Mechanical Plants allow engineers to create and customize a wide range of central equipment which circulates either heating, cooling, or condenser fluid through a building. These include boiler plants, chiller plants, central heat pump plants, and much more! Default 'ideal' plants are included on every project, these are auto-assigned to Air Systems and allow for sizing of Systems without the need to define a mechanical plant. Following are the detailed inputs for mechanical plants, follow links for more in-depth information.

## Plant Sizing

**Fluid Type:**the type of fluid that's circulating through the plant loops. Options are:*Water, Steam, Propylene Glycol, Ethylene Glycol***Glycol Concentration:**percentage of glycol present in the plant loop fluid.**Max Temperature****[°F (IP) | °C (SI)]:**the maximum allowable temperature for the loop**Min Temperature****[°F (IP) | °C (SI)]:**the minimum allowable temperature for the loop**Max Flow Rate [GPM (IP) | L/S (SI)]:**the maximum loop flow rate**Min Flow Rate [GPM (IP) | L/S (SI)]:**the maximum loop flow rate**Load Distribution Scheme:**selects the algorithm used to sequence equipment operation in order to meet the plant loop demand.Options are:

operates each piece of equipment at its optimal part-load ratio. Any remaining loop demand is distributed evenly to all of the components*Optimal -*loads each piece of equipment sequentially in the order specified in the Plant Equipment List to its maximum part load ratio and will operate the last required piece of equipment between its minimum and maximum part load ratio in order to meet the loop demand.*Sequential Load -*evenly distributes the loop demand among all available components on the equipment list for a given load range. If some components do not have the capacity to meet the uniformly distributed load, the remaining load is distributed sequentially to the other available components.*Uniform Load -**Sequential Uniform***PLR -**will load all equipment on the Plant Equipment List to a uniform part load ratio (PLR). No equipment will be loaded below its minimum PLR. If the total load is less than the sum of all equipment on the Plant Equipment List operating at their respective minimum PLRs, then the last item in the equipment list is dropped and the load is distributed based on a uniform PLR for the remaining plant equipment*Uniform PLR -*

**Sizing Option:**Options are:*Coincident, Non-Coincident***Coincident Sizing Mode:**Options are:*None, Global Heating Sizing Factor, Global Cooling Sizing Factor, Component Sizing Factor*

## Electric Chiller

**Name:**A unique name for the equipment can be provided**Type**: determines what type of condenser will be modeled with this chiller.**Reference Capacity:**the reference cooling capacity of the chiller at the specified temperatures and water flow rates. Defaults to Autosized.**Reference COP:**the chiller’s coefficient of performance at the specified reference temperatures and water flow rates.**Leaving Chilled Water Temperature****[°F (IP) | °C (SI)]:**the chiller’s reference leaving chilled water temperature**Entering Condenser Water Temperature****[°F (IP) | °C (SI)]:**the chiller’s reference entering condenser fluid temperature**Chilled Water Flow Rate [GPM (IP) | L/S (SI)]:**for a variable flow chiller this is the maximum water flow rate and for a constant flow chiller this is the operating water flow rate through the chiller’s evaporator.**Condenser Water Flow Rate [GPM (IP) | L/S (SI)]:**the chiller’s operating condenser fluid flow rate**Minimum Part Load Ratio:**the chiller’s minimum part-load ratio. Must be between 0 and 1, but less than or equal to the Maximum Part Load Ratio.**Maximum Part Load Ratio:**the chiller’s maximum part-load ratio. This value may exceed 1, but the normal range is between 0 and 1.0. The Maximum Part Load Ratio must be greater than or equal to the Minimum Part Load Ratio.**Reference Part Load Ratio:**the absorption chiller’s optimum part load ratio at which the chiller performs at its maximum COP.**Minimum Unloading Ratio:**the chiller’s minimum unloading ratio. This is where the chiller capacity can no longer be reduced by unloading and must be false loaded to meet smaller cooling loads. Must be greater than or equal to the Minimum Part Load Ratio, and less than or equal to the Maximum Part Load Ratio**Internal Flow Mode:**determines how the chiller operates with respect to the intended fluid flow through the device’s evaporator. Choices are:useful for either variable or constant speed pumping arrangements where the chiller is passive in the sense that although it makes a nominal request for its design flow rate it can operate at varying flow rates.*Passive -*changes the chiller model to internally vary the flow rate so that the temperature leaving the chiller matches a setpoint.*Temperature Control -*useful for constant speed pumping arrangements where the chiller’s request for flow is stricter and can increase the overall loop flow.*Constant Flow -*

**Priority:**details the order in which the chiller is prioritized in the loop.**Performance Curve:**This connects the chiller to it's corresponding performance curve, defined in performance curve page.

## District Cooling Connection

**Name:**A unique name for the equipment can be provided**Nominal Capacity [Btu/h (IP) | Watts (SI)]:**the nominal demand that the district cooling will meet. Defaults to Autosized.

## Constant Pump Speed

**Name:**A unique name for the equipment can be provided**Location:**If the pumping strategy is set to primary-secondary, this input will specify which loop the pump is located on.**Rated Flow Rate [GPM (IP) | L/S (SI)]:**the pump’s design volume flow rate. Defaults to Autosized.**Rated Pump Pressure [psi (IP) | Pa (SI)]:**the pump’s design head pressure.**Rated Power [Watts (IP/SI)]:**the pump’s design power consumption.**Motor Efficiency:**the pump motor’s efficiency in decimal form.**Control Type:**Choices are:the pump will run regardless of whether or not there is a load. This may have the net effect of adding heat to the loop if no equipment is turned on.*Continuous -*the pump will run at its capacity if a load is sensed and will shut off if there is no load on the loop.*Intermittent -*

## Variable Pump Speed

**Name:**A unique name for the equipment can be provided**Location:**If the pumping strategy is set to primary-secondary, this input will specify which loop the pump is located on.**Rated Flow Rate [GPM (IP) | L/S (SI)]:**the pump’s design volume flow rate. Defaults to Autosized.**Rated Pump Pressure [psi (IP) | Pa (SI)]:**the pump’s design head pressure**Rated Power [Watts (IP/SI)]:**the pump’s design power consumption. Defaults to Autosized.**Motor Efficiency:**the pump motor’s efficiency in decimal form.**Minimum Flow Rate [GPM (IP) | L/S (SI)]:**the minimum volume flow rate while operating in variable flow capacity rate. Defaults to Autosized.**Control Type:**Choices are:the pump will run regardless of whether or not there is a load. This may have the net effect of adding heat to the loop if no equipment is turned on.*Continuous -*the pump will run at its capacity if a load is sensed and will shut off if there is no load on the loop.*Intermittent -*

**Minimum Flow Fraction:**the minimum fluid volumetric flow rate for pumps, specified as a fraction of the maximum fluid flow rate

## Pumping Strategies

**Pumping Strategy:**Options are:*Primary -*means that the plant loop does not attempt any temperature control, it only satisfies secondary (demand side) flow requests.*Primary-Secondary Flow Control -*allows control of the secondary (demand side) inlet temperature or the primary (plant side) inlet temperature by placing a setpoint on the corresponding node.*Primary-Secondary Temperature Control -*

**Primary Pump Type:**Specifies the type of pump placed on the primary plant loop.*Variable, Constant***Secondary Pump Type:**Specifies the type of pump placed on the secondary plant loop. Options are:*Variable, Constant*

## Heating Hot Water Boiler

**Name:**A unique name for the equipment can be provided**Fuel Type:**specifies the type of fuel used by the boiler. Options are:**Electricity, Gas, Propane, Fuel Oil #1, Diesel****Nominal Capacity [Btu/h (IP) | Watts (SI)]:**the nominal operating capacity of the boiler. Defaults to Autosized.**Nominal Thermal Efficiency:**the heating efficiency (as a fraction between 0 and 1) of the boiler’s burner. This is the efficiency relative to the higher heating value (HHV) of fuel at a part load ratio of 1.0**Design Fluid Flow [GPM (IP) | L/S (SI)]:**the maximum design water volumetric flow rate. This should be the largest flow rate than can be heated.**Minimum Part Load Ratio:**the boiler's minimum part-load ratio. Must be between 0 and 1, and less than or equal to the Maximum Part Load Ratio.**Maximum Part Load Ratio:**the boiler’s maximum part-load ratio. This value may exceed 1, but the normal range is between 0 and 1.0. The Maximum Part Load Ratio must be greater than or equal to the Minimum Part Load Ratio.**Reference Part Load Ratio:**the boiler's optimum part load ratio at which the boiler performs at its maximum COP.**Max Leaving Heating Hot Water Temperature Limit****[°F (IP) | °C (SI)]:**the outlet temperature upper limit.**Internal Flow Method:**determines how the boiler operates with respect to the intended fluid flow through the device. Choices are:useful for either variable or constant speed pumping arrangements where the boiler is passive in the sense that although it makes a nominal request for its design flow rate it can operate at varying flow rates.*Passive -*changes the boiler model to internally vary the flow rate so that the temperature leaving the boiler matches a setpoint.*Temperature Control -*useful for constant speed pumping arrangements where the boiler’s request for flow is more strict and can increase the overall loop flow.*Constant Flow -*

**Priority:**details the order in which the boiler is prioritized in the loop.

## District Heat Connection

**Name:**A unique name for the equipment can be provided**Nominal Capacity [Btu/h (IP) | Watts (SI)]:**the nominal demand that the district heating will meet. Defaults to Autosized.

## Cooling Tower

**Name:**A unique name for the equipment can be provided**Tower Type:**Dropdown menu with the following optionsutilizes a single-speed fan to control exit water temperature.*Single Speed:*utilizes a variable speed fan to control exit water temperature.*Variable Speed:*

**Nominal Capacity****[Btu/h (IP) | Watts (SI)]:**This numeric input field contains the “nominal” heat rejection capacity of the cooling tower in watts**Design Water Flow Rate [GPM (IP) | L/S (SI)]:**This numeric field contains the design water flow rate through the tower. This value is the flow rate of the condenser loop water being cooled by the tower (not the flow rate of water being sprayed on the outside of the heat exchange coil)**Design Fan Power****[hp (IP) | Watts (SI)]:**This numeric field contains the fan power at the design air flow rate specified in the previous field. A value greater than zero must be specified.**Design Air Dry Bulb Temperature****[°F (IP) | °C (SI)]:**This numeric field specifies the inlet air dry-bulb temperature (˚C) at design conditions.**Design Air Wet Bulb Temperature [°F (IP) | °C (SI)]:**This numeric field specifies the inlet air wet-bulb temperature (˚C) at design conditions. This design temperature should correspond with the design values for range temperature, approach temperature, water flow rate, and airflow rate specified in the following fields.**Design Approach Temperature****[°F (IP) | ∆°C (SI)]:**This numeric field specifies the tower approach temperature (˚C) at design conditions. The approach temperature is the outlet water temperature minus the inlet air wet-bulb temperature.**Design Range Temperature****[∆°F (IP) | ∆°C (SI)]:**This numeric field specifies the range temperature (˚C) at design conditions. The range temperature is defined as the inlet water temperature minus the outlet water temperature.

## Ground Heat Exchanger

**Name:**A unique name for the equipment can be provided**Max Flow Rate [GPM (IP) | L/s (SI)]:**The maximum flow rate through the system**Number of Bore Holes:**The total number of boreholes in the system.**Bore Hole Length [ft (IP) | m (SI)]:**The active length of the borehole, referenced from the starting location (potentially below the ground surface) to the end of the borehole, in meters.**Bore Hole Radius [ft (IP) | m (SI)]:**the radius of the borehole**Ground Thermal Conductivity [Btu/h/ft (IP) | W/m-K (SI)]:**the thermal conductivity of the ground**Ground Thermal Heat Capacity****[Btu/F (IP) | J/K (SI)]:**the thermal heat capacity of the ground**Ground Temperature [°F (IP) | °C (SI)]:**the ground's**Design Flow Rate [GPM (IP) | L/s (SI)]:**The total flow rate for the entire borehole field. The flow will be assumed to be evenly distributed across all boreholes.**Grout Thermal Conductivity [Btu/h/ft (IP) | W/m-K (SI)]:**the thermal conductivity of the filler material**Pipe Thermal Conductivity [Btu/h/ft (IP) | W/m-K (SI)]:**the thermal conductivity of the pipe**Pipe Out Diameter [ft (IP) | m (SI)]:**the outer diameter of the U-tube (pipe)**U-Tube Distance [ft (IP) | m (SI)]:**the distance between the two legs of the U-tube in meters {m}. Distance is measured from the u-tube pipe center.**Pipe Thickness [ft (IP) | m (SI)]:**the outer diameter of the U-tube (pipe)**Max Length of Simulation:**

## Water To Water Heat Pump - Heating Configuration

**Name:**A unique name for the equipment can be provided**Load Side Flow Rate [GPM (IP) | L/s (SI)]:**The design volume flow rate on the load side of the heat pump. This corresponds to the highest load-side heat transfer rate listed in the catalog data. This field is autosizable.**Source Side Flow Rate [GPM (IP) | L/s (SI)]:**The design volume flow rate on the source side of the heat pump. This corresponds to the highest load-side heat transfer rate listed in the catalog data. This field is autosizable.**Heating Capacity [Btu/h (IP) | Watts (SI)]:**The design heating capacity of the heat pump in W. This corresponds to the highest load-side heat transfer rate listed in the catalog data. This field is autosizable.**Heating Power [Watts (IP) | Watts (SI)]:**The design electric power consumption for heating, in W. This corresponds to the electric power use at the Heating Capacity. This field is autosizable. When autosized, the field called Coeﬀicient of Performance must be used.**Heating COP:**The Design Heating Power Consumption is set to autosize. The nominal COP is defined by the Heating Capacity divided by the corresponding Heating Power Consumption and is non-dimensional. This field is only used for sizing; if the Heating Power Consumption is set to a fixed value then the COP of the component during simulation will be determined by the ratio of Heating Capacity divided by the corresponding Heating Power Consumption and not by the value in this field.**Heating Sizing Factor:**The user to specify a sizing factor for this component. The sizing factor is used when the component design inputs are autosized: the autosizing calculations are performed as usual and the results are multiplied by the sizing factor. For this component, the sizing factor's inputs would alter are: Load Side Flow Rate, Source Side Flow Rate, Heating Capacity, and Heating Power Consumption. The Sizing Factor allows the user to size a component to meet part of the plant loop’s design load while continuing to use the autosizing feature. For example, if there are two heat pumps on the supply side, each one could be sized to be half of the design load.

## Water To Water Heat Pump - Cooling Configuration

**Name:**A unique name for the equipment can be provided**Load Side Flow Rate [GPM (IP) | L/s (SI)]:**The design volume flow rate on the load side of the heat pump. This corresponds to the highest load-side heat transfer rate listed in the catalog data. This field is autosizable.**Source Side Flow Rate [GPM (IP) | L/s (SI)]:**The design volume flow rate on the source side of the heat pump. This corresponds to the highest load-side heat transfer rate listed in the catalog data. This field is autosizable.**Cooling Capacity [Btu/h (IP) | Watts (SI)]:**The design cooling capacity of the heat pump in W. This corresponds to the highest load-side heat transfer rate listed in the catalog data. This field is autosizable.**Cooling Power [Watts (IP) | Watts (SI)]:**The design electric power consumption for cooling. This corresponds to the electric power use at the Cooling Capacity. This field is autosizable. When autosized, the field called Cooling COP must be used.**Cooling COP:**This field is required if the Cooling Power Consumption is set to autosize. The nominal COP is defined by the Cooling Capacity divided by the corresponding Cooling Power Consumption and is non-dimensional. This field is only used for sizing; if the Power Consumption is set to a fixed value then the COP of the component during simulation will be determined by the ratio of Cooling Capacity divided by the corresponding Cooling Power Consumption and not by the value in this field. This COP does not include power for fluid circulation pumps, it is just the heat pump itself.**Cooling Sizing Factor:**This optional numeric field allows the user to specify a sizing factor for this component. The sizing factor is used when the component design inputs are autosized: the autosizing calculations are performed as usual and the results are multiplied by the sizing factor. For this component, the inputs that the sizing factor would alter are: Load Side Flow Rate, Source Side Flow Rate, Cooling Capacity, and Cooling Power Consumption. The Sizing Factor allows the user to size a component to meet part of the plant loop’s design load while continuing to use the autosizing feature. For example, if there are two heat pumps on the supply side, each one could be sized to be half of the design load.

## VRF Heat Pump and Heat Recovery

**Name:**A unique name for the equipment can be provided**.**## VRF Cooling Configuration

**Rated Cooling Capacity[Btu/h (IP) | Watts (SI)]:**The nominal cooling capacity, defaults to Autosized**Rated cooling COP:**Coefficient of performance for cooling**Minimum Outdoor Temperature[°F (IP) | °C (SI)]:**Minimum outdoor dry bulb temperature**Maximum Outdoor Temperature[°F (IP) | °C (SI)]:**Maximum outdoor dry bulb temperature## VRF Heating Configuration

**Number of Compressors:**This field defines the number of compressors in the heat pump condensing unit and is used exclusively to determine the operating characteristics of the crankcase heater**Size to Capacity Ratio:**## VRF System Setting

**Minimum Heat Pump Part Load Ratio:**the VRF plant minimum part-load ratio. Must be between 0 and 1, but less than or equal to the Maximum Part Load Ratio.**Heat Pump Waste Heat Recovery:**This field allows user to enable transferring exhaust heat (or waste heat) from a zone being cooled to a zone that requires heating.**Equivalent Piping Length [ft (IP) | M(SI)] :**Equivalent piping length used for piping correction factor in cooling mode**Vertical Height Difference [ft (IP) | M(SI)]:**Vertical height used for piping correction factor defines the vertical pipe height in meters between the highest or lowest terminal unit and the heat pump condenser. This value defines the gravitational losses due to a change in height between the highest (positive value), or lowest (negative value) terminal unit and the heat pump condenser. The distance specified here is applied to the piping correction factor calculation for both cooling and heating.**Max Outdoor db Temp for Crankcase Heater[°F (IP) | °C (SI)]:**This numeric field defines the maximum outdoor temperature, in degrees Celsius, below which the crankcase heater will operate. If this field is left blank, the default value is 0 C. This field is only used to calculate crankcase heater power and has no impact on heat pump performance.**Basin Heater Setpoint Temp [°F (IP) | °C (SI)]: This value**defines the set point temperature (˚C) for the basin heater.## VRF Heat Recovery Configuration

**Minimum Outdoor Temperature[°F (IP) | °C (SI)]:**Minimum outdoor dry-bulb temperature allowed for heat recovery operation.**Maximum Outdoor Temperature[°F (IP) | °C (SI)]:**Maximum outdoor dry-bulb temperature allowed for heat recovery operation.**Initial Cooling Capacity Fraction:**This value defines the fraction of cooling capacity available when the system transitions from cooling only operation to simultaneous cooling and heating. It is common for the cooling capacity to decrease before the system recovers.**Cooling Capacity Time Constant:**This field defines**Initial Cooling Energy Fraction:**value assigned to this field defines the fraction of cooling energy consumed when the system transitions from cooling only operation to simultaneous cooling and heating.**Initial Heating Capacity Fraction:**This field indicates the fraction of cooling energy consumed when the system transitions from cooling only operation to simultaneous cooling and heating**Initial Heating Energy Fraction:**Value assigned to this field defines the cooling energy time constant, in hours, used to model the time it takes for the system to transition from cooling only operation to simultaneous cooling and heating. Total response time is defined as 5 time constants.