Amp Rating of Fused Disconnect

I inspected a fourplex today in Brooklyn. The main disconnect was a switch with two knife blade 150-amp cartridge fuses that were fed with 1/0 copper cable (175-amps). The panel label stated that it was rated for 200-amps. Since the fuses were the lowest rated component, shouldn’t the overall rating of the panel be 150-amps?




It should but it doesn’t have to be.
A panel is limited to 42 breaker poles. Any panel.
The 150 is your main disconnect. It does not matter how many breakers this 150 amps serves, even if these breakers are in a 200 amp rated panel.
What matters is the calculated load.

As a HI, with Bill’s supplied info, I would call it 150 amps. :wink:

Speedy gave the correct answer based on this question.

However, the question should have been - “what is the service capacity?”

Based on the information provided by Bill, the service capacity is 150 amps.

I agree guys…DO NOT get involved in anything to do with Calculations…Just refer to it as the Service Capacity and in this case the weakest link applies…

Take a closer look at this picture. There are other issues I would be concerned with than the size of the service…

line/load side of the fused blades.

Pierre, I have seen a number of these discos fed backwards like this. Sometimes I think it is done for convienence, ie shorter conductor runs. Other than a 110-3 violation, do you see any problems that could arise from this installation? I suppose someone servicing the equipment could be injured if they took the wording alone for fact, but if they did then I wouldn’t consider them qualified in the first place. Do you suppose if it weren’t marked line and load it would still be wrong?

Thank you all for your excellent replies.

Jeff- you always catch me on terminology - That is one of my weak points and I appreciate your input.

Pierre- The GEC is too small. There were numerous other issues with the system.

The problem is the fuse itself is hot with the disconnect off. That makes it dangerous to change. There would be a dead front cover over the line terminals on a new one.


The disconnect is fed from the top - before the meters. I should have mentioned that earlier but I was more concerned with the service capacity. The system in general was a mess.

The GEC is marked with white tape. White is not permitted as a color for the GEC. Also the GEC is required to be bonded to the enclosure where it enters or exits. This is usually performed by skinning the insulation at the fitting.

I see a white MBJ wire, and lug where the jumpers are installed, and the short fuses. Is the switch rated at 200 amperes?

Free Electricity is available too, how were you able to get into the switch?

The cover for the swich box opened with the removal of two screws. The service points were readily accessible as well.