Energy Management Systems

In Canterra Tower, Oxford properties Group Inc., installed a Johnson Controls Ltd. 85/40 building automation system, in 1988. This system was upgraded to JCL’s Metasys Building Management System in June 1995 and incorporates a distributed processing network which broadens the scope of opportunities for building management, costs, savings and control. The system is capable of controlling 2,000 plus points including VAV terminal units, radiation control, fans, pumps, chiller and boiler plant electronic sensors.
With the cooperation of the City of Calgary we are using their Rate 680, which helps reduce the summer and winter peak demands by operating at reduced loads during specific times.
The Johnson Controls Ltd. Metasys System uses programs to facilitate energy management. Programs such as “Load Manager”, “HVAC Manager” and ‘’Chiller Manager” work together in reducing the peak demand of the building.
“Load Manager” controls the electrical consumption and demand in the building. It does this by using integrated routines for duty cycling and demand limiting. The “Load Manager” also provides dynamic management and system analysis reports.
The “Peak Demand Limiting” program controls the building peak demand at a pre-selected KVA to prevent excessive demand charges. The demand limiting routine has the ability to calculate the amount of load which should be shed or restarted to keep the demand at the target value. The load manager bases it’s control strategies on load parameters such as priority, minimum “On” time, minimum “Off” time and maximum “Off” time.
“HVAC Manager” reduces the cost of operating air handling equipment with the use of such functions as Enthalpy Switch Over and Supply Air Reset. Enthalpy Switch Over saves cooling energy while Supply Air reset reduces both heating and cooling energy.
“Chiller Manager” module works to reduce the cost of operating the chiller plant. The strategies it uses include: chilled water reset, condenser water reset and chiller sequencing. The cooling system also includes a free cooling plate-to-plate heat exchanger as well as a precoil system on make-up air fans. This provides cooling during the peak demand period and any other time the temperature permits.
The Energy Management Program has contributed to electrical, natural gas and water reductions of approximately $300,000, over the past two years. These energy management savings have assisted Canterra Tower to reduce its fixed operating costs from $5.15 square foot in 1992 to $4.60 square foot in 1994.

The above initial system installation in the Tower, followed by electrical and mechanical enhancements have all contributed to reductions in electricity, natural gas and water consumption.

Summaries of the electrical and mechanical enhancements are as follows:

One compartmentalized VAV air handling unit is installed on each floor for cooling and ventilation. Each unit includes a supply fan, chilled water cooling coil and filters. Controls are pneumatic. Static pressure and discharge temperature control ensures that the unit operates efficiently and in a stable fashion. The compartmentalized approach was selected because of the following advantages it offers over conventional central systems. Fan energy is reduced by approximately 2%.
In 1992, the two base building cooling towers were equipped with pressure transducers receiving a pneumatic signal to sense the sump water levels. This system provides a more accurate level control and reduces water consumption and maintenance.
In 1993 modifications to the existing chilled water system were made to obtain approximately 200 additional hours of free cooling per year. The enhancements include installing new piping and three-way valves to permit the operations team to gain additional free cooling by flowing the chilled water through the two make up air unit precoils and recoils to gain as much free cooling as possible. The two base building cooling towers were upgraded with type ‘A’ spray nozzles to provide a finer spray and increase the cooling tower operating point to -1.10 C (300 F) from 2.80 C (280 F). The operations team were able to obtain a six month payback period on an expenditure of approximately $60,000.00. Excess heat in the chilled water logs is transferred to a plate heat exchanger.
Canterra Tower has dedicated condenser water loop that operates twenty-four hours per day, year round. The condenser water is used as a heat rejection medium for tenant's self-contained air conditioning units. Most of the units were installed in computer rooms or other sensitive areas. If the condenser water system was not installed, domestic cold water would have to be used to reject the heat of compression from the tenant’s air conditioners. The condenser water system saves approximately two million gallons of domestic cold water annually from being dumped to drain.
In 1994, the five gas fired forced draft water tube boilers were upgraded with new super heater tubes, new “Firewall” target wall material and new boiler re-circulation pumps. The re-circulation pumps help to reduce shocking the boilers by recirculating hot water heating supply water into the return header within the boiler. The result was an approximate reduction on natural gas consumption of approximately twenty-five percent.
The PDM lighting control system installed is a computer based system which provides individual or group control of each lighting circuit. Each circuit can be automatically controlled by an individual schedule established to suit the time requirements of the occupants in the particular area, or circuits can be grouped together to simultaneously control a larger area. This state-of-the-art system is equipped to provide the building owner/manager with the means to minimize the energy consumption while providing the very best of service to the tenants.
In 1993, the domestic water systems were upgraded to prevent any cross connection that could contaminate the domestic water supply. Premise isolation in the form of two double check valve assemblies (DCVA) were added to the water service at the point of entry to the building. This enhancement will protect the municipal water supply from any contamination that may occur within The Canterra Tower. The installation of two DCVA’s allows one to be isolated for service without disrupting the service to the building. All of the cross connection control devices within the building are inspected and re-certified annually.
Group lamp replacement with energy saving fluorescent tubes; reduction of lighting in washrooms and lighting zone changes were done in October 1992.
On the main floor and plus 15 lighting power consumption, contributed to reductions. The parkade carbon monoxide detectors were re-calibrated to maintain the new eight hour exposure limit of 25 ppm as set by the February 16, 1993 issue of The Occupational Health and Safety Act, Chemical Hazards Regulation.
In July 1995 Greystone Energy Systems were installed to monitor Air Quality (Carbon Monoxide (CO), Cigarette Smoke, Benzene, Alcohols, Hydrogen, Hydrocoslon, etc., Temperature Sensor, Humidity Hazardous Gas (Ammonia, combustibles, Freon and Carbon Dioxide (CO2).
In 1992, the two base building cooling towers were equipped with pressure transducers receiving a pneumatic signal to sense the sump water levels. This system provides more accurate level control and reduces water consumption and maintenance.
In 1993, the two Carrier model 19DR chillers were upgraded with high efficiency purge units to reduce CFC omissions to 0.1 lb. of R-11 per lb. of air. New non-fragmenting rupture disks and supervised relief valves were also added to prevent the loss of the complete CFC charge. The chiller room has been equipped with new oxygen and refrigerant sensors and will activate the new exhaust system to purge the chiller room of any refrigerant.
Upon detection of a refrigerant leak strobe lights inside and outside of the chiller room will activate, warning people to vacate the room and put the self-contained breathing apparatus on before entering the chiller room. Complete safety procedures are posted on both doors entering the chiller room.
In 1992 lighting in washrooms was reduced to lower levels yet not compromising acceptable lighting levels. This reduction has reduced energy costs.
Also in 1992 power factor correction capacitors were added to the incoming main electrical distribution. This addition provides reduced energy costs.
A Thompson Technology bumpless transfer switch was installed to be utilized in conjunction with the 750 KW emergency generator for peak shedding (reduction of the peak electrical consumption).

In addition to the above Energy Management Programs, the Base Building Environmental Program has been an integral part of not only energy costs savings, but maintaining or increasing levels of air quality to not only meet but exceed ASHRAE levels of air quality for high rise buildings.

Since the beginning of 1994, the Base Building Committee in conjunction with Thurber Environmental and TMP Consulting, have produced an audit and two major air quality studies that have not only assisted in energy savings but increased Canterra Tower's air quality.