E3 Designs

INTRODUCTION

In the summer of 2002, E3 Designs L.L.C. was hired to perform an assessment of the mechanical systems in buildings 118, 123, 128, 200, 206, 319, and 330. The scope of the project included a site survey to evaluate HVAC components in each building, a review of available documentation including utility bills, mechanical plans, and identification of any operational problems.

The goals of this project include providing a complete life cycle analysis of the HVAC systems: operating efficiency, maintenance requirements, remaining useful life, and an estimate of replacement costs. Recommendations are also made to address any problems identified in the individual buildings, and to provide general suggestions for improving the operation of the HVAC systems.

EXECUTIVE SUMMARY

The facility includes just over 350,000 square feet of buildings, mostly of pre-World War II vintage. During the 1990’s, an 80,000 sq ft office building was built and many of the HVAC systems were upgraded.

The HVAC systems were reviewed in eight buildings including 118, 121, 123, 128, 200, 206, 319, and 330. Heating is provided by oil-fired boilers located in each building. Three of the buildings, 128, 319, and 330 have steam boilers feeding the original perimeter radiators. Buildings 121 and 123 are heated with hot water unit heaters, and 110 and 206 were retrofit with perimeter baseboard and hot water convectors. Only building 200 is equipped with central HVAC, providing heating and cooling from three central air handling units and perimeter fan coil units. Other buildings have individual offices cooled by window air conditioners.

It appears that a control retrofit was performed in the past 10 years. Self-contained thermostats were installed on individual perimeter units to provide rudimentary temperature control. Heat timers were also installed on some boilers to provide temperature reset and optimize boiler control. Building 200 has a pneumatic control system that provides central temperature control functions including scheduling and night setback.

The HVAC components are at various stages in their useful life. The equipment was evaluated based on remaining useful life and cost to replace. The following chart represents future capital budget requirements for the replacement of HVAC systems that have reached the end of their useful life. The costs shown are in current year dollars and assume replacement of existing systems in-kind.

The central HVAC equipment at the facility appears to be adequately maintained. No historical information was available on the costs and man-power used to maintain the HVAC systems. Estimates of maintenance requirements based on equipment type and age are included in this report.

Operating costs typically represent the largest expenditure over the useful life of a mechanical system. HVAC energy use accounts for 50% of the overall building electrical usage. The estimated operating cost for the HVAC systems range from $0.50 to $0.80 per square foot per year, which are generally within acceptable limits for buildings of similar use and geographic location. The exception is Building 200, which operates at an annual HVAC cost of $1.25 per square foot. These costs could be reduced substantially by the installation of a DDC control system, which would improve system performance while reducing operating expenses.

The biggest issue that needs to be addressed is the long-term viability of the buildings at the site. Most of the older buildings would need a substantial upgrade to provide an adequate working environment. Issues such as humidity control, ventilation, and air filtration are not provided under the current system design. The costs to perform an upgrade and the impact on utility costs are included in this report.

SYSTEM DESCRIPTION

The facility includes nine buildings with a combined area of just over 350,000 square feet. Most of the buildings are pre-World War II vintage, with a newer office building being constructed on the site in the early 1990’s.

HEATING: All of the buildings are heated by individual boilers firing #2 oil. Buildings 128, 319, and 330 have steam boilers supplying radiators along the perimeter. The steam radiators are original equipment with the buildings and are modulated to maintain space temperature by self-contained Spence valves. The steam in buildings 128 and 330 are provided by HB Smith fire-tube boilers installed in 1996 and are in fair to good condition. Building 330 has two boilers serving different areas of the building. The boiler in building 319, a Weil-McLain cast iron sectional, was installed in 1984 and is in fair condition. The boilers are manually energized and space temperatures are continuously maintained at occupied temperatures.

Building 118 was retrofit in 1995 with a Slant-Fin hot water boiler serving baseboard radiation, and is in fair condition. The hot water circulating pump is energized by a space thermostat that continuously maintains occupied set-point.

Building 121/123 has two HB Smith hot water boilers that were installed as part of a retrofit in 1994. They are equipped with Heat Timers that allow the hot water temperature to be reset based on ambient conditions. There are two pumps that provide hot water to two air-handling units and 30 unit heaters located throughout the building. The unit heaters have thermostats that cycle their fans to maintain space temperatures. There is a large ceiling-mounted make-up air unit with a hot water coil serving the garage area in the back. The unit is manually energized to provide ventilation air during the cold winter months. The unit appears to be in fair condition. There is also a smaller ceiling mounted air handler serving an office area in the back that also appears to be in fair condition.

Building 200, the new office building, also has two HB Smith hot water boilers equipped with Heat Timers. A single hot water pump delivers hot water to three main air-handling units along with terminal reheat coils and perimeter fan coil units. The air-handlers and reheat coils are controlled by a pneumatic temperature control system with a timeclock to allow for an unoccupied cycle. Perimeter fan coil units can provide either heating or cooling and have self-contained controls.

Building 206 also has an HB Smith hot water boiler with a Heat Timer. The building was retrofit in 1992 with hot water convectors along the perimeter, served by two hot water pumps. The hot water pumps are cycled based on a signal from a space thermostat.

AIR-CONDITIONING: The only building with central air-conditioning is building 200, which has a chilled water system supplying 3 main air-handling units and perimeter fan coil units. The chilled water is generated by a 200 ton air-cooled condensing unit, equipped with two 100-ton rotary compressors. The unit is matched with a DX chiller barrel that provides chilled water for the building, via a single 25 hp chilled water pump. The water is supplied to three main air-handling units, one serving each floor. The units provide a constant supply air temperature by varying the amount of air going through the coil in a face and bypass arrangement. The perimeter fan coil units modulate chilled water through the coil based on return air sensors in the self-contained controls.

There are also five split-system air conditioners serving specific areas within the building. Each unit is manually enabled and controlled by wall thermostats in the space. There are no other central air-conditioning systems at the facility. The remaining buildings have some offices that are cooled using window air conditioners.

CONTROLS

Temperature: All of the buildings have some degree of temperature control. The older buildings (128,319,330) with the steam heating systems rely on self-contained Spence valves to modulate the temperature based on a cooler or warmer setting. The buildings with hot water systems (118,121,206) can cycle the hot water pump based on an actual temperature setting. Individual terminal units will cycle to maintain temperatures.

Building 200 has a pneumatic control system that uses air pressure to sense temperatures and actuate valves and dampers. The air-handling units are designed to provide a constant discharge air temperature that is reheated through individual zone reheat coils. The air-handling unit coils and the perimeter fan coil units are supplied with either hot water or chilled water depending on a manual selection made by the building operators. The fan coil units are equipped with a strap-on aquastat that will sense entering water temp to determine if the self-contained thermostat should be direct or reverse acting. The control sequence for the building includes a night shutdown temperature setback routine.

Humidity: There is no direct sensing or control of humidity in any of the buildings. The central chilled water system in building 200 provides dehumidification during the summer by means of a low discharge air temperature, but the system often removes more moisture than is necessary, increasing system loads and operating costs.

Fresh air / Ventilation: The only building with the means to provide fresh air is building 200. Outside air is introduced through the main air-handling units. The outside air dampers will modulate open to maintain the discharge air temperature. When the outside air temperature exceeds the return air temperature, the dampers revert to minimum position. The dampers remain closed during the unoccupied cycle.

Fresh air in the remaining buildings is provided through natural ventilation and infiltration and is assumed to be adequate. There is no method to monitor the amount of fresh air being introduced into the buildings or to sense and control the CO2 levels in any of the spaces.

LIFE CYCLE ANALYSIS

The scope of the project includes a review of the life cycle components of the building mechanical systems. These components; operating cost, maintenance requirements, remaining useful life, and replacement cost, are helpful in developing long term planning for equipment replacement and upgrades.

MAINTENANCE COSTS: Maintenance costs represent a significant expenditure over the life of a system, often rivaling installed cost in total economic impact on a project. However, there is limited available data on HVAC maintenance costs to use as a guideline to estimate these costs. Efforts to collect and summarize maintenance data by organizations like ASHRAE, has met with limited success. The best available method for determining these costs is to establish a benchmark based on historical data and to use vendor full coverage service pricing.

An estimate of labor and material requirements for preventative maintenance and repair has been made for the HVAC components. This information can be used for budgeting and man-power planning or as a comparison with historical information.

REMAINING USEFUL LIFE

A determination of future capital budget requirements cannot be developed without a discussion on the remaining useful life of the major mechanical components. Equipment service life continues to be the most difficult information to collect reliably. Most studies attempting to define useful life end up as average age of death studies, ignoring the vast number of components still in operation. With a lack of quantifiable data to access, the best alternative is to rely on experience to estimate remaining useful life. During our field survey, an attempt was made determine the condition of the HVAC equipment in each building. The following tables identify the mechanical components with general condition, remaining useful life, and estimated replacement cost.

OPERATING COSTS: Operating costs typically represent the largest expenditure over the useful life of a mechanical system. A mathematical model was developed to approximate the operating costs for the individual mechanical components in each building. These costs vary based on equipment size, efficiency, operating hours, and utility rate structure. The electric utility bills were used to fine-tune the accuracy of the model.

The buildings are supplied electricity General Large service rate structure. This rate structure has both consumption (KWH) and demand (peak KW) components. The kwh rate averages $.08 per kwh. Peak demand charges can exceed $20 per kw during summer occupied periods. In reviewing the electric bills, kwh consumption accounts for 60% of the electric bill cost, with the remaining 40% due to demand charges.

All of the buildings are heated using #2 oil. Historical oil delivery information for each building was not available. Estimates of oil usage were calculated based on design load and weather data information. Based on these calculations, total annual oil cost should be $150,000 assuming standard system efficiencies.

According to the building model, HVAC energy use accounts for just over 50% of the overall building electrical usage. The peak air conditioning usage currently adds 250 kw to the base system load. The model was used to estimate electrical and oil consumption by building. HVAC operating costs range from $.50 per square foot to $1.25 per square foot depending on building type and complexity. Most of the buildings are within typical operating costs for buildings of similar size, use, and geographic location. The exception is building 200, which has an operating cost well above the norm. Following some of the upgrade recommendations in this report will help to bring operating costs in the building down into the typical range.

OBSERVATIONS AND SUGGESTIONS

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)[1] defines thermal comfort as “…that condition of mind that expresses satisfaction with the thermal environment.” This definition correctly emphasizes that the judgment of comfort takes into account many elements influenced by physical, physiological, and psychological factors. The ultimate role of the building HVAC system is to deliver clean, appropriately conditioned air to the space, while providing a means to remove indoor contaminants.

Using this definition, we can establish a standard to determine the overall effectiveness of the HVAC systems. The original buildings provide some control of temperature through individual control valves on the perimeter heating systems. Some of the office areas have window air-conditioners to provide cooling and dehumidification in the summer months. There was no mechanical ventilation found, except in the garage areas of Buildings 121 / 123. In the office areas, fresh air is introduced through open windows or through natural infiltration with no means to condition or filter particulates out of the air.

The system in Building 200 does a much better job of providing acceptable environmental conditions. Fresh air is introduced into the air-handling units where it is filtered and conditioned before being supplied into the space. The units are also equipped with reheat coils to allow independent control of humidity and temperature. The pneumatic control system is in poor condition and should be upgraded to a DDC control system. Building 200 accounts for a large portion of the HVAC electrical energy use. A DDC control system would provide the ability to implement and verify system wide energy saving strategies.

The remaining buildings should be evaluated based on the long-term infrastructure requirements of the entire organization. Operating costs for these buildings are relatively low, and should not be a significant factor in the decision making process. However, the quality of the indoor environment for the occupants that continuously serve in these areas is cause for concern. Consideration should be given to consolidating the functions in these buildings to a single location. If this is not feasible, a general upgrade of the HVAC systems in these buildings should be planned. The following chart provides an estimate of the cost to upgrade the HVAC systems in each building along with the impact on annual operating costs. It can be used as a guideline for future budget requirements.

[1] The American Society of Heating, Refrigerating, and Air-Conditioning Engineers www.ashrae.org