grocery store

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lmchenry

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There is a new store going into a existing building. They have completely remodeled the building. They had an existing 4000 amp service that covered the new connected load of 2600 amps. So they left the main swithgear alone and went from there. They finished the store and I passed the final inspection. Now they have decided to add a transfer switch for a portable generator. From the transformer they pulled new conductors. They were 4 750 kcms good for 1900 amps. The transfer switch which is now the main service disconnect has a 2500 amp adjustable trip breaker. They, the engineers, said that the store will never reach the connected load and they sent me loads for "similar" stores. I said sorry no way. You must meet the connected load of the store. So they have an energy management system that they say they can use to change the load. They have sent me new drawings with the adjusted load using the ems and it is 2297 amps. They are going to install another 750 to get to 2375 and then they are going to dial down their breaker to 2300 amps. What are the issues to consider here? Should I allow the changed load with the ems used? Should the store be formally informed of the new load? Another issue is that there are no more conduits to the transformer, so they will have to cut the concrete between the transformer and the transfer switch and add a conduit for the extra 750. Thoughts?
 
I would think the load shedding via the EMS would satisfy 220.60 and 702.5(B)(2) {Assuming this is an "optional" system}, although I think it's asinine to cut it that close. Our job is to assure Code compliance not regulate "stupid".
I'd be sure and keep all documentation:smile:
Their added conduit /conductors will have to meet the requirements of 310.4 which I would think might prove tricky.
I would make sure the adjustable breaker is properly sealed and would ask that a plaque be placed showing the service capacity.
 
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thanks Gus! Yes the system is optional. I agree that the engineers are cutting it too close. They have shown to be unprofessional in their approach to the whole installation of the switch. I have decided to allow their design but with some particular restrictions including the placard.
 
Grocery Store, EMS as Load Limiter

Grocery Store, EMS as Load Limiter

Hi, I'm alittle late to your post but, I would have a problem with the EMS being used as a load limiter. All EMS's can be overriden, Temperature Setpoints raised/lowered, fans run longer than scheduled, etc.
I hope you are conformtable with the load actually never exceeding the calculated connected load. But at the end of the day, as is, the circuit breaker would trip on overload.
 
markstg said:
Hi, I'm alittle late to your post but, I would have a problem with the EMS being used as a load limiter. All EMS's can be overriden, Temperature Setpoints raised/lowered, fans run longer than scheduled, etc.
Click to expand...

What type of load shedding equipment can not be tampered with?
 
Hard wired interlocks, with NO override devices. I should also say EMS's are not load limiters, which is equipment/wiring designed to prevent the load from exceeding a set value.
 
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markstg said:
Hard wired interlocks, with NO override devices.
Click to expand...

If someone is capable of intentionally changing the load shedding programing they are just as likely to be able to bypass hard wired devices.

If I swing open the door of many standard emergency ATS I can quickly change the operating perimeters of the ATS and generator without needing any tools.
 
we're talking about a "calculated" load anyway and any "load shedding" can be circumvented or any load added. The bottom line we have to depend on the overcuurent device.
 
But the OP's concern was that the Overcurrent Protective Device would activate at 2:00 in the afternoon, with a full store of people, all because the service conductors were too small, and the OCPD had to be set to low.
 
There is nothing wrong with using the EMS to shed loads if necessary to keep to a certain size service or generator, this falls under 220.60. I also agree with Iwire that using the excuse that it can be reprogrammed is not a good one. Like he said, anything can be "tampered with". Grocery stores are quite unique in loads and are NEVER close to the connected loads. We've done quite a few grocery stores and have used this approach at times to show compliance with the NEC when the service is restricted to existing conditions. The required NEC service load calcs and actual loads for grocery stores are a ways apart. It would be nice to see the NEC have a separate calculation like they do for restaurants available based on actual experience. And while I am on it, the NEC should get rid of the antiquated requirements for 150 watt per 2' of track and 200 watts per foot of show window lighting as you would never even come close to passing the energy codes if you installed those amounts of lights. (Sorry for the rant).
 
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