Recovering Air Handler Condensate
Without Disrupting the Campus Infrastructure
Pat Guccione, Vice President Business Development, Chem-Aqua
Olen Pruitt, Asst Vice President for Facilities Management, UAB
The University of Alabama at Birmingham
The University of Alabama at Birmingham
• UAB is a research university
and academic health center
• 18,619 employees
(Alabama’s largest employer)
• $4.6 billion annual economic
impact
• 17,543 students
• 166 owned buildings and 50
leased buildings
• 16 million square feet of space
Three Central Plants
Physical Plant Operations
• 15 centrifugal chillers (2,000 to 4,000 tons)
• 19 cooling towers
• Nine condenser systems
• 42°F supply
• 54°F return
• PLC controlled to maximize operation and
efficiency
UAB Physical Plant
• 52 of our most critical buildings served
– Approximately 8 million ft2
• 60% of the buildings are hospital operations
• 40% are research labs and comfort cooling
• Every building is connected to the distribution
system with a flow meter measuring CHW flow
– Supply and return temperatures are also recorded
– Buildings are charged monthly for MMBTU usage
Central Plant #3
FUTURE UAB Building with
Fin Water Recovery System
Central Plant #1
Central Plant #5
UAB Physical Plant
• 2006 chilled water production
– 81 million ton-hours
• 2010 chilled water production
– Over 99 million ton-hours
– 18% increase
• 2010 power consumption
– 93 million kwh
– This is 33% of total energy consumed by UAB
Other Physical Plant Projects
• Removed all three-way valves in entire
distribution system
– Eliminated low delta T syndrome
– Increased delta T, which increased overall efficiency
• High-efficiency cooling towers
– Replaced old 78°F wet bulb towers with new
high-efficiency 80°F wet bulb towers
– Allowed us to reduce entering condenser water
temperatures below design
• Average chiller efficiency is now 0.59 kw/ton
UAB Background
• Reliability of water supply is mission critical
at UAB
• Hospital Critical Care Units
– A/C is a life-support issue
– Temperature dependent surgeries
• Specialized Research Labs
– Animal housing and procedural space
– Research stored in freezers sensitive to
temperature
UAB Challenges Regarding Water Supply
• Frequent droughts in the Southeast US
• Typically are water restrictions every year
• Squabbles over intra-state water rights
• 86 blocks of campus
• Alabama experiences about 100 days of very
hot summer weather
UAB Central Chilled Water System
During peak hot
summer months,
over 1.2 million
gallons of makeup
water required per
day for the cooling
towers due to
evaporative and
blowdown losses.
UAB Challenges Regarding Water Supply
The Solution
Recover and use the millions of gallons of
high-quality condensate water currently
going down the drain.
UAB Challenges Regarding Water Supply
The Obstacle
Most of the condensate would be collected
blocks and blocks from the towers. It would
be cost prohibitive and very disruptive to dig
up the streets in downtown Birmingham for
this project.
UAB Challenges Regarding Water Supply
Potential Solution for this Obstacle
Rather than installing a dedicated
distribution system to pipe the air handler
condensate back to the chilled water plant’s
cooling tower, use the existing chilled water
distribution system piping as a transport
system to get the condensate from the
buildings to the main plants.
Typical Collection System
Building B
Building A
AH 1
AH 2
AH 3
110 volt
Submersible
Sump Pump
w/ Internal
Float Controller
AH 4
Condensate Recovery Tank
(100 gallons each)
Large Collection
Tank (500 gallons)
Float
Level
Controller
Data
Collection
F
I
L
T
E
R
80 psig
45678
3 Phase 480v
55 gpm Rated
Grundfos Pump
C
H
I
L
L
E
D
Chilled Water
Return Line to
Central Plants
65-75 psig
Condensate Recovery Systems
Fin Water Recovery Tank
Sump
Pump
Discharge
Fail Safe
Overflow
Gravity
Drain
Condensate
Condensate
Entire Fin Water Recovery System
Central Plant’s Control System – relieving fin water to cooling tower
Basic Concept – utilizing CHW distribution piping to transport
recovered fin water to plants’ cooling towers
• Over pressurize the chilled water
– Typically maintain chilled water at 76 psig
– Allow pressure to build by pumping in the AHC
– Bleed into the towers when you exceed 76 psig
• Have remote safety to cut off pressure by stopping
all condensate pumps – set point 80 psig
• Also, controls are programmed so if any makeup
pump is running, the fin water control valve that
relieves to the cooling towers remains closed
Project Concerns
• Success depends on the details
• Uncertainty about over pressurization
• Concerns about flooding in collection areas
• What changes are needed in the water
chemistry?
• What are the increased maintenance items?
Safeties and Redundancies
• High pressure safety set point in PLC logic
– Stops the remote collection pumps in case the
pressure builds above 80 psig
• All collection tanks and pumping tanks fail back
to drain by gravity
– To protect against power outage or pump failure
• The discharge temperature of the water at each
pumping location is monitored with RTD’s
– Indicates that water is actually being pumped
– If the temperature increases, the water is not flowing
Water Chemistry
• Now we are putting “pure” distilled quality
water into the chilled water loop
• Plus, this water is “oxygen rich”
– Required a change in corrosion inhibition
• AHC water is “dirty”
– Required filtration plus a biological control package
• Chilled water chemistry must be compatible
with cooling tower water chemistry
• Cooling tower program must be adjusted to
allow for variable makeup water quality
Condensate Recovery Systems
Filtration is Necessary
Planned Changes to Water Chemistry
• Change conventional chilled water program
to silica/azole-based inhibition package
• Use chlorine dioxide (ClO2) as biological
control program for chilled water
• Tower treatment program was profiled to
ensure compatibility with chemistry being
added to the chilled water
Additional Program Benefits
• Allowed us to eliminate bromine from
cooling tower treatment program
– Availability of ClO2 generators allowed for the
low-cost addition of ClO2 to the towers
– Feed the ClO2 based on makeup water
• ATP and dip slide results in towers are
excellent
ClO2 Generators
• Three Pureline PureClO2 model HP-10
– 10 pounds per day (ppd) of ClO2 each
– One installed at each of the three central plants
– Can feed both the chilled water and the condenser water
– Monitored by SensoreX low-range ClO2 probes
ClO2 Residuals
Chilled Water MB Results
Corrosion Rates via Corrator
Average Copper
Corrosion Rate: 0.025 mpy
Average Mild Steel
Corrosion Rate: 0.015 mpy
Project ROI
ROI Calculated on a “Per Building” Basis
Example
Bevill Biomedical Research Building
• 223,712 gsf
• 100% outside air
• Condensate collected from five air handlers
• Peak gpm = 5
• Annual gallons 1.29 million/year
• Water cost = $3.12/ccf
• Annual savings $27,027.00
• Estimated project costs $32,914.00
• Simple payback is approximately 1.2 years
ROI was calculated on water savings ONLY
UAB: The Challenges
• Focus on ROI first
– Many research and healthcare buildings are
turning the air 25-40 turns per hour
– Typically need a 15-18 month payback to justify
• Sell the building occupants
• Convince veteran maintenance and
operating staff
– Get their ideas and input
Program Results
• First recovery system installed May 2011 at
McCallum – Kaul buildings. The other systems were
phased in during the year.
• Since May 2011 we have collected 3.7 million gallons.
• Currently we have six large research buildings with
fin water recovery systems in place. With these six
buildings we project to collect over 10 million gallons
in 2012.
• Before summer 2012, two more large research
buildings will be online.
Conclusions
Benefits
• Reducing wastewater
• Reducing domestic water usage
• By making up CHW losses with 45° water
instead of 70° water, saved 730 MM BTU
– Approx $10,000/year
• Using the cold condensate provides
additional free cooling of the cooling tower
circulating water
– Approx. 1° better than design on approach
Goals
• Get to 15,000,000 gallons recovered in 2012
• Get to 20,000,000/year recovered within
three to five years
• As new buildings are constructed, build the
fin water recovery system into the plan
during the design phase