Load Bank Testing for Parallel Genset with 3 ATS Branches

E

elecshop

Member
Location
FL, USA
Occupation
Electrical Engineer
I am trying to figure out the best docking station size to test two parallel gensets. This parallel genset feeds 3 ATS branches:
- optional standby/legally required (combined in one branch)
- emergency (NEC 700)
- critical (NEC 708)

I know that I will not need temp generator connection because the emergency and critical branches can both be supplied by only 1 of the 2 parallel generators.

My question is, if I plan for a docking station that load bank at least 30% of both generators' capacity combined (looking at them as 1 generator), to meet NFPA 110 8.4.2, will I be required to test the separate ATS branches too? Should I plan for load banking each branch separately? If not, I will be testing the generators only, not the ATS's. But I think NFPA 110 requires rotational testing of all ATS's in the EPSS monthly to ensure starting of each, etc. although I think this can be under no load condition.

Thank you!
 
ron said:
1st, I'm sorry to see that you are using Article 708, as that is generally not required by most AHJs for anything.
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NEC Article 708.6: Testing and Maintenance
(E) Testing Under Load. Means for testing all critical power systems during maximum anticipated load conditions shall be provided.

This is also treated like an emergency branch: 708.10(B) Wiring - sates that wiring from COPS source or source OCPD (i.e., the OCPD in the emergency switchboard powering the ATS for this branch) should be entirely separately and independent of all other wiring.
 
elecshop said:
NEC Article 708.6: Testing and Maintenance
(E) Testing Under Load. Means for testing all critical power systems during maximum anticipated load conditions shall be provided.

This is also treated like an emergency branch: 708.10(B) Wiring - sates that wiring from COPS source or source OCPD (i.e., the OCPD in the emergency switchboard powering the ATS for this branch) should be entirely separately and independent of all other wiring.
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Article 708 is only used when forced and classed by municipal, state, federal, or other codes by any governmental agency having jurisdiction or by facility engineering documentation establishing necessity for such a system. Look at Section 708.1

The requirements of 708 are very challenging and expensive, so no agency that I know of establishes the necessity for such a system. No building code, Electrical code, etc requires it, just someone that mandates it locally, usually because they don't realize the extra cost / headache.
 
ron said:
The requirements of 708 are very challenging and expensive, so no agency that I know of establishes the necessity for such a system. No building code, Electrical code, etc requires it, just someone that mandates it locally, usually because they don't realize the extra cost / headache.
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I have only dealt with one 708 project. It was for the 911 call center 'room' in a police station. I don't think the owner/engineer knew what that classification would result in.
 
ron said:
Article 708 is only used when forced and classed by municipal, state, federal, or other codes by any governmental agency having jurisdiction or by facility engineering documentation establishing necessity for such a system. Look at Section 708.1

The requirements of 708 are very challenging and expensive, so no agency that I know of establishes the necessity for such a system. No building code, Electrical code, etc requires it, just someone that mandates it locally, usually because they don't realize the extra cost / headache.
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I agree. Almost impossible to meet the requirements.
 
jim dungar said:
I have only dealt with one 708 project. It was for the 911 call center 'room' in a police station. I don't think the owner/engineer knew what that classification would result in.
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The 911 people may have directed compliance with NFPA 1221 Standard for the Installation, Maintenance, and Use of Emergency Services Communications Systems and that requires the power system to comply with Article 708 in the NEC.
 
don_resqcapt19 said:
The 911 people may have directed compliance with NFPA 1221 Standard for the Installation, Maintenance, and Use of Emergency Services Communications Systems and that requires the power system to comply with Article 708 in the NEC.
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I ran into this once and the client didn't understand that NFPA 1221 is a Standard and not a Code, which means compliance is "optional". They removed the requirement after I showed them what it entails, and as typical, the extra cost changed their mind.
 
The owner is a jail facility subject to local AHJ requirements and they have a 911 call center branch. I believe they do want the article 708 implemented, and they have the budget for that.
But anyhow, to test the parallel genset, would you recommend testing one or both? And how would you size the docking station? NFPA 110 8.4.2 requires 30% of standby generator rating for 30min for a monthly test. Also, will I be required to test the separate ATS branches too? Should I plan for load banking each branch separately? If not, I will be testing the generators only, not the ATS's.
 
Isn't load bank testing an issue for just the generators? Aren't the transfer switches tested monthly by a simple voltage loss test?

Is your entire facility subject to 708 or is it just the call center?
 
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