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question about sub panels

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  • question about sub panels

    Originally posted 11-19-2017 4:17 PM
    By: dman

    My church is updating the kitchen after we added a building that connects two buildings. The new building has two panels. one is the main, that feeds three sub-panels. one subpanel goes to the sanctuary, that feed is 200 amps (this panel is at 90% capacity). the next sub goes to the new building it is also has a feed of 200 amps this was installed by a electricain that had to pass a inspection the next sub feeds the old main panel of the old chruch this also has 200 amps and also has a sub panel which has 100 amp feed. all panels are correctly marked on the main panel and the subs. our feed to the main is 800 amps and has a open breaker spot for a future 200 amp panel.

    There were a lot of unexpeted problems during the build out. we had to finish the kitchen by volenteers. a new sub panel was installed on the old main which already had a sub panel both of these are 100 amps. the main panel only has 200 amps. the main panel also feeds power to 4 central air conditioners. the new sub panel to the kitchen will feed a electric stove, refrigerator, an instant hot water heater, lighting and etc. the second sub panel feeds the old church lighting outside lights, outside sign and etc.

    my questions are.

    Is the old main with two subs overloaded? would it not be better to run one sub off the new main which has 200 amps availble? I can send pictures of all the boxes if needed and i am in the state of Ohio
    Thanks for your advi2e

  • #2
    Originally posted 11-19-2017 11:21 PM

    It could be, but you can't tell just by adding up breakers. If all the air conditioners are 2 ton and the instant water heater is a small one by a sink, it may be OK. If these are all 5 ton ACs and the instant water heater feeds showers and multiple sinks, it probably isn't large enough. So you need to do a load calculation. A church is not a house, so you have to do the tougher calculation that doesn't allow for much diversity. Receptacle outlets are 180VA per strap and the lighting load (lighting only, not receptacles) is 1 VA per square foot. Known appliances are added by their nameplate value. I'd consider going heavy in the kitchen calculation since code only requires 180VA per outlet strap and if it is full of crock pots and toasters and microwaves, 180VA per outlet is not enough. Maybe used the planned average nameplate load instead.

    If it turns out 200A for the old church is not enough, then yes it would be good to bring another 200A feeder in there. The only issue would be if any of these buildings are separate buildings. If you've combined everything into effectively one large building, you're fine. If the church is a separate building, then it can generally only have one feeder so you'd need to make the 200A feeder a 400A feeder which adds greatly to the cost. The local building inspector can tell you if any of the old buildings are separate or its one large building if there is a question.
    Kent, WA