Question about UMC

Racerx22b · Dec 4, 2014

I am scheduled to have my 14/50 outlet installed next week and was thinking of having it setup with a disconnect switch. I plan to purchase a 2nd UMC to leave in the car and keep one always connected in the garage. Overkill, I know.

My question is.... Is a disconnect switch needed or can you just leave the UMC plugged in with current running through it all the time? I have read that these outlets aren't really designed for continuous plugging/unplugging and I don't think my wife could actually unplug the cord anyway. She has real small hands.

I don't have dual chargers so I am not interested in the HPWC. Plus the install is twice as much and the charger is $100 more expensive. Finally, I like the idea of having a backup UMC just in case something malfunctions.

Jason

FireLT · Dec 4, 2014

A disconnect switch is not required and as far as I know, you can leave the UMC plugged in 24/7.
I would recommend having a back up outlet installed as well, in case your outlet fails. I have had to replace two HPWC and with no back up outlet, I was not a happy camper. Just a thought.

glhs272 · Dec 4, 2014

Racerx22b said:
I am scheduled to have my 14/50 outlet installed next week and was thinking of having it setup with a disconnect switch. I plan to purchase a 2nd UMC to leave in the car and keep one always connected in the garage. Overkill, I know.

My question is.... Is a disconnect switch needed or can you just leave the UMC plugged in with current running through it all the time? I have read that these outlets aren't really designed for continuous plugging/unplugging and I don't think my wife could actually unplug the cord anyway. She has real small hands.

I don't have dual chargers so I am not interested in the HPWC. Plus the install is twice as much and the charger is $100 more expensive. Finally, I like the idea of having a backup UMC just in case something malfunctions.

Jason

Some local jurisdictions may require a disconnect switch to be to code. Not a requirement for the Tesla though. You are correct that plugging/unplugging cycles will wear out the outlet quickly. So if you must do this, plan on replacing the outlet regularly before it gets weak and starts getting hot. As some have found, running the UMC at 40 amps everyday tends to wear them out much quicker than running them at 30 amps. The HPWC being designed for 80 amp means it is more robust than the UMC and will likely last longer than the UMC. But certainly not necessary (I don't have one yet).

Racerx22b · Dec 4, 2014

Let's say I get a HPWC. Does it have to be wired up to provide 80amps or could I just wire it up with a 50amp breaker (and corresponding wire) and use it to charge at 40amps. Then have electrician place a 14/50 outlet adjacent to it as a backup in case the HPWC takes an unexpected crap.

This way I would save on the install.

Lloyd · Dec 4, 2014

Get the 14-50 plug made by Hubbell. It is more robust (Heavy Duty Spec Grade) than some of the others and IMO will withstand better the plugging and unplugging of the HPC when needed.

glhs272 · Dec 4, 2014

Yes you can set the HPWC to run at only 40 amps (50 amp breaker). But I don't think you can have more than one outlet/device connected to a 240 volt breaker to be to code. So you would have to have separate breakers and cable runs between your breaker box and your HPWC and 14-50 location.

Edit: another option might be to just run the 14-50 only as you had originally planned. But buy the HPWC instead of the UMC and get a 14-50 cord to plug the HPWC into the 14-50 socket. That way if the HPWC craps out, just unplug and use your UMC. I am not sure how kosher this idea is, but I don't know why it wouldn't work if the cord was installed properly.

Racerx22b · Dec 4, 2014

glhs272 said:
Yes you can set the HPWC to run at only 40 amps (50 amp breaker). But I don't think you can have more than one outlet/device connected to a 240 volt breaker to be to code. So you would have to have separate breakers and cable runs between your breaker box and your HPWC and 14-50 location.

Yeah, that makes sense. Fingers were working faster than my brain.

FireLT · Dec 4, 2014

Racerx22b said:
Let's say I get a HPWC. Does it have to be wired up to provide 80amps or could I just wire it up with a 50amp breaker (and corresponding wire) and use it to charge at 40amps. Then have electrician place a 14/50 outlet adjacent to it as a backup in case the HPWC takes an unexpected crap.

This way I would save on the install.

If you have space in breaker for 100 amp breaker, I would strongly suggest you get a 100 amp breaker for HPWC and appropriate wiring done. Then in HPWC, there are pins, that you can set to for charging at 40 amps. You can also get a 14-50 outlet installed next to it, to use as a back up (on the same circuit). Just make sure you don't use full 80 amps of HPWC and connect something in 14-50 at the same time. And in future, when you get your second MS or MX :biggrin:, you won't have to do anything.

glhs272 · Dec 4, 2014

FireLT said:
If you have space in breaker for 100 amp breaker, I would strongly suggest you get a 100 amp breaker for HPWC and appropriate wiring done. Then in HPWC, there are pins, that you can set to for charging at 40 amps. You can also get a 14-50 outlet installed next to it, to use as a back up (on the same circuit). Just make sure you don't use full 80 amps of HPWC and connect something in 14-50 at the same time. And in future, when you get your second MS or MX :biggrin:, you won't have to do anything.

If it were me, I too would go with the 100amp even though I don't have the dual chargers (assuming my breaker box has the capacity, which it doesn't). That way it's future proof. Just the cost of copper being the only difference.

As far as having both the HPWC and 14-50 connected to the same circuit/breaker, that would be a poor choice. The 14-50 would therefore have no circuit protection being connected to the 100 amp breaker. You could do something like that if you had a small subpanel to break out a separate breaker for the HPWC and 14-50, all running from the original 100amp circuit. But that would be adding cost.

FireLT · Dec 4, 2014

you are correct, you will need a small sub panel. But it will also give a back up in case HPWC or 14-50 goes down.

glhs272 · Dec 4, 2014

FireLT said:
you are correct, you will need a small sub panel. But it will also give a back up in case HPWC or 14-50 goes down.

Yep. It's a belt and suspenders approach. But will be what I do when I get my main panel upgraded beyond the current 100amp limitation. It's going to cost a bit more now, but completely future proofs and adds the redundancy. It will cost more if you have to go through this all again when you get your second tesla..

Racerx22b · Dec 4, 2014

glhs272 said:
Yep. It's a belt and suspenders approach. But will be what I do when I get my main panel upgraded beyond the current 100amp limitation. It's going to cost a bit more now, but completely future proofs and adds the redundancy. It will cost more if you have to go through this all again when you get your second tesla..

Maybe I'll look into a HPWC.

Cottonwood · Dec 4, 2014

Racerx22b said:
Maybe I'll look into a HPWC.

+1 on the HPWC, even if you only run it at 40 Amps. For $100 more in parts cost over a UMC, you get a much heavier-duty, robust device.

smsprague · Dec 4, 2014

glhs272 said:
Yes you can set the HPWC to run at only 40 amps (50 amp breaker). But I don't think you can have more than one outlet/device connected to a 240 volt breaker to be to code. So you would have to have separate breakers and cable runs between your breaker box and your HPWC and 14-50 location.

Edit: another option might be to just run the 14-50 only as you had originally planned. But buy the HPWC instead of the UMC and get a 14-50 cord to plug the HPWC into the 14-50 socket. That way if the HPWC craps out, just unplug and use your UMC. I am not sure how kosher this idea is, but I don't know why it wouldn't work if the cord was installed properly.

This is my setup and it works perfectly (6 Gauge Cord). I already had a 50 amp plug in my garage for other uses.

shady · Dec 4, 2014

May I ask what your reasoning is for having 2 UMCs?
Before I bought my car I was considering the same (not wanting to be left stranded anywhere), but after 21 months and 50k miles and a few road trips, I've never found a need to use the UMC outside of my garage.

smsprague · Dec 4, 2014

I visit my Daughter who lives about 150 miles away quite often. I had a 14-50 plug installed at her house for charging. So I just leave my UMC in my car to use at her house. I have also used my UMC at a vacation home.

Racerx22b · Dec 4, 2014

smsprague said:
This is my setup and it works perfectly (6 Gauge Cord). I already had a 50 amp plug in my garage for other uses.

Would you be kind enough to post pictures of this setup? Or email/text them to me?

I would like 2 UMCs (assuming I don't get a HPWC) just for piece of mind for my wife. It'll make her feel more comfortable and $650 is a small price to pay for that. One stays at house and the other in the car.

I've sent you a PM with my email and phone #.

Jason

smsprague · Dec 4, 2014

Here is a picture - I figured for only $100 go with the HPWC - used SOOW 6/3 wire - the neutral is not used so you don't need it

Racerx22b · Dec 4, 2014

Thanks!

I wanted to see the plug end but I'm guessing you just wired in a male 14/50 plug on it. Correct?

smsprague · Dec 4, 2014

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