Back to basics

Helpful Hints

* Refer to this month's "HVACR Designer Tips" for the emergency generator system with cogeneration system application design review and startup checklist

* Refer to the 2004 ASHRAE Handbook--HVAC Systems and Equipment, Chapter 1, for an analytical process for determining the optimum system selection. For the next three months, "Back to Basics" will cover a 200kW emergency generator hospital installation supplemented with a 200kW cogeneration unit (August 2004 "Back to Basics"). The emergency power system distribution includes life safety systems, critical systems (e.g., health care systems), and noncritical systems (e.g., heating system).

* Refer to the IEEE Recommended Practice for Electrical Systems in Health Care Facilities (IEEE Std 602-1996) for a comprehensive overview of emergency generator planning and design.

* "Back to Basics" is focused on the HVAC system associated with an emergency generator application. For more specific questions regarding the electrical functional performance associated with these three months worth of tests, contact Tom Cooke, director of construction quality Helpful Hints-Design Phase

* Design engineers need to consider both combustion air requirements to the generator engine and ventilation air requirement for limited space heat gain within a generator room.

* If the generator room is located with an exterior wall to accommodate air intake and exhaust louvers, consideration should be given to the short-circuiting of warm-to-hot room. Termination point for engine exhaust is also a short circuit concern when locating air intakes (e.g., operable widows, ventilation louvers, etc.).

* When specifying exterior louvers, consideration should be given to sound attenuator louvers to limit the ambient noise leaving the generator room. For cogeneration equipment, which operates continuously, this type of louver treatment will most likely be mandatory, due to local regulations regarding noise impact on the surrounding neighborhood.

* If the generator room is located within the building and away from any exterior wall, consideration should be given to the air static resistance when sizing the makeup air fan, and it should be determined if the generator manufacturer's standard propeller exhaust fan can overcome exhaust duct air resistance.

* An alternative to large makeup air and exhaust air ducts serving a generator room within a building is to furnish and install a remote radiator to reduce duct sizes.

* For fuel oil/diesel emergency generators, consideration should be given to locating the storage tank indoors to avoid underground storage tank failure later in the life of the tank. Locating the tank indoors can avoid potential hazardous waste material contamination associated with underground fossil fuel tanks.

* Design engineers must comply with codes that dictate the criteria for designing an indoor storage tank as it pertains to rated wall construction, ventilation, and containment/dike wall construction.

Helpful Hints-Commissioning

* The commissioning team for this month's application should include the commissioning engineer, the owner's project manager and facility engineer, facility technicians responsible for operating and maintaining the equipment, the general contractor or construction manager's commissioning coordinator, the electrical trade contractor and HVAC trade contractor, and emergency generator manufacturer's representative(s). It shall be the responsibility of the contractor to demonstrate the emergency generator system performance to the owner and the commissioning engineer.