Why Retro-Cx
What is Retro-Cx ?
How do you do it / what to look for
Case Studies
Take-Away

• Older bldgs. (Pre 1990) on average consume more energy
• Antiquated control systems that don’t work
• Energy saving control strategies missed in design
• Neglected maintenance wasting energy and/or causing
IAQ problems
• System upgrades that miss the mark
• Building usage / floor plans changed

• Energy cost are only expected to rise
• Economic outlook may prevent new construction
• Employee / Community goodwill – “It’s the right thing to do”
• Owners learn more about their own facilities
• Benefits intended to be long lasting
• Simple payback typically less than two years

Leased Buildings
• LEED EB / ENERGY STAR buildings may become a differentiator
• High energy costs translate into increased rent cost

Source: US Government Energy Information Administration
Consumption in Gross Energy by Year Constructed - 2003
Energy intensity
10% less
45% less energy consumed
New buildings 35% to 57% more efficient

A study by Lawrence Berkeley National Laboratory (LBNL) -
2004
Retro-Cx results
• Whole-building electricity savings range from 5% to 15%
• Gas savings range from 1% to 23%
• Payback ranged from 0.2 to 2.1 years
• The bigger the building typically the better the payback period
• Small buildings have opportunity as well
Source: A RetroCommissioning Guide for Building Owners -
PECI

Lawrence Berkeley National Laboratory (LBNL) – 2004
Value of Energy Savings
Value of Non Energy Savings
$0.11 - $0.72/ft
$0.10 - $0.45/ft
2
2
Non Energy: Equip Life, thermal comfort, IAQ, productivity, liability, etc.

•
1996 PECI/EPA/DOE Study of 60 Commercial
Buildings:
15%
33%
40%
HVAC
Problems
Sensors not operating properly
Missing
Equipment

Energy Savings $/sf
Annual Savings Building Sq.Ft.
Savings $/sf % Energy Savings
Hospital
Healthcare
Hospital
Hospital
Office Bldg
Building
Hospital in Orlando
University Research Bldg
Aquarium
Casino
Hospital in Central Florida
185,000
100,000
190,000
150,000
54,000
$100,000
$135,000
$75,000
$80,000
$38,500
ROI
Annual Savings
$200,000
$114,000
$200,000
$75,000
$200,000
$0.54
$1.35
$0.39
$0.53
$0.71
5 year ROI
2,000 %
2,000 %
350 %
400 %
450 %
18%
30%
13%
18%
40%

If Retro-commissioning our existing buildings can save just 10% energy consumption
•Reduce oil imports by 50%.
•Almost meets Kyoto Protocol.
Exploit our existing buildings, not the environment !

RETRO-Commissioning is evaluating and performance testing an Existing building’s HVAC….
Design
Installation
Set-up / TAB
Controls /
Optimization
Operation
Maintenance

•
•
•
Reveals hidden deficiencies that could have been avoided by commissioning.
Highlights O&M problems that could have been avoided through better training.
Reveals hidden control system problems, lowering energy costs.

Retro-Cx is NOT an energy study!
• Energy studies leave the Owner with proof of what they already suspect , something is wrong .
• It provides no answers as to what to do or were to start.
• Skip all the paperwork and go find the MONEY

Retro-Commissioning Defined: It’s a Tune-up, not just an
ECM list
PROCESS: An experienced commissioning team investigates the existing systems operation looking for equipment and systems that are not operating “properly”.
RESULT: The most common HVAC discovery is even though the space temperatures are comfortable, the systems are consuming much more energy than necessary due to overcooling, over-heating, over-ventilating. Reveals hidden problems in DISCO&M.
COST: Retro-commissioning’s cost is a few weeks of time for the commissioning team. The cost savings discovered usually pay back the retro-commissioning cost in months.

Uncovering the waste in
DISCO&M

HVAC Energy Cost Can Vary Widely
“ Average” building = 46%
HVAC
Energy Cost vs. HVAC Complexity
$2.00/sf Light Commercial
$3.00
Office/School
$4.00
$5.00
$6.00
Institutional
24/7 Hospital
Laboratory
“Wasteful” building =
2X
HVAC Energy Cost
Variation
$1-2 = Good
$4-6 = Evil

HVAC systems have many combinations of gas pedal / brake pedals that could be affected by improper
DISCO&M.

Although each building and system is unique you can start with the following:
• Interview facility personnel
• Review construction documents
• Review the controls workstation
• Walk the site

Interview facility personnel
• They are a great resource as to why things are the way they are but not necessarily on how they should be
• Keep them informed on what you find, it may trigger additional thoughts
• If interested, train them on how the systems work

Review construction documents
• Understand the design and how the systems are supposed to work
– Use the schedules and rules of thumb
– Sum up connected loads (air and water)
– Compare design installation to installed
– Check coil ∆Ts

Review the Controls workstation and look for:
– Incorrect AHU leaving air temperature set points
– Valve commands at 0% or 100%, or valves fighting
– OA Damper commands
– Controlling sensors like RH and CO2
– Pump / fan status on when command is off (in
HAND?)
– Chilled water ∆T (secondary supply & primary return)
– Chilled water supply temperature / set point
– General space temperatures
– System stability

Retro-Cx Example
Dehumidification
Setpoint
Search for
Improper
•
Set points
•
Device Operation
•
Modes
•
Input values
OA damper position
Coil LAT
Unit LAT
Setpoint
Most common discovery during Retro-Commissioning –
CONTROLS not Optimized:
GAS PEDAL is floored, but the BRAKES are used to control the speed of the systems.
SA SP
Setpoint

Hidden DISCO&M Problems = High Energy
Costs
VFD
DP
OA
SA
T
T
VAV
RA
“DIS” Problems
Improper programming sequence
Coils piped backwards
OA damper occ. / unocc. set points
VAV damper actuator / calibration
Service access restricted
Space thermostat calibration
Sensors in wrong location
VFD / fan sheave sized for ‘max concurrent’
“CO&M” Problems
Overridden BAS temp space set points
Increased VAV airflow set points
High duct static DP set point
Disabled duct static DP reset logic
Decreased cooling coil setpoint
Preheat and Cooling coil fighting
Disable supply air temp reset logic
Actual OA damper position
Dirty filters
T

Chiller Plants
•
Add / subtract logic
•
Incorrect set points (chiller and system)
•
Chillers / pumps / tower fans in manual
•
Condenser water control
•
Controlling sensor calibration
•
Chiller isolation valves

• Does the number of operating chillers / boilers make sense?
– Add/subtract logic
– Sensor calibration
– Decoupler issues
• Does the duct static pressure set point seem right?
– Who’s set point is it?
– Sensor calibration?
• Does the number of pumps operating make sense?
– Do the differential water pressure set points make sense?
– Sensor location / calibration

1 hp motor =
Annual Elec Cost
$500
1 Ton cooling (MA unit)
1,000 CFM OA (8 tons)
1 degree Setpoint on AHU
$750 = DX
$400 = CHW
$10,000 = DX
$5,000 = CHW
7% of cooling capacity
(10,000 cfm = 35 tons)
CEP generation capacity = ‘Load’, Attack the Load first

One foot on the gas, one on the brake
T T
VFD
DP
VAV
T
One foot on the gas
T T
VFD
DP
VAV
T
Identical air handling systems keep the space comfortable at 72F.
One uses twice the energy.
HOW? Systems sized for peak loads and operates inbetween .

Evil Performance = 2 x Groovy
T
T
VFD
DP
Both set-ups have comfortable 72F space temps !!
VAV
T
System Component
Performance
Cost (6 summer months) =
Fan 7,500 cfm =
OA 2,500 cfm (95F/78F) =
(50F LAT, +OA)
Preheat coil =
Reheat coils 20% =
Chilled water 45F =
(42F)
The
Good!
Performance
$12,000 (62 kW, $.07)
5 kW
0 kW
9.5 kW
47 kW (45F)
33 tons (52 LAT)
The
Bad!
$25,000 (129 kW)
10 kW
45 tons
23 kW
23 kW (50%)
72 kW

Building
“CO&M”
HVAC System operators and the
Controls vendor were not familiar with the basis of design.

University Biological Science Bldg: Fan Frame
Problems
Two parallel
AHUs headered together
30,000 CFM variable speed fans
4 Different stories of how the ‘system’ was supposed to operate ??
Fan motor frame that kept breaking requiring rewelding

University Biological Science Bldg: – Fan Operation in Surge
Turbulent
‘surge’ zone of fan curve
60 Hz
Design
Adjusted operating point, 49Hz.
45 Hz
30 Hz
Fan Curve #1: Occupied Conditions
Fan Curve #2: Unoccupied Conditions untrained staff
Savings:
How:
$15,000
Fans allowed to back off from 60Hz to 30Hz at

University Biological Science Building Hidden
Discoveries
Static pressure setpoint set too high at 2.2” , instead of 1.0”.
VFD
Fan always at 60Hz.
DP
OA
SA
T
T Re-heat coil required to heat the overcooled air.
VAV
RA
T
Pre-heat Coil improperly on.
Heating summer air from 84F up to 104F .
Cooling Coil actuator broken. Overcooling the air to 49F instead of 55F.
2-position VAV box closing more than necessary to ‘eat’ excess static pressure.
Water Side
Gas: pre-heat coil
Brakes: cooling coil
Gas: re-heat coil
Air Side
Gas: Supply fan
Brakes: VAV damper

University Biological Science Bldg: Retro-Cx Results
PROBLEM
AHU 1-1 Low Leaving Air Temp – Re-heating by VAV:
AHU 1-1 Low Leaving Air Temp – Over-cooling:
AHU 1-1 Pre-heat Coil Operation – Pre-heating:
AHU 1-1 Pre-heat Coil Operation – Re-cooling:
AHU Excess Fan Speed:
Total:
SAVINGS DISCO&M
$15,000 C,O
$30,000 M
$27,000 M
$25,000 M
$17,000 C,O,M
$114,000 per year.
Baseline Savings:
($0.90 / sf)
$114,000 /yr
Prevention: Training
Legacy

“DSCO&M”
Corporate Mandate: 10% energy savings.
HVAC operators did not understand where the ‘optimized’ operating points were
.

Improper Technician set-up of Drives. Release 60hz ceiling for direct drive fans .
Should be
<100% at part load
1.5” ???
Overflowing = extra pumping

Optimization Opportunities from Base Design
Min airflow, max heating, still over-cooling the space?
Room is 2 deg lower than setpoint
.

Bad Operating Advice from Technician
Technician said lower CW temp.
When OA is 65ºF WB, you cant get less than
71ºF regardless of tower speed.
(6F approach)

Installation Defects, Bad Data
How did the CHWS go from 44ºF to
50ºF ?
“Short
Decoupler
Effect”

Improper Base Sequence of Operations
Design coil delta-T is
40ºF
The boilers are dying from short cycling at
20% loading
.

Primary Items
Cooling Tower Operation – Turn 1 off, and modify software for condenser water reset based upon wet bulb temp. Save $1200 /wk for 20 weeks = $24,000
Hot Water Boiler Sequence – Revise controls to turn off lag boiler properly. Save boiler fuel from eliminating pre- and post-purge heat loss. +/- $20,000
Fix CHW Low Delta-T Problem – save secondary pump energy by pumping less colder water. Save 40kw for ½ year = $80,000
AHU Static Pressure 1.5” Setpoint – Optimize SP’s lower to save fan energy.
Assume 5% savings of 475 bhp fan motors = $50,000
Secondary Items
CHW – Constant speed pumps with variable 2-way valves; design oversight? Can save pump energy by going variable primary (add drives). $20,000
VAV with Reheat – many are reheating. Min cfm setting could be lowered to avoid reheating. And SATR logic can be implemented. Save +/$big

PROBLEM
DISCO&M
Cooling Tower Operation:
O
Hot Water Boiler Sequence:
Chilled Water: Low Delta-T Syndrome
AHU Static Pressure Setpoint Optimization:
S
SAVINGS
$24,000
$20,000 IS
$80,000 D or I
$50,000
Constant pump CHW system with 2-way valves : $20,000
VAV re-heating setpoints:
Baseline Savings:
$200,000 /yr
($0.50 / sf)
$ big
D
Total: $200,000 per year.

“O&M”
Looking for HIDDEN CAPACITY resulting from possible improper operation.

Hospital BAS Interrogation - Typical Air Handling
Unit
1. Chilled Water Valve – failed open, making 49.6ºF air. 5.4ºF colder than set point
2. Supply Fan VFD – is at 100%, no spare capacity for filter loading
3. Outdoor air damper – Software Override (SWO), changed from design setpoint

Hospital BAS Interrogation - Chiller Plant
Return Chilled water temperature is too low. The return temperature should be 58F. Too many chilled water coils are over-flowing, and producing low return water temperatures. Another LOW
DELTA-T PROBLEM.
The flow of 1149 gpm and the calculated tons of 359, calculate a flow rate of 3.2 gpm/ton. The secondary CHW is pumping over 50% more chilled water than it should be due to failed open
AHU chilled water valves.

Case Study #3: Summary Not-for-profit Hospital
6 of 30 Air Handling Units had hidden cooling coil valve problems.
Heating boilers are re-heating the overcooled air.
The spare central plant capacity that was ‘discovered’:
Cooling:
Heating:
142 Tons (new spare capacity)
1.7 million btuh (25% of one big boiler)
Baseline Savings: sf)
$200,000 /yr ($0.90 /
Retro-Cx Investment: 1 day
Value:
($1000/ton)
( Incidental)
Defer new 1000 ton chiller

“DISCO&M”
Administration wanted energy savings.
Facilities Staff did not want anyone
(us) to look at their system and find potential problems – it might make them look bad.

Hospital BAS Interrogation - Chiller Plant Logic
Problems
Three 550 ton chillers
ON.
(1650 tons)
Building
Load 1000 tons.
(2 chillers needed)
Improper Chiller OFF Logic – Operating more pumps & towers than necessary

For-Profit Hospital: Improper Constant Volume
Pump Set-up
Circuit Setter – 80%
Closed.
Should have trimmed impeller

For-Profit Hospital: AHU Investigation – Improper
Design
Original Design / Construction
Problems: Low first cost solutions = high long term operating costs

PROBLEM
DISCO&M
SAVINGS
AHU Supply Air Temp Reset Logic
Condenser Water Reset Temp Reset Logic
Chiller ON/OFF Logic
Pump Valve Adjustment
AHU Device Tune-up
DIS
Baseline Savings:
($1.50 / sf)
$10,000
$26,000
$58,000
$385,000 /yr
$72,000
$33,000
D
S
O&M
$186,000
Total: $385,000
Implementation Cost: $150,000
Retro-Cx Investment: 5 month
Prevention:
Design review ,
Performance Testing
Training
D
D

WHAT TO LOOK FOR:
• “Variable” systems and their set points
• Gas/Brake systems – pre/re-heat, humidity, VAV, parallel equip
• Starters in ‘Hand’ mode because a control device isn’t working
• ‘HVAC loads’. CEP’s can only meet loads.
• BAS Computer Screens = anything at 100% capacity