I currently have a Retirement Home with a 2500 Amp, 480 Volt, Three Phase Service. It has an Emergency Generator for some of its Emergency Lighting, and other parts of the facility have battery backup exit signs and bug eyes. The facility wants to install a new 500KW backup generator for the whole facility. They want to interrupt the line between the Main Disconnect Switch and the Main Distribution Panel to install a transfer switch which would provide power to the whole facility if they lose their permanent power. My concern with this is that all of the power, both emergency power and normal building power would transfer at the same time. Is this allowed by code? If it is allowed, then I would think that the automatic transfer switch would need to be 2500 Amps to match the Main Disconnect Switch. I look forward to your comments on this.
New Emergency Backup Generator
- Thread starter Moore9449
- Start date
- Status
The existing battery operated emergency lights would operate as intended between the time the power goes out until the load is transferred to the generator. I don't see a problem with this. I am not aware of any code issues in what you are describing. I've installed many generators on existing services that had battery units. No one has ever raised an issue about it.
The ATS should be sized the same as the service disconnect.
The ATS should be sized the same as the service disconnect.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Make sure you pay attention to 700.5 especially (B), also keep in mind the requirements of 700.12 still apply (10 second rule)
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
Since you mentioned there is some emergency power supplied by the generator and some is "unit powered", there are some considerations for this generator installation.
1. You will need 2 transfer switches - one for normal powered circuits, and one for emergency powered circuits.
2. if the generator is not large enough for the entire load, the transfer switches will have to be capable of load shedding.
1. You will need 2 transfer switches - one for normal powered circuits, and one for emergency powered circuits.
2. if the generator is not large enough for the entire load, the transfer switches will have to be capable of load shedding.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
If I'm reading your post correctly, you have an exsisting generator for the emergency lighting, and adding a second generator to run the entire building. The second generator could be classified as an optional standby system, and would work with no problem feeding the line side of the emergency generator's transfer switch. The emergency generator can crank and transfer within the required time for emergency lighting, then re-transfer back after the normal time delay after the secondary generator has cranked and transfered. This relieves the requirements for the second generator to be tested as an emergency generator. This also simplifies the installation greatly, and if the second generator fails, the first generator takes over.
Pierre C Belarge
Senior Member
- Location
- Westchester County, New York
It would seem like the facility is adding a new generator, which will power the entire load.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
There is nothing wrong in having the original generator as a redundant system, would simplify the installation greatly.
- Status