Conduit getting warm during charging

[regazzoni]

Just completed my install on the wall charger with 3/4 EMT conduit, 6AWG hots and 8AWG ground.
Interesting to observe that conduit actually gets warm. 60A circuit breaker even slightly hot when touched on front. Assuming this is expected?

 

[mongo]

Likely normal. The lowest temperature rating on wire insulation/ contacts is 60C / 140F.
At a 48A charge rate, each 6 AWG dissipates .9 Watt per foot. Since the circuit is two wires, that is 1.85W per foot inside the conduit.

 

[Petrlol]

How long is your conduit?

 

[TomB985]

What’s your charging voltage for current?

 

[Octo]

I have the same setup. L1 and L2 get warm to the touch (feels like 120F) after 2 hours with ambient temperature 100F.

 

[eprosenx]

Just completed my install on the wall charger with 3/4 EMT conduit, 6AWG hots and 8AWG ground.
Interesting to observe that conduit actually gets warm. 60A circuit breaker even slightly hot when touched on front. Assuming this is expected?

Sounds totally normal. Warm is normal and expected. Hot is bad.

Breakers are actually tested at like 104 degrees Fahrenheit to make sure they don’t trip at their 100% rating.

If the heat seems to be close to the ends of the conduit then check your connections to ensure no insulation was stuck under the terminal and that you stripped enough insulation to fully insert it all the way and to make sure they are tightened properly.

Beyond that, as long as your amperage is charging at 48 amps and the voltage does not drop much from when you first start charging (zero amps of load) to full load charging and the voltage is around 240v then you are golden.

Nice job!

I would love to see pictures of your install! Did you set the rotary dial to the proper 48/60 amp setting?

 

[regazzoni]

Thanks for all the replies. A couple of answers;
- conduit is about 60ft long
- I can't access conduit in all places, but where I can it seems that the conduit is evenly warm. There is a 90 degree conduit bend near middle that actually appears to vibrate just slightly.
- split phase 240V. Have not measured yet actual or drop
- dial is set to 48A
- measuring with a simple IR tool, the circuit breaker was about 105F in the front.

 

[mongo]

Thanks for all the replies. A couple of answers;
- conduit is about 60ft long
- I can't access conduit in all places, but where I can it seems that the conduit is evenly warm. There is a 90 degree conduit bend near middle that actually appears to vibrate just slightly.
- split phase 240V. Have not measured yet actual or drop
- dial is set to 48A
- measuring with a simple IR tool, the circuit breaker was about 105F in the front.

You're fine.
There are no splices in the conduit. Breaker can operate in 104 abient temp before self heating is included.
The vibration is due to the wires moving due to the magnetic field genersted by the charge current. My hot tub does the same thing. Is the conduit well secured?

 

[eprosenx]

Thanks for all the replies. A couple of answers;
- conduit is about 60ft long
- I can't access conduit in all places, but where I can it seems that the conduit is evenly warm. There is a 90 degree conduit bend near middle that actually appears to vibrate just slightly.
- split phase 240V. Have not measured yet actual or drop
- dial is set to 48A
- measuring with a simple IR tool, the circuit breaker was about 105F in the front.

Yup! You are totally fine. This is all 100% normal.

FWIW, the reason for the 80% derate for “continuous loads” (like car charging) is because of the uncertainty of when a breaker will blow due to the heat generated. It is to avoid nuisance trips. So that is why you can only charge at 48 amps on that 60a breaker.

Nice job on the install, I see zero issues. Also, you could have used 10awg for the ground if you had wanted (that is what I did), but 8 awg is even better.

My conduit vibrates a little also. That is just normal for wiring in conduit under heavy load. It is 60 cycle hum (from the frequency of the alternating current). Not a ton you can do about it other than making sure the conduit is strapped down well enough. Backing the car charge rate down could help maybe, or over sizing the wire perhaps? But it really is not an issue.

 

[eprosenx]

Breaker can operate in 104 abient temp before self heating is included.

The one thing to add to this is that the test breakers are put under is at 104f (40c) but it is done in free air conditions (no surrounding breakers to hold in heat or to contribute their own heat). So in the real world, breakers heat beyond the standard test conditions all the time. Hence the 80% derate requirement. Since in this case more than 48a on the 60a breaker will never be drawn things will be just fine for sure!

 

[mongo]

My conduit vibrates a little also. That is just normal for wiring in conduit under heavy load. It is 60 cycle hum (from the frequency of the alternating current). Not a ton you can do about it other than making sure the conduit is strapped down well enough. Backing the car charge rate down could help maybe, or over sizing the wire perhaps? But it really is not an issue.

FWIW oversizing the conductors won't help the hum. For high power machinery cabinets, the wiring sometimes calls for twine installation to hold the conductors in position during overcurrent events.

 

[regazzoni]

Twine going around conductors every x feet?

I was actually thinking to use conduit seal in accessible places to dampen and hold conductors in place:
Black Electrical Tape
Not sure if this is code... I am assuming it woudl also block heat

 

[mongo]

Twine going around conductors every x feet?

I was actually thinking to use conduit seal in accessible places to dampen and hold conductors in place:
Black Electrical Tape
Not sure if this is code... I am assuming it woudl also block heat

I mean you could give them a wrap of tape every foot or so, or rotate the reel while feeding to produce a twisted assembly, but I don't think any industrial installations go that far (and it makes the pull more difficult).