Connected loads breakdown.

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San Jose California
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Electrical contractor
I’m a new contractor. There’s a machine shop that has 200amps going to it but the sub panels maxed out. There’s room for another breaker in the main switch gear, but the line side from each breaker goes straight to the meter. Has anyone ever encountered something like this before?

Pg&e said they can do a shut down for me to take off the dead front to see what materials I need.

also having trouble filling out this connected load breakdown sheet.
 

tom baker

First Chief Moderator
Staff member
Hopefully when you get the DF off you can get the make model of the gear. If its Sq D, they have good tech support Chat and lots of info on old gear, if those numbers are still readable
 

__dan

Senior Member
The load calc can be all over the place depending on the duty cycle, do they run only a few machines at a time or do they go production all shift with everything running at the same time. Caveat, I am using duty cycle not in the same way the code will, where it permits a derating of the load value. I would be using 'duty cycle' as something the operator does manually when he starts and stops the machine.

You can have ten machines on a service sized for one as long as they are not automatincally started and it is up to the operator to only run one machine at a time. However, what they want to run simutaneous and work them in production, those motors I would put in for 100% plus 125% of the largest motor. It's a good bet they are not doing any auto load shedding to avoid overloads, they will just load it up until it trips, and it's a good bet a lot has changed over the years, removing and adding loads.

In the code I believe you can do a table listing of loads or a peak measured running loads survey. I would want both probably, the peak load meter reading, and then a table listing of what they really want to run all at the same time.

Of note, your post did not specifically refer to doing the load calc before adding load. The POCO's load sheet is something different. They are not going to do the load calc for you, but for their own use, they want to have an idea of what ballpark you are in.

I usually want to do a load calc before adding load just to see, before proceeding with building it.
 
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