I am working on a remodel of an existing commercial space in a strip mall. The building department is requiring me to show a meter gutter load summary. I know the main breaker size for each tenant, but how do I determine each tenant's demand using demand factors from the NEC? Do I have to get access to each tenant's panelboards and try to estimate all of their loads?
Load calculations
- Thread starter thais
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- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Load calculations
What if you used the breaker size as the demand load? It can certainly be no higher, without the breakers starting to trip. It would be the quickest way to provide a reasonable number. What would that do to your service calculation for the entire mall? Given that the serviced calc is intended to ensure that the service size is at least as much as the minimum required to serve the load, it would be an acceptable answer to the building department. So al long as this does not cause you to have to upsize the service, it should work.
What if you used the breaker size as the demand load? It can certainly be no higher, without the breakers starting to trip. It would be the quickest way to provide a reasonable number. What would that do to your service calculation for the entire mall? Given that the serviced calc is intended to ensure that the service size is at least as much as the minimum required to serve the load, it would be an acceptable answer to the building department. So al long as this does not cause you to have to upsize the service, it should work.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Load calculations
OK, so the easy way is not an option. The next easiest (by that I mean one that requires the least amount of physical installation work) is to use 220.35. Since you are doing a remodel for the entire facility, perhaps the owner can arrange to get you copies of the utility bills for each of the tenants for the past year. If not, then perhaps you can place a recording meter on each of the tenant feeders, and measure the peak load over a 30 day period. Take the highest demand reading for each feeder (KVA, not KW-Hrs), add 25%, and call that the existing load.
OK, so the easy way is not an option. The next easiest (by that I mean one that requires the least amount of physical installation work) is to use 220.35. Since you are doing a remodel for the entire facility, perhaps the owner can arrange to get you copies of the utility bills for each of the tenants for the past year. If not, then perhaps you can place a recording meter on each of the tenant feeders, and measure the peak load over a 30 day period. Take the highest demand reading for each feeder (KVA, not KW-Hrs), add 25%, and call that the existing load.
Re: Load calculations
I have usually been able to get old plans from the property manager or maintenance. Next, you can follow 220.10 using general lighting, show window load, track lighting, and HVAC, which you can get by a quick inventory as long as you don't have food places. The alternate is 220.35 with a 30 day meter.
I have usually been able to get old plans from the property manager or maintenance. Next, you can follow 220.10 using general lighting, show window load, track lighting, and HVAC, which you can get by a quick inventory as long as you don't have food places. The alternate is 220.35 with a 30 day meter.
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