Water Source Heat Pump (WSHP) System


This template generates a central DOAS air handling unit that provides a constant volume of conditioned outside air to all zones. It also generates water source heat pump zone units in each zone.


This template system only applies to water source heat pump system units

Air Handling Unit (AHU) – Return Air

The table below describes the key properties of the AHU for this system where there is return air:

AHU Feature


Extent of user-control

Airflow Rate

Constant area-weighted rate for all zones

Can change constant

Supply Air dry bulb Temperature

Constant with defaults as follows:

Can change constant value

Supply Air Temperature Reset Controls


No control

Supply Air Dew Point Controls

Constant with defaults as follows:

Min: -5 C or 23 F

Max: 13 C or 55.4 F


Supply Air Humidification Controls

Via Min Supply Air Dew Point Control


Peak Fan Power

3.5 W/(L/s) or

1.65 W/cfm

Can control peak load

Fan Curve

Standard ASHRAE.

Click to see fan curve

No control

Outside air configuration

100% outside air

No control

Return Air Rate

100% of air assumed to be returned for heat recovery

No control

Heat Recovery Efficiency

Sensible and Latent effectiveness available. Default is 50% sensible and 0% Latent.

User can change sensible and latent effectiveness

Cooling Coil

Direct Expansion coil post heat recovery

No control

Heating Coil

Hot water coil post chilled water coil

Can change to electric coil or direct gas

Frost Coil

Electric coil pre-heat recovery

Can change to hot water

Frost Coil Setpoint

Setpoint for coil – default is 2C

Can Change default

Zone WSHP Units

Zone WSHP units are self-contained heat pump fan coil units that are connected to the condenser water loop. Zone units absorb or reject heat to the condenser water loop depending on if they are in the heating or cooling mode.

The table below describes the key properties of the zone level WSHP units for this system:

Fan Coil Unit Feature


Extent of user-control

Heating Coil Type

Heat pump

Can change to electric or gas coil

Supplemental Heating Source

Hot water

Can change to electric coil

Cooling Type

Direct Expansion

No control

Fan Coil Motor Type


No control

Peak Fan Power

0.64 W/(L/s) or 0.3 W/cfm

Can control peak load

Fan Curve

Constant Volume Fan

No control

Supply Air Temperature - Heating

Constant for all zones (35C / 95F)

User can change constant

Supply Air Temperature - Cooling

Constant for all zones (13C / 55.4F)

User can change constant

Demand Control Ventilation



Dehumidification Load

Air dehumidified to achieve the cooling setpoint at 60% Relative Humidity in the zone


Central Plant Configuration

The base case option is assumed to have a central plant that provides heating hot water to the AHU and zone.  

Central Plant Feature


Extent of user-control

Heating Hot Water Source

Natural Gas

Can change to electric boiler

Boiler Peak Efficiency

Assumed to be 0.9

Value can be changed

Boiler Performance Curve

Click to see curve

No Control

Supply and Return Temperatures – hot water

80/70 C or 176/158 F

User can control

System losses

Constant loss of 15%

User can control loss rate only.

Peak Pumping Energy

1.32 W/(L/s) or 21 W/gpm

No control

Pump Efficiency Controls

Variable Speed Drives

No control

Efficiency Curve for Variable Pumping

Click to see pump curve

No control

Pumping Configuration

Primary Only

No control

Condenser Water Source

Cooling Tower

No extra options

Cooling Tower Efficiency

245.7 W/(L/s) or

15.5 W/gpm

Value can be changed

Supply and Return Temperatures – condenser water

29/35 C or

84.2/95 F

User can control

System losses

Constant loss at 5%

User can control loss rate only.

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  • Avatar
    Philip Horn

    Could you please add a simple sketch of an exemplary System architecture and describe which components are modelled (i.e adiabatic pipes etc.) ?

  • Avatar
    Samuel Letellier-Duchesne

    I agree with Philip

  • Avatar
    Francisco Contreras

    Could you add some detail around the "Ground Heat Exchanger"?

  • Avatar
    Rob Olden

    Why have the moderators not responded? These are good questions.

  • Avatar
    Andrew Corney

    Hi Rob,
    Thanks for bringing my attention to this. April who originally wrote this has moved on and I guess at the time she assumed these questions were reaching other people.
    I'll see if we can find some diagrams to add to this information - I agree they would be helpful.