On a recent project, I discovered a service disconnect fused at 700A feeding the normal power to an ATS. An 800A main breaker generator feeds the emergency sides. ATS load is connected to two 600A power panelboards. This violates 408.36B (NEC 2005) and 408.36 (NEC 2008). I can't find that this has changed from earlier codes (1999 on). Work was performed after 2000. I think it's an incorrect installation. Is there any way that this may be correct?
OCP for panelboards
- Thread starter DW98
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- Lockport, IL
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- Semi-Retired Electrical Engineer
Do the two 600 amp panels have main breakers of their own, each being rated 600 amps or less? If so, the installation is compliant. If not, then you have a 600 amp panel being protected by a 700 amp fuse (or an 800 amp breaker, when the ATS is on alternate power). In that case, I agree with your assessment that this would violate 408.36.
The panelboards are m.l.o.
first has a 60A 3P (spare), 600A 3P (75 ton rooftop), 100A 3P (panelboard),
second has a 100A 3P (panelboard), 60A 3P (5 ton rooftop), 600A 3P (fused to protect 150KVA xfmr).
historical load is 187kw (240V 3P high leg delta system) - 561A @ 233kva. We're renovating building and putting in smaller RTU and better lighting so load should drop.
Thanks again for the help. I want to double/triple check with others before I submit findings.
first has a 60A 3P (spare), 600A 3P (75 ton rooftop), 100A 3P (panelboard),
second has a 100A 3P (panelboard), 60A 3P (5 ton rooftop), 600A 3P (fused to protect 150KVA xfmr).
historical load is 187kw (240V 3P high leg delta system) - 561A @ 233kva. We're renovating building and putting in smaller RTU and better lighting so load should drop.
Thanks again for the help. I want to double/triple check with others before I submit findings.
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