Multistage Gas
The fuel heating coil is a simple capacity model with a user inputted gas burner efficiency at different stages. The coil can be used in the air loop system or in the zone equipment as a reheat coil. Depending on where it is used determines if this coil is temperature or capacity controlled. If used in the air loop system it will be controlled to a specified temperature scheduled from the setpoint controller. If it is used in zone equipment, it will be controlled from the zone thermostat by meeting the zone demand.
Product tab
Nominal Capacity (Different Stages)
|
Default: Auto size
|
|
Typical Range: NA
|
|
Min Max: 0 to 999,999,999
|
|
Units: W, kW, tons, Btu
|
This is the maximum capacity of the coil. This controlled coil will only provide the needed capacity to meet the control criteria whether it is temperature or capacity controlled. This field is autosizable.
Full Load Efficiency (Different Stages)
|
Default: 100%
|
|
Typical Range: 80 to 95%
|
|
Min Max: 0 to 100
|
|
Units: NA
|
This is user-inputted efficiency (decimal units, not percent) and can account for any loss.
Parasitic Electric Load (Different Stages)
|
Default: 0 W
|
|
Typical Range: NA
|
|
Min Max: 0 to 999,999,999
|
|
Units: W, kW, HP
|
This is the parasitic electric load associated with the coil operation, such as an inducer fan, etc. This will be modified by the part-load ratio to reflect the time of operation in a simulation timestep.
Parasitic Gas Load (Different Stages)
|
Default: 0 W
|
|
Typical Range: NA
|
|
Min Max: 0 to 999,999,999
|
|
Units: W, kW, Btu, Mbh
|
This numeric field is the parasitic fuel load associated with the coil’s operation, such as a standing pilot light. The model assumes that this parasitic load is consumed only for the portion of the simulation timestep where the heating coil is not operating.
Curve tab
Part Load Fraction Correlation Curve
This curve parameterizes the variation of fuel consumption rate by the heating coil as a function of the part load ratio (part load ratio, sensible heating load/nominal capacity of the heating coil). For any simulation timestep, the nominal fuel consumption rate (heating load/burner efficiency) is divided by the part-load fraction if a part-load curve has been defined. The part-load curve accounts for efficiency losses due to transient coil operation.
If part load fraction < 0.7 a warning message is issued during simulation and the program resets the part load fraction value to 0.7, and the simulation proceeds.