Hello All,
I am working on a project where we are adding a new fire pump late into the design of a mixed-use building. An issue has come up regarding the service calculations and the RLC requirements for the fire pump. We currently have a 600A service pulled to the space and are being requested to upsize to 800A. I would appreciate some insight from other engineers, since I have gotten a lot of mixed opinions.
Project Information:
We are designing the main power service tap for a 7.5HP (34.6 FLA) 230V/1PH fire pump and plan to tap directly into our commercial CT cabinet. This would allow the fire pump to be metered without a dedicated service meter and ensure it remains powered independently of any main service disconnect.
Problem:
The code inspector has approved the CT tap but has informed us that the main service must be capable of carrying the locked-rotor current of the fire pump motor indefinitely per 695.3(A) and requested we add a minimum 208A (FLA x 600%) to the service size.
Argument:
To my understanding, we shouldn't size the service based on the RLC and the unrealistic expectation that the building would be running at 100% during an emergency fire situation. My assumption would be to size per the FLA and ignore the RLC for service calculation, but follow all other RLC requirements to compensate for inrush, so that the system does not trip before the fire pump can activate.
Our service is currently calculated at 520A, which includes the fire pump load at 43.25A (FLA * 125%). We are expected to add the RLC at 600% of the FLA, which would be a service load calculated at 684.75A (FLA * 125% removed for RLC) and would require an 800A service.
In NYC, high-rise buildings with fire pumps can exceed 150 HP and can have RLCs that would exceed 1000A, but I don't see 1000A being added to the service loads. There seem to be mixed opinions on the subject even on the forums.
My solution is to add a load-shed panel that would turn off the main mechanical units when the fire pump starts as to compensate for the RLC, but I still wanted other people's opinions on the subject.
I am working on a project where we are adding a new fire pump late into the design of a mixed-use building. An issue has come up regarding the service calculations and the RLC requirements for the fire pump. We currently have a 600A service pulled to the space and are being requested to upsize to 800A. I would appreciate some insight from other engineers, since I have gotten a lot of mixed opinions.
Project Information:
- General: Commercial/Residential 2FL building, 5000 Sqft
- Location: New Hope, PA
- Service size: One 600A utility pole that has been split into two services to feed a 200A residential and 400A commercial space.
- Code in effect: 2017 NEC
- Current Load on service per load calculations with fire pump (FLA * 125%): 520A
- Reason for fire pump: Well system and low PSI
We are designing the main power service tap for a 7.5HP (34.6 FLA) 230V/1PH fire pump and plan to tap directly into our commercial CT cabinet. This would allow the fire pump to be metered without a dedicated service meter and ensure it remains powered independently of any main service disconnect.
Problem:
The code inspector has approved the CT tap but has informed us that the main service must be capable of carrying the locked-rotor current of the fire pump motor indefinitely per 695.3(A) and requested we add a minimum 208A (FLA x 600%) to the service size.
Argument:
To my understanding, we shouldn't size the service based on the RLC and the unrealistic expectation that the building would be running at 100% during an emergency fire situation. My assumption would be to size per the FLA and ignore the RLC for service calculation, but follow all other RLC requirements to compensate for inrush, so that the system does not trip before the fire pump can activate.
Our service is currently calculated at 520A, which includes the fire pump load at 43.25A (FLA * 125%). We are expected to add the RLC at 600% of the FLA, which would be a service load calculated at 684.75A (FLA * 125% removed for RLC) and would require an 800A service.
In NYC, high-rise buildings with fire pumps can exceed 150 HP and can have RLCs that would exceed 1000A, but I don't see 1000A being added to the service loads. There seem to be mixed opinions on the subject even on the forums.
My solution is to add a load-shed panel that would turn off the main mechanical units when the fire pump starts as to compensate for the RLC, but I still wanted other people's opinions on the subject.