire + the 18 foot UMC. (the 6-20R, which I'd put in for a table saw, is about 20 feet of wire from my panel and was delivering 241V to the car...) This cord is small enough I'm comfortable carrying it in my UMC adapter bag all the time. by providing a 5-20P to 6-20R, I can use it as a 5-20 extension, too.
comments? I'd like to convince Tesla to make an L6-30P to UMC adapter, which would let me dispose of the kludgey wall mount 10-30R I've put on a piece of 10/3 SOOW. I'll have to be careful with this thing. cord mount receptacles are designed to be stepped on and such, which this is not. (I've even thought about building one of ABS pipe and RTV....UL would probably freak out...)
Sounds like a good setup. I wouldn't bother wasting my time trying to convince Tesla of anything. I mean, they aren't even selling a 14-30 adapter anymore for Pete's sake.
I have a 14-50 at home with a UMC for daily charging, but I am seriously thinking of swapping that out for an HPWC.
I've been taking some longer commutes lately and I've noticed that the car isn't done charging sometimes at 7am (starts at midnight for cheaper rates) - well that's because the car will randomly back off to 30A charging from the 40A setting. Bottom line is that the UMC just isn't very robust at 40A charge rates.
I'm just holding off until the Model X announcement - I'm hoping they'll also announce a new UMC or new lower power wall unit (since they do ship those in other countries right now).
I have a 14-50 at home with a UMC for daily charging, but I am seriously thinking of swapping that out for an HPWC.
I've been taking some longer commutes lately and I've noticed that the car isn't done charging sometimes at 7am (starts at midnight for cheaper rates) - well that's because the car will randomly back off to 30A charging from the 40A setting. Bottom line is that the UMC just isn't very robust at 40A charge rates.
I'm just holding off until the Model X announcement - I'm hoping they'll also announce a new UMC or new lower power wall unit (since they do ship those in other countries right now).
In fact there is! I have one that I've used to make a similar extension to yours. But it wasn't cheap. http://www.mcmaster.com/#7120k65/=xthgou
Seems pretty reasonable as long as you're considering all the factors and labeling them six ways to Sunday. In my opinion, the most important factor is ensuring that you ensure you can't draw too much from a receptacle, even inadvertently.
There is an interesting element inside the NEC that I haven't chased down quite yet... NEC 2014, 625.44(B)(1) specifically states that plug-and-cord connected EVSE must be intended for connection to "nonlocking, 2-pole, 3-wire and 3-pole, 4-wire, grounding-type receptacle outlets rated not more than 50 amperes".
I haven't looked through minutes or comments to figure out why they specifically called out non-locking, which seems to rule out "L" series receptacles. In addition, depending upon how it's read, it could rule out 10-series receptacles as well (as they're non-grounding). The style guide certainly wasn't followed here, because you could choose to read "nonlocking" to go with 2-pole, 3-wire and "grounding-type" to go with 3-pole, 4-wire, and it changes what's legal - L14's would be legal but L6's would not.
Regardless, it seems silly to parse the details in this way, but it's what the Code says. I doubt an inspector would have an issue with properly addressing it the way you did.
As for the Zinsco panel, you can only try to inform him of the issues... I tend to point people at the inspect-a-pedia site, which collects reports of failures and photographs of them:
http://inspectapedia.com/electric/GTE_Sylvania_Kearney_Zinsco_Failure.php
bsd
Member
I have been charging using a UMC for 1.5 years now and it is pretty solid at 40A. Your UMC may be faulty but I wouldn't write them all off.
snort
Member
Of course! I should have thought of McMaster-Carr. I tried basically everywhere else. the order is placed... thanks.
snort
Member
since other places say that you're not supposed to put EVSEs on an extension, perhaps this simply means they don't want //wall mount// locking receptacles. I bet somebody is thinking that there might be a fire or shock nearer the car, and they want to be able to whack the plug out of the receptacle with a 2x4. since most of my primary connections are things like TT-30s and 10-30s, which are non-locking, should that issue arise, the 2x4 will work. obviously I'm trying really hard to make that not come up...
I may wind up switching to the cord mount 10-30Rs from mcmaster carr anyway. they're 8 times the cost of the L6-30Rs I've been using though.
snort
Member
I've been using HPWC with dual chargers. It's on #2AWG in a conduit, about 20 feet from my (non zinsco) breaker box. 59-60 Rated MPH @ 80A, 239-241V. the cord never gets much warmer than my arm. the conduit stays room temperature. the longest it's needed to run so far in the 3 months I've been using it is < 3 hours.
a Medium Power Wall Connector isn't going to save much money, so it's unlikely they'll bother to make one. by going to smaller wires and relays, they'll save maybe $25. the electronics and case and such is the same price, and the really expensive stuff, the labor, is the same. this includes assembly, of course, but also stuff like inventory and shipping.
what I do hope they do is make a tesla car connector available for the OpenEVSE crowd. that way, we can make exactly the cord we need. what about a 200 foot, 12Amp only trickle charger for when you've left the car in the airport?
Debating about calling an electrician or doing a DIY NEMA 14-50 outlet installation (I don't want an electricain to pull one over me, so I want to make sure I have my bases covered).
The distance from the breaker box in the basement to the carport outside is about 50' feet. I'll be remodeling the basement soonish, so I'm not worried about ripping up some drywall, most of the cable run should be going through an exposed/unfinished part of the basement anyways.
99.9% of the wiring/etc. is indoors, I just need to drill a hole in the drywall and bricks to get the cable outdoors and install the outlet at exactly the location of the hole that I'm going to make (I'm not planning to use any conduit to run the outlet/enclosure to a separate location)
Now my questions:
1. I'm assuming that I'll need to use outdoor cable, even if everything is indoors and the only cable outdoors will be going straight into a waterproof enclosure (i.e. drill a hole in the brick, put enclosure over the hole, stick wire through and connect everything)?
If so, what kind of wire am I supposed to use (I believe it's 6/3 for the NEMA 14-50), can I use UF-B or do I need THWN for outdoors?
2. Can I use this as my enclosure/outlet: http://www.homedepot.com/p/GE-50-Am...gclid=CI-m2uaP6sYCFcESHwodwqAMjQ&gclsrc=aw.ds
3. I have a 200A service panel, and plenty of room for an added 50A circuit. Is there anything I need to be concerned about here? (I can do a load calculation if it's required to get the permits, but I'm positive that I have enough load capacity to add a 50A circuit)
Am I missing anything?
Looking at costs
-Permits ($108)
-Wire $200 ($4/ft UF-B)
-Enclosure ($30)
-Circuit breaker ($25)
If I can get an electrician to come in under $600 - perfect, otherwise I think I'll do it myself (should be a 2-3 hour job).
The distance from the breaker box in the basement to the carport outside is about 50' feet. I'll be remodeling the basement soonish, so I'm not worried about ripping up some drywall, most of the cable run should be going through an exposed/unfinished part of the basement anyways.
99.9% of the wiring/etc. is indoors, I just need to drill a hole in the drywall and bricks to get the cable outdoors and install the outlet at exactly the location of the hole that I'm going to make (I'm not planning to use any conduit to run the outlet/enclosure to a separate location)
Now my questions:
1. I'm assuming that I'll need to use outdoor cable, even if everything is indoors and the only cable outdoors will be going straight into a waterproof enclosure (i.e. drill a hole in the brick, put enclosure over the hole, stick wire through and connect everything)?
If so, what kind of wire am I supposed to use (I believe it's 6/3 for the NEMA 14-50), can I use UF-B or do I need THWN for outdoors?
2. Can I use this as my enclosure/outlet: http://www.homedepot.com/p/GE-50-Am...gclid=CI-m2uaP6sYCFcESHwodwqAMjQ&gclsrc=aw.ds
3. I have a 200A service panel, and plenty of room for an added 50A circuit. Is there anything I need to be concerned about here? (I can do a load calculation if it's required to get the permits, but I'm positive that I have enough load capacity to add a 50A circuit)
Am I missing anything?
Looking at costs
-Permits ($108)
-Wire $200 ($4/ft UF-B)
-Enclosure ($30)
-Circuit breaker ($25)
If I can get an electrician to come in under $600 - perfect, otherwise I think I'll do it myself (should be a 2-3 hour job).
If you are going through an indoor space directly into the back of a NEMA 3R-rated enclosure, it is generally accepted that you can use NM cable for this. This is done for A/C disconnects all the time. You will need an appropriate clamp to hold the NM cable in place. The only time when you are required to use outdoor-rated cable (THWN in conduit, UF, etc.) is when you need to run it outside of a single enclosure outside, or when it does not enter an enclosure directly (requiring conduit). It isn't explicitly stated in the Code book how to approach this and I haven't seen an inspector fail an A/C disconnect yet. Be sure you seal the box well - top and two sides as well as the hole through the structure.
Yes.
Some inspectors will want to see your calculations per the NEC, so it may be good to work up a quick spreadsheet just in case, if inspections are required.
As noted, you won't have to use UF cable - 6/3 NM cable will work sufficiently as long as you enter from the back. You will want to use an NM cable clamp in the box to hold the NM cable in place. Don't forget the caulk and fasteners to mount the box properly to the wall.
FlatSix911
Porsche 918 Hybrid
Flasher, thank you for providing this great FAQ resource to the TMC members!
After reading the thread, I am ready to install a HPWC in my garage and have a few questions:
1. I only have a 240V/30 Amp circuit available, so the electrician has recommended 24 Amp charging?
2. He recommended running 10 Awg wire to the new HPWC which is a 50 foot run in the garage?
3. Would you recommend running the new wires in a conduit or go with cheaper NM cable?
4. Any other suggestions? I want to minimize the cost and can live with 17Mph charging.
Thanks
FlatSix911
Porsche 918 Hybrid
I should have mentioned that the existing 30A circuit to the Dryer uses 10 Awg wire.
I am planning to extend the unused Dryer circuit to the garage to service the HPWC.
My answers are based upon what you have written here, plus - based on your clarification - that you're going to extend the dryer circuit from your laundry room to the garage, instead of running new wire all the way from the panel. Based on that assumption:
1) yes, on a Wall Connector configured for 30A, the charge current will be 24A; this is because a circuit must be sized at 125% of the offered load. 24 * 125% = 30A.
2) yes, a 30A circuit requires a #10 copper conductor
3) this can vary by code... if running inside the walls, NM cable is just fine unless code prohibits it (Chicagoland and some NY localities). If running on the surface of walls, NM cable must be protected from "physical damage", a term interpreted by AHJ's. The most common interpretation requires the NM cable be encased in an EMT sleeve and fittings anywhere below a line drawn 7' above the floor surface. So if your plan is to have the cable run on the surface of walls, you'll likely use some form of conduit anyway to protect it from damage.
The plan you are envisioning is likely the lowest-cost approach. Your connection to the existing 30A circuit must be made inside a junction box or wall box with an appropriate cover -- will you be making it inside a receptacle box behind the dryer?
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