Today’s HVAC&R engineer, or mechanical engineer of record (MER), continues to be a steward of the basic discipline issues identified by Mr. Wilson nearly 100 years ago. Roles have expanded, though, to address more modern quality of life issues. ASHRAE offers the current vision of the MER’s stewardship responsibilities: to improve the quality of life by helping keep indoor environments comfortable and productive; by helping to deliver healthy food to consumers; and by helping to preserve the outdoor environment.
As part of a holistic controlled environment design solution, the MER is responsible for addressing seven major processes. These are:
- Heating—the addition of thermal energy to maintain space or process conditions in response to thermal heat loss
- Cooling—the removal of thermal energy to maintain space or process conditions in response to thermal heat gain
- Humidifying—the addition of water vapor to maintain space or process moisture content
- Dehumidifying—the removal of water vapor to maintain space or process moisture content
- Cleaning—the process of removing particulate and bio-contaminants from the conditioned space.
- Ventilating—the process of providing suitable quantities of fresh outside air for maintaining air quality and building pressurization.
- Effectiveness—the process of achieving the desired thermal energy transfer, humidity control, filtration, and delivery of ventilation air to the breathing zone of the occupied space in accordance with required needs.
It is important for the MER to be involved early in the project, even as early as the programming stage, so that mechanical system space issues and facility energy budgets can be evaluated and integrated into the design process before building construction elements, configurations, and orientations are finalized (see also WBDG High-Performance HVAC). A few critical issues that need to be considered early are:
- Financial Focus: Will the project be a code minimum type facility or will total ownership cost perspectives be considered that balance capital first costs against long-term ownership and operating costs?
- Owner Sophistication: The MER needs to understand the abilities of the owner and keep these in mind as mechanical system architecture issues are considered. The best of design solutions aren’t much good if operators do not understand how to correctly operate or control the equipment.
- Operations and Maintenance: No matter what level of system complexity is applied, it is imperative that suitable space be made available for equipment without compromising performance or maintenance access. A good MER will understand the requirements published in equipment installation manuals and focus on providing prescribed minimum service and operating considerations in the planning of a facility layout.
Before any equipment selections can be finalized, the MER will need to perform a thermal load calculation for the developing facility based on internal and external influencing factors. In many cases, this activity will be expanded to include analysis of comprehensive energy models. These models will foster dynamic integration opportunities whereby the design team and owner can evaluate the impacts of trade-offs between facility construction elements, mechanical system alternatives, and available operating efficiencies. Load calculations can be utilized for any or all of the following design activities:
- Defining the basic load dynamics
- Evaluating solution alternatives via life-cycle analysis
- Optimizing system performance
- Selecting final HVAC equipment
- Establishing energy budgets for owners
- Verification of proposed equipment performance
- Commissioning Design Intent for seasonal comparison
The MER will be responsible for securing/developing the following fundamental information from the Owner and design team members:.