Coordination of Emergency system with small generators

[mshields]

I inherited a project (from an engineer who left the company) with a 25kW Generator used primarily to provide life safety lighting in a Cancer Treatment facility. The main breaker on the generator is appropriately 40Amps. As this is the next size up when you take the FLA times 1.25, this is the maximum it may be.

We've just received the results of the coordination study required by the CD's and they indicate that the Life Safety system does not coordinate to .01 (or even to .1 for that matter).

I don't think given that the main is 40amps, that there is anyway to coordinate that with the 20A branch breakers down stream. It strikes me that 40 is simply too small a size to get to .01 coordination with the down stream 20A breakers.

My questions are: 1. Do you agree that this is impossible. 2. Would it have been possible if I used a 40A fuse but even if I did, wouldn't I have to use fuses on the branch breakers. Other than European standard devices, are there any available.

3. If it is impossible to coordinate this, can the code be inforced. I'm being told that the engineer who designed this should have made the generator a standby generator with which he could have had optional standby lighting to suppliment emergency lighting. But the egree lighting would nevertheless need to be done with battery packs or an inverter. That seems like a poor design and one that is to the detriment of the end user who then has to worry about the maintenance of these things.

Thanks,

Mike

 

[chris kennedy]

We've just received the results of the coordination study required by the CD's and they indicate that the Life Safety system does not coordinate to .01 (or even to .1 for that matter).

I don't think given that the main is 40amps, that there is anyway to coordinate that with the 20A branch breakers down stream.

Excuse my ignorance here Mike but what type of 'coordination study' is this? Appears your not talking trip curves here.

 

[mshields]

Actually Chris we are talking about trip curves here. Although to achieve the .01 coordination, as you know, we have to rely on tested combinations by the vendor. But in this case, even forgetting about the .01 requirement for emergency systems, I'm not sure it's possible to coordinate a 20A breaker with a 40Amp breaker. The curves are too tight.

But again, even if you get past that, vendor has no listed combination between a 40A trip breaker and a 20A trip. I know that often times, going to larger frame albeit with the trip required, does the trip. But I'm told we don't even have that option here.