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Square D 200amp main JGL 480v

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Brownetown

Member
Location
Va
Occupation
Electrican
I have a brand new square d JGL 200 amp breaker 480v panel as a main for service. Engineer load calculations for entire service 156amps. Load has been running small while we were in middle of constructions. Lights/recps etc.. the HVAC guys turned on all 4 rooftop units on at once. 25amp 3p 2 minutes later the main tripped. Once I turned it on I turned on 2 rooftop units back on. One at at time. Now breaker is humming/clacking sound. Do you think may main is now bad??
 
H

hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
That breaker should have magnetic trip adjustment dials, they come from the factory at the minimum setting, that is probably why it tripped. The humming and crackling sound may be from a loose buss connection.
 
B

Brownetown

Member
Location
Va
Occupation
Electrican
Connections are tight and torqued. Only started to hum/crackling after breaker tripped and added the extra load from rooftop units. The dial is set at the minimum setting.
 
J

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
If the load was carried for several minutes the tripping was most likely not from the HVAC inrush current, even though the magnetic minimum may be as low as 2X its frame size.

When you turn the HVAC load off does the breaker stop making noise?
 
B

Brownetown

Member
Location
Va
Occupation
Electrican
When I remove the load from the rooftop units it stops making noise. I have only turned one at a time on since the main tripped.
 
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