High Current Draw During Charging

[EVBill]

I have a Leviton 40A charging station connected thru an electrical safety box with 50A fuses.
For 4 years it has worked fine, but now the fuses in the safety box are blowing roughly every 3-4 weeks. Any thoughts on what could be causing it? Charging station going bad?

 

[miimura]

Check the torque of wire termination at the circuit breaker. The breakers work on a thermal profile, so if there are loose connections they generate extra heat causing false trips. Well, actually, it's not false because there is extra heat present that shouldn't be there. Inspect the breakers and every other connection point in the circuit to check for any signs of high temperature conditions. There can also be a poor connection between the breaker and the panel back plane (there's probably another more appropriate term that I can't think of) that may be generating extra heat too.

 

[smkettner]

Low cost clamp-on ammeter would verify fuse issue or overload.

 

[EVBill]

Thanks for the tips. I checked the connections in the circuit breaker panel and the electrical safety box/switch and they are all nice and tight. The fuse that is blowing is the replaceable one in the electrical safety box/switch, not the circuit breaker in the electrical panel. After replacing several fuses it's safe to say there is an overload issue vs a fuse issue.

 

[GlennD]

Fuses blow (fuse) strictly by heat. If the holder is a little loose it can make a difference. OpenEVSE originally used a 30A rated 3AG style holder. it got so hot at half current that they switched to a 5AG style for larger fuses to better dissipate the heat.

 

[miimura]

Thanks for the tips. I checked the connections in the circuit breaker panel and the electrical safety box/switch and they are all nice and tight. The fuse that is blowing is the replaceable one in the electrical safety box/switch, not the circuit breaker in the electrical panel. After replacing several fuses it's safe to say there is an overload issue vs a fuse issue.

If it is the type that allows the fuses to snap in, not screw in, then the connection is not tight and is overheating, blowing the fuse. The more times you change it the looser it will get. Like someone said above, use an inexpensive clamp meter to verify the current and either bypass the fuses or replace the fuse holder portion inside the safety switch.

This one is available at Harbor Freight for under $15.

 

[EVBill]

The clamp meter was a great idea. Turns out it was overheating, likely due to the connection not being tight. I replaced the safety switch and it has been working fine since, thanks for the tips!