Air Temperature Coordination for E-Quest

          What is asked for must be delivered.  Declaring temperatures without a understanding of their relationship with other temperatures in the same model and among the baseline and design case information may result in a model with improper hours of load not met.   Below is a summary of DOE-2 information, please refer to the "?" button and help sections for accurate and not summarized information.

• Per HVAC system type, per area thermostat type, make all Temperature coordinate among each other.  Note: systems like VAV, Economizers, and HRV have unique setup of temperatures (they include hot-deck leaving temperature, reset temperatures etc.).  Information below has omissions and non applicable information to such instances.  Most Hvac systems have their unique temperature setups, but they generally follow the information on this page.
• A few temperatures are specific to HVAC systems and thus may be altered to address %hours of load not met reduction strategies. 
• In most cases, temperature cordination among all zones in a model may be the same.   However, peak loading conditions occuring in solar effected zones may not equal across an entire project.   Some zones with glass, may have a peak cooling outside of typical peak cooling day common among the rest of the model.   A quick check for this is checking the SSR report for particular rooms, and those rooms possessing walls with large windows.  In such cases, the design day conditions need to be altered and be different than rest of project.

The diagram below hopes to show graphically the relationship between these temeperatures.  

Figure 1.1    Diagram of Temperature values in Equest.  

Note 1:  Throttling temperature is not shown as it is per thermostat type, per hvac system type. 

Note 2:  The Heating Design T and Cooling Design T are not necessarily the same as Heating Design Day Temperature and Cooling Design Day temperatures embedded in the week level Thermostat Schedules.  For an explanation for this see text section about Heating Design T and Cooling Design T.  

Note 3:  Heating design day temperature and Cooling design day temperatures  (both found in the thermostat schedules among the zones) are not shown.   These must equal the maximum energy using temperature found among the thermostat schedules applied.

Note 4:  The 20 degree Delta T between the supply and the return is only for the Baseline ASHRAE 90.1 2004 system. 

Definitions and descriptions of each temperature type

Format:

Common Name of Value

(location on equest interface) (searchable name among .inp file or 'help' search term)

Thermostat schedule

(Schedules, annual, week, day) (SCHEDULE-PD, WEEK-SCHEDULE-PD,  DAY-SCHEDULE-PD).  This is the desired temperature of the rooms, on hvac spec's it is the design temperature of the room.  On hvac drawings it is not the "design temperature" for the system.

• This is used in the program to asign the space temperature at any given hour throughout the year.   It also contains the design day conditions for the sizing of the HVAC systems. 
• Week to week, day to day, hourly thermostat values.  -This is a series of points of type temperature.  Zones reference this.  The indicator of model result accuracy, "% hours of load not met" generate when this value is not maintained, described by cv services .
• Design Day temperatures (defined as a day schedules, pointed to by the week schedules) This is used on the hvac sizing run on design day conditions in the model.   It reflects the desired temperature maintained on only that day.  IMPORTANT: The Design Day Temperatures found among the thermostat schedules is a different number than the Heat Design T, Cool Design T values.   Thermostat Schedule Heating/Cooling Design Day Temperatures should match worse case among the temperature schedules (for heating or cooling, respectfully).  See Cool Design T and Heat Design T for more information. 
• If no cooling schedule referenced = no cooling in zone
• if no heating schedule referenced = no heating in zone
• A temperature schedule where setback and setpoint occur:  A HVAC system may not have the capacity (attained from the auto sizing runs) to deal with the sudden shift of temperature in the transition from set back to set point.   Example: Winter in an office, of 72 occupied day and 67 at night unoccupied.   The hvac system will likely not have the capacity to jump the space temperature 5 degrees in one hour in the beginning of the work day.  The energy output needed for that shift is large in relation to the capacity of the system.   This will result in % hours of load not met.  Remedy: gradual climbs in temperature when temperature schedules go from set back (unoccupied) to set point (occupied).  Gradual high to low temperature in cooling seasons, gradual low to high temperature in heating seasons. 
• Baseline and Design case temperature schedules must equal unless a measure (like setback thermostats with a BMS) is being analyzed on the design case model. You can learn about it within cv writing service .

Heat Design T, Cool Design T

(Zone, basic specifications) (DESIGN-HEAT-T, DESIGN-COOL-T)

• This is used in the program to gauge the airflow rates into the space.   These values do not have to equal the design day conditions found among the thermostat schedules (Design Day Heating Schedule, Design Day Cooling Schedule)  Heat Design T and Cooling Design T often has an offset that helps the oversize of equipment.  It is particular to HVAC system type and other factors.   As example, a heating thermostat schedule only reaches 70 degrees max (among all of the day heating schedules, including the heating design day schedules), but the Heat Design T is shown as 72 degrees.   The result is a system that serves a room needing 70 F temperature with system aspects (fan etc.) sized to what would be required to keep it at 72.   
• This temperature may have a built in safety margin per hvac system type.
• Baseline and Improved model relationship with regard to this parameter is not established.   They should equal but do not have to, as baseline and design case HVAC systems will be different.

Heating/Cooling Supply Temperature or Zone Supply Temperature

(Hvac, Heating/cooling tab, Control and reset, zone entering max (min) supply temperature) (MAX-SUPPLY-T, MIN-SUPPLY-T)

• This is used in the program as the last point of control onto the air as it enters the room, mixes with all other modeled elements of the room.  Different HVAC systems may or may not refer to pest control service this.   
• Baseline model has to be 20 degrees F above the thermostat set point for the room (one for heating +20F and one for cooling -20F) (if the model is ASHRAE 90.1 2004), the design case model is according to design documents (if not known assume delta T of 20 same as baseline).    Note: Some hvac system types do not operate well with this condition of 20 degree delta T, namely Unit Heater gas Furnaces who often have 135 F output air temperature.   The simulation program must blast air across such a hot coil, in order to get the output temperature in the ballpark of 20 degrees F.

Throttling Range Temperature

(zone, Basic Specifications, thermostat) (THROTTLING-RANGE) (SSF)

• This is used in the program to define the hours of load not met.  If the temperature drifts outside 2x the throttling temperature (below thermostat schedule in heating season ephedra, and above thermostat schedule in cooling season), an hour of load not met is recorded.     
• Commonly .5 F if thermostat is Reverse-Action type or Proportional type. 
• Commonly 2.0 F if the thermostat is Two-Position type.  
• Thermostat types (Reverse action/proportional/two position types):
• From Doe2 help: "The default value for THERMOSTAT-TYPE varies by system type and by how the system is used:
• MZS, DDS and PMZS systems:  The default is PROPORTIONAL for constant-flow mixing boxes and REVERSE-ACTION for others. This allows the hot deck to pass the same maximum air flow as the cold deck. Otherwise, the hot deck side of the box will be sized to the heating load.  Constant-volume systems:  If HEAT-SOURCE = HOT-WATER the program assumes the heating valve can modulate output and the thermostat type defaults to PROPORTIONAL. Otherwise, it is TWO-POSITION.
• Variable-volume systems:  Normally, the thermostat type defaults to PROPORTIONAL. However, if SYSTEM:MIN-FLOW-RATIO is less than 0.4, and SYSTEM:HMIN-FLOW-RATIO is not specified, then a REVERSE-ACTION thermostat is assumed. Otherwise, temperature stratification problems might arise when attempting to heat a space with a small volume of air."
• Baseline and Design case model throttling ranges should be per the thermostat type.  Thermostat type is per HVAC system, HVAC systems on the baseline and design case models may not be the same, said professional resume writer .  Therefore, throttling range temperatures in the baseline and design case models do not have to equal.   

Space temperature

(space, general) (TEMPERATURE)

• This is used in the program to compute loads.
• For unconditioned space, this should be the likely room temperature throughout the year.
• For Conditioned space:  The value should be midway between the heating and cooling setpoints. It is best set equal to the design cooling temperature or design heating temperature, whichever will most probably be used to set the HVAC equipment size.  Otherwise, it should be shifted to accommodate under cooling or under heating.  (Text from DOE /Equest 3.63e internal help menu)
• Baseline and Design case model should equal as this value has an impact on system sizing.    The value of the temperature on both models may be played with to bring the overall project into compliance with standards, so long as it is within the two setpoint boundaries (heating setpoint making low boundary, cooling setpoint making upper boundary. 

Here is where the different temperatures are found among the E-Quest interface and inp. file.

Chart T.1   Where to find the temperatures among the E-Quest interface and Inp. files.

     Here is how the baseline and design case buildings temperatures relate to each other, which values can be adjusted (to bring down %hours of load not met) and which are bonded between the baseline and design case models in order to follow ASHRAE 90.1 2004 Appendix G requirements.  Often the design and baseline must match-but as hvac types are likely different the systems must first work.   There may be a difference between temperature coordination that allows two different HVAC systems work properly, and design conditions that must match among the two models so undersize/oversize concerns of modeling codes are not disobeyed.

Chart T.2 Design Case and Baseline model coordination of temperatures.

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