Trying to understand aic. I do mostly hvac, chillers and pumps. I am normally in a existing building where i need to find a extra space in the existing main panelboard.As a example I just installed a 800a 3p 480v mlo panel in a mech. room with 2 400a breakers each feeding a new chiller. This panel is fed from a 800a fused disconnect in the main panel. Do fuses get aic ratings? Can i just copy the rating of other branch panels in the building? Is the rating of all panels in a building the same, if not does the rating go up or down the farther you get from the main panel? john
aic ratings
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Re: aic ratings
Suggest you go to www.bussmann.com and download their SPD booklet file.
Or if you can find out what tha Available Short Circuit Current (ASCC) is at the Utility Company transforme, the Service Entrance conductor type, Length, raceway type, and the Kair or the Kaic ratings of any OCPD and Panelboards ahead of your new 800A panel and other pertinent information as in the SPD.
Remember, the Kaic or the Kair Ratings of the electrical equipment must be equal to or greater than the ASCC at each point of the circuit.
Suggest you go to www.bussmann.com and download their SPD booklet file.
Or if you can find out what tha Available Short Circuit Current (ASCC) is at the Utility Company transforme, the Service Entrance conductor type, Length, raceway type, and the Kair or the Kaic ratings of any OCPD and Panelboards ahead of your new 800A panel and other pertinent information as in the SPD.
Remember, the Kaic or the Kair Ratings of the electrical equipment must be equal to or greater than the ASCC at each point of the circuit.
ron
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- New York, 40.7514,-73.9925
Re: aic ratings
Ideally you should performa calculation (or have one done for you) when you install any new electrical equipment.
Theoretically, you could check the AIC rating of the panel/switchboard that will be directly upstream of your equipment, and match that rating (assuming it is correct).
Everything has an AIC or withstand rating, fuses, starters, breakers, even a safety switch.
I have run into problems where the available short circuit current at a motor was 12,000, and the unfused safety switch was rated at 5,000, so it had to be replaced with a fused safety switch at a higher rating.
Ideally you should performa calculation (or have one done for you) when you install any new electrical equipment.
Theoretically, you could check the AIC rating of the panel/switchboard that will be directly upstream of your equipment, and match that rating (assuming it is correct).
Everything has an AIC or withstand rating, fuses, starters, breakers, even a safety switch.
I have run into problems where the available short circuit current at a motor was 12,000, and the unfused safety switch was rated at 5,000, so it had to be replaced with a fused safety switch at a higher rating.
Re: aic ratings
If the safety switch is used to open the circuit to the running motor, very good practice to increase the kaic rating of the interrupting equipment.
Just as a note, see 430.109(E) for greater than 40 HP DC or 100 HP AC motors isolating switch labeling.
These switches are not to be operated under load.
If the safety switch is used to open the circuit to the running motor, very good practice to increase the kaic rating of the interrupting equipment.
Just as a note, see 430.109(E) for greater than 40 HP DC or 100 HP AC motors isolating switch labeling.
These switches are not to be operated under load.
- Location
- Illinois
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- retired electrician
Re: aic ratings
gwz,
430.109(E) only applies when using a general use switch, that is a switch that does not have a horsepower rating. Disconnect switches that have a horsepower rating are suitable for opening motor circuits under load up to the rating of the switch. I know that there are disconnect switches available that have a 3 phase 480 volt horsepower rating of at least 400 hp.
Don
gwz,
430.109(E) only applies when using a general use switch, that is a switch that does not have a horsepower rating. Disconnect switches that have a horsepower rating are suitable for opening motor circuits under load up to the rating of the switch. I know that there are disconnect switches available that have a 3 phase 480 volt horsepower rating of at least 400 hp.
Don
Re: aic ratings
The original post of this thread of the aic at the 800A panel for this mechanical room, I would think needs some serious consideration(s) of the ASCC (Available Short Circuit Current ) from the utility transformer to the last current interrupting equipment on the circuit.
Locally, the utility has transformers at 208V with 103,600 ASCC and 480V with 49,700 ASCC.
Electrial equipment with-in short distances from these ASCC's could well be under-sized in aic capability.
The original post of this thread of the aic at the 800A panel for this mechanical room, I would think needs some serious consideration(s) of the ASCC (Available Short Circuit Current ) from the utility transformer to the last current interrupting equipment on the circuit.
Locally, the utility has transformers at 208V with 103,600 ASCC and 480V with 49,700 ASCC.
Electrial equipment with-in short distances from these ASCC's could well be under-sized in aic capability.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
Re: aic ratings
Just for discussions sake, in the NYC area, the utility company (ConEd) has the secondary side of most all transformers in the area paralleled together. A letter sent to the utility generally gets a response of 200kAIC avaialble at the meter.
Just for discussions sake, in the NYC area, the utility company (ConEd) has the secondary side of most all transformers in the area paralleled together. A letter sent to the utility generally gets a response of 200kAIC avaialble at the meter.
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