The simplified approach shall be an optional path for compliance where the following conditions are met:
- The building is not more than two stories in height.
- Gross floor area is less than 25 000 square feet (2322.6 m2).
- The HVAC system in the building is in accordance with the requirements listed in Section E503.3.1. [ASHRAE 90.1:6.3.1]
The HVAC system shall comply with the following criteria:
- The system serves a single HVAC zone.
- The equipment shall comply with the variable flow requirements of Section E503.5.6.2.
- Cooling (where any) shall be provided by a unitary packaged or split-system air conditioner that is either air-cooled or evaporatively cooled, with efficiency that is in accordance with the requirements shown in Table E503.7.1(1), Table E503.7.1(2), or Table E503.7.1(4) for the applicable equipment category.
- The system shall have an air economizer in accordance with Section E503.5 and Section E503.4.6.13.
- Heating (where any) shall be provided by a unitary packaged or split-system heat pump that is in accordance with the applicable efficiency requirements shown in Table E503.7.1(2) or Table E503.7.1(4), a fuel-fired furnace that is in accordance with the applicable efficiency requirements shown in Table E503.7.1(5), an electric resistance heater, or a baseboard system connected to a boiler that is in accordance with the applicable efficiency requirements shown in Table E503.7.1(6).
- The system shall comply with the exhaust air energy recovery requirements in accordance with Section E503.5.10.
- The system shall be controlled by a manual changeover or dual setpoint thermostat.
- Where a heat pump equipped with auxiliary internal
electric resistance heaters is installed, controls shall
be provided that prevent supplemental heater operation
where the heating load is capable of being met
by the heat pump alone during both steady-state
operation and setback recovery. Supplemental heater
operation shall be permitted during outdoor coil
defrost cycles. The heat pump shall be controlled in
accordance with one of the following:
- A digital or electronic thermostat designed for heat pump use that energizes auxiliary heat where the heat pump has insufficient capacity to maintain setpoint or to warm up the space at a sufficient rate.
- A multistage space thermostat and an outdoor
air thermostat wired to energize auxiliary heat
on the last stage of the space thermostat and
where outdoor air temperature is less than 40°F
Exceptions: Heat Pumps that comply with the following:
- Have a minimum efficiency regulated by NAECA.
- In accordance with the requirements shown in Table E503.7.1(2).
- Include all usage of internal electric resistance heating.
- The system controls shall not permit reheat or other form of simultaneous heating and cooling for humidity control.
- Systems serving spaces other than hotel or motel
guest rooms, and other than those requiring continuous
operation, which have both a cooling or heating
capacity more than 15 000 Btu/h (4.4 kW) and a
supply fan motor power more than 0.75 horsepower
(hp) (0.56 kW), shall be provided with a time clock
that is in accordance with the following:
- Can start and stop the system under different schedules for seven different day-types per week.
- Is capable of retaining programming and time setting during a loss of power for a period of not less than 10 hours.
- Includes an accessible manual override that allows temporary operation of the system for up to 2 hours.
- Is capable of and configured with temperature setback down to 55°F (13°C) during off hours.
- Is capable of and configured with temperature setup to 90°F (32°C) during off hours.
- Except for piping within manufacturer's units, HVAC piping shall be insulated in accordance with Table E503.7.3(1) and Table E503.7.3(2). Insulation exposed to weather shall be suitable for outdoor service (e.g., protected by aluminum, sheet metal, painted canvas, or plastic cover). Cellular foam insulation shall be protected as above or painted with a coating that is water retardant and provides shielding from solar radiation.
- Ductwork and plenums shall be insulated in accordance with Table E503.7.2 and shall be sealed in accordance with Section E503.4.7.2.
- Construction documents shall require a ducted system to be air balanced in accordance with industry-accepted procedures.
- Outdoor air intake and exhaust systems shall comply with Section E503.4.6.4 through Section E503.4.6.5.
- Where separate heating and cooling equipment serves the same temperature zone, thermostats shall be interlocked to prevent simultaneous heating and cooling.
- Systems with a design supply air capacity more than 10000 ft3/min (4.7195 m3/s) shall have optimum start controls.
- The system shall comply with the demand control ventilation requirements of Section E503.4.6.9 and the ventilation design requirements of Section E503.5.6.6.
- The system shall comply with the door switch requirements of Section E503.5.14. [ASHRAE 90.1:6.3.2]
Climate zones identified in this appendix shall be determined in accordance with ASHRAE 90.1. For locations in the United States and its territories, the assigned climate zone and, where required, the assigned climate zone letter shall be in accordance with ASHRAE 169.
Exception: Where recorded historical climatic data are available for a construction site, it is permitted to be used to determine compliance where approved by the Authority Having Jurisdiction. [ASHRAE 90.1:22.214.171.124]