Weekday, Saturday, and Sunday hot water consumption values are determined using typical usage rates for a given use-area type, along with the number of occupants and occupancy schedule for each day type. Values are also adjusted according to such parameters as the presence or absence of showers and high efficiency fixtures.
During a month that has been identified as seasonally unoccupied (also referred to as non-operating), FEDS assumes zero occupancy, all lights are off (except exit signs), and the cooling system is shut down. Heating is operated at a reduced level generally for the purpose of preventing the pipes from freezing (temperature kept at low setpoint specified by the unoccupied season thermostat setting). General plug loads are assumed to be non-operational, as are most motors (although this may be overridden by specifying monthly motor load factors).
Unoccupied hours or day types of occupied months are those periods during which there is reduced occupancy of the building. These are referred to as low occupancy periods in FEDS. For a typical commercial facility this might occur during the night and on weekends. A small number of occupants might be present (though less than during normal operating hours), and all energy systems remain active although they may operate at reduced levels. The operation of HVAC, lighting, plug loads, and motors are all controlled by inputs such as thermostat setpoints (enabling temperature setback), ventilation control mode, and utilization/load factors.
Full 24-hour occupancy can be specified for any day type by entering the same start and end hours (except 0 and 2400). For unoccupied day types enter 0 for both start and end times (or leave them blank). Note: if you do not specify occupancy hours, they will remain blank and FEDS will model the buildings as though they are unoccupied (reduced occupancy). Shortcut buttons are available on the standard occupancy inputs screen to make specifying continuously occupied and unoccupied day types easier.
FEDS assumes circulating (or loop) hot water systems serve entire buildings. Specifying a loop system for use-area 1 automatically identifies that it also serves use-area 2. Loop systems that only serve use-area 2 cannot be modeled, and the loop selection box is unnecessary and is disabled.
Generally, it is best to specify the original purpose of the building as the building type, and then modify the use-area type to reflect its current use. Select building type = "Education", use-area type = "Office." The building's construction characteristics are inferred based on building type, while usage parameters (including occupancy, lighting and equipment use, and hot water demand) are based on the use-area type.
The inputs may be accessed within the operational and control technologies section of the ventilation inputs screen. A number of technology and control parameters are available for each. A two-position or continuously modulated damper is required for some of these options.
The air leakage into a building is determined from the inferred or user-specified infiltration rate. The infiltration rate is the amount of outside air entering the building during periods when the ventilation system is either not operating or not supplying outside air (i.e., times when building is not under a positive pressure).
Storage capacity for hot water is calculated using the building type and building's design occupancy. For distributed tank systems, values are rounded up to the next increment of typical tank capacity.
There is effectively no limit to the number of building sets allowed in a single case if there is enough hard drive space. Currently, each building set occupies approximately 4.3 megabytes of space across all file types. Given adequate storage space, FEDS can be—and has been—used to model an entire community, city, or utility service area.
There is no real limit to the number of buildings that can be modeled in a building set. However, building sets are designed to model buildings that share similar characteristics. The more similar buildings are within a given building set, the more accurate the results will be.
No. If a building (or use-area) has any hot water available users should specify 100% of it is served by hot water. As long as there is hot water available in a space, occupants will utilize it even if it is not immediately accessible. The purpose of having the portion served input is to allow the FEDS user to specify entire buildings (or use-areas) within a building set that do not have any hot water. For example, for a building set consisting of 10 buildings in which two of the buildings have no hot water service, they would enter that two buildings (or 20%) for the portion of buildings in this set that have no water heating.
Use the building type or use-area designation that best fits regardless of which list it is on. The building set classes were grouped this way to aid in the selection of common types, but either list may be selected.
Variable occupancy is an improved approach to the seasonal occupancy option which allows users to specify that certain months are non-operating (e.g., schools may be shut down over summer break). Variable occupancy also offers greater flexibility by allowing users to specify the percent of days within specific months which follow the general occupancy and operation schedule defined in the standard occupancy inputs. One hundred percent indicates the building or use area operates all days of that type during the month according the standard schedule. Zero percent indicates the building (use area) is either non-operating (shut down) or in a low occupancy state (occupied at the low occupancy and equipment use level) for all days of that type during the month. For any value between 0% and 100%, FEDS will multiply that value by the actual number of days of that type in the month and model the resulting number of days (rounded to the nearest whole day) as operating according to the standard schedule. The remainder of the days of that type in the month will be deemed either non-operating or at low occupancy (depending on the selection of non-operating period status type). As a convention, FEDS will model the first X days in the month as occupied and operating to the standard schedule, and the remaining days of that type in the month as non-operating or at low occupancy. The variable occupancy capability provides significant modeling flexibility and is particularly useful in modeling occupancy and building operation that varies within the course of a month, such as for National Guard or Reserve buildings that may only be heavily occupied on certain weekends through much of the year.
Another option for even greater control over building and use-area operation and occupancy (for each hour of the year) is also available. Contact FEDS Support for more information if interested in using this approach.
The ventilation end use inputs screen contains very basic information on the ventilation motors (total capacity and efficiency). The fan motors button simply enables a user to specify more detailed motor parameters by accessing the underlying fan motor inputs screen. From here, information, such as speed, enclosure type, voltage, vintage, and number of motors can be specified. It is important to realize that if any of this information has been entered, the fan motor inputs on the main ventilation screen will be inaccessible without first deleting the more detailed inputs.
For distributed tank systems, FEDS assumes commercial tanks are 80 gallons, while residential units are 50 gallons.
FEDS assumes loop (circulating) systems serve an entire building and, therefore, the number of tanks is inferred to be one for each building, regardless of the number of use areas present.
No. All occupancy hours must be specified by the user. Failing to do so will indicate to the model that the building is operating in the unoccupied mode each day during the week.