2018 75D home charging circuit breaker

[Hpnewport]

Wonder what (or how much) they changed in the components.... a 120V outlet, of course, can be on a GFCI circuit, where the EVSE/high current 14-50 isn't. But you shouldn't be seeing the kind of current imbalance to trigger the GFCI.

Have you tried resetting the GFCI? Some that don't get reset in years have issues and they should tested monthly (and almost never are).

Don't want to turn this into a general electrical troubleshooting thread, but this might be useful.

my outlet is not on a GFCI, just tied into circuit breaker at the panel...

 

[Hpnewport]

@Hpnewport ,

1. What amperage if your breaker?
2. Is there anything else connected to the same breaker?
3. When you say UMC trips, do you mean the breaker trips or the UMC kills the charging?

Typically it is not recommended to draw over 80% of the breaker current for sustained, long periods of time. Maybe Tesla got cleaver and they do a quick "test spike" to 40A to ensure that they are running on a minimum 40A breaker before drawing 32A safely? This would help them not burn down places which have a NEMA 14-50 on a 30A circuit (and breaker), which might not trip at 32A.

@Qbenjamin , do you have a NEMA-14-50 with GFCI, or are you talking 120V 15A or 20A plug?

I believe I have 40A outlet tied directly to house panel. nothing else is connected. UMC kills the charge...when I first plug into the car, the UMC cycles twice through the green letters, then clicks and top letter turns red.

 

[Hpnewport]

Wonder what (or how much) they changed in the components.... a 120V outlet, of course, can be on a GFCI circuit, where the EVSE/high current 14-50 isn't. But you shouldn't be seeing the kind of current imbalance to trigger the GFCI.

Have you tried resetting the GFCI? Some that don't get reset in years have issues and they should tested monthly (and almost never are).

Don't want to turn this into a general electrical troubleshooting thread, but this might be useful.

I don't believe this outlet is on a GFCI as I think it is tied directly into house panel on its own circuit...nothing in the panel trips, just the UMC...

 

[boaterva]

Yeah, unless the pigtail is shorting out, that sounds like a bad unit. Of course the other test as we said originally is to test with the 120 pigtail on a different circuit to rule out the circuit and the pigtail totally.

 

[Hpnewport]

Would love a picture of it saying 48 amp charging. Maybe you got a new special cable.

I posted some pics and a description of what I tried tonight. before plugging in, it said 48A, but as soon as I plugged in cord to car charging port, it did drop immediately to 32A, but then the UMC still tripped...

 

[HX_Guy]

What rating is the breaker in the panel?

My car charges at 48A but it’s on a 60A breaker.

 

[Hpnewport]

@Hpnewport ,

1. What amperage if your breaker?
2. Is there anything else connected to the same breaker?
3. When you say UMC trips, do you mean the breaker trips or the UMC kills the charging?

Typically it is not recommended to draw over 80% of the breaker current for sustained, long periods of time. Maybe Tesla got cleaver and they do a quick "test spike" to 40A to ensure that they are running on a minimum 40A breaker before drawing 32A safely? This would help them not burn down places which have a NEMA 14-50 on a 30A circuit (and breaker), which might not trip at 32A.

@Qbenjamin , do you have a NEMA-14-50 with GFCI, or are you talking 120V 15A or 20A plug?

I have a nema 14-50 with no GFCI that I can see...I believe it was wired directly from the house panel (only about 5' away...)

 

[Hpnewport]

@Hpnewport ,

1. What amperage if your breaker?
2. Is there anything else connected to the same breaker?
3. When you say UMC trips, do you mean the breaker trips or the UMC kills the charging?

Typically it is not recommended to draw over 80% of the breaker current for sustained, long periods of time. Maybe Tesla got cleaver and they do a quick "test spike" to 40A to ensure that they are running on a minimum 40A breaker before drawing 32A safely? This would help them not burn down places which have a NEMA 14-50 on a 30A circuit (and breaker), which might not trip at 32A.

@Qbenjamin , do you have a NEMA-14-50 with GFCI, or are you talking 120V 15A or 20A plug?

not sure if my reply posted... I have a NEMA 14-50 wired directly to the house panel 40A circuit breaker...no GFCI that I can fine...

 

[Hpnewport]

What rating is the breaker in the panel?

My car charges at 48A but it’s on a 60A breaker.


View attachment 290916

40A

 

[HX_Guy]

With a 40A breaker it should work fine at 32A. What’s with the side gate label?

 

[Hpnewport]

Yeah, unless the pigtail is shorting out, that sounds like a bad unit. Of course the other test as we said originally is to test with the 120 pigtail on a different circuit to rule out the circuit and the pigtail totally.

I did try the 120 pigtail and everything worked fine...

 

[Hpnewport]

With a 40A breaker it should work fine at 32A. What’s with the side gate label?

we put in a 2nd receptacle on the side of our house for our Airstream... it is not being used now

 

[BigTonyTones]

Could be a bad breaker. Not common but they do go bad. Have you tried metering both plugs on your outlet?

Also, did the electrician use right gauge wire when you had that installed?

 

[Qbenjamin]

@Hpnewport ,

1. What amperage if your breaker?
2. Is there anything else connected to the same breaker?
3. When you say UMC trips, do you mean the breaker trips or the UMC kills the charging?

Typically it is not recommended to draw over 80% of the breaker current for sustained, long periods of time. Maybe Tesla got cleaver and they do a quick "test spike" to 40A to ensure that they are running on a minimum 40A breaker before drawing 32A safely? This would help them not burn down places which have a NEMA 14-50 on a 30A circuit (and breaker), which might not trip at 32A.

@Qbenjamin , do you have a NEMA-14-50 with GFCI, or are you talking 120V 15A or 20A plug?

@whitex I'm referring to 120V 15A.

 

[pmc1]

I have a nema 14-50 with no GFCI that I can see...I believe it was wired directly from the house panel (only about 5' away...) View attachment 290918 View attachment 290921

A 14-50 circuit should have a 50 amp breaker. With only a 40 amp breaker you shouldn't pull more than 32 amp continuously.

 

[murphyS90D]

If an EVSE is not plugged into the car, the current setting in the car can be set to the maximum the charger in the car can support. As soon as the EVSE is plugged into the car it will reduce to the maximum the EVSE can support.

 

[Hpnewport]

If an EVSE is not plugged into the car, the current setting in the car can be set to the maximum the charger in the car can support. As soon as the EVSE is plugged into the car it will reduce to the maximum the EVSE can support.

got it! my issue is that even though the car drops by itself to 32A, it trips the circuit in the UMC every time I plug in the evse. if I manually lower the charge to about 20A it works fine, then I can manually put it back to 32A and it stays charging...???

 

[Hpnewport]

A 14-50 circuit should have a 50 amp breaker. With only a 40 amp breaker you shouldn't pull more than 32 amp continuously.

maybe we didn't have room for a 50 amp breaker so he used a 40, but this set up has worked fine for 3 years with my 1st Tesla. there is obviously something different in the new UMC...

 

[Hpnewport]

Could be a bad breaker. Not common but they do go bad. Have you tried metering both plugs on your outlet?

Also, did the electrician use right gauge wire when you had that installed?

can't be sure without pulling the panel, but he knew that we were adding this for the Tesla charging and had the spec sheet from Tesla. Again, this set up has worked for 3 years with my 2013 Tesla...

 

[murphyS90D]

A 50 amp breaker and a 40 amp breaker are exactly the same size. Both are the same size as a 100 amp breaker.
A 50 amp breaker requires that the wire be 6 gauge wire. Maybe the restriction to a 40 amp breaker was because the existing wire was #8.