Temperature UMC vs Wall Connector

[GJ79]

My UMC gets incredibly hot when charging at 30-40 amps. Mainly the cable between the wall Plug and the UMC. It gets piping hot and from what I am hearing that is considered normal. Service center checked it and says that is normal. The Wiring Cable going to the 14/50 outlet only warms up very little and is AWG 6. Being an Electrical Engineer by trade I can't belive they get away with this and allow them to become so hot. In my days we would not have designed anything like this and would use a heavier gauge that dissipates the heat bettter. In any case, I had a house fire before which (what a coincidence) was caused by a Battery Charger (Dewalt Power Drill), I don't feel very good at going to bed and leave the car charging knowing the Temperatures in the equipment raise like this. Being a fire victim once which happened during lunchtime I certainly don't want that to happen at night while I am sleeping. If I charge overnight I usually dial down to 15 amps.

Does the Hardwired Wall connector become this hot as well or is this just a UMC issue ?

 

[thecloud]

Is it actually hot at 30A, or did you set the amperage to something higher? I've definitely noticed the MC becomes hot when pulling 40A continuously, so I set it to 32A in the car and now it's barely even warm to the touch.

If the MC is "piping hot" at only 30A, then something is either wrong with it, or with your receptacle. I'm betting you could have some corrosion on the contacts in the receptacle which is causing high resistance and heating up that segment next to the wall plug.

You've already had one electrical-system house fire. Did they determine the fire started in the outlet, or in the drill charger? And just how old is this outlet where your MC is plugged in?

 

[GJ79]

Is it actually hot at 30A, or did you set the amperage to something higher? I've definitely noticed the MC becomes hot when pulling 40A continuously, so I set it to 32A in the car and now it's barely even warm to the touch.

If the MC is "piping hot" at only 30A, then something is either wrong with it, or with your receptacle. I'm betting you could have some corrosion on the contacts in the receptacle which is causing high resistance and heating up that segment next to the wall plug.

You've already had one electrical-system house fire. Did they determine the fire started in the outlet, or in the drill charger? And just how old is this outlet where your MC is plugged in?

Mine gets hot at 30amps too. There is absolutely nothing wrong with the receptacle, It is not even 6 months old. The Plug itself is not getting that hot, just the short piece of cable between the plug and the UMC.

The House Fire was in a different house and yes it was determined that the Dewalt Charger itself.

 

[GJ79]

I have to dial down to below 25 amps for it to be just warm.

 

[thecloud]

Well, what I do know is that my MC cable barely gets warm when pulling 32 amps continuously. It has to be pulling 40A for the cable to get physically hot to the touch. So, what you're describing does not sound right.

You might want to see if you can replicate this issue using the same MC at a different 14-50 outlet, to make sure it isn't the outlet. Or just take it in to the service center in Tampa and explain the problem, then see if they are able to replicate it.

From what I've read, the HPWC can run hotter than the MC because it's usually configured to deliver >40 amps.

Edit: I missed the part in your original post where you said the service center already checked it and said it was normal. So I would definitely try to find other 14-50 outlets for comparison purposes.

 

[Rocky_H]

Oy. I agree with @thecloud that it doesn't sound right. Both the UMC at 40A and the HPWC at 80A get noticeably hot at their maximum current. But turning them down a little bit usually cools them off considerably. I can run low to mid 30's on my UMC, and it doesn't feel very warm. If yours still feels too hot around 30, I am surprised the service center would think that is OK.

 

[BrokerDon]

I routinely charge overnight at 50A on my Gen 1 HPWC and it just gets warm. Charging at 80A and it gets HOT which I believe isn't good for our 2015 Model S P85D's receptacle... nor the HPWC plug... since in my experience HOT electronics die quicker than those kept cooler.

YMMV

 

[mspohr]

The HPWC has larger gauge wire since it is designed to deliver up to 80 amps vs. 40 for the mobile charger.
I run my HPWC at 40 amps and it barely gets warm.
If your mobile charger cable is getting too hot for your comfort, dial the amps down.

 

[Fiddler]

... I had a house fire before which (what a coincidence) was caused by a Battery Charger (Dewalt Power Drill) ...
Does the Hardwired Wall connector become this hot as well or is this just a UMC issue ?

Thanks for sharing. My Dewalt Power Drill Charger is mount on a solid wood wall. I will remount that charger before I use it again.
Since the Wall Connector is made for much higher current it should not get hot at 40A.

 

[GJ79]

I just ordered a infrared temperature gauge and will measure actual temperatures over the weekend to share. Maybe we can compare ?!

 

[GJ79]

Thanks for sharing. My Dewalt Power Drill Charger is mount on a solid wood wall. I will remount that charger before I use it again.
Since the Wall Connector is made for much higher current it should not get hot at 40A.

Yeah since that incident I never keep unused chargers plugged in. It could have killed us all if it happened while everyone was asleep. On a side note, the fire inspector said that many fires in the US are started by those cheep plug in fragrance diffusers (glade / wall flower) and such as well....

 

[u00mem9]

I have the HPWC at home, but had to charge with the UMC at work the other day. Parked in the direct sun on a 90 degree day, the UMC cable to the car became hot enough to surprise me and current flow eventually restricted down to 36A (from 40A originally). Someone said the wire inside is 14ga x2 for each conductor, or something like that. I'm ready to buy the Heavy Duty UMC because this is madness.

 

[GJ79]

I have the HPWC at home, but had to charge with the UMC at work the other day. Parked in the direct sun on a 90 degree day, the UMC cable to the car became hot enough to surprise me and current flow eventually restricted down to 36A (from 40A originally). Someone said the wire inside is 14ga x2 for each conductor, or something like that. I'm ready to buy the Heavy Duty UMC because this is madness.

Which heavy Duty UMC ???

 

[GJ79]

I have the HPWC at home, but had to charge with the UMC at work the other day. Parked in the direct sun on a 90 degree day, the UMC cable to the car became hot enough to surprise me and current flow eventually restricted down to 36A (from 40A originally). Someone said the wire inside is 14ga x2 for each conductor, or something like that. I'm ready to buy the Heavy Duty UMC because this is madness.

My UMC always restricts over time down to 32 Amps. Some say it's the service and the transformer is giving in but given my 400amp service panels I highly doubt that.

 

[u00mem9]

Which heavy Duty UMC ???

Yeah, it was kind of a joke / wishlist item for future Tesla development!

 

[GJ79]

Yeah, it was kind of a joke / wishlist item for future Tesla development!

Well that's kind of my whole point here. Being an electrical Engineer I don't know how they get away with UL and TUV certifications for this connector when using these small wire gauges. It's a joke and it's asking for more home fires.

 

[GSP]

I just ordered a infrared temperature gauge and will measure actual temperatures over the weekend to share. Maybe we can compare ?!

GJ79,

Good idea. I remember other owners doing that and posting the results here at TMC years ago, so data for normal UMCs should already be available. As others have said, yours doesn't sound normal.

If the Tesla service folk are saying the problem is your wiring, try measuring the voltage at your 14-50 outlet while charging. That should show where the Voltage drop is: in your UMC cabling, or the house wiring.

Even if you get your UMC replaced and everything works to spec, you still may want to buy the HPWC for peace of mind. Tesla designs to the edge of what is possible. For example, I believe the relays in the UMC are rated at 30 A by their supplier, and Tesla runs them at 40 A continuous. Running the 80 A HPWC at 40 A provides a nice fat design margin for long life and peace of mind (and you can just keep the UMC in the trunk).

Good Luck

GSP

 

[ecarfan]

Does the Hardwired Wall connector become this hot as well or is this just a UMC issue ?

My "classic" S has Dual Chargers (no longer available) and my HPWC is set to 80A on a 100A circuit. The cable can get warm when charging but I would not describe it as "hot". I use my UMC occasionally on trips and it can get quite warm at 30A but I don't think I have ever used it at 40A.

Being an electrical Engineer I don't know how they get away with UL and TUV certifications for this connector when using these small wire gauges. It's a joke and it's asking for more home fires.

I respect your professional qualifications, and I have no electrical expertise (I work with current flows in humans, not machinery ;-) but I would point out that with over 100,000 Teslas in use I am only aware of one garage fire (in Canada somewhere) that occurred with a Tesla plugged in at home. Probably there are a handful of other incidents but I am not aware of any fire that was demonstrated to have been caused by a UMC while charging. So it seems that the UMC is safe, in my non-expert opinion at least on a statistical basis. And as you point out the UMC is UL and TUV certified of course.

 

[ecarfan]

Running the 80 A HPWC at 40 A provides a nice fat design margin for long life and peace of mind (and you can just keep the UMC in the trunk).

Agreed. I always recommend that Tesla owners with their own garage buy the HPWC and keep the UMC in the trunk. At just $500 with the 8.5 ft cable it is a tiny fraction of the cost of the car. Of course there are installation costs, but if you can't run a 90 or 100A circuit you can always run a 50A circuit and keep the charge to 40A. The HPWC is just a nicer and more convenient setup than charging with the UMC and having to remember to take it with you when you travel.

 

[habanero69]

My UMC gets incredibly hot when charging at 30-40 amps. Mainly the cable between the wall Plug and the UMC. It gets piping hot and from what I am hearing that is considered normal. Service center checked it and says that is normal. The Wiring Cable going to the 14/50 outlet only warms up very little and is AWG 6. Being an Electrical Engineer by trade I can't belive they get away with this and allow them to become so hot. In my days we would not have designed anything like this and would use a heavier gauge that dissipates the heat bettter. In any case, I had a house fire before which (what a coincidence) was caused by a Battery Charger (Dewalt Power Drill), I don't feel very good at going to bed and leave the car charging knowing the Temperatures in the equipment raise like this. Being a fire victim once which happened during lunchtime I certainly don't want that to happen at night while I am sleeping. If I charge overnight I usually dial down to 15 amps.

Does the Hardwired Wall connector become this hot as well or is this just a UMC issue ?

I'm an EE by trade too, but got sucked into I.T. long ago so most of my head thinks in 1's and 0's, not amps/volts... I couldn't tell for sure from the thread, but have you be able to swap out your UMC for a different one and see if your particular cable might have some high impedance defect? Also, if you have access to an amp meter, clamp on style, you might be able to see if there is some imbalance or over current draw on one of the conductors.

Sorry about the house fire. I can understand how you feel about leaving "charging" items unattended. I would dial down the amps from the car until it seems not so hot (whatever that is) and until a solution can be found. Good luck.