ASHRAE Journal - August 2011 - 50

ambient allows. It is not unusual to see the system pressure January. During free cooling, the pressure experienced at the around 75 to 90 psig (5.2 to 6.2 barg). lower end of the range is due to the parallel relationship between The temperature of the refrigerant leaving the condenser is the ambient and liquid refrigerant temperatures. Comfortable within one degree of the ambient temperatemperatures are consistently maintained ture. By controlling the refrigerant flow in the building while achieving considerBuilding at a Glance and fan speed, we can control the liquid able energy savings. Name: 62 and 18 Tilly Drive refrigerant temperature. The controller The retrofit (see sidebar, “Floating monitors the chiller barrel glycol temHead Pressures, Bypassing CompresLocation: South Burlington, Vt. perature and keeps it at setpoint without sors”) allows the condensing temperatures Owner: Pizzagalli Properties much drift. On a graph, the minimal power to float with ambient with no loss of consumption flatlines, without spikes up capacity, while simultaneously achieving Principal Use: Medical or down. energy savings. This project achieved Includes: Offices The energy saving results were signifiits design objectives while maximizing cant, especially in colder weather. The kW energy savings throughout the year. The Gross Square Footage: 28,000 per ton pre-retrofit (mechanical cooling) sequence of operation and setpoints are Substantial Completion: 2009 was 1.2 kW or greater. After retrofit in controlled by a DDC system and change the free cooling mode, the kW per ton in operation throughout the year based on Occupancy: 100% during retrofit dropped to 0.18 kW or lower under the outside temperatures and load conditions. same conditions. The power consumption The chillers are using R-22 and operate and chiller capacity is driven by ambient temperature. from a saturated condensing temperature setpoint of 105°F Because of the new equipment installed and the system set- (40.6°C) and will drop down to as low as 30°F (–1.1°C), depoint changes, there is no “normal” system pressure. It ranges pending on the outside air temperature. from 250 psig (17.2 barg) in mid July to 70 psig (4.8 barg) in Because our design has no compressors in operation below 40°F (4.4°C) outside air temperature, there is no heat from compression, and the condensers approach is within approximately a 1°F (0.6°C) difference between the outside air temperature and the refrigerant temperature in the condenser. This low-temperature differential allows more energy savings than a traditional glycol-free cooling system as the differential temperature for glycol-free cooling is typically 6°F to 8°F (3°C to 4°C) above ambient due to its heat transfer properties. We Standard 90.1-2010 is an indispensible reference also circulate the same refrigerant in the circuit whether we for engineers and other professionals involved in are in the mechanical cooling mode or in the refrigerant-free the design of buildings and building systems. cooling mode.

NEW Energy Standard for Buildings

• Increased precision for building envelope requirements • Lower interior lighting power densities • New day lighting requirements and power density tables • Expanded coverage of receptacles and process loads
Price: $125 (ASHRAE Member: $106)

Energy Efficiency

For every 1°F (0.6°C) that the saturated condensing temperature is reduced in a refrigeration system, the energy savings on the compressor will range from 1.2% to 1.6%. By lowering discharge pressures, the energy consumption goes down while the capacity in the system goes up. Our system uses a fractional horsepower, magnetically coupled, centrifugal pump to move refrigerant from the condenser to the evaporator. This eliminates flash gas when the condensing pressures are reduced.
Energy Use

• Incorporates over 100 addenda

www.ashrae.org/standard901-2010
www.info.hotims.com/37989-91

Using data collected prior to retrofit, a base model was created that revealed that the chiller used an average of 638.60 kWh per day over a period of one year at an average demand of 26.61 kW. Following the retrofit, empirical data was collected for a period of 467 days. The data showed that the post-retrofit chiller consumed an average of 267.50 kWh per day. The average demand was 11.15 kW, compared to the 26.61 kW pre-retrofit. This is an average savings of 15.46 kW. The building owner’s chiller problem was solved, and a substantial amount of energy was saved.
August 2011

50

ASHRAE Journal



ASHRAE Journal - August 2011

Table of Contents for the Digital Edition of ASHRAE Journal - August 2011

ASHRAE Journal - August 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
Retrocommissioning Older Buildings
Liquid Refrigerant Pumping in Industrial Refrigeration Systems
Technology Award Case Studies:
Hospital Upgrade: Heat Recovery, Geothermal Save Energy
Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
Special Section
InfoCenter
Standing Columns
Solar NZEB Project
Emerging Technologies
Special Products
IAQ Applications
Washington Report
People
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - August 2011 - Intro
ASHRAE Journal - August 2011 - ASHRAE Journal - August 2011
ASHRAE Journal - August 2011 - Cover2
ASHRAE Journal - August 2011 - 1
ASHRAE Journal - August 2011 - 2
ASHRAE Journal - August 2011 - Contents
ASHRAE Journal - August 2011 - Commentary
ASHRAE Journal - August 2011 - 5
ASHRAE Journal - August 2011 - Industry News
ASHRAE Journal - August 2011 - 7
ASHRAE Journal - August 2011 - 8
ASHRAE Journal - August 2011 - 9
ASHRAE Journal - August 2011 - Letters
ASHRAE Journal - August 2011 - 11
ASHRAE Journal - August 2011 - 12
ASHRAE Journal - August 2011 - 13
ASHRAE Journal - August 2011 - 14
ASHRAE Journal - August 2011 - 15
ASHRAE Journal - August 2011 - Meetings and Shows
ASHRAE Journal - August 2011 - 17
ASHRAE Journal - August 2011 - 2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
ASHRAE Journal - August 2011 - 19
ASHRAE Journal - August 2011 - 20
ASHRAE Journal - August 2011 - 21
ASHRAE Journal - August 2011 - 22
ASHRAE Journal - August 2011 - 23
ASHRAE Journal - August 2011 - 24
ASHRAE Journal - August 2011 - 25
ASHRAE Journal - August 2011 - Retrocommissioning Older Buildings
ASHRAE Journal - August 2011 - 27
ASHRAE Journal - August 2011 - 28
ASHRAE Journal - August 2011 - 29
ASHRAE Journal - August 2011 - 30
ASHRAE Journal - August 2011 - 31
ASHRAE Journal - August 2011 - 32
ASHRAE Journal - August 2011 - 33
ASHRAE Journal - August 2011 - 34
ASHRAE Journal - August 2011 - 35
ASHRAE Journal - August 2011 - Liquid Refrigerant Pumping in Industrial Refrigeration Systems
ASHRAE Journal - August 2011 - 37
ASHRAE Journal - August 2011 - 38
ASHRAE Journal - August 2011 - 39
ASHRAE Journal - August 2011 - 40
ASHRAE Journal - August 2011 - 41
ASHRAE Journal - August 2011 - 42
ASHRAE Journal - August 2011 - 43
ASHRAE Journal - August 2011 - Hospital Upgrade: Heat Recovery, Geothermal Save Energy
ASHRAE Journal - August 2011 - 45
ASHRAE Journal - August 2011 - 46
ASHRAE Journal - August 2011 - 47
ASHRAE Journal - August 2011 - Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
ASHRAE Journal - August 2011 - 49
ASHRAE Journal - August 2011 - 50
ASHRAE Journal - August 2011 - 51
ASHRAE Journal - August 2011 - InfoCenter
ASHRAE Journal - August 2011 - 53
ASHRAE Journal - August 2011 - 54
ASHRAE Journal - August 2011 - 55
ASHRAE Journal - August 2011 - 56
ASHRAE Journal - August 2011 - 57
ASHRAE Journal - August 2011 - 58
ASHRAE Journal - August 2011 - 59
ASHRAE Journal - August 2011 - 60
ASHRAE Journal - August 2011 - Solar NZEB Project
ASHRAE Journal - August 2011 - 62
ASHRAE Journal - August 2011 - 63
ASHRAE Journal - August 2011 - 64
ASHRAE Journal - August 2011 - 65
ASHRAE Journal - August 2011 - Emerging Technologies
ASHRAE Journal - August 2011 - 67
ASHRAE Journal - August 2011 - 68
ASHRAE Journal - August 2011 - 69
ASHRAE Journal - August 2011 - 70
ASHRAE Journal - August 2011 - 71
ASHRAE Journal - August 2011 - 72
ASHRAE Journal - August 2011 - 73
ASHRAE Journal - August 2011 - 74
ASHRAE Journal - August 2011 - Special Products
ASHRAE Journal - August 2011 - IAQ Applications
ASHRAE Journal - August 2011 - 77
ASHRAE Journal - August 2011 - 78
ASHRAE Journal - August 2011 - 79
ASHRAE Journal - August 2011 - Washington Report
ASHRAE Journal - August 2011 - 81
ASHRAE Journal - August 2011 - People
ASHRAE Journal - August 2011 - 83
ASHRAE Journal - August 2011 - Products
ASHRAE Journal - August 2011 - 85
ASHRAE Journal - August 2011 - Classified Advertising
ASHRAE Journal - August 2011 - 87
ASHRAE Journal - August 2011 - Advertisers Index
ASHRAE Journal - August 2011 - Cover3
ASHRAE Journal - August 2011 - Cover4
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