Requirement Summary
This measure can be claimed if the HVAC system has installed Variable Speed Drive (VSD) pumps, that is pumps with VSD motors.
Intention
The aim is to encourage the project team to specify VSD pumps, as energy consumption will be reduced, and therefore the utility costs. The lifetime of the system components is increased and less maintenance is needed.
Approach/Methodologies
In most cases, the HVAC system needs to operate at the maximum (peak) load only at certain times because its load is not continuous. VSDs control and regulate the speed of the flow depending on the load of the HVAC system. Therefore, installing VSD pumps on the cooling/heating system will reduce energy consumption. The following are the pros and cons of VSD motors for pumps:
Table 37: Benefits and limitations of VSD motors for pumps
| Benefits and Limitations of VSDs for Pumps | ||
| Benefits | Improved Process Control: | Provide regulation functions that improve the entire system and protect the other components of the system. |
| Improved System Reliability: | Lower chance of failure | |
| Simplified Pipe Systems: | Elimination of control valves and by-pass lines | |
| Improved System Lifetime: | Avoidance of soft start and stop, and resulting mechanical overload and peak pressures implied by on-off systems | |
| Reduced Energy Costs and Maintenance: | Ability to modulate speed and torque at part-loads reduces energy use, and wear and tear | |
| Limitations | Minimum speed may be required (typically 30%) | Manufacturers may require a minimum speed to avoid problems with overheating and lubrication |
To claim this measure, the design team must demonstrate that only VSDs pumps are installed. The HVAC system must require pumps, such as air or water-cooled chillers, heat pumps or absorption chillers, which must be previously selected.
Potential Technologies/Strategies
Various methods can be used to regulate the speed of the flow in the pumps to modulate its use in tandem with the load on the system, therefore reducing the energy consumption.
Variable Speed Drive (VSD) pumps use electronics to control the power used by the motor of the pump to adjust the speed of the flow into an HVAC system in response to the demand.
VSDs offer a high degree of control and are extremely versatile. They are available as standalone devices that are connected to the motor of the pump except for motors below 15kW, which are embedded or integrated into the motor.
Relationship to Other Measures
When VSDs for the pumps is selected as an energy efficiency measure, it is required that the HVAC system selected are either air or water-cooled chillers, heat pumps or absorption chillers for savings to show. Reduced pump energy use will also reduce the heat loss from pump motors and, therefore, the load on the cooling energy.
Assumptions
The base case for the air conditioning system varies based on ASHRAE 90.1-2007, and is typically a standard Packaged Terminal Air Conditioner (PTAC), as listed in the Key Assumptions for the Base Case in the Design section*. This measure will show savings only if the improved case includes air- or water-cooled chillers, heat pumps, or absorption chillers, that is, systems in which pumps are a part of the system. The assumption is that all pumps in the HVAC system will be provided with VSDs.
Compliance Guidance
To demonstrate compliance, the design team must describe the specified system and provide documentation to support the claims.
| Design Stage | Post-Construction Stage |
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At the design stage, the following must be used to demonstrate compliance:
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At the post-construction stage, the following must be used to demonstrate compliance:
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