energy & heat transfer in healthcare hvac -...

Energy & Heat Transfer in Healthcare HVAC

12/5/2013 HAAHE/TAFHM Facility Manager Basic Training 1

Shawn Wilson, PE

TME, Inc.

[email protected]

Agenda

• Why target HVAC Systems?

• Shifting the Paradigm

• Controls are the Key

• 4 Opportunities

– Chilled Water Pumping

– Cooling Tower Relief

– Air Handler Controls, Resets

– Air Terminal Controls, Troubleshooting

• Closing, Q&A


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Hospital HVAC

• Unique regulatory requirements for temperature and RH, airflow, and pressure relationships.

• Special applications (Surgery, Lab, Pharmacy, Sterile Processing etc…)

• Energy intensive facilities.

• Complex Systems, Complex Controls


Hospital Operating Costs

60% 20%

10% 3% 7%

People

Supplies

Debt Service

Energy

Other


Hospital Business Environment

• Higher Costs

• Lower Revenues

• Insufficient Margins for Reinvestment

• Mounting Backlog of Deferred Maintenance


Hospital Energy Costs

Average $4.09/SF

Hospital Operating and Maintenance Budgeting

27%

8%

14%

51%

Materials

Service Contracts

Staffing

Energy

Typical Hospital Operating and

Maintenance Budget ($7 to $12 per SF)


• Reduced Operating Budgets

• Staffing Levels are already too Low

27%

8%

14%

51%

Materials

Service Contracts

Staffing

Energy





• Higher Material Costs 27%

8%

14%

51%

Materials

Service Contracts

Staffing

Energy





• Higher Material Costs

• Higher Service Contract Costs

27%

8%

14%

51%

Materials

Service Contracts

Staffing

Energy





• Higher Material Costs

• Higher Service Contract Costs

• Energy Costs must be Reduced

27%

8%

14%

51%

Materials

Service Contracts

Staffing

Energy



Energy Use In Hospitals

HAAHE/TAFHM Facility Manager Basic Training 12 12/5/2013

Agenda





• 4 Opportunities





• Closing, Q&A


Current Paradigm

• Selecting Systems and Equipment based on First Cost

• Using the Same Design for Every Project

• Conservative Over-Sizing of Equipment

• Selecting Systems and Equipment without Considering Current and Future Utility Rates

• Control Systems Designed by Control System Manufacturers (not the Engineer)

• Commissioning included but often becomes construction phase QC and documentation exercise.


Current Best Practices Don’t Always Yield High Performance

• LEED

• Efficient Design

• Standard Commissioning


LEED Certification

• LEED Buildings are no more Energy Efficient than their Peers

• More than half of LEED Buildings not eligible for Energy Star Label

• 15% of LEED Buildings have an Energy Star Rating less than 30

• LEED is not Bad…

Some Buildings not Living up to Green Label

By Mirya Navarro August 30, 2009


Standard Commissioning

• LEED Certified Facilities have been Commissioned

• Many low Performing Hospitals were Commissioned

• Standard Commissioning is not bad…


Potential Causes of Low Performance

• Energy Efficient Features are frequently “Value Engineered” out of the Project

• Systems are too complex for O&M Staff to Operate and Maintain

• “Drive By” Commissioning does Occur

• Facility Performance is not Measured and Verified

• Commissioning Agent Design Reviews are restricted to “Commissionability” Only

• O&M Staff have traditionally focused on Regulatory Compliance, Infection Rates, Comfort, and not Energy Efficiency


Potential Causes of Low

Performance

• Control System Programming is not Consistent with the Design Intent

• Energy Management Systems are under Utilized

• Air Terminal Air Flow Setpoints are not Programmed in Correctly

• O&M Staff Training by Contractors does not Focus on Energy Conservation

• CxA is not Responsible for Building Performance

• O&M Staff are not Vested in a Positive Outcome

• Excess Simultaneous Heating and Cooling


Shifting the Paradigm

Albert Einstein’s Definition of Insanity:

“Doing the same thing over and over again and expecting different results.”

12/5/201

3

HAAHE/TAFHM Facility Manager Basic Training 20

ASHE’s Commissioning Guidelines and Handbook

• Meeting the Energy Efficiency Goals is not Optional

• Current Best Practices don’t always Work

• Causes of Low Performance are Known

• ASHE’s Commissioning Guidelines and Handbook focus on Meeting Facility and Project Energy Efficiency Goals


New Paradigm

• Construction Costs and Operating Costs must be Considered Holistically

• Minimize Reheat

• Create Synergy between Systems that Remove and Generate BTUs

• Pay Attention to the Control Programming


Setting the Energy Efficiency Goal

“If you aim at nothing, you’ll hit it every time.”

Zig Ziglar


Benchmarking


• EPA “Target Finder”

• Weather Adjusted

• Occupancy Adjusted

• Free Service

• Internet Based

• Simplified Input

• Percentile Ranking

Measurement and Verification


• Measuring on routine basis is critical.

• Review regularly.

Agenda





• 4 Opportunities





• Closing, Q&A


Designing the Control System

• Consider Design Conditions and Off-Design Conditions

• Design should Include Diagram, Sequence of Operation, Point List, Valve Schedule, and Damper Schedule

• Design should be Detailed, but not Manufacturer Specific

• Control System Design, Sequence, and Programming have more Impact on Hospital Energy Efficiency than System and Equipment Selections

27 HAAHE/TAFHM Facility Manager Basic Training 12/5/2013

Developing the Sequence of Operation

• Goal is Optimum Performance

• Include Fail-Safe Provisions

• Identify Inputs, Loop Statements, Table Statements, Logical Operators, Setpoints, Local Variables, and Outputs

• Consider Using a Flow Chart to Convey Design Intent

• Must be Very Detailed to Prevent Misunderstandings

• Lack of a Detailed Sequence is the Reason why most Buildings Fail to Achieve their Energy Efficiency Goals


Developing the Sequence of Operation


AHU Supply Air Temperature Reset

Control Loops

Cooling Loopout /Chilled Water Control Valve is equal to the

output of the following PI loop:

Action – Direct

Input – Supply Air Temperature

Setpoint – Cooling Setpoint

Minimum Output – 0

Maximum Output – 100

Supply Air Temperature: The supply air temperature setpoint

(“cold deck temperature”) is increased and decreased from the

minimum to the maximum and vice versa according to the

following logic:

Input – Request for more cooling from Air Terminals

Output – Supply Air Temperature Setpoint. Equal

to the lower of comparison of Calculated Supply Air

Temperature Setpoint (reset based on polling

zones described in this section) and

Dehumidification Override Supply Air Temperature

Setpoint (section 9.c).

Minimum SAT Setpoint (60F)

Maximum SAT Setpoint (65F)

Sampling Rate/Rate of Change: 1F/5 mins

Agenda





• 4 Opportunities





• Closing, Q&A


Chilled Water System Issues

• Improper Chiller, Cooling Tower, and/or Pump Sequencing

• Differential Pressure Setpoint Reset Overridden

• Condenser Water Supply Temperature Reset Overridden (or not programmed).

• Low Chilled Water Temperature Difference (Low Delta T)


CV Primary/ Variable Flow Secondary

Chilled Water System

• First developed by B&G in 1954.

• 2 Hydraulically Independent loops via Decoupler bypass pipe (“neutral bridge”).

• Primary pumps interlocked with each Chiller to provide design (constant) gpm.

• Secondary pumps are modulated to meet system DP requirement.


CV Primary/ Variable Flow Secondary Chilled Water System

• Perfect world – Primary Loop GPM = Secondary Loop GPM.

• No flow in Decoupler pipe.

• In the real world this is seldom the case.



KEY PERFORMANCE INDICATORS

• Secondary Loop Delta T.

– Low Delta T indicates excessive pumping.

– Chillers, AHU Coils are more efficient at higher delta T.

• System Operating DP.

– High system differential pressure can mask other problems.

– Higher DP = higher pumping horsepower.

– High DP’s can adversely affect control valve/coil performance.

T500Btu/h GPM

For a given load, Flow and ΔT are inversely proportional.

As GPM increases, ΔT drops.



Control Sequence

• Reset DP setpoint based on actual AHU demand (chilled water valve positions).

• Stage chillers based on tonnage but watch the temperature of water in decoupler and secondary loop Delta T for fault detection.

• Add secondary loop Delta T to dashboard.


Variable Primary Chilled Water

• Variable Flow through Chillers

• Only 1 Set of Pumps

• Pumps Sequenced to Maintain Delta P and Minimum Flow

• Bypass Valve Modulates to Maintain Minimum Flow

• Requires Electronic Flow Safeties

• Lower Capital Cost, Energy Cost, and Maintenance Cost


Agenda





• 4 Opportunities





• Closing, Q&A


Condenser Water Relief

• Still many plants control tower water to single setpoint (80F aquastat)

• Chiller Efficiency improves with colder condenser water.


Lots of hours of operation – even in South Texas…

It’s all about LIFT

• Condensing temperature minus the suction temperature

• Two ways to decrease Lift by adjusting DDC:

– Lower Condenser Water Temperature

– Raise Chilled Water Supply Temperature


Condenser Water Relief Implementation for Constant Volume Pumping

• Tower fan energy versus lower chiller kW

• Reset loop setpoint based on wet bulb and run the condenser loop as cold as possible

– 2 tower cells paired with 1 Chiller

• Be aware of lower limit.


Variable Volume Condenser Water

System

• Valves Modulate to Maintain Proper Flow

• Flow at Design with Minimum Refrigerant Lift Override

• Chillers can Operate with Very Cold Condenser Water (eliminates transition issues with hydronic free cooling)

• Any Chiller with any Tower with any Pump

• Pumps Sequenced in a Best Efficiency Manner

• Towers Sequenced in Best Efficiency Manner


3.0 GPM per Ton Condenser Water Flow Rate


Agenda





• 4 Opportunities





• Closing, Q&A


Air Handling Unit Issues

• Static Pressure Setpoint Reset Overridden

• Malfunctioning Control Valves

• Supply Air Temperature Setpoint Reset Overridden

• Failed Air Flow Measuring Stations

• Malfunctioning Dampers

• Weekly Schedules Overridden

• Simultaneous Heating and Cooling


Multiple Loop Temperature Control

Loop 1

Loop 2 Loop 3

Loop 4


Multiple Loops

2022 Loop (0, Input, Output, Setpoint, P, I, D, Min, Max, Bias)

• 4 Setpoints

• 4 Sets of Proportional and Integral Gains

• Setpoints may Inadvertently Overlap

• Tuning is very Difficult

• Outputs will Overlap due to Hunting



Multiple Loops

Time

Mixed Air Preheat CHW Coils

Mixed Air Temperature

Mixed Air Setpoint

Output Preheat

Temperature Preheat Setpoint

Output Coil Leaving

Air Temperature

Supply Air Temperature

Supply Air

Setpoint Output

3:00 55.3 55 51 55.3 50 0 40.7 47.5 48 24

3:05 48.0 55 76 57.6 50 24 41.6 48.1 48 27

3:10 57.7 55 42 57.7 50 0 42.0 48.9 48 26

3:15 60.5 55 33 60.5 50 0 42.2 48.3 48 30

3:20 54.9 55 51 54.9 50 0 40.9 47.2 48 23

3:25 47.5 55 79 54.7 50 18 41.0 47.6 48 23

3:30 58.3 55 39 58.3 50 0 41.8 48.4 48 28

3:35 62.0 55 29 62.0 50 0 42.3 48.7 48 33

3:40 54.1 55 55 54.1 50 0 41.4 48.2 48 21

3:45 48.5 55 75 52.9 50 11 41.1 47.6 48 20


Overlapping Setpoints

Time



Mixed Air Setpoint

Output Preheat


Output Coil Leaving

Air Temperature


Supply Air

Setpoint Output

3:00 55.3 55 51 55.3 50 0 40.7 47.5 48 24

3:05 48.0 55 76 57.6 50 24 41.6 48.1 48 27

3:10 57.7 55 42 57.7 50 0 42.0 48.9 48 26

3:15 60.5 55 33 60.5 50 0 42.2 48.3 48 30

3:20 54.9 55 51 54.9 50 0 40.9 47.2 48 23

3:25 47.5 55 79 54.7 50 18 41.0 47.6 48 23

3:30 58.3 55 39 58.3 50 0 41.8 48.4 48 28

3:35 62.0 55 29 62.0 50 0 42.3 48.7 48 33

3:40 54.1 55 55 54.1 50 0 41.4 48.2 48 21

3:45 48.5 55 75 52.9 50 11 41.1 47.6 48 20

50 12/5/2013 HAAHE/TAFHM Facility Manager Basic Training 50

Simultaneous Heating and Cooling

Time



Mixed Air Setpoint

Output Preheat


Output Coil Leaving

Air Temperature


Supply Air

Setpoint Output

3:00 55.3 55 51 55.3 50 0 40.7 47.5 48 24

3:05 48.0 55 76 57.6 50 24 41.6 48.1 48 27

3:10 57.7 55 42 57.7 50 0 42.0 48.9 48 26

3:15 60.5 55 33 60.5 50 0 42.2 48.3 48 30

3:20 54.9 55 51 54.9 50 0 40.9 47.2 48 23

3:25 47.5 55 79 54.7 50 18 41.0 47.6 48 23

3:30 58.3 55 39 58.3 50 0 41.8 48.4 48 28

3:35 62.0 55 29 62.0 50 0 42.3 48.7 48 33

3:40 54.1 55 55 54.1 50 0 41.4 48.2 48 21

3:45 48.5 55 75 52.9 50 11 41.1 47.6 48 20


What is the Problem?

Time



Mixed Air Setpoint

Output Preheat


Output Coil Leaving

Air Temperature


Supply Air

Setpoint Output

3:00 55.3 55 51 55.3 50 0 40.7 47.5 48 24

3:05 48.0 55 76 57.6 50 24 41.6 48.1 48 27

3:10 57.7 55 42 57.7 50 0 42.0 48.9 48 26

3:15 60.5 55 33 60.5 50 0 42.2 48.3 48 30

3:20 54.9 55 51 54.9 50 0 40.9 47.2 48 23

3:25 47.5 55 79 54.7 50 18 41.0 47.6 48 23

3:30 58.3 55 39 58.3 50 0 41.8 48.4 48 28

3:35 62.0 55 29 62.0 50 0 42.3 48.7 48 33

3:40 54.1 55 55 54.1 50 0 41.4 48.2 48 21

3:45 48.5 55 75 52.9 50 11 41.1 47.6 48 20


Single Loop Temperature Control

0

20

40

60

80

100

0 20 40 60 80 100

Ta

ble

Sta

tem

en

t

Ou

tpu

t

Supply Air Temperature Control Statement Output

Preheat Valve

First Stage Economizer Cycle(Maximum OSA Damper)

Second Stage EconomizerCycle (Return Air and ReliefAir Dampers)

Secondary Chilled Water Valve

Primary Chilled Water Valve

Stage 1

Stage 4

Stage 3

Stage 2

Stage 5


Single Loop Humidity Control

0

20

40

60

80

100

0 20 40 60 80 100

Ta

ble

Sta

tem

en

t O

utp

ut

Return Air Humidity Control Statement Output

Disable Second Stage ofEconomizer Cycle (OpensReturn and Closes ReliefDampers)

Disable First Stage ofEconomizer Cycle (ClosesMaximum OSA Damper)

Humidifier Steam Valve

Stage 3 Stage 2 Stage 1

12/5/2013 ©2012 American Society for Healthcare Engineering of the American Hospital

Association 54

Adaptive Resets

• Reset Supply Air Temperature (“Cold Deck Reset”).

• Reset Duct Static Pressure Setpoint

• ASHRAE 90.1, Energy Code


Dedicated Outside Air AHU

• Pre-treat ventilation air. Ducted to outside air damper on individual AHUs.


Air-Side Economizer Cycles

• Air-Side Economizer Cycles often incorrectly programmed/configured and difficult to maintain.


Economizer Damper Control Loop not Tuned

0

10

20

30

40

50

60

70

80

90

3:0

0

3:0

5

3:1

0

3:1

5

3:2

0

3:2

5

3:3

0

3:3

5

3:4

0

3:4

5

EconomizerDamper Output

Mixed Air Setpoint

Mixed AirTemperature


Air-Side Economizer Cycles on AHU’s with Humidifiers

• ASHRAE Standard 90.1 Requires Hydronic Free Cooling if Humidification Dewpoint is > 35 deg. F (30% RH at 68 deg. F)

• Cooling Savings are more than Offset by Higher Humidification Costs

• Air-Side Economizer Cycles are Costly to Implement and Difficult to Maintain


Operating Room Challenges

• Surgeons/staff want 60F/50% rh

• Difficult if not impossible to achieve with typical chilled water system




• Desiccant Technology provides lower dewpoints.

• Dedicated OSA AHU with Type III passive dessicant wheel shown.



Air change rates, pressure differentials difficult to optimize – often are not reset based on occupancy.

Unoccupied/Occupied Reset for Operating Rooms

• Occupied – 15 to 25 ACH

• Unoccupied – 5 to 8 ACH

• DP – 0.01” w.g.

Agenda





• 4 Opportunities





• Closing, Q&A


Air Terminal Issues

• Failed Averaging Velocity Sensors

• Malfunctioning Terminal Dampers

• Malfunctioning Heating Water Control Valves

• Insufficient Air Flow to Accommodate Space Sensible Cooling Load

• Incorrect Air Flow Setpoints

• Deadband too Small

• Thermostat Range not Restricted

• Weekly Schedules Overridden

• Occupancy Sensors Overridden

• Failed Points



VAV Air Terminal with Heating


VAV Air Terminal with Heating – Minimizing Reheat

Best Practice: Modulate HW Valve to a Discharge Setpoint and Reset the Setpoint from Minimum up to Maximum before Increasing Air Flow.


VAV Air Terminal Troubleshooting


• Failed Averaging Velocity Sensors

• Malfunctioning Terminal Dampers

• Malfunctioning Heating Water Control Valves

• Insufficient Air Flow to Accommodate Space Sensible Cooling Load

• Don’t apply a system wide correction to a zone level problem.

Closing Thoughts • You can’t manage what you

don’t measure.

• The code is the key. Get it right and good things happen.

• Don’t use a sledge hammer to drive a finish nail.



Thank You! Questions?

“The only constant is change.” - Heraclitus

12/5/201

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©2012 American Society for Healthcare Engineering of the American Hospital Association 71

“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.” Charles Darwin

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