The cavalry arrives on the scene: Enterprise's Field Technician Foreman, Joe Azara, at Fairview Hospital. The medical office building is the building to the left.
An Enterprise technician points to one of eight refrigerant expansion valves the company reconfigured.
A new condenser fan variable frequency drive allows the system's low ambient control to stage properly.
Enterprise relocated the global outside air temperature and humidity sensors to utilize outside air for 'free' cooling.
What is retro-commissioning? The National Environmental Balancing Bureau (NEBB) defines retro-commissioning as the systematic process by which the owner ensures that a building and its systems are optimized to perform interactively to meet the current operational needs as closely as possible. This may include remodeled design and construction to accomplish this goal.
That's a pretty straightforward definition, but a better explanation might be this: For savvy commercial contractors, retro-commissioning is a solid niche business. There is a huge market of buildings that need it; it's interesting, challenging and satisfying work for your people; and, when done properly, it creates extremely happy and loyal customers. Retro-commissioning gets you out of the cutthroat new construction market, and allows you to position yourself as a premier existing building specialist.
The Enterprise Corp. positioned itself for retro-commissioning as part of our "reengineering" strategy in the late 1990s. We went from a new construction mode (primarily with building controls) to an existing building contractor. We always had an active service business, a strong building controls knowledge, and we've been a NEBB certified air/water balance company for some time. These capabilities are fundamental to a specialty contractor performing start-up and commissioning service.
For 20 years (up until 2001), our company was a significant building controls contractor/ subcontractor. In the building control business, it's incumbent that you understand how the entire design and installation of the HVAC system come together.
As a controls contractor, you're much like the "finish carpenter" on a new house. The HVAC system never functions properly until the control components are in harmony with the installed HVAC hardware. Now superimpose the dynamics of the construction industry with its value-engineered design limitations, prime contractor failures, and project timeline adjustments. It can result in total chaos by the time of owner turnover. What a perfect recipe for system dysfunction and payment obstacles for all contractors involved.
Within the new construction world, we found ourselves correcting as many HVAC sins as possible through the building control system. Financial success was risky because of dependence upon the design/installation and timeline we inherited. It became increasingly obvious that this was no way to run a specialty contracting business that requires highly skilled personnel and consistent cash flow. That's when we opened the door to the world of retro-commissioning.
An Epidemic of Dysfunctional Systems
The number of dysfunctional HVAC systems is scary. It's a virtual epidemic from coast to coast. How do you know an HVAC system is dysfunctional? If it suffers from any combination of factors that prevent occupants from being productive and safe due to the mechanical-electrical-plumbing systems. It usually results in higher-than-normal energy costs as well.
Let's take a look at a retro-commissioning project The Enterprise Corp. recently completed to give you an idea how the concept works in the real world.
The internationally recognized Cleveland Clinic Foundation (CCF) comprises a network of hospitals and medical office buildings throughout our service area of Northeastern Ohio. One of the larger facilities within the CCF network is Fairview Hospital. Recently, Fairview made a $12 million dollar acquisition of a 53,000 sq. ft. medical office building (MOB) and 765-car open-air parking garage located adjacent to its campus.
A property management firm is responsible for leasing tenant space in the MOB, while another company operates the garage. Meanwhile, Fairview Hospital's operations department is 100% responsible for the MOB infrastructure, including HVAC, plumbing, and electrical.
When Frank Simecek, Fairview's director of facility services, called about this new acquisition, the situation in the MOB sounded dire: doctors were threatening to move out, there were numerous complaints of temperature discomfort, and indoor air quality was poor. It was time for a retrocommissioning.
The first step in a retro-commissioning is to find out what you're working with. In this case, the building's core system consists of two condensing units which total 175 tons of cooling (one 75 ton, one 100 ton); a cooling only air handling unit with supply and return fan variable frequency drives (VFDs), and 65 variable air volume boxes with electric reheat. The controls are a hybrid configuration: a manufacturer's building automation and direct digital control system (BAS/DDC) integrates the central equipment, while pneumatic temperature controls power the VAV boxes.
Our initial site visit was designed to inspect, test, evaluate, and listen to the occupants' complaints, while also promoting the hospital's initiative to fix the problems to everyone's satisfaction.
After this first phase was completed, we were able to centralize the problems around four main issues:
- The space temperature within the building was unpredictable. Tenants might need a sweater one day and a bathing suit the next, no matter whether it was winter or summer.
- The doctors suites were stuffy. Air stagnation was everywhere.
- Indoor air quality (IAQ) was a pressing issue. Some days garage odors permeated the entire building.
- Building energy costs exceeded $3.50 per sq. ft. The International Facility Manager's Association (IFMA) Operations and Maintenance Benchmarks 2005 estimates an average healthcare institution's utility costs at $2.28/sq .ft., an average clinic at $2.06/sq. ft. This facility far exceeded any utility benchmarks the hospital had studied.
A Four Month Process
From the initial inspection in February 2006, through the discovery and implementation process, it took Enterprise approximately four months to resolve the HVAC system's dysfunctions using the retro-commissioning process. Here's how we did it.
When we arrived, supply air duct static pressure of the building's 125-ton air handling system was set at and operating at 2.5-in. w.c. The industry standard for this type of system is 1.5-in. w.c.
This over-pressurization of the supply ductwork was placing undue stress on the 75-hp. supply fan and its associated ductwork. This also contributed to the building's high electrical energy costs. Our experience with systems that are set to run at excessive static pressure is that the higher set point conceals the real problems that are present.
Our first step was to lower the static pressure set-point from 2.5-in. w.c. to 1.5-in. w.c. to see what would happen. Immediately there was tenant fallout of "it's too hot." This feedback occurred on a 38F outside air temperature day in early March. When we accessed the complaining zones, we found their VAV boxes (remember, the BAS only read the central systems, not the zones) with any or all of the following problems: missing damper actuators, space thermostats loose on the wall, disconnected pneumatic control lines, and failed components.
The most prominent complaints were in the perimeter suites (about one-third of the building), where the air was stale and musty and return air was non-existent. After researching the original drawings of record, we learned that somewhere during the build-out of this five-story facility, return air was stubbed at the return air risers and never run out to the perimeter zones.
To provide proper return paths for these suites, we used a reverse engineering approach to size and locate the new return air openings.
The return air system is an often over-looked component of a healthy and properly functioning HVAC system. Providing a path for the building air to get back to the HVAC equipment is as important as the supply air that heats and cools the building.
We then created all new return air openings during early morning hours to reduce impact on tenant activity and comfort. Results were immediately felt as return air openings were cut in. Previously stagnant areas now had proper air movement.
When the occupants felt the results of our work, they were immediately convinced the hospital was serious about making this building a productive facility.
Another issue found during our discovery phase was that both supply and return VFDs were operating from the same static pressure signal. Minimum industry standards mandate the return fan track at a speed 10% less than the supply. This "as found" condition resulted in the return fan moving excessive amounts of air, which caused a building negative pressure condition and hallway draftiness.
This was most noticeable in every floor's elevator lobby. Each floor lobby was connected to one of the six level open-air garage doors, and negative pressure presented a wind tunnel of air, dirt, and odors that permeated each floor's environment whenever any garage access door was opened.
This also meant the lobbies were cold in the winter and hot in the summer. We fixed this condition by allowing the exhaust fan to track correctly with the supply.
When we accessed the building automation/DDC system, the programming was a mess. We corrected many control issues, with one of the most major being revising the existing sequence by letting the return air fan be controlled through building static. This was a win-win modification, because now the return fan speeds up only when required, which means electric costs are lowered.
When the air conditioning was activated, we found compressors short-cycling due to refrigerant flood back. The expansion valves were set improperly, and the hot gas bypass was incorrect. Furthermore, the sensing bulbs were also mounted in a poor location. They were relocated to achieve proper superheat control.
As a further refinement, we also installed a separate condenser fan VFD to the lead 50-ton unit. This ensures reliable hot gas to aid capacity control. It also minimizes premature compressor failures.
And what a surprise it was when we found the global DDC outside air temperature and humidity sensors located in the bathroom and AHU exhaust ducts. Depending upon wind conditions, one of the two exhaust temperatures would always have a negative effect on the building control sequence.
Turning Over a Functional System
With each day on site, we continued to make improvements to the building mechanical and control systems (both pneumatic and DDC). Work included decluttering 120V control wiring between the condensing units and the central equipment room on the fifth floor, and also reconfiguring the owner's front end building automation system.
At the owner turnover meeting, Fairview's staff was given final submittal information that included a pictorial of the correction process. Similarly, as-built drawings were also included, complete with sequence of operation.
True to the retro-commissioning model, the hospital staff was shown how to keep the HVAC system functional. During a training session with the hospital's maintenance personnel, we reviewed and distributed submittal booklets that described the retrocommissioning work we had done, including the revised mechanical and control schematics and new return air openings.
A Good Investment
Fairview's investment to diagnose and repair their dysfunctional HVAC system, document the results, and train their personnel was approximately $2/sq. ft. Was this a good investment for them? Let's ask.
Paul Slebodnik, Fairview Hospital's vice president of facilities, sent over one unsolicited e-mail during the peak of cooling season which read, "Dick, I have to tell you that we are very happy with the work your technicians are doing. I cannot believe how the previous contractor thought they were doing a good job. I'm certain the tenants will be very appreciative. I know that we are."
During the fall changeover season, Frank Simecek wrote a ringing endorsement to the incumbent property manager that read, in part, "I just recently had Enterprise do the MOB next to the hospital and redo the whole system that [the previous company] used to manage. I am complaint free now since they did all the work to get the system running properly. I just thought I'd shoot you a note to tell you what a great company they are. They're very professional and they get the job done right."
Retro-commissioning: it's good for your company, and it's good for you customers. Any further questions?
|Dick Starr is president of The Enterprise Corporation, Twinsburg, OH, a Design/Build mechanical service contractor. The company operates throughout Northeast and North Central Ohio. He is past chairman of the Cleveland MSCA and currently on the MSCA's National Education Committee. The company is an MSCA STAR contractor, NEBB Air/Water balance certified, and a Tridium "Vykon" Systems Integrator. Starr can be reached at firstname.lastname@example.org.|