NEC 700.(D)

[anbm]

NEC 700.(D) Use - Transfer equipment shall supply only emergency loads.

I am working in a building with a 150kW, 280V/3PH outdoor backup diesel generator. The generator feeds one ATS and one downstream panel (EM). Panel EM has both emergency loads (egress lights, exit signs and fire alarm panel) and other non-emergency loads.

To comply with above NEC rule without adding another ATS/panel to separate emergency loads from non-emergency loads, I am thinking to install an inverter, then disconnecting all emergency circuits from panel EM and re-feed them from the inverter. This meant the emergency loads are now backuped by another source not generator as allowed by NEC 700. Questions:

1) Can the inverter still be fed out of panel EM or it has to be fed from another non-generator panel?

2) If the inverter can be fed out of panel EM, technically, the emergency loads now have two backup power sources (inverter and generator) is but still on same ATS as other loads, will this comply with NEC 700(D) above?

3) In either scenario, the generator is no longer classified as generator, correct?

 

[anbm]

NEC 700.(D) Use - Transfer equipment shall supply only emergency loads.

I am working in a building with a 150kW, 280V/3PH outdoor backup diesel generator. The generator feeds one ATS and one downstream panel (EM). Panel EM has both emergency loads (egress lights, exit signs and fire alarm panel) and other non-emergency loads.

To comply with above NEC rule without adding another ATS/panel to separate emergency loads from non-emergency loads, I am thinking to install an inverter, then disconnecting all emergency circuits from panel EM and re-feed them from the inverter. This meant the emergency loads are now backup-ed by another source not generator as allowed by NEC 700. Questions:

1) Can the inverter still be fed out of panel EM or it has to be fed from another non-generator panel?

2) If the inverter can be fed out of panel EM, technically, the emergency loads now have two backup power sources (inverter and generator) but it is still fed out of same ATS as other loads, will this comply with NEC 700(D) above?

3) In either scenario, the generator is no longer classified as emergency generator, correct?

Revised missing word

 

[anbm]

Anyone has any inputs for my questions above?

 

[Fred B]

One thing that routinely comes up is the identification that the gen is "Emergency". Is this designation coming from AHJ? If so then only "emergency" circuits to be supplied from this generator. If not designated by AHJ or engineer as "Emergency" then it is regardless of HO statement, the gen is just standby and any loads within limit of gen can be served. "Emergency generator" has very specific criteria to be such, thus the additional requirements within the codes.

 

[anbm]

One thing that routinely comes up is the identification that the gen is "Emergency". Is this designation coming from AHJ? If so then only "emergency" circuits to be supplied from this generator. If not designated by AHJ or engineer as "Emergency" then it is regardless of HO statement, the gen is just standby and any loads within limit of gen can be served. "Emergency generator" has very specific criteria to be such, thus the additional requirements within the codes.

I think if a generator powers "emergency load" (egress lights, exit signs, alarm, ect. as listed in NEC), it automatically become an emergency generator. So, I am guessing the inverter in my posted must be fed from non-generator power panel unless ... the generator is considered as standby generator after the inverter installed.

 

[Fred B]

I think if a generator powers "emergency load" (egress lights, exit signs, alarm, ect. as listed in NEC), it automatically become an emergency generator. So, I am guessing the inverter in my posted must be fed from non-generator power panel unless ... the generator is considered as standby generator after the inverter installed.

Well it might be, but the designation as an "emergency generator" comes from AHJ or engineer. If existing installation, it might be safe to assume it's an emergency generator given loads supplied. A true "emergency generator" also has startup criteria for allowable utility power outage time that is almost no delay compared to other generator applications.

 

[d0nut]

1) Can the inverter still be fed out of panel EM or it has to be fed from another non-generator panel?

2) If the inverter can be fed out of panel EM, technically, the emergency loads now have two backup power sources (inverter and generator) is but still on same ATS as other loads, will this comply with NEC 700(D) above?

3) In either scenario, the generator is no longer classified as an emergency generator, correct?

1. The inverter can be fed out of panel EM or it can be fed from a non-generator panel. It is your choice. If the building won't be immediately evacuated upon a power loss, you should feed the inverter from the generator. That way you aren't discharging the batteries while the building is still occupied. If the generator were to fail during a utility outage, you would still have the 90 minutes of inverter battery to evacuate the building. You may need to modify the lighting controls to get the emergency egress lighting to function properly.
2. The emergency system would begin at the inverter. Anything upstream would be optional standby. Article 700 would only apply downstream of the inverter.
3. If you have an emergency inverter, the generator can be an optional standby generator.

 

[GoldDigger]

By inverter, are you referring to a grid-interactive PV inverter or a battery powered inverter?
A standard PV inverter should never be online when running from a generator or other backup power source. The problem is that if the PV output is ever greater than the local load it will try to backfeed the alternate source.
A battery powered inverter may or may not need special treatment.

Sent from my Pixel 4a using Tapatalk

 

[don_resqcapt19]

Don't forget that an inverter used for EM lighting must be listed for the purpose and comply with the requirements of UL924.

 

[anbm]

By inverter, are you referring to a grid-interactive PV inverter or a battery powered inverter?
A standard PV inverter should never be online when running from a generator or other backup power source. The problem is that if the PV output is ever greater than the local load it will try to backfeed the alternate source.
A battery powered inverter may or may not need special treatment.

Sent from my Pixel 4a using Tapatalk

Central emergency battery inverter cabinets.

 

[anbm]

Don't forget that an inverter used for EM lighting must be listed for the purpose and comply with the requirements of UL924.

Of course, these are very popular on the market recently, they power egress lights at full bright output.

 

[anbm]

1. The inverter can be fed out of panel EM or it can be fed from a non-generator panel. It is your choice. If the building won't be immediately evacuated upon a power loss, you should feed the inverter from the generator. That way you aren't discharging the batteries while the building is still occupied. If the generator were to fail during a utility outage, you would still have the 90 minutes of inverter battery to evacuate the building. You may need to modify the lighting controls to get the emergency egress lighting to function properly.
2. The emergency system would begin at the inverter. Anything upstream would be optional standby. Article 700 would only apply downstream of the inverter.
3. If you have an emergency inverter, the generator can be an optional standby generator.

Thank you. # 2. is an interesting code topic.