Packages (PTACs & VTACs) or Split Direct Expansion (DX) Air Conditioning System with Electric Heat:
Each residential unit will be served by individual air conditioning unit with electric heating coil. In the case of using split systems, fan coil units will be located inside the units and condensing units (heat pumps) will be located outside, on the balcony, roof or parking deck.
Pros:
- No central or shared system is required
- Requires the least initial cost and maintenance
- Allows HVAC power consumption to be metered per tenant
- All mechanical contractors are familiar with this system type and equipped to work on them
Cons:
- Many Condensing Unit locations on roof, balcony or parking deck are unsightly
- Refrigerant piping limitations will drive condensing unit locations (i.e. desired locations may not be possible)
- Long refrigerant line piping reduces efficiency
- Poor efficiency on cooling unless higher efficiency units are purchased at a premium
- Electric strip heat is least efficient heating system
- In the case of packaged systems, an exterior wall louver will be required for each residential unit and will impact exterior elevations
Chilled Water and Electric Heat System:
The central system will have a chilled water loop system (43-58 F typically) with chiller(s), cooling tower(s), pumps, heat exchanger, and controls.
Chilled water piping will be piped from the chiller to each chilled water fan coil unit (FCU) located in each residential unit.
Pros:
- Provides the best end user environment with low noise and best control
- Chilled Water FCU in Residential Unit is quiet (no compressor like WSHP)
- Minimal maintenance in the Residential Unit (no compressor like WSHP)
- Separation of chiller & FCUs has minimal effect on efficiency/performance of system
Cons:
- Initial cost is higher
- Space will need to be allocated for a central plant housing pump(s), heat exchanger and chillers (if water cooled).
- Tenant consumption has to be metered via BTU Meter (chilled water usage) or included in rent/association fees
- Not all mechanical contractors are familiar with this system type or equipped to work on them
Water Source Heat Pump (WSHP) System with Cooling Tower/Boiler:
The central system will have a tempered (condenser) water loop system (85-95 F typically) with cooling tower(s), boiler(s), pumps, heat exchanger, and controls.
Condenser water piping will be piped from the cooling tower/boiler to each WSHP (typically constant volume water to air heat pump units) located in each residential unit.
Pros:
- Higher efficiency
- Separation of cooling tower & WSHP has minimal effect on efficiency/performance of system
- Cooling tower has much smaller footprint on exterior than a condensing unit farm
- Allows HVAC power consumption to be metered per tenant although the condenser water loop power consumption will need to be on house meter
Cons:
- Initial cost is higher than split systems
- Space will need to be allocated for a central plant housing pumps and heat exchanger.
- Maintenance of cooling tower/water quality
- With the compressor integral to the indoor WSHP, there will be more noise generation within the residential unit
- A larger mechanical closet will be required in each residential unit. Stacking of the WSHP above a water heater will not be possible.
- Not all mechanical contractors are familiar with this system type or equipped to work on them
Water Source Heat Pump (WSHP) System with Geothermal:
This system will have a tempered (condenser) water loop system (40-85 F typically) with either a series of ground wells (vertical loops) or buried pipes (horizontal loops), pumps, and controls. Depending on the design of the ground wells or buried pipes, cooling tower(s) and boiler(s) may be needed to assist.
Condenser water piping will be piped from the geothermal pipes to each WSHP (typically constant volume water to air heat pump units) located in each residential unit.
Pros:
- Higher efficiency
- Separation of ground wells & WSHP has minimal effect on efficiency/performance of system
- Allows HVAC power consumption to be metered per tenant although the condenser water loop power consumption will need to be on house meter
- Only pump power required on condenser water loop if cooling tower(s) and boiler(s) are not needed for assistance
- Less maintenance than cooling tower if cooling tower(s) are not needed for assistance
Cons:
- Initial cost is highest
- Space will need to be allocated for a central plant housing pumps.
- A Geothermal Consultant will be required to conduct the design of the ground wells or buried pipes. Extensive soil testing will be required at the start of design.
- With the compressor integral to the indoor WSHP, there will be more noise generation within the residential unit
- A larger mechanical closet will be required in each residential unit. Stacking of the WSHP above a water heater will not be possible.
- Not all mechanical contractors are familiar with this system type or equipped to work on them
