CSE User's Manual

California Simulation Engine


TERMINAL constructs an object to represent equipment that transfers energy to or from the current zone from a local heating device (coil, etc.) and/or one AIRHANDLER. A terminal serves a zone (and, internally, is owned by a zone). Up to three terminals can be defined for each zone.

A terminal can have local heating capability, using a simulated reheat coil, baseboard heater, etc. and/or air heating/cooling capability, using a simulated variable air volume (VAV) box connected to an AIRHANDLER (Section 0). Since a TERMINAL can only connect to a single air handler, use two terminals per zone to model systems where separate air handlers supply hot and cool air (dual duct). If a local heat capability utilizes the air flow (e.g. a reheat coil), model it in the terminal connected to the air handler; if a local heat capability is independent of air flow (e.g. electric baseboard heaters), it doesn’t matter whether you model it with a separate terminal.

Each capability can be set output, in which the output is constant or determined by external conditions such as in an outdoor reset baseboard situation or set temperature, in which the output is modulated to maintain the zone temperature at a set point. Set temperature operation is established by giving the setpoint for the capability (tuTLh, tuTH, tuTC); set output operation is established by specifying the local heat output (tuQMnLh) or air flow (tuVfMn) without specifying a setpoint.

Hourly variable expressions may be used as desired to schedule setpoints and flow limits. Figure 1 shows [need sentence describing the figure.]

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Optional name of terminal; follows the word “TERMINAL” if given.

UnitsLegal RangeDefaultRequiredVariability
63 charactersNoconstant

4.22.1 TERMINAL Local Heating

These commands establish the TERMINAL’s local heating capability and determine whether it operates in set output or set temperature fashion. Additional details of the local heating mechanism are given with commands described below under terminal heating coil.

Either tuTLh or tuQMnLh must be given to establish the TERMINAL’s local heat capability:


Local heating thermostat setpoint. Hourly expression may be used to schedule as desired. Giving this implies set temperature local heat from this terminal; omitting implies no local heat or, if tuQMnLh is given, set output local heat.

UnitsLegal RangeDefaultRequiredVariability
oFx \(>\) 0no thermostat controlNohourly


Minimum local heat output or set local heat output. If tuTLh is given, this is the minimum output, used when the thermostat is not calling for (local) heat. If tuTLh is not given, giving tuQMnLh implies set output local heat and specifies the set output level. An hourly expression may be used to schedule as desired.

UnitsLegal RangeDefaultRequiredVariability
Btuhx \(\ge\) 00 if tuTLh given else no local heatFor set output local heathourly

The next three items are allowed only for thermostat controlled local heating (tuTLh given):


Maximum desired power, used when thermostat is calling for heat continuously, subject to coil capacity, and to HEATPLANT limitations where pertinent (see tuhcCaptRat description). If tuQMxLh is less than minimum power (tuQMnLh), the latter is used, effectively disabling setpoint control.

UnitsLegal RangeDefaultRequiredVariability
Btuhx \(\ge\) 0Yes, if tuTLh givenhourly


Setpoint priority: when there is more than one capability with the same setpoint, that with the highest priority (lowest value) is used first. The defaults for tuPriLh (100) and tuPriH (1) cause maximum air heat to be used before local heat, if both are present and the setpoints are the same. Two or more equal setpoints with equal priorities in the ZONE cause an error, even if in different TERMINALs.

UnitsLegal RangeDefaultRequiredVariability
x \(>\) 0100Noconstant


YESlocal heat being modeled requires terminal air flow (e.g. reheat coil). Local heat is then disabled when there is zero air flow through the terminal (when simulated VAV damper set to 0 flow, or when air handler fan and terminal fan both off)
NOno local heat or does not require air flow (e.g. baseboard heaters).
UnitsLegal RangeDefaultRequiredVariability
YES, NONONoconstant

4.22.2 TERMINAL Air Heating and Cooling

These commands establish whether the TERMINAL has air capability (heat, cool, or both), and whether the capability operates in set temperature mode (tuTH and/or tuTLh given) or set output mode (tuVfMn given without tuTH and tuTLh). They further establish the setpoints, flow limits, leakages, and losses.

Caution should be exercised in using air heat and air cooling in the same terminal. The supply air for both comes from the same air handler; it is up to you to make sure the terminal only calls for heat when the air handler is blowing hot air and only calls for cooling when the air handler is blowing cold air. This is done by carefully coordinating the variable expressions for terminal air heating and cooling setpoints (tuTH and tuTC here) and the air handler supply temperature setpoint (AIRHANDLER ahTsSp, Section 0).

Note: To autosize air flows for a constant volume terminal, use the following



Name of air handler supplying this terminal.

UnitsLegal RangeDefaultRequiredVariability
name of an AIRHANDLERIf omitted, terminal has no air heating nor cooling capability.Noconstant

If both of the following (tuTH and tuTC) are specified, be careful not to accidentally permit the heating setpoint to be active when the air handler is blowing cold air, or vice versa. CSE’s simulated thermostats and VAV boxes are at least as dumb as their real counterparts; if the thermostat calls for heat, the VAV damper will open even if the supply air is colder than the zone. To schedule deactivation of the air heating or cooling capability, schedule an extreme setpoint, such as 1 for heating or 199 for cooling.

Giving neither tuTH nor tuTC implies that the terminal has no set temperature air capability; it will then have set output air capability if tuVfMn is given.


Air heating thermostat set point; implies set temperature air capability. May be scheduled as desired with an hourly expression; to disable set temperature operation at certain times (as when air handler is scheduled to supply cold air), schedule a low temperature such as 1.

UnitsLegal RangeDefaultRequired**Variability
oFx \(\ge\) 0No thermostat-controlled air heatingNohourly


Air cooling thermostat set point; implies set temperature air capability. May be scheduled as desired; to disable at certain times, schedule an extreme temperature such as 199.

UnitsLegal RangeDefaultRequired**Variability
oFx \(\ge\) 0No thermostat-controlled air coolingNohourly


Design air flow rate. (“Vf” in member names stands for “Volumetric Flow”, to emphasize that flow is specified by volume at actual air temperature (cfm), not by mass (lb/hr), nor heat capacity (Btuh/F), etc.)

The design air flow rate is used to apportion the available cfm among the terminals when the total flow demand of the terminals exceeds the air handler’s supply fan capacity; it is unimportant (but may nevertheless be required) if the total of the tuVfMx’s of the terminals on the air handler is not greater than the air handler’s fan capacity including overrun.

CSE will default tuVfDs to the largest of tuVfMn, tuVfMxH, and tuVfMxC unless a variable expression is given for any of them. Thus, you must given tuVfDs only when a variable minimum or maximum flow is used, or when you wish to override the default cfm apportionment under fan overload conditions.

UnitsLegal RangeDefaultRequiredVariability
cfmx \(\ge\) 0largest of tuVfMn, tuVfMxH, and tuVfMxC if all are constantYes, if tuVfmn, tuVfmxH, or tuVfMxC is variablehourly


Sizing factor for autosized terminal air flows. Default value (1.1) specifies 10% oversizing.

UnitsLegal RangeDefaultRequiredVariability
x \(\ge\) 01.1Noconstant


Determines autosizing strategy for heating and cooling air flows.

SAMEtuVfMxH and tuVfMxC are set to the larger of the autosized values
DIFFERENTtuVfMxH and tuVfMxC are autosized independently
UnitsLegal RangeDefaultRequiredVariability
choices aboveDifferentNoconstant


Minimum terminal air flow rate or set output air flow rate. An hourly expression may be used to schedule the minimum or set output flow as desired.

If neither tuTH nor tuTC is given, giving tuVfMn implies set output air capability for the terminal; the tvVfMn value is the set output cfm.

If either setpoint (tuTH or tuTC) is given, tuVfMn is the cfm used when the thermostat is not calling for heat nor cold; it might be non-0, for example, to meet ventilation requirements. If tuVfMn is larger than tuVfMxH (when heating) or tuVfMxC (when cooling), it overrules them; thus a minimum (e.g. ventilation) requirement need not be considered in formulating expressions for the maximum flows.

UnitsLegal RangeDefaultRequiredVariability
cfmAUTOSIZE or x \(\ge\) 0if tuTH or tuTC given, else no air heat/coolFor set output air operationhourly


Maximum heating air flow rate, subject to air handler limitations. This terminal flow is used when the thermostat is calling for heat continuously. Hourly schedulable. If not greater than tuVfMn, the latter flow is used, thus disabling thermostat control.

UnitsLegal RangeDefaultRequiredVariability
cfmAUTOSIZE or x \(\ge\) 0noneIf tuTH givenhourly


Maximum cooling air flow rate, before air handler limitations, used when the thermostat is calling for cooling continuously. tuVfMn overrides if larger.

UnitsLegal RangeDefaultRequiredVariability
cfmAUTOSIZE or x \(\ge\) 0noneIf tuTC givenhourly


Cool setpoint priority. The lowest numbered priority is used first when there are equal setpoints in a zone; equal heat or cool setpoints with equal priority in same ZONE (even if on different TERMINALs) constitute an error.

UnitsLegal RangeDefaultRequiredVariability
x \(>\) 01Noconstant


Heat setpoint priority. Lowest numbered priority is used first when there are equal setpoints in a zone. Default for tuPriLh is larger, so that by default local heat is not used unless maximum air heat is insufficient, when both local heat and air heat are present in zone and have same setpoint.

UnitsLegal RangeDefaultRequiredVariability
x \(>\) 01Noconstant


Leakage of supply air to return, increasing supply volume and return temperature. Note that this is a fraction of current cfm, whereas air handler leak (before VAV dampers) is a fraction of maximum cfm. TfanOffLeak is added to this if terminal has a fan that is not running (future, 7-92).

UnitsLegal RangeDefaultRequiredVariability
0 \(\le\) x \(\le\) 10.05Noconstant


Supply air to return plenum heat loss as a fraction of supply air to return air temperature difference. Not allowed if return is ducted (no plenum).

NOT IMPLEMENTED as of July 1992 – Plenums are unimplemented.

UnitsLegal RangeDefaultRequiredVariability
0 \(\le\) x \(\le\) 10.1Noconstant

4.22.3 TERMINAL Heating Coil

These members are disallowed if terminal has no local heating capability, that is, if neither tuTLh nor tuQMnLh is given.


Local heating coil type:

ELECTRICElectric coil or heater, including separate heaters such as electric baseboards. 100% efficient; rated capacity always available.
HWHot water coil, using hot water from amHEATPLANT. Available capacity may be limited by HEATPLANT total capacity as well as by coil rated capacity.
UnitsLegal RangeDefaultRequiredVariability
ELECTRIC (future: HW)ELECTRIC, or NONE if no local heatNoconstant


Rated capacity of the heating coil. The coil will never supply more heat than its capacity, even if tuQMxLh and/or tuQMnLh is greater. For an ELECTRIC coil, the capacity is always the rated capacity. For an HW coil, the capacity is the rated capacity when the HEATPLANT can supply it; when the total heat demanded from the HEATPLANT by all the HW coils in TERMINALs and AIRHANDLERs exceeds the HEATPLANT’s capacity, CSE reduces the capacities of all HW coils proportionately until the plant is not overloaded.

UnitsLegal RangeDefaultRequiredVariability
Btu/hrAUTOSIZE or x \(\gt\) 0noneYesconstant


Capacity factor for autosized terminal heating coil. Default value (1.1) specifies 10% oversizing.

UnitsLegal RangeDefaultRequiredVariability
x \(\ge\) 01.1Noconstant


Name of meter, if any, which accumulates input energy for this coil. End use category used is “Htg”. Not allowed when tuhcType is HW, as the energy for an HW coil comes through a HEATPLANT; the input energy is accumulated to a meter by the HEATPLANT.

UnitsLegal RangeDefaultRequiredVariability
name of a METERnot recordedNoconstant


Name of HEATPLANT for HW coil; disallowed for other coil types.

UnitsLegal RangeDefaultRequiredVariability
name of a HEATPLANTnoneIf tuhcType is HWconstant

4.22.4 TERMINAL Fan

Presence of a terminal fan is indicated by specifying a tfanType value other than NONE.

Terminal fans are NOT IMPLEMENTED as of July 1992.


Choice of:

NONENo fan in this TERMINAL (default); input for other terminal fan members disallowed.
SERIESFan runs whenever scheduled ON (see tfanSched, next); if VAV cfm < terminal fan cfm (tfanVfDs), the additional flow comes from the return air.
PARALLELFan runs when scheduled ON (see tfanSched) and terminal’s simulated VAV cfm is less than tfanVfDs plus tuVfMn ?? plus tuVfMn??. Terminal fan cfm is added to VAV cfm from AIRHANDLER to get cfm to ZONE.
UnitsLegal RangeDefaultRequiredVariability
NONE, SERIES, PARALLELnoneYes, if fan presentconstant


Terminal fan schedule. May be scheduled with an hourly variable expression.

OFFfan does not run
ONfan may run
HEATINGfan may run when local heat is in use
VAVfan may run when AIRHANDLER supply fan is on or when doing setback headting and ssCtrl is ZONE_HEAT or BOTH (future).

A series fan (see tfanType) runs whenever on; a parallel fan runs only enough to keep terminal cfm at terminal minimum plus fan cfm; thus it may not run at all when the VAV flow from the AIRHANDLER is sufficient.

UnitsLegal RangeDefaultRequiredVariability
OFF, ON, HEATING, VAVnoneYes (if fan present)hourly


Backdraft leakage when terminal fan off., as a fraction of tfanVfDs.

UnitsLegal RangeDefaultRequiredVariability
0 \(\le\) x \(\le\) 10.1 if fan presentNoconstant


Terminal fan design flow rate. To specify .x times zone or terminal cfm, use a CSE expression.

UnitsLegal RangeDefaultRequiredVariability
cfmx \(\le\) 0noneYes (if fan present)constant


Terminal fan external static pressure.

UnitsLegal RangeDefaultRequiredVariability
inches H2Ox \(\ge\) 00.3Noconstant


Terminal fan/motor/drive combined efficiency.

UnitsLegal RangeDefaultRequiredVariability
0 \(le\) x \(le\) 10.08Noconstant

tfanCurvePy=k0, k1, k2, k3, x0

k0 through k3 are the coefficients of a cubic polynomial for the curve relating fan relative energy consumption to relative air flow above the minimum flow x0. Up to five floats may be given, separated by commas. 0 is used for any omitted trailing values. The values are used as follows:

\[z = k_0 + k_1 \cdot (x - x_0)| + k_2 \cdot (x - x_0)|^2 + k_3 \cdot (x - x_0)|^3\]


If \(z\) is not 1.0 for \(x\) = 1.0, a warning message is displayed and the coefficients are normalized by dividing by the polynomial’s value for \(x\) = 1.0.

UnitsLegal RangeDefaultRequiredVariability
0, 1, 0, 0, 0 (linear)Noconstant


Name of meter, if any, which is to record energy used by this terminal fan. The “fans” category is used.

UnitsLegal RangeDefaultRequiredVariability
name of a METERnot recordedNoconstant


Optional to indicates the end of terminal definition. Alternatively, the end of the door definition can be indicated by END or by beginning another object.

UnitsLegal RangeDefaultRequiredVariability
x \(\ge\) 0noneNoconstant

Related Probes: