Integration: electrical and HVAC systems

Integration of electrical and HVAC systems requires both careful design and integrated controls. This type of system integration can provide a more energy-efficient building.

07/14/2017


Learning objectives:

This article is peer-reviewed.

  • Understand how building systems can be integrated, such as electrical and mechanical systems.
  • Learn about building management systems and building automation systems.
  • Assess ways to integrate engineered systems to achieve greater energy efficiency in buildings.

Technology has changed the way modern buildings are designed and operated. It has improved the reliability and efficiencies of the modern electrical and mechanical systems. Equipment is more efficient due to advanced component design and the incorporation of onboard computer controls and logic.

Building management systems (BMS) are more advanced than ever and can operate the systems to much tighter tolerances. The improvements have changed the way today’s engineers can design and operate buildings to maximize energy consumption and minimize their impact on the environment.

Figure 1: Modern central utility plants are purpose-built spaces that house large heating, cooling, and power equipment. These systems are critical to the building performance and requires extensive coordination between trades to insure proper operation, fit, and service clearances. Using data analysis to right size building loads during design can have a significant impact on the cost of the building and the equipment. All graphics courtesy: NV5

To achieve these goals, the various building systems must operate together instead of working as stand-alone systems. Integration has compelled electrical and mechanical engineers to work more closely together during the various design phases so they can incorporate the required tools and logic to seamlessly operate the modern smart building.

The integrated design team

For many years, projects were designed by teams comprised of architects and engineers (civil, structural, fire/life safety, mechanical, plumbing, and electrical). This team approach worked well for most projects because the design expertise was contained within the group. The design team was a stand-alone component that had limited exposure with the construction team and the owner once the building was in operation. This relationship is illustrated in Figure 2.

Figure 2: The graphic at left illustrates the disjointed process of design, construction, and operation that has been used for many years. Each phase was seen as independent functions that did not require input or feedback from the various parties. The operation-driven design model at right seeks to break down these barriers by introducing various feedback loops and verification steps that are meant to influence design.Although each team was coordinating internally, the coordination efforts between the design team, contractor, and owner were disjointed and disconnected. This resulted in buildings that were designed with specific efficiency measures but constructed with systems that were more cost-effective than base design, which resulted in them not operating according to the original design intent. This dynamic needed to change as buildings became more complex due to advancements in technology, building materials, and construction methods. It was necessary for the traditional design team to expand and seek advice from specialized consultants who work for the architect (acoustics, vertical transportation, building envelope, audio/video, security and surveillance, information technologies, etc.) and nontraditional resources that work for the owner.

As building systems become more advanced and energy consumption becomes a prime driver in system design, it is imperative that the systems operate according to the design intent. Building owners have been turning to commissioning agents (CxA; often called commissioning providers, or CxP), energy engineers, and in some cases, various specialized trade contractors to certify the actual system operation meets the design specifications. In the past, these consultants and contractors were typically hired by the owner and operated independently of the design team.

In recent years, however, the various experts have become involved early in the design process and are integral members of any successful design team. This model has become so successful that many engineering firms have hired these consultants and contractors to provide an expanded service offering to their clients. Allowing these specialists to participate in the early phases of design is key to delivering a successful smart building to the owner.

These specialized disciplines can assist the engineers by providing operational feedback during design that can greatly influence how systems are sized, configured, and operated. This feedback can include but is not limited to:

  • Review of sequence of operations to incorporate practical experience
  • Preliminary electrical, heating, and cooling load profiles based on region and building type
  • Estimated energy consumption for proposed systems to identify the most efficient system option
  • Financial models to assist the owner in making informed decisions
  • Review of equipment submittals to assist the engineers in identifying variances
  • Review and analysis of potential value-engineering (VE) solutions proposed by trade partners.

The feedback loop between operations and design allows the integrated team to operate under a different model that includes more communication and coordination throughout the entire lifecycle of the building (see Figure 2). The operation-driven design model facilitates sharing of information between the design team, contractor, and owner. The model produces a building with integrated systems that are operated as they were designed and to peak efficiency. As the building ages, the operational feedback is used to tweak the systems to improve efficiency or identify areas of the building that may require maintenance or upgrades.Figure 3: The chart represents the expected breakdown of the energy usage for a typical integrated resort building, showing that the building systems are the major consumers of power, not the occupants.

Coordination during the design phases

The design effort required to successfully integrate the building electrical and mechanical systems cannot be viewed as a single checkbox in the designer’s to-do list. Integration must be a conscious effort among the various design professionals involved in the project. As each member of the team begins their respective designs, information needs to pass freely from one discipline to the other. Coordination between the engineers must be intentional to deliver the appropriate information at the right time so as to minimize mistakes and prevent wasted effort.

For example, as the electrical engineer begins to conceptualize the electrical distribution system, that engineer will need to understand the impact that the mechanical systems will have on the electrical infrastructure serving the building. What are the estimated equipment loads? Where are the loads located? How does the equipment operate? The electrical engineer can make assumptions based on experience, but will need the input of the mechanical engineer to finalize the design.

As buildings systems become more advanced, collaboration during each phase of design is crucial to the successful delivery of a high-performing building. It is even more critical when design services are provided by multiple firms or the design is dependent on the input from architects and other specialized consultants. To make the collaboration effort meaningful, each member of the design team needs to understand what information is important to the other designers and when it is required.

Schematic design phase

The schematic design (SD) phase of the project is the starting point for every design and is the time where the electrical and mechanical engineers begin to conceptualize the building systems to meet the project needs. The intent of this phase is to investigate various system options and arrive at a clearly defined concept that meets the owner’s objectives. The SD phase defines the parameters that will influence how the building systems are sized and configured.Figure 4: The energy consumed in a typical central utility plant is primarily associated with the chillers.

The concept design is typically conveyed through a basis-of-design (BOD) narrative and large-scale drawings that can demonstrate basic spaces, scale, and relationship of components. Once approved, this concept will guide the engineers through the design evolution of the various building systems.

During the SD phase, the electrical and mechanical engineers begin to investigate different system options that meet the needs of the project. Each discipline starts to perform calculations and develop technical schematics to define the various options.

Expected engineering tasks that require coordination and input from others at this stage are:

  • Review applicable building codes, building certifications (LEED, Green Globes, Energy Star, etc.), and design standards to identify impacts on the proposed building systems.
  • Determine the level of energy performance based on building-use type and define key metrics, such as energy use intensity or power usage effectiveness.
  • Estimate electrical loads for the project and begin coordination with the civil engineer and electrical utility.
  • Estimate mechanical loads (heating, cooling, water, sewer, and gas) and begin coordination with the civil engineer and utility companies.
  • Preliminary sizing of electrical and mechanical equipment.
  • Preliminary sizing of required plant rooms.
  • Preliminary electrical single-line distribution.

Coordination efforts between the various disciplines should begin to ensure that the proposed systems can integrate. At this point, much of the coordination is kept within the mechanical, electrical, and plumbing (MEP) design team. Critical information required to preliminarily size the electrical and mechanical systems include:

  • Estimated electric loads for the major mechanical equipment (chillers, cooling towers, pumps, air handling units, large fan systems)
  • Estimated heat-rejection rates of major electrical equipment (substations, transformers, uninterruptible power supplies, also known as UPS)
  • Preliminary locations of major electrical and mechanical equipment
  • Available power and voltage
  • Estimated UPS and generator loads (if applicable).

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