Description of Three Existing Projects m
Appendix D pg.2
360 Court Street, Brooklyn Description
This building was originally a church in the gothic style built in 1890. The 1980 conversion to residential use was accomplished by adding a floor in the nave and apse. A total of 34 apartments were fitted into the original volume. The lower floor (basement) of the Church is above grade on the south side, and this space was converted to professional and mechanical space. The first floor of the nave was converted to fourteen condos, with the new second floor containing 20 units. Apartments were approximately 800 square feet in space and included a high bay living area and a loft with ladder sleeping area.
The project was subsequently converted to condominium ownership in 1988. Geothermal Configuration
This geothermal installation is one of the oldest in the New York City area. Geother-mal heat pumps were selected by the developer as it was impossible to install exterior equipment on this historic building, and allowed one appliance to perfor both heating and cooling duties.
The geo-heat exchanger used is an open system taking advantage of the porous overburden geology as discussed above. The system has been operational since commissioning.
Each apartment has its own vertical or horizontal geothermal water to air heat pump and its own thermostat control. Each dwelling unit is independent, and heating and cooling is available at all times. The only common portion of the geo-exchange system is the well water supply , its pump and controls.
Each heat pump is centrally located, allowing for short duct run to all areas requiring climate control. Most apartments have ducted returns, with some having a central return.
The heat pumps installed in the apartments is a mixture of ClimateMaster, Florida Heat Pump and TempMaster geothermal type in the 3 to 5 tonrange. Each heat pump originally had, and today again has, a motorized shut off valve which automatically opens when the heat pump's thermostat alls for conditioning. An end-switch on the valve then energizes the compressor. Each apartment has its pressurized well water piping from a common pressurized supply manifold. The well water flows through the heat pumps and flows into a common return manifold to the diffusion well.
The building site has narrow open earth corridors along the north and south (long) sides. The south side contains a small garden area and is approximately 25 feet wide and provides a site for a single 150 feet deep supply well. The well has a yield of 250 gpm and is typical of the shallow wells that would be found in the BrooklynQueen overburden, particularly in sites that are south of the Terminal Moraine area. The north side of the Building has a single diffusion well that is located behind a decorative iron fence bordering the side walk. The well originally had a single 25 hp submersible well pump that provided a constant 45 psig to a well manifold located on the mechanical room on the south side of the Building. This room contains pressure tanks originally installed to inhibit pump short cycling and the associated wear and tear. A piped distribution system brings well water to all heat pumps.
During the period after the formation of the condominium legal structure, the heat pump maintenance was abrogated to contractors retained by individual unit owners. This personnel had minimal geothermal experience and eventually removed all automatic shut off valves from the heat pumps. As these valves were removed, the submersible well pump was forced to run continuously, substantially increasing common costs. Additionally, the diffusion (return) well, which was designed for approximately 3,000 hours per year of equivalent full load, now was faced with absorbing 8,760 hours of continuous recharge to the earth. The return/diffusion well became saturated and started to overflow onto the street. High energy bills and water overflowing from the diffusion well prompted a reevaluation of the building geo controls.
In 1998, the automatic shut off valves were again installed on all of the heat pumps, and a small and properly sized 15 hp well pump was installed. A variable frequency drive (VFD) pump motor controller was included to reduce the work done by the pump. The VFD provided significant energy savings with the use of a single pump and 1 - 34 heat pumps calling at random times. Before the installation of the VFD a single heat pump calling for water would be required to absorb the full flow, creating a substantial energy penalty. A VFD is essential for economical operation with widely varying loads. Well pump short cycling has been proven to lead to well pump life reduction.
9 East 64th Street, Manhattan - Standing Column Wells
9 East 64th Street, NYC is a new building of approximately 14,000 square feet, with 5 aboveground floors and a cellar and sub-cellar. The location in the Upper East Side Historic District prevented the use of cooling towers or any other bulky equipment on the roof. Originally conceived as a sustainable design, it was to house the non-profit groups working on behalf of the environment, such as the Earth Pledge Foundation; Experiments for Art and Technology; and Theodore Keel's Foundation on Prevention and Early Resolution of Conflict. The building itself was to have been a model for environmentally friendly design, being energy efficient and using recycled and low environmental impact materials. Mr. Kheel sold the project due to high projected costs, and the structure is now residential.
Henry George Greene Architects, Leslie Gill, Architect, the energy consultant Steven Winter Associates and the project consulting engineer P. Andrew Collins, P.E. constituted the original design team. The geothermal consultant was Carl Orio of Water and Energy Systems. J and P Engineers, P.A. of Kendall Park, N.J. suggested to the Architects and Engineers for the project that geothermal heat pumps might be the best method for space conditioning this new building.
Subsequent analysis by Water & Energy Systems Corp., of Atkinson, NH, under contract to Consolidated Edison and The Electric Power Research Institute bore this out. A cost analysis and concept design of a geothermal heating and cooling system for the building was provided. A series of reports detailing New York City geology, earth coupling and geothermal heat pump approaches were issued to Con Ed during early 1997.
Two 1,500 foot deep Standing Column Wells were completed in April 1997. The wells are approximately 60 feet apart. The ground water level is just below the sub-cellar slab, and water crossing the site before construction appeared to be channeled by adjacent buildings, requiring a water resistant sub-cellar floor slab, below slab drainage, a sand trap weir and drains around the well heads to catch any water flowing out during maintenance that needs to be performed when the water table is high.
CONFIGURATION of GEOEXCHANGE SYSTEM
With the change in building use the heating and cooling loads were reduced, so the two Standing Column Wells were more than adequate.
Final well and pipe configuration was modified and a variable speed drive system was added. Note that early designs had a relatively small number of centralized geothermal heat pumps. Each heat pump is provided with the correct water flow and pressure at the motorized valve. This source side, well water valve automatically opens when the heat pump thermostat calls for heating or coling and the well water flows through the heat pump until the thermostat is satisfied.
The original well pumping scheme specified involved simple pressure logic, as the ratio of well pumps to the number of heat pumps was relatively high. The water flow requirement for any one heat pump is relatively large and the well water pumping energy used is then a relatively small portion of the total (heat pump + well pump) energy, i.e. the well water pumping penalty during partial flow is relatively small.
The new residential configuration of the building led to a marked increase in the number of zones, and the over-all number of heat pump units. The pump controls were then changed to variable speed driives. Well pumpng energy savings when only a small number of smaller heat pumps are active are then realized. As installed, a call from a single small heat pump, results on a well pump responding only with enough energy use to satisfy that low water flow. The ber of individual heat pump units increased due to the change in use from office to residential. Many of these heat pumps were of the split type, which allowed for the grouping of the compressorized sections in the sub-cellar, and the placement of the quieter blower section in the dwelling units.
Master (M) and slave (S) variable frequency drive (VFD) system is now installed. As there are now two occupants, with many more smaller heat pumps in the installation, any one call could result in a substantially lower well water flow rate. The VFD provides these small flow rates with commensurate power reductions in well pumping costs and prevents short cycling and the over pressurization of the well water manifold throughout the building.
Also note the use of the VFD has removed the requirement for the two relatively costly WX-350 pressure tanks. A small WX-104 pressure tank remains on-line to inhibit the effects of any possible small leak-back in the well pressured line due to check valve fouling or the like. Without this small accumulator the VFD could find itself in a rapid short-cycling if a small leak-back occurred in the well line.
GEOTHERMAL HEAT PUMPS & WELL WATER DISTRIBUTION
Heat pump configurations and distribution are essentially identical to conventional Boiler/Cooling Tower water source heat pump installations - a common multistory building configuration. The original design of the distribution system conformed to the commercial layout, with a large roof top unit and sepaate systems for each use. Large riser supply and return piping risers had already been installed when the decision to convert the system to residential was made.
The final building design, with more stringent noise reduction requirements, utilized a large portion of "split" geothermal heat pumps with the compressors and water heat exchangers in a basement mechanical room. The piping distribution system was then redesigned to accommodate the increase in heat pumps.
The building incorporates ClimateMaster brand geothermal heat pumps in vertical, horizontal and split configurations. The split heat pumps have the unit containing the compressor, controls and water side heat exchangers in a mechanical room in the basement. Refrigerant piping rises to the blower unit with a refrigerant coil in the various zones on upper floors. The building is commissioned and functional.
Long Island Power Authority Brentwood Facility
This article courtesy of the ClimateMaster Corporation
With R-12 refrigerant being rapidly phased out, many companies have had to evaluate the operating condition of their heating systems and many have taken the opportunity to review their expectations about their systems. The Long Island Lighting Co., a utility company in New York was just such a company.
The Brentwood facility, a 6000 square meter, two storey building, provides office accommodations for 300 operations staff and boasts a large cafeteria. Some offices are located in a basement which also contains the equipment room housing the HVAC system.
The old system was a hydronic, chiller system built in 1958 when energy was cheap and hydronic system technology was in its infancy. The system consisted of two 350 kW reciprocating chillers, a 900 kW gas fired boiler to heat make-up air in winter and a standby steam heat converter. Well water was continually circulated through the system by two alternating pumps with a total capacity of 50 HP. In-duct air coils heated or cooled discharge air in core areas, while fan coils heated the perimeter. The hydronic system was equipped with well water preheating coils, hot water coils, chilled water coils and reheat coils. Since the system was built before automation, water flow had to be changed over manually in the early summer and the late fall. The maintenance supervisor personally had to nursemaid the system from season to season.
Although the basement was never designed to be a conditioned space, a makeshift system was in use. Humidity was high and comfort low most of the year
Maintenance on the system was constant, costly and environmentally unacceptable. R-12 to replenish the refrigeration circuits on the chillers had become cost prohibitive as well as environmentally unsound. Without water regulators, acidic well water running continuously through the system at 30 flow litres per second corroded and eroded the copper and steel piping. Over the 30 year life of the system, the piping was completely replaced five times, section by section.
In 1990, the company approached the ClimateMaster agent to design a ground source, hydronic system to replace the old system. The requirements laid down for a new system included low first cost, low operating cost, low maintenance and improved comfort. The company also requested that the new system be contained within the existing mechanical room and that the system change-out be transparent to employees.
Bids were also secured for direct expansion style air-cooled condensers (split systems), air cooled chillers and water cooled chillers.
When all the bids were in, the hydronic system designed using ClimateMaster equipment had the first cost advantage of 35% - 50% over the alternative systems and the system fit comfortably within the existing equipment room. In contrast, some of the alternative systems required that the equipment room be enlarged.
The preliminary study performed by ClimateMaster's agent identified that the old system had been altered over time by undocumented changes so air performance was unknown. The complexity of the duct system was a limiting design factor, as was the client's desire to contain cost by saving much of what was operational in the existing system.
The new system kept the existing air handlers and some fan coils in place. Sixty percent of the in-duct coils had to be discarded. Reheat coils were removed since they were no longer required. The two 350 kW chillers were replaced with eighteen 37 kW water-to-water heat pumps. The existing wells were found to be stable and were allowed to remain in place. The well loop was separated from the building loop and adjustable, variable drive pumps were installed to control the flow of well water.
The new system was substantially repiped. Reductions in the amount of piping required allowed the 2 existing circulating pumps (50 HP) to be replaced by 9 pumps with a total capacity of 10 HP. For the convenience of the maintenance staff, the new system was designed with reversing valves and a Honeywell Energy Management system was specified.
The final design of the system divided the building into 5 zones, each with an air handler and in-duct coils. Every zone was supplied with one or more ClimateMaster WE Series heat pumps based on the air delivery of the air handlers. The basement zone has 4 dedicated WE units; the perimeter zone has 3 WE units;the 24 hour service system has I WE unit; the core was divided into 3 sub-zones with 2 WE units dedicated to each; and the cafeteria was divided into 2 sub-zones with I WE unit each. The make-up air supply was split. Two WE units are dedicated to one side for cooling only. The other side has no air tempering. A full economiser cycle can be operated in mid-season periods.
Motorised dampers on the make-up air system are controlled by the Honeywell EMS system. Renovation of the facility began on December 1, 1993. According to the contractor on the job, the biggest challenge was to keep the building space conditioning system operational while the retrofit was taking place. The standby steam heat converter was temporarily piped into the well water coils and the hot water heat coils. Because hundreds of feet of old pipe were paper thin and could be perforated by a finger, extreme care was necessary to install and remove the temporary piping. The retrofit system was put into operation May 1, 1994. During the 5 month project, construction had been almost entirely transparent to the office staff.
Although outdoor ambient temperatures have been higher than normal this year, no complaints have been received from employees since the system was placed on-line. In fact, it was only when summer heat came without expected discomforts that employees realized something had changed. The basement offices are comfortable now, both in terms of relative humidity and temperature. The Honeywell EMS system monitors both temperature and humidity. To date, average temperature holds within 2° C of set-point. Estimated energy savings is expected to be 600,000 kwh per year and maintenance costs should be reduced by 90% over the next 5 years.
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