TT-30 RV park "30 amp service" adaptor

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TonyWilliams

Well-known member
Joined
Nov 14, 2012
Messages
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Location
San Diego county, California USA
miimura said:
I don't see why you would fault this device for not supporting 120VAC. The car comes with one that supports the maximum power you can draw from a normal 15 amp outlet.

The Tesla charger onboard the Rav4 EV can pull 20 amps.

Almost every RV park in the USA has "30 amp service", which is nothing but a 30 amp circuit with 120 volts. With the correct "TT-30" plug, you could pull 20 amps all day.

That's getting close to double the speed of 12 amps / 120 volts. That's a lot of capability to leave on the table.
 
TonyWilliams said:
miimura said:
I don't see why you would fault this device for not supporting 120VAC. The car comes with one that supports the maximum power you can draw from a normal 15 amp outlet.
The Tesla charger onboard the Rav4 EV can pull 20 amps.

Almost every RV park in the USA has "30 amp service", which is nothing but a 30 amp circuit with 120 volts. With the correct "TT-30" plug, you could pull 20 amps all day.

That's getting close to double the speed of 12 amps / 120 volts. That's a lot of capability to leave on the table.
I have no experience with RV parks. Is it common to have only TT-30's and no NEMA 14-50's? Obviously if 240V is available, go for that. Most city folk will never encounter a TT-30.

If you buy the Clipper Creek portable unit with the L6-30 plug and then buy the NEMA 14 to L6-30 adapter from EVSEadapters.com you would be all set for NEMA 14-50 and NEMA 14-30. If you have a family member or another place to charge with an old dryer outlet, then go for the NEMA 10 adapter as well. This is totally turnkey. Personally, I would buy the "hardwire" version of the LCS-25 and make my own cables, but many people just want something that is known to be safe and ready to use.
 
miimura said:
I have no experience with RV parks. Is it common to have only TT-30's and no NEMA 14-50's? Obviously if 240V is available, go for that. Most city folk will never encounter a TT-30.

If the RV park has electricity, it will have at least a TT-30, "30 amp service". Most have NEMA 14-50, "50 amp service" also.

The two are usually side by side in the breaker panel.


"NEMA TT–30 (TT stands for Travel Trailer) is a 30 A, 125 V recreational vehicle standard (hot-neutral-ground), also known as RV 30. It is frequently (and sometimes disastrously) confused for a NEMA 10–30. The RV receptacle is common in nearly all RV parks in the United States and Canada, and all but the largest RVs manufactured since the 1970s use this plug. The hot and neutral blades are angled at 45° from vertical and 90 degrees to each other, similar to NEMA 10 devices."
 
TonyWilliams said:
miimura said:
I have no experience with RV parks. Is it common to have only TT-30's and no NEMA 14-50's? Obviously if 240V is available, go for that. Most city folk will never encounter a TT-30.
If the RV park has electricity, it will have at least a TT-30, "30 amp service". Most have NEMA 14-50, "50 amp service" also.
Speaking of which, does anybody know or has tried to use a 14-50 to TT-30 adapter like this one with the RAV4 and Tony's "Jesla" (modified Tesla UMC for J1772):
http://www.evseadapters.com/index.php?route=product/product&path=57&product_id=57

That product is designed to interface with the Tesla UMC and I have Tony's modified version, but the question is, what will the RAV4 EV do in this situation? Will I get 20 amps?

I ask because, for example, the RV park at Pinnacles National Park only has TT-30. UPDATE: A different source (a web site of reviews of RV parks) claims that this RV park has mixed service – some sites do actually have 240V 50 amp service. The recreation.gov site for reservations does not agree with this.
 
Incredulocious said:
TonyWilliams said:
miimura said:
I have no experience with RV parks. Is it common to have only TT-30's and no NEMA 14-50's? Obviously if 240V is available, go for that. Most city folk will never encounter a TT-30.
If the RV park has electricity, it will have at least a TT-30, "30 amp service". Most have NEMA 14-50, "50 amp service" also.
Speaking of which, does anybody know or has tried to use a 14-50 to TT-30 adapter like this one with the RAV4 and Tony's "Jesla" (modified Tesla UMC for J1772):
http://www.evseadapters.com/index.php?route=product/product&path=57&product_id=57

That product is designed to interface with the Tesla UMC and I have Tony's modified version, but the question is, what will the RAV4 EV do in this situation? Will I get 20 amps?

I ask because, for example, the RV park at Pinnacles National Park only has TT-30.

Just to be clear, the "30 amp" RV service is only 120 volts. But, with a 40 amp pilot signal from the 14-50 plug on the UMC / JESLA, it should do 20 amps at 120 volts.

I'm anxiously awaiting your results.
 
TonyWilliams said:
But, with a 40 amp pilot signal from the 14-50 plug on the UMC / JESLA, it should do 20 amps at 120 volts.

I'm anxiously awaiting your results.
Ah, that gets to the heart of my question... So it will see the 40 amp 240 adapter but because there's only the one side (120V), it'll end up pulling only 20 amps. Good, no specific smarts required in the RAV4 software.

I'll order the TT-30 adapter then. I don't know how long your wait will be for me to try it though! Was thinking about going to either Pinnacles or Big Sur on Thursday, which made me lookup what was available at that RV park. Won't get the part in time anyway.

Thanks though!
 
Incredulocious said:
Ah, that gets to the heart of my question... So it will see the 40 amp 240 adapter but because there's only the one side (120V), it'll end up pulling only 20 amps. Good, no specific smarts required in the RAV4 software.

Well, that's the theory. The Tesla charger has been demonstrated at 20 amps maximum at 120 volts, but that wasn't done with a UMC / JESLA. That means that ANY pilot signal over 20 amps will be truncated at 20 amps when only 120 volts is present.

So far, you're the guinea pig :)
 
TonyWilliams said:
So far, you're the guinea pig :)
Heh. ;-) So what is the risk? What *could* happen if it goes wrong?

[And is there someone around who can move postings? I should have started this discussion over on the Jesla thread.]
 
Incredulocious said:
Heh. ;-) So what is the risk? What *could* happen if it goes wrong?
The RAV could try to pull MORE than 20a @ 120v and blow the breaker. After all, the Jesla will still be advertising 40a. We're counting on the the RAV to limit itself to 20a. In that case, you'd have go ahead and purchase the 5-20 adapter to get this functionality...which you might just want to do anyway.
 
davewill said:
Incredulocious said:
Heh. ;-) So what is the risk? What *could* happen if it goes wrong?
The RAV could try to pull MORE than 20a @ 120v and blow the breaker. After all, the Jesla will still be advertising 40a. We're counting on the the RAV to limit itself to 20a. In that case, you'd have go ahead and purchase the 5-20 adapter to get this functionality...which you might just want to do anyway.
Oh... I was interpreting your previous comment that the absence of the full 240V would naturally leave the RAV4 pulling just 20A on the 120V without needing specific smarts in software to do so. But after having just now looked up how amperage on 240V circuits work, I see that the amperage on the two 120V legs is not additive. It really tries to pull 40A on each 120V leg. (Or, I guess I should more properly say, across both 120V legs.)

So what it comes down to is that the RAV4 should probably only ever try to pull 20A when it sees 120V, but that's not guaranteed. And if the breaker is faulty or has the wrong amperage on the TT-30 outlet, this could lead to trouble/fire. And unlike a Tesla Model S, we can't manually dial down the amperage that the car will pull. I'm not so keen on trying this now.

I really just wanted a TT-30 adapter for the Tesla UMC but of course it's not available. To use that 5-20 adapter, I would need an adapter to go from it to TT-30, rather than the one I just ordered that goes from 14-50 to TT-30. But then of course I wouldn't get 20A, just 16A. Erg.
 
Incredulocious said:
Oh... I was interpreting your previous comment that the absence of the full 240V would naturally leave the RAV4 pulling just 20A on the 120V without needing specific smarts in software to do so. But after having just now looked up how amperage on 240V circuits work, I see that the amperage on the two 120V legs is not additive. It really tries to pull 40A on each 120V leg.

So what it comes down to is that the RAV4 should probably only ever try to pull 20A when it sees 120V, but that's not guaranteed. And if the breaker is faulty or has the wrong amperage on the TT-30 outlet, this could lead to trouble/fire. And unlike a Tesla Model S, we can't manually dial down the amperage that the car will pull. I'm not so keen on trying this now.

I really just wanted a TT-30 adapter for the Tesla UMC but of course it's not available. To use that 5-20 adapter, I would need an adapter to go from it to TT-30, rather than the one I just ordered that goes from 14-50 to TT-30. But then of course I wouldn't get 20A, just 16A. Erg.
I'm going to pick a little nit here.... When you have a 240VAC or 208VAC circuit, an EVSE will put the load between the two hot wires, L1 & L2, with the neutral carrying no current at all. So, it is not "each 120V leg" because 120V is only present between each hot and the neutral. I realize that you may understand this, but you said it in a way that could be confusing to others.

In any case, it would be interesting to see what the RAV's on-board charger would do with a 40A pilot and 120VAC.
 
Incredulocious said:
Oh... I was interpreting your previous comment ... I really just wanted a TT-30 adapter for the Tesla UMC but of course it's not available. To use that 5-20 adapter, I would need an adapter to go from it to TT-30, rather than the one I just ordered that goes from 14-50 to TT-30. But then of course I wouldn't get 20A, just 16A. Erg.
I'm not Tony, but that's all right. Another possibility (I don't know why I didn't think of it first) would be to get the 14-30 adapter, which would advertise 24a, which should be safe for the TT-30. If you were to saw off the unused neutral pin, it would even plug into the adapter you already bought.

That said, I think the 14-50 solution is going to work. Just be observant the first time you try it.
 
davewill said:
Incredulocious said:
Oh... I was interpreting your previous comment ... I really just wanted a TT-30 adapter for the Tesla UMC but of course it's not available. To use that 5-20 adapter, I would need an adapter to go from it to TT-30, rather than the one I just ordered that goes from 14-50 to TT-30. But then of course I wouldn't get 20A, just 16A. Erg.
I'm not Tony, but that's all right. Another possibility (I don't know why I didn't think of it first) would be to get the 14-30 adapter, which would advertise 24a, which should be safe for the TT-30. If you were to saw off the unused neutral pin, it would even plug into the adapter you already bought.

That said, I think the 14-50 solution is going to work. Just be observant the first time you try it.
Oops, sorry not Tony! :)

Yeah, the 14-30 idea occurred to me too after I wrote that. I also wrote to Tesla and already received this response:

Thank you for contacting Tesla Motors. We appreciate your feedback and the request for the NEMA TT-30 adapter. We have had several requests for this adapter and the charging team has been informed. We are optimistic that the TT-30 will be considered for addition to our adapter lineup in the future.

Regards,
Hugh
 
It's interesting to consider how and why the Rav would limit itself to 20a on 120v if the EVSE shows a 40a pilot. The Rav's charger doesn't even know the voltage until it starts charging, so I wonder if it might start out trying to pull 40a but then dial it down after some period. Measuring that period would be a worthwhile exercise.

I'd also love to know precisely what the threshold is that the charger uses to determine L1 vs L2. Since L2 is nominally anywhere from 208-277v, I'd expect that it'd allow for voltages at least as low as ~190 and still call it L2. After all, the car's on board timer functions as if L2 is 140v. :roll:

I'll second the suggestion that the best way to charge from a TT-30 with a Jesla is to use Tesla's 14-30 adapter together with a 14-30r to TT-30p adapter, which you can easily make yourself.

The idea of sawing off the neutral on the Tesla adapter (or using the 14-50 Tesla adapter) and plugging it in to an off-the-shelf 14-50r to TT-30p for RVs might not work, however, as that adapter might map the TT-30's neutral to the 14-50's neutral and leave the 2nd hot unused, while you'd want to map the TT-30's neutral to the 14-30's 2nd hot, and leave the 14-30's neutral unused. I'm not sure if that's how RV adapters are wired but I'd think they'd need a neutral since everything on board the RV is 120v.

EDIT: Yup, as I suspected a standard RV 30 amp to 50 amp "dogbone" adapter won't work. Explanation here - skip to the bottom. Seems these connect the 1 hot in TT-30 to both hots in the 14-50, which means if you're trying to charge your EV from hot to hot you'll see 0v instead of 120v. Hopefully you didn't already buy a standard RV adapter and got one wired for EV charging instead. Since the site you linked to is EVSEadapters.com you're probably fine.
 
fooljoe said:
I'll second the suggestion that the best way to charge from a TT-30 with a Jesla is to use Tesla's 14-30 adapter together with a 14-30r to TT-30p adapter, which you can easily make yourself.

EDIT: Yup, as I suspected a standard RV 30 amp to 50 amp "dogbone" adapter won't work. Explanation here - skip to the bottom. Seems these connect the 1 hot in TT-30 to both hots in the 14-50, which means if you're trying to charge your EV from hot to hot you'll see 0v instead of 120v. Hopefully you didn't already buy a standard RV adapter and got one wired for EV charging instead. Since the site you linked to is EVSEadapters.com you're probably fine.

Interesting how they do that for the RV world. Certainly, we can build a proper adaptor until Tesla does.

NEMA 14-30R to TT-30

This will give the correct 24 amp continuous for the circuit, however, again, we already know that the Tesla charger won't pull more than 20 amps on 120 volts.
 
RV only uses 120v Hot to Neutral. (no 240v) The two Hots need to be connected to the 30-TT Hot in order for both sides of the RV panel to power everything.

You could easily build your own 30-TT to 14-50 with Hot/Neutral connected to the Hot connections in the 14-50.
 
TonyWilliams said:
smkettner said:
I assume Jesla used the two hot terminals and ground only. No neutral. :?
Yes, it's L1 and L2 on the UMC / JESLA connected to L1 and Neutral on the 120 volt circuit.

Neutral isn't used on a 240 volt circuit. On 120 volts, it MUST be used.
Tony, Reading through your last two posts, I think this one is correct and the one two posts above is wrong, which led to smkettner's confusion.

Adapter wiring for EV Charging:
TT-30___14-30
Gnd ----- Gnd
Neutral -- L1
Hot ------ L2
N/A ------ N (Open)
 
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