Frequently Asked Questions
Weather Data | Prototype Building / Geometry | Occupancy | Lighting
Heating/Cooling | Ventilation | Service Hot Water | Miscellaneous Equipment
Motors | Economic Analysis | Reports
Using FEDS
How much hard disk space is required to install and use FEDS?
Installing FEDS will require approximately 15 MB of hard disk space. It is also important to have enough free disk space for case files. We recommend another 10-30 MB for this depending on the number of case files you will have.
Can FEDS run on/from a network?
FEDS can be run on a machine that is connected to a network. In some circumstances FEDS can even be run remotely from a network computer. However, because each network is different and interference is possible, for the best performance (and fewest hassles) it is recommended that FEDS be run from a non-networked computer.
How long does a FEDS run take?
FEDS 5.0 takes considerably less time to run than previous versions. The four building set Sample-2 case that comes with FEDS took 9 minutes for full optimization on a 600 MHz Pentium III (5 times faster than under FEDS 4.1 on the same computer). On a 1.4 GHz Pentium IV, it took just 5 minutes to complete optimization (a full 10 times faster than FEDS 4.1). However, completion time on your computer will vary based both on machine and on complexity of the case you are running (number of use areas and technologies).
TIP: Disable any sleep modes that are active on your computer (except for screen savers) when running FEDS. Energy saving features of newer computers that shut down the processor after sensing no input from the keyboard or mouse for a specified time will halt execution of a FEDS run.
Can I work on other applications when FEDS is running?
Yes, FEDS will run in the background to enable you to use your computer for other applications during that time. This will typically have no adverse impact on FEDS unless there are so many applications (or processor intensive applications) running that FEDS must compete for system resources. In this case, the run time of FEDS may be extended slightly.
How do I check the reasonableness of my inputs and FEDS model before I commit to a full FEDS run?
The best way to check the accuracy of the model you've developed is to run FEDS without optimization and compare the annual consumption estimated by FEDS to actual metered data. To do this, go to the Exclude Building Sets from Optimization screen under the Advanced Options. Make sure the 'Pick Building Sets' method is selected then press the 'Select All' button on the left side of the screen (under the list of building sets). After saving, go back and Run FEDS. This will only take on the order of a matter of seconds to a couple minutes for FEDS to run the baseline load and consumption calculations for the buildings. Once complete, generate the *.txs report for the case and check the following data:
- General case and building inputs on the first five pages (for any obvious input errors)
- Energy consumption data by fuel type (page 7)
- Electric peak demand value and time of occurrence (page 8)
- Annual energy consumption by fuel type and end use (page 10)
Do not expect these to be identical to the metered data - this is a model representation of your buildings and even if extremely precise, will vary due to discrepancies such as actual vs. average weather, human behavior, etc. Therefore, achieving consumption values from FEDS that are within 10-15% of actual values are considered quite good.
How many {casename}.* files are generated for a single case?
When a case is created there are 10 basic files associated with it (these are listed in Section 1 of the FEDS User's Guide). These are the files necessary for FEDS to run. In addition, during the optimization process another nine files are generated, and up to four output reports are available, for a total of 20-23 files per case.
What do the different icons mean next to the FEDS inputs?
There are a couple of new icons that appear next to the input cells as of release 5.0. The blue arrows indicate inputs that belong to the minimum set and are required for FEDS to run. If any of these cells do not have a value provided FEDS will not be able to run and will alert you to this either upon saving a screen or updating inferences. Once a valid value has been provided for the input and saved, the blue arrow will disappear.
The lock symbol that appears next to many of the input cells indicates that the value is inferable by FEDS and do not require an input. These are the parameters that are hidden at Minimum Set display and become accessible once Maximum Detail display is selected. An open lock icon means that the value is not locked and may be changed by FEDS when inferences are updated. The closed lock symbol represents inputs whose value is locked and protected from being changed when inferences are updated. A user may lock a value by either entering a value into one of these cells, or by clicking on an open lock symbol to lock the value that is currently present in the cell.
Input cells that do not have an icon next to them are for values that are not absolutely required for FEDS to run, but are highly recommended. Such values as the fuel price data and occupancy hours are extremely important (yet a value may not be required for each fuel or day type). Others, such as the energy consumption inputs and building/technology identifications, are not used by FEDS except for reporting and aiding the user in understanding the output.
What does 'MBtu' represent in FEDS?
In FEDS MBtu signifies Million British Thermal Units. Throughout the program, the 'M' prefix represents million or 106 (MW, MBtu), while 'k' represents thousand or 103 (kWh, kBtu).
FEDS (or my computer) just crashed and upon restarting it is acting "flaky" or unstable - what do I do?
Sometimes when the system or software crashes, certain files are locked in the system's memory which can sometimes cause strange or unstable behavior upon restarting. If this occurs, try quitting FEDS and restarting again. When closed properly, FEDS will tidy up the system resources it is using and work properly the next time it is run.
Inferences (General)
What are inferences and how do they work?
FEDS contains a built-in database of building survey data and is able infer a number of building parameters based on the small set of required (minimum set) inputs provided by the user. For example, FEDS uses information such as building type, location, floor area, and vintage to determine the most likely construction type and geometry. It uses similar information along with heating fuel type and cooling equipment to determine the most likely heating technology and ventilation system parameters for a building. All inferences are there to enable a user to model buildings without having intimate knowledge of the detailed engineering parameters. The resulting building prototype parameter values are statistically the most likely values based on the limited set of information provided. Of course, all inferred data may be easily overwritten by simply entering (locking) a value in the user interface screens.
What are the sources for the inferred data?
FEDS draws upon a number of sources to determine inferable parameter values. Major sources include national building energy consumption surveys such as the Nonresidential Buildings Energy Consumption Survey (NBECS), Commercial Buildings Energy Consumption and Expenditures (CBECS), and Housing Characteristics, large end-use studies such as the End-Use Load and Consumer Assessment Program (ELCAP), ASHRAE Handbooks, building and equipment codes and standards, and manufacturers' data.
What does 'Locking' mean?
A locked value, in terms of FEDS inputs, is one that the user has entered for an inferable parameter. This indicates to the model that this is a user-entered value and should not be updated (inferred). Clicking on the lock symbol can also lock a currently inferred value. When a value is locked, the lock icon will appear as a latched or closed lock. To unlock a value, simply click the icon again, changing it to an open or unlatched lock. This value will now be inferred the next time inferences are run.
For a building built in 1820 will FEDS infer parameters for its original, as-built condition?
No - FEDS infers parameters based on the most likely current condition of a building and it's equipment. Inferences for an 1820 vintage building will reflect the typical improvements and upgrades that have occurred over time.
How does FEDS infer the remaining life of a piece of equipment?
If the building is newer than the rated life of the equipment in question, then the remaining life is equal to the difference of rated life and building age. If the building is older than the equipment's rated life, FEDS assumes that on average, equipment will be halfway through their life. Rated lives vary by equipment technology - some examples of rated lives used in FEDS are:
- Envelope components (windows, insulation, etc.) - 40 years
- Lights - typically 25 years (although the cost of replacing lamps and ballasts is figured into the analysis based on specific replacement intervals and hours of operation)
- Boilers - 40 years
- Furnaces - 20 years
- Chillers - 20 years
- Package Units - 15 years
- Heat Pumps - Air Source/15 years, Ground-Coupled/20 years
- Motors - 15 years
- Hot Water Heaters - Electric/12 years, Gas/10 years, Distributed Heat Pump/12 years, Central Heat Pump/15 years
Building Sets
How many building sets can I have in a case?
The only limit to the number of building sets that you may have in a single case depends on the amount of hard drive space your computer has available. Currently, each building set occupies approximately 60 kilobytes, so 10 megabytes of space could hold a case with 160 building sets.
How many buildings can I have in a building set?
There is no real limit to the number of buildings you can model in a building set, although at absurdly high numbers (> 1x108) some computational errors/peculiarities may result.
What do I do if I have a Civilian building, but the building type is best described by a type under the FEDS Military Building Set Class?
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 you may select from either list.
How do I model a building used as an office that was constructed as a school?
Generally, it is best to specify the original purpose of the building as the building type, and 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 hot water parameters) are based on the use-area type.
What are the Special building classes?
The 'Special' building are designed to allow the user greater ease and flexibility in modeling certain unique buildings or systems. Currently there are only two types of special buildings - "commissary-sales" and "commissary-warehouse." If these building types are selected, FEDS will set up the use-areas for typical commissaries and will enable detailed modeling of refrigerated cases. Input screens will appear and baseline consumptions will be calculated and incorporated with the rest of the building loads, but no retrofits will be considered for the refrigeration systems at this time. For more information, refer to Appendix E of the FEDS User's Guide.
Fuel Types & Energy Prices
Will FEDS provide default energy prices based on my location?
No - there are no default or inferred electric or non-electric fuel price data. Make sure that you enter the value of all fuels available to your buildings!
Do I need to input prices for all fuel types, or only those used in the buildings being modeled?
Prices must be provided for all fuels being used in the buildings being modeled. In addition, prices may also be provided for fuels not currently being used if you would like FEDS to consider those fuels in its economic calculations (e.g., to consider fuel-switching opportunities).
TIP - watch units required for fuel price parameters! Electric energy prices are requested in ¢/kWh while demand charges are in $/kW.
What is meant by 'Marginal' price?
A marginal price is the price you pay for the last increment of energy purchased. For example, if you have a block electric rate structure, and pay a certain amount depending on how much electricity you use during the month, then the value of electricity you would input would be the price corresponding to the amount the building generally consumes in a month. Another way to look at it is that the marginal rate is the value of a unit of energy saved (i.e., the value of a kWh saved by an efficiency measure).
What is a demand ratchet?
A demand ratchet is a billing method commonly imposed by electric utilities on large commercial or industrial customers. It specifies that the billed demand level in kW be the larger of the actual peak demand for the billing period, or a percentage of the highest peak reached during the previous X months. A typical demand ratchet uses 80% of the peak demand occurring during the previous 11 months as the comparison point. Under this scenario, if your facility experiences a peak demand of 1000 kW for one hour (or 15 minute period) you will be billed for a minimum of 800 kW during the next 11 months, even if your actual demand is much lower. Demand ratchets are generally used by utilities to reduce the risks of serving certain types of customers who have potentially large swings in demand during the year - it makes them pay for the luxury of having the high capacity available when needed.
Where do I value a self-generated fuel and how do I specify it's price in FEDS?
Fuels are valued in FEDS at the building or end-use. However, the value for district fuels (self-generated or purchased steam/hot water) are entered as the generation cost or value at the boundary of the installation. These costs should account for the value of the source fuel being burned, the efficiency of the boiler or chiller plant, as well as other items such as chemicals and labor required to keep the plant operating. Distribution losses (for steam and hot water systems) between the central plant or installation boundary and the building can be significant and must be accounted for in the actual fuel valuation at the point of use. FEDS assumes an average loop loss value of 1/3 and thus automatically adjusts the price entered for these fuels by a factor of 1.5 [price / (1 - 1/3)] to account for this. Hence it is important to enter the value of district steam or hot water on the Non-Electric Energy Price Inputs screen as the value of the energy at the plant or installation boundary.
What is the difference between distillate and residual oil?
Distillate oil is light fuel oil that has been further refined than heavier oils. Examples include #2 fuel oil and diesel fuel. Residual oil, as its name suggests, is the oil residue that remains after distilling out the lighter grade oils. It is generally designated as #4, #5, or #6 fuel oil, is much more viscous than ordinary oils, and must be heated to allow it to flow and be burned.
What does the 'Other' fuel type represent?
Typically, the 'Other' fuel type represents LPG or Propane fuel. However, if you use another fuel type (i.e., wood chips) that is not listed, you may use 'Other' to represent this fuel type.
Weather Data
What type of weather data does FEDS use?
FEDS contains 218 stations of Typical Meteorological Year (TMY) data and 12 Weather Year for Energy Calculations (WYEC) stations. From this data it derives such information as heating and cooling design day, hourly temperature profiles for hot day, cold day, and average day for each month, plus hourly clearness and humidity profiles.
My city is not listed as a weather station. What do I do?
Choose a weather station that most closely represents the weather at your location. Most times it will be a city in the same state as you, but can be in a neighboring state, or in some instances in another region altogether.
What if I'm modeling buildings in Japan?
Again, choose a weather station from the list that most closely represents the weather at the location of the buildings you are modeling. In this case select a weather station that has similar weather patterns to that particular region of Japan. Characteristics to consider for selecting an appropriate weather station include minimum, maximum, and average temperatures, insolation, elevation, latitude, and proximity to features such as mountains and oceans that can impact weather.
Can I enter my own weather data?
No - at this time FEDS does not allow users to input specific weather data.
Prototype Building / Geometry
What does the FEDS prototype building look like?
Prototype buildings in FEDS are modeled as basic rectangles, with the actual geometry calculated based on the total floor area, number of floors, floor-to-floor height, and aspect ratio.
What is the Aspect Ratio?
The aspect ratio is used to define the geometric orientation of the buildings in a building set. It is a ratio of length to width, and is calculated by dividing the typical north-facing length by the typical east-facing length.
What is Solar Normalization?
Solar normalization is used when the orientation of a single building is unknown, does not align with N/S/E/W directions, or when there are multiple building of differing orientations in a building set. It can be used to avoid biasing the solar gains calculation by normalizing the exterior wall, window, and roof areas, such that the resultant loads are roughly the average of two buildings; one with an east/west orientation and one with a north/south orientation. To use solar normalization, set it to ignore facing directions.
What are 'Linked Building Sets'?
Linking two distinct building sets together allows greater flexibility in modeling complex building geometries, or uses. The linking of buildings was designed to model two buildings that share a common wall, or are stacked on top of one another. Specifying that the buildings are linked directs FEDS to automatically (based on the geometry information for each building) determine the wall area (or roof/ceiling area) that is shared and hence not exposed to ambient conditions. It essentially calculates the portion of each buildings shell that is a adiabatic surface (i.e., does not experience conductive heat transfer) and does not receive solar gains. It uses this information in the loads calculations to appropriately account for the impact of the buildings being connected. There are some rules, however, that must be satisfied in order to link building sets. First, both sets must contain the same number of buildings so that a direct one-to-one linking is achieved. Second, both sets must have the solar normalization turned off (calculate solar gains by facing direction). Also, FEDS currently does not model cantilevered buildings so for top/bottom linkings, the N/S and E/W lengths of the top building must not be greater than the corresponding lengths of the bottom building.
Occupancy
Will FEDS provide default occupancy hours based on building or use-area type?
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.
How can I specify a 24-hour occupancy schedule? An unoccupied day type?
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).
How are unoccupied periods (of occupied months) modeled?
Unoccupied hours or day types of occupied months are those periods during which there is reduced occupancy of the building. 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.
How are seasonally unoccupied months modeled?
During a month that has been identified as seasonally unoccupied, FEDS assumes that not only are there no occupants, but 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 you may override this by specifying monthly motor load factors).
Lighting
How do I decipher the lighting technology configuration?
Refer to Appendix G of the FEDS User's Guide. Ex: FL 2x4 4F40T12 STD2 = a 2 foot by 4 foot fluorescent fixture, with four 40 watt T12 (1.5 inch diameter) lamps, operated by 2 standard magnetic ballasts (designed to operate two lamps each).
What is the use-area fixture density?
The lighting use-area fixture density is the inferred fixtures per square foot are based on ELCAP lumen levels for different use-area types. It represents the average fixtures per square foot over the entire use-area (or building for single use-area buildings). Typically, the user will know the total number of fixtures in a use-area and can enter this and allow the software to calculate the fixtures per square foot.
What do the utilization factors represent?
The utilization factors for lighting represent the portion of time that the particular lights are on, on average over the building set. They are expressed as a fraction of the maximum possible load (i.e., 100% of the lights are on 100% of the time) for a given time period. FEDS infers the occupied and unoccupied period utilization factors based on lighting technology and use-area type. FEDS typically assumes that some lights are on even during unoccupied times for security, safety, or janitorial staff, or simply because lights were left on. During seasonally unoccupied months, utilization factors are set to 0 for all lighting records except for exit lights, which are assumed to operate constantly.
Will FEDS correct for under/over lit conditions when considering retrofits?
No, at this time FEDS considers only fixture per fixture replacements that provide similar light output. However, the energy impact of correcting an over/under lit condition could be analyzed comparing by two consecutive FEDS baseline runs (by running without optimization)
How are lamp failures and replacement requirements handled in FEDS?
Each lamp and ballast modeled within FEDS has a rated life (specified in hours) associated with it. Actual replacement intervals are calculated within the model based on the light's actual operating hours (based on utilization factors and occupancy schedules) and rated life of each component. When a lamp or ballast fails, FEDS accounts for the cost to replace the component by figuring both materials and labor requirements. These costs are tallied over the economic study period as the "non-annual maintenance cost." FEDS uses the non-annual maintenance cost along with energy and capital costs in determining which fixture can best provide the required level of service at the lowest life-cycle cost.
How can I model exterior lights?
Exterior lighting such as security or parking lot lights can be included in FEDS as a regular lighting record by setting the heat-to-space input to 0. It is also important to change the utilization factors to appropriate values (to specify mostly nighttime operation). Exterior lights can either be included as a lighting record in an existing building set or can be modeled separately in an "Exterior Lighting" building set that has no other equipment specified.
Does FEDS consider lighting occupancy sensors?
No, FEDS does not currently directly model occupancy sensors for controlling lights nor consider them as retrofit technologies. However, the savings potential associated with equipping a space with such devices can be estimated by comparing two consecutive FEDS baseline (no optimization) runs. First, run your current case as is to determine the actual baseline energy consumption and cost. Then (you may want to copy the case first), for the lighting records that would be controlled by an occupancy sensor, adjust the utilization factors (both occupied and unoccupied values) according to the estimated reduction in operating time for those lights. This should be determined after careful consideration to the use of the space as such sensors only save when people aren't in the space being controlled. Typically, they will drop the unoccupied utilization to zero. Once the utilization rates have been changed, run this case without optimization and (as long as nothing else was changed) comparing the consumptions and costs from the *.txs reports will give you the expected savings. Comparing these results against the expected cost to install the sensors will tell you whether or not it's a good idea.
Heating/Cooling
What is the thermostat dead band?
The "Thermostat dead band" for heating represents the range of temperatures below the set point at which the thermostat does not call for heat. For example, at a 70 degree set point and a 2 degree dead band, the temperature will drop to 68 degrees before heating is activated, raising the temperature back to 70. It may also be referred to as the throttling range or differential. It operates similarly for cooling, allowing the temperature to rise a number of degrees equal to the dead band before cooling is activated.
How do I model a building with multiple heating or cooling technologies?
FEDS is designed to model buildings with single, homogeneous heating and cooling technologies within each individual building. The "Portion of building set served" inputs are available to specify whole buildings within a building set that are served by a given technology. If your building has more than one type of heating or cooling technology, there are a couple of options. If the majority of service is provided by one system you might simply model that one as if it were the only system serving the building. If the occupants use portable space heaters you could account for the energy consumed and heating service provided by representing them as a miscellaneous equipment record. If, on the other hand, one system does not dominate, it would be best to model the building as a pair of linked buildings, with one technology serving each portion. Or, if a major renovation is being contemplated, you might wish to model the building once as if it were served by one technology, and once by the other. Optimizing each case separately, the results will provide insights into which system type would be best for the building.
What does "tech ventilation linking scenario for percent served by heat tech [2] does not match preceding techs" mean?
This is an error message that comes up when there are incompatible heating or cooling systems defined in a building set. This can occur when you try to model one building with linked heating (requiring a fan) with one served by an unlinked heating system (no fan required - such as a radiator or baseboard system) together in the same building set. The situation can be remedied by separating the buildings into distinct building sets. For more information about allowable HVAC combinations, refer to Appendix I of the FEDS User's Guide.
What is meant by 'linked' and 'unlinked' heating and cooling?
Linked: the heating and/or cooling coil is integrated with the ventilation system, employing air as the distribution fluid (air handler, fan coil, packaged unit, furnace, etc.)
Unlinked: the ventilation system is separate from the heating coil, such as for a radiator or baseboard electric heat.
Currently, FEDS assumes that all cooling is linked, with the exception of evaporative coolers, which are assigned a separate, special ventilation scenario. For more detailed information see Section 2.8.6 of the FEDS User's Guide.
If my building is heated by steam from a boiler which fuel type / equipment type combination do I select?
If the boiler serves only that building, select single building boiler as the equipment type and the fuel type that fires the boiler (natural gas, distillate oil, etc.). If the steam is piped in from a central boiler plant or purchased from offsite, select either the self-generated or purchased steam as the fuel type and specify the equipment type as either a radiator, fan coil, or air handling unit using central steam or hot water (in-building equipment is a heat exchanger).
What is a 'Heat/Cool Pair'?
The heat/cool pair is a concept added to FEDS with the advent of considering heat pumps as replacements to conventional heating and cooling technologies. A heat/cool pair identifies to the model which heat and cool technologies jointly serve a particular building or group of buildings in the building set, and may be considered for joint replacement by a heat pump technology. In order to consider heat pumps or any other integrated heating and cooling technology as replacements for existing heating and cooling technologies, the heat/cool pairs must be defined. Baseline heat pump records are automatically paired (as long as their fuel type, equipment type, number of units, and vintages match) upon updating inferences, while all non-heat pump technologies must be paired manually.
What is the difference between a 'Separate' and 'Integrated' heat/cool pair?
A separate heat/cool pair is a pair of heating and cooling technologies that are completely separate units yet serve the same area/building (i.e., a furnace and separate package unit, or a boiler and a chiller). An integrated heat/cool pair is one in which the heating and cooling sources are packaged together in the same unit (e.g., a packaged cooling unit with integral gas burner or 'gas-pack' system). Identifying a heat/cool pair as 'integrated' tells FEDS that individual heating and cooling replacements cannot be considered as a direct replacement.
What is a dual-fuel heat pump?
A dual-fuel heat pump is an electric air-source heat pump that uses another fuel source (natural gas, LPG, oil) for the auxiliary or backup heat (instead of electric resistance coils). It can be accomplished within a single integrated unit, or pieced together by mating a standard air source heat pump with a furnace via a controller. The controller determines which unit to operate based on outside temperature, efficiencies, and relative cost of fuels.
What is the difference between a 'Separate' and 'Integrated' dual-fuel heat pump?
Similar to the Separate vs. Integrated discussion for heat/cool pairs, a separate backup source for a dual-fuel heat pump indicates that there is a separate furnace that is connected to the heat pump via a controller. A dual-fuel heat pump with integrated backup is a heat pump unit with a built-in gas or LPG auxiliary heat source. For modeling purposes, the only real difference is that FEDS will consider replacing the individual components (heat pump or backup furnace) of a separate dual-fuel heat pump in addition to replacing the entire system.
What is the crossover temperature of a dual-fuel heat pump?
The crossover temperature is the outdoor air temperature at which a dual-fuel heat pump switches operation from the heat pump to the backup technology. This is typically the control methodology for these systems and can be entered or determined by FEDS. FEDS will calculate the optimal crossover temperature based on electric and backup fuel prices, heat pump performance and capacity vs. temperature, and furnace efficiency.
Ventilation
How does FEDS calculate building air leakage?
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 not under a positive pressure).
What is the 'Fan Motors' button for?
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, such information as speed, enclosure type, voltage, vintage, and number of motors can be specified. However, 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.
How do I specify parameters for a desiccant dehumidification system?
The desiccant dehumidification inputs may be accessed only when the ventilation control mode is set to constant operation. Parameters available include fuel type used for regeneration, outdoor and return air fractions passing through the unit, humidistat setpoint, and regeneration and motor efficiencies.
Service Hot Water
If a building only has hot water in a pair of restrooms that comprise 4% of the total building floor area, do I specify that 96% of the building is not served by hot water?
No - if a building (or use-area) has any hot water available you should specify that 100% of it is served by hot water. The reason is that 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' inputs 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 2 of the buildings have no hot water service, you would enter that 2 buildings (or 20%) for the "Portion of Buildings in this Set that have No Water Heating".
How are hot water consumption values calculated?
Weekday, Saturday, and Sunday hot water consumption values are determined based on 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 the such parameters as the presence or absence of showers.
How is hot water storage capacity calculated
Storage capacity for hot water is calculated based on the building type and building's design occupancy. For distributed tank systems, values are then rounded up to the next increment of typical tank capacity.
What tank capacity does FEDS use?
For distributed tank systems, FEDS assumes that commercial tanks are 80 gallons, while residential units are 50 gallons.
FEDS assumes that 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.
How come I cannot specify a loop system in use-area 2?
FEDS assumes that circulating (or loop) hot water systems serve an entire buildings. Specifying a loop system for use-area 1 automatically identifies that it also serves use-area 2. You cannot model a loop system that only serves use-area 2 and therefore, the loop selection box is unnecessary and is greyed out.
Miscellaneous Equipment
Do I have to specify plug load levels for my buildings?
Normal/typical plug loads are accounted for (inferred) automatically within FEDS. These values can be viewed and/or changed from the Miscellaneous Equipment inputs in maximum detail display. The data is based on major end-use load surveys for typical plug load levels and accounts for the typical levels of equipment loads in a given use-area type. For example, for an office building this will account for typical levels of such things as computers, copiers, fax machines, clocks, vending machines, and kitchenette equipment.
When would I want to modify or enter miscellaneous equipment records?
The typical FEDS user will not have detailed information available regarding plug load levels in order to adequately model them and will need to rely on the inferred values. However, you may want to modify or add new miscellaneous equipment records if you have a load that is unusual or atypical of the use-area type or have an extremely large load (or one that sees extensive use) that is above and beyond what would be considered typical.
What if a piece of equipment is a cooling device with its condenser located outside the building?
FEDS will allow you to enter a negative value for "Percentage of heat to the conditioned space." For example, if the equipment has a COP of 2.0 and operates with an exterior condenser, then you should enter -200 for this value. (Heat in the amount equivalent to 200% of the unit's capacity is rejected outside.)
Otherwise, if the building is a supermarket or commissary type of building containing refrigerated cases you may wish to select one of the Special commissary building types and model the cases and compressor racks in greater detail. For more information on this refer to the discussion of the Special Building Types in Appendix E of the FEDS User's Guide.
Motors
Where does FEDS get its motor data?
Motor inference data and an extensive list of replacement motors (including performance and cost data) have been compiled from the MotorMaster+ 3.0 software's database of over 18,000 three-phase motors. MotorMaster+ was developed under the U.S. Department of Energy's Motor Challenge Program by the Washington State University Cooperative Extension Energy Program.
Do the motors in the FEDS retrofit database comply with EPAct motor efficiency standards?
Yes. All motors in the FEDS retrofit database meet current applicable EPAct efficiency standards that vary depending on such parameters as motor horsepower, enclosure type, and speed.
What is a 'Combined Utilization and Load Factor'?
The utilization factor represents the percentage of time during a particular period that the motor is operating. The load factor indicates the typical operating output of the motor as a percentage of rated output. For example, a 10-horsepower motor driving a 6-horsepower load and operating 50% of the time would have a load factor of 60% and a combined utilization/load factor of 30%.
FEDS allows the user to specify this information separately for occupied and unoccupied hours, either constant over the year or varying from month to month. FEDS uses these values to calculate the hours of operation and hence the consumption and demand implications of each motor record. FEDS also calculates the heat output of the motors and its impact on the HVAC system.
What is meant by the 'required motor capacity'?
Many motors in use today are oversized for the load they are driving, and some grossly oversized. In such situations, the motor is driving a load equal to only a fraction of its rated capacity, and if too low the operating efficiency of the motor may suffer. Most importantly, when it's time to replace the motor, purchasing a motor with far excess capacity for its load will cost much more than a properly sized motor. Why spend more than necessary for the same (or even worse) level of service? FEDS understands that many motors may be over- (or under-) sized and allows the user to specify the required capacity of a motor. FEDS will use the required capacity in order to select a replacement motor of the proper size, and base its performance and cost calculations accordingly.
If I run my motors through FEDS, do I need the MotorMaster+ software?
While FEDS models motor energy use, demand, and interactions with the HVAC system quite well, it is not a substitute for the MotorMaster+ software. MotorMaster+ contains extensive motor management and analysis capabilities that are found in no other software program. FEDS recommends general categories and performance levels of motors based on what is currently available but does not specify particular manufacturers or special features. It is recommended that results of motor analyses from FEDS be used in MotorMaster+ to further refine and specify motor purchase requirements.
For example, the effect of cube law loads on fan motors can have a significant impact in degrading the efficiency of an energy-efficient motor if it has less slip than the original motor. While it is true that many energy-efficient motors run faster than their standard efficiency counterparts, there are typically energy-efficient motors available with a full-load rpm equivalent to that of the motor it is replacing. FEDS does not account for the effect of speed on energy consumption in centrifugal loads but assumes that the user can find a motor with an equivalent slip as their current motor. MotorMaster+ is an invaluable tool to help users assess the impact of speed on energy consumption and finding the right motor for a given application.
Economic Analysis
What does the 'Installed Capital Cost' include?
FEDS project costs include any materials, taxes, and labor costs that are applicable for a given retrofit measure. Additionally, a 15% contractor overhead is applied, along with any multipliers specified on the "Alter Cost Data" screen of the Advanced Options.
What does the 'Non-Annual Maintenance Cost' represent?
The non-annual maintenance cost is used by FEDS to account for costs recurring on a non-annual basis, such as incremental equipment replacements and replacing failed lamps and ballasts. For example, the present value of the non-annual maintenance cost for lighting represents the present value of the total cost (including materials and labor) to replace the burned out lamps and ballasts of a particular lighting technology over the course of the study period (generally 25 years).
What economic methodology does FEDS use?
FEDS employs the same standard life-cycle costing methodology and algorithms as the Basic Life-Cycle Costing (BLCC) computer model.
What is the 'Discount Rate'?
The discount rate is the factor used to adjust (discount) future sums of money into the equivalent current year dollar amount. It can also be thought of as the interest rate or hurdle rate (i.e., the rate of return required by a company for it to undertake a project). FEDS uses the real discount rate, which has the effect of inflation removed. FEDS provides the current Federal real discount rate as the default, but the user may enter any discount rate appropriate for their projects. Energy service companies performing shared energy savings contracts typically require real rates of return in the neighborhood of 15 to 20%.
Where does the cost data come from that is used in FEDS?
The cost data is drawn from a variety of sources including standard cost estimating manuals, manufacturers, and distributors.
When would I use an End-Use or Technology Multiplier?
FEDS project costs are based on industry averages and will not match the exact costs you will be charged. The end-use and technology multipliers are intended to enable the user to adjust for these discrepancies so that the costs used in the FEDS analyses are as close to actual as possible. The recommended approach (after satisfying yourself that you've modeled the building energy systems accurately) would be to first enter any known cost data (such as labor rates, tax rate, discount rate, etc.). Then run FEDS, generate reports, and see what types of projects are coming up. Compare the project costs to actual known costs or bids for similar projects of that type. If any of the technology costs are grossly high or low, adjust them appropriately with a technology multiplier. Rerun FEDS to 1) see if the same technology is being selected, and 2) make sure that the costs more closely represent what you would have to pay to complete the project. Because of the complex nature of the FEDS cost data this iterative multiplier approach is the best way for users to modify project costs.
What is the Global Cost Multiplier?
The Global Cost Multiplier is an overall cost multiplier applied to the total project cost (including all materials, labor, taxes, overhead). It can be used to adjust the total project costs (all of them) used in FEDS economic calculations. This could be used for such purposes as to account for special cost-impacting requirements of working at a facility with stringent security requirements or health and safety risks, or to assess the impact of varying costs on project economics.
Reports
What is the best way to format the *.txs or *.txd reports in my word processor?
In order for all of the information to be aligned properly and not wrap to the next line, it is recommended to select an 8 pt. non-proportional font (e.g., Courier New), and ½ inch left/right margins.
Do the dollar amounts displayed for electricity on the *.txs report include demand (kW) charges, or only the energy (kWh) charges?
On the *.txs report, the Electricity Dollar values listed under the "Annual Installation Energy Use by Fuel Type" and "Annual Energy Use by Building Set and Fuel Type" pages include both energy and demand charges. To determine how much of that total cost is attributable to the energy vs. demand, the demand component (reported on the following page) may be subtracted from this total value.
How are the air pollution emissions calculated?
Emissions factors are used which relate a quantity of pollutant emitted (e.g., tons of CO2) per unit of fuel burned. There are factors for each of the six pollutant types corresponding to each main fuel type. To estimate emissions, FEDS multiplies the consumption value for each fuel type by the appropriate emission factor. The emissions factors for certain fuel types, such as electricity, can vary significantly depending on such factors as plant type (coal, gas, nuclear, hydro) and source fuel composition (e.g., sulfur content) such that state average values are used. For more details refer to Appendix L of the FEDS User's Guide, containing the original paper from which the emissions data were derived.
What does it mean when it says the "* These dollar values reflect the value of distribution system losses" on the *.txs report?
Fuels are valued in FEDS at the building or end-use. However, the value for district fuels (self-generated or purchased steam/hot water) are entered as the generation cost or value at the boundary of the installation. Distribution losses between the central plant or installation boundary and the building can be significant and must be accounted for in the actual fuel valuation at the point of use. FEDS assumes an average loop loss value of 1/3 and thus adjusts the price entered for these fuels by a factor of 1.5 (price / [1 - 1/3)] to account for this. Hence it is important to enter the value of district steam or hot water on the Non-Electric Energy Price Inputs screen as the value of the energy at the plant or installation boundary.
Why is the "Installed Cost" different than the "Installed Capital Cost" on the *.txd report?
The Installed Capital Cost listed at the very bottom of the *.txd report represents the actual total cost including materials, labor, taxes, and overhead. It is the cost you would actually pay to complete a project. The "Installed Cost" value listed under the Life-Cycle Costs Savings section displays both the present and annualized values of the installed cost, as used in the life-cycle cost analysis. The present value of the installed cost may be less than the "Installed Capital Cost" if the study period for the analysis is less than the life of the new equipment. This can occur when the remaining life of the existing technology is less than the life of the retrofit technology. In this case the cost of the retrofit technology is annualized over its full rated life, but only the annualized costs occurring during the remaining life of the existing equipment is discounted back to the analysis year and used, for a fair cost/benefit comparison.
What does the {H1} or {C1} signify on the *.csv report?
The code in {braces} following the existing technology description for a heating or cooling technology represents the technology record number. For example, an {H2} indicates that this heating technology is actually heating record #2 (as input in the user interface). This information can be valuable when dealing with heat/cool pairs with several heating and cooling records in a single building set.
What is the 'Heating/Cooling' end use on the *.csv report?
The [Heating/Cooling] end use designation is used for existing heat pumps or heat/cool pairs. Because such technologies provide both heating and cooling, two rows are needed to describe them on the *.csv report. [HEATING/Cooling] indicates that the data on that row pertain to the heating technology (and overall economic impacts) while [Heating/COOLING] indicates that the data describes the cooling portion of the equipment (and no overall energy and economic data are shown).
Why do some paired heating and cooling technologies appear twice on the *.csv report?
For heat/cool pairs (separate heating and cooling technologies), information may be listed for both retrofits to new, more efficient equipment and to a heat pump. In some cases, it may be cost effective to replace the heating equipment (or cooling only, or both) with a newer unit of similar type, as well as replace both heat and cool simultaneously with a heat pump system. All cost-effective options will appear on the *.csv report. The best option can be determined by comparing the sum of the individual heat and cool annualized total Life-Cycle Costing (LCC) savings with that of the combined heat/cool system (i.e., heat pump).
What is the ECIP report for?
The ECIP report (*.ecp) is a special form required by certain DoD agencies in order to qualify for the Energy Conservation Investment Program (ECIP) funding. The ECIP report is designed to facilitate the form preparation and submittal process.
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