Transcript HVAC Seasonal – Equipment Operational Considerations

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Seasonal Equipment Operational Considerations
Joe Leichner, Daikin Applied Strategic Sales Project Developer
September 9, 2014
©2014 Daikin Applied
People and ideas you can trust.TM
Agenda
1. “Seasonal” – Means not full load heating or
cooling!
2. Controls settings to save energy and optimize
comfort
3. Designing/selecting new systems for replaced
equipment
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Seasonal = 99.9% of the Year
Historical data and choosing weather criteria for a hospital:
1. If there is a “worst-case scenario”, your hospital will see it.
2. Seems to not account for north winds through north-facing outside
air dampers!
3. Does not account for 100 and -10 degree F. days.
4. When designing a new building, help guide your design team.
5. Systems and equipment degrade in performance and capacity.
6. Bigger equipment will help handle “peak” loads, but affect efficiency
at part-load.
7. Diversity is tough to estimate, but it very important to equipment
selection and operation.
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Heating Design Temperatures
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Cooling Design Temperatures
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Seasonal = 99.9% of the Year
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Seasonal Weather and Internal Loads
Not only is the weather dynamic, your internal loads
are dynamic as well.
• Surgery suite loading
• Emergency room usage
• Patient flow and overnights
• Conference rooms/meetings
• Others
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Seasonal Weather and Internal Loads
The use of your building affects your support systems:
•
•
•
•
Food service
Laundry
Housekeeping
Many others
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Seasonal Weather, Internal Loads, and Comfort
Human comfort is both physical and mental. Physical aspects are:
• Airflow
• RH%
• Air Temperature
• Odor
• CO2
• and more!
HOW DO YOU KEEP EVERY OCCUPANT AND PATIENT COMFORTABLE?
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Seasonal Control Settings
Controls settings for patient comfort
Controls settings for medical staff comfort
Controls settings for safety
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Seasonal Control Settings
Controls settings for patient comfort
• Patient satisfaction surveys and reimbursements
• Healing rate improvement if person is
comfortable?
Controls settings for medical staff comfort
• Physician and nursing staff retention
• Job satisfaction improved if environment of care is
comfortable
• Productivity enhanced if conditions are maintained
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Seasonal Control Settings for Safety
• Air pressurization maintenance for critical
environments
• Airflow for biological safety cabinets, fume hoods
• Airflow for surgery suites and burn treatment areas
(and others)
• Food storage and food preparation areas
IT IS NOT JUST ABOUT THE TEMPERATURE; FLOWS
AND PRESSURES MATTER AS WELL.
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Seasonal Control Settings for Occupant Safety
First Priority – Airflow and pressure maintenance
In ante rooms, isolation rooms, and other specialized areas, the
difference in room pressures must be maintained.
How many of you fight with negative air pressure in the building
especially in the winter?
Load and ventilation analysis – Not expensive, but very worthwhile for
comfort and energy.
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Load and Ventilation Analysis
• Optimizes recirculation requirements based upon space
type determination
• Defines exact minimum outside air requirement by zone
• Defines inflow and exhaust flow for each zone
• Identifies lighting, people, computer, medical equipment
loads (by room or zone)
• Measures current AHU peak airflow and pressure delivery
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Load and Ventilation Analysis
• Measures current outside air intake quantity, zone temps
and settings
• Identifies needs for fan/coil cleaning, damper repairs, etc.
• Provides information for optimizing comfort in the occupied
spaces through air/water bal.
• Creates awareness of concern by your staff for patient
outcomes, staff satisfaction, etc.
• Can assure of proper AHU ventilation control throughout
facilities
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Seasonal Control Settings for Occupant Comfort
Second Priority – Occupant Comfort
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Seasonal Control Settings for Occupant Comfort
Second Priority – Occupant Comfort
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Seasonal Control Settings for Occupant Comfort
Many other considerations for occupant comfort:
• Physical health of the individual
• Use of clothing (sweaters, thin shirts, etc.)
• Density and length of hair (traps heat from head)
• Air velocity across the skin
• Noise of the air and within the rooms
• Lighting (% of natural lighting, color of lighting, etc.)
• Wall and room aesthetics (white, shiny painted walls vs.
calm colors and artwork, etc.)
• Sensitivity to temperature swings (heating dead-band and
cooling dead-band)
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Seasonal Control Settings for Occupant Comfort
Second Priority – Occupant Comfort
Energy Policy – Temperature settings by functional space
Given all of this information, where should you set the room
temperature?
74 Degrees is the mid-point between heating and cooling. Expensive.
76 for Cooling is most common; 78 may be too high (Dehumidification
<50%)
72 for Heating is most common; 68 may be too low (Humidity at
30%/35%)
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Ventilation Quantities
• Set outside air quantities as required to meet minimum volumes
(periodically check the damper positions to ensure these are set in the
proper position during occupancy and un-occupied conditions)
• Maintain annual certifications for FHs/BSCs and space pressurization
controls
• Test and adjust kitchen, laundry, and other exhaust systems
periodically as renovations happen (adjust sheaves as needed) – Turn
on only when needed
• Maintain and calibrate building static pressure controls and relief
systems
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Ventilation Quantities
• Check economizer sequences of operation for AHUs that vary
outside air quantity
• Check and calibrate CO2 sensors/transmitters/controllers (Ambient
air 350 ppm CO2 – adjust to control less than 800 ppm appx. – above
this, people can sense the air is “stuffy” and can begin to feel tired.)
(If set lower than 800 ppm, energy cost increases significantly.)
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Ventilation Quantities
Normal CO2 Levels*
The effects of increased CO2 levels on adults at good health can be
summarized:
• normal outdoor level: 350 - 450 ppm
• acceptable levels: < 600 ppm
• complaints of stiffness and odors: 600 - 1000 ppm
• ASHRAE and OSHA standards: 1000 ppm
• general drowsiness: 1000 - 2500 ppm
• adverse health effects expected: 2500 - 5000 ppm
• maximum allowed concentration within a 8 hour working period:
5000 ppm
* Source: EngineeringToolbox.com
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Seasonal Control Settings for AHUs
Mixed air temperature and economizer control – 55 degrees
+/- with reset from OAT (Minimize chilled water cooling as
much as possible.)
Supply air temperature
• Low temp systems – 40 degrees (maintains fan
efficiency)
• Normal systems – 55 degrees (VAV systems reset from
zone average to limit)
• Minimize fan energy as much as possible
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Seasonal Control Settings for AHUs
Supply air pressure – Duct static to maintain +/- 0.5” at furthest outlet
(dumping and throw/noise concerns can happen if static too low or
too high) (minimize fan motor energy)
Hot deck temperature – reset 180 to 120 from OAT 0 to 60 degrees
(minimize hot water pump energy)
Cold deck temperature – maintain at 52 to 55 degrees depending
upon fan size (heat from fan motor) and duct heat absorption (long
runs of duct) (minimize chilled water pump energy)
Building pressure (Return air fan or relief air damper) – +0.1” normal
(can vary by zone)
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Seasonal Control Settings for Heating Plants
Deaerator pressure – 3 to 5 psig (for aeration efficiency and feed
water heating)
Boiler feedwater pressure – 10 psig over generation pressure (reduce
pump energy)
Steam pressure – minimum pressure for loads served – distribution
pressure losses (Autoclaves, sterilizers, linen presses, cooking,
humidification, etc.) (Can reset pressure setting on a schedule when
high pressure loads are not in operation – do not set too low as
condensate volume increases drastically on large campus systems)
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Seasonal Control Settings for Heating Plants
Hot water supply temperature – 180 reset to 120 from outside air at 0
to 60 degrees
Re-heat loop supply temperature – 140 reset to 120 from outside air
at 0 to 60 degrees
Perimeter heating system supply temp – 180 to 120 reset. Cycle off
pump at OAT>60.
Hot water pumping system pressure – minimum to maintain sufficient
circulation and not below 25% flow (surging and cavitation)
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Seasonal Control Settings for CHW Plants
Constant flow pumping system – reset chilled water supply
temperature to highest temp to satisfy all zones (one valve at 100%
open)
Variable flow pumping system – maintain 42/43 degree chilled water
supply temp to minimize pumping energy – may reset chilled water
supply temp up if chiller efficiency gain is more efficient than pumping
energy spent by pumping more flow.
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Seasonal Control Settings for CHW Plants
Chilled water supply temperature – maintain 42 to 45 degrees for
variable water pumping systems or chillers with VFDs. For constant
pumping systems and chillers without VFDs, reset the chilled water
supply temperature as high as possible while maintaining space
temperature and relative humidity.
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Seasonal Control Settings for CHW Plants
Condenser water supply temperature – maintain lowest inlet
temperature to chiller to reduce chiller lift requirement to minimum
input temperature permitted by chiller design. Outdoor air wet-bulb
temperature reset of condenser water supply temperature based
upon your load and equipment. Fan speed control given constant
condenser water flow. (Sorry, not a definitive answer.)
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Designing New Systems for Replaced Equipment
Chiller Replacement
• Evaluate chillers based upon the Integrated Part Load Value (IPLV)
(This is intended to show the part load performance/efficiency and is
weighted based upon some assumed capacities and hours of use.)
(The IPLV is an ARI/ASHRAE Standard that all manufacturers must use
and will clearly indicate which chiller is the most efficient given the
stated parameters.)
• Consider redundancy; low load operation needs (Mutt chillers, plant
configuration, VF pumping conversion, etc.); and future load additions
(remodels, additions, expansions, etc.)
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Designing New Systems for Replaced Equipment
Cooling Tower Replacement
• Evaluate towers based upon chiller installed capacity and freecooling needs/wants
• Consider redundancy, fan speed control type and drive, and future
load additions
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Designing New Systems for Replaced Equipment
Pump Replacement
• If you are replacing your chiller or tower, you should also replace
your pump and motor. Choosing the new pump in the highest
efficiency portion of the curve can save lots of money every hour the
pump runs.
• Consider conversion to variable flow systems on hot water and
chilled water systems; but be very cautious on condenser water and
water source heat pump loops. (Requires pressure control and 3-way
to 2-way control valve replacement.)
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Designing New Systems for Replaced Equipment
Boiler Replacement
• Consider the boiler efficiency at part load, once sizing is confirmed.
• Consider redundancy, low load operation needs (Mutt boilers, etc.)
• Consider future load additions (remodels, additions, expansions,
etc.)
• Consider redundant fuel supply (fuel oil, propane, and required
storage)
• Consider cost for alternative fuels
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Designing New Systems for Replaced Equipment
RTU Replacement
• Consider overall cost for energy, repairs and maintenance given unit
life time. Much higher efficiency units are available.
AHU Replacement/Refurbish
• Consider conversion of constant volume to VAV system for supply
fan motors greater than 20 hp. (See table on next page.) Best
seasonal performance versus constant volume.
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Designing New Systems for Replaced Equipment
Existing AHU System Type
Single Zone, Constant Volume
Single Zone, Constant Volume
Recommended System Conversion Ideas
Simple VAV Conversion - variable flow based
upon average space temperature; add
economizer if not existing
Variable air volume diffusers; add economizer if
not existing
Advantages
Lower cost than
other retrofits.
Lower cost than
adding boxes.
Disadvantages
Less energy savings as still
have over ventilation of
spaces without sensors.
Less energy savings as still
have potential for overventilation of spaces due
to accuracy of damper
operation.
Most energy
Add VAV boxes with reheat; add economizer if
efficient retrofit.
Single Zone, Constant Volume
Most costly of conversions.
not existing
Will result in highest
comfort.
Less energy savings as still
have potential for overSingle Zone, Terminal Reheat, Variable air volume diffusers; add economizer if
Lower cost than
ventilation of spaces due
Constant Volume
not existing
adding boxes.
to accuracy of damper
operation.
Most energy
Single Zone, Terminal Reheat, Add VAV boxes upstream of reheat coils; add
efficient retrofit.
Most costly of conversions.
Constant Volume
economizer if not existing
Will result in highest
comfort.
Lower cost than
Less energy savings as still
isolating decks and have potential for overVariable air volume diffusers; add economizer if
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Applied
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Multizone,
Constant
Volume
adding boxes. May ventilation of spaces due
not existing
increase comfort
to accuracy of damper
Designing New Systems for Replaced Equipment
to accuracy of damper
operation.
Most energy
Single Zone, Terminal Reheat,
Add VAV boxes upstream of reheat coils; add
efficient retrofit.
Most costly of conversions.
Constant Volume
economizer if not existing
Will result in highest
Existing AHU System Type
Recommended System Conversion Ideas
Advantages
Disadvantages
comfort.
Simple VAV Conversion - variable flow based
Less
Lower cost than
Less energy
energy savings
savings as
as still
still
Lower
cost
than
have over
potential
for overSingle Zone, Constant Volume Variable
uponairaverage
temperature;
add if isolating decks and have
ventilation
of
volumespace
diffusers;
add economizer
otherboxes.
retrofits.
Multizone, Constant Volume
adding
May
ventilation of spaces due
economizer
if not existing
spaces without sensors.
not existing
increase comfort
to accuracy of damper
Less energy
savings as still
over existing.
operation.
have
potential
for overSimple VAV Conversion - isolate decks and
Less
energy
savings
as still
Variable
air
volume
diffusers;
add
economizer
if
Lower
cost
than
install individual deck and zone dampers.
have over ventilation of
Single Zone, Constant Volume
Lower
costboxes.
than VAV ventilation of spaces due
not existing
adding
Multizone, Constant Volume
Variable flow based
upon zone with highest
spaces without sensors.
to accuracy of damper
box retrofit.
demand temperature OR can operate on deck
May still have comfort
operation.
static pressure; add economizer if not existing
issues.
Most energy
Most energy
Most costly of conversions.
Add
VAV
boxes
with
reheat;
add
economizer
if
efficient
retrofit.
efficient retrofit. Highest energy savings and
Single
Zone,Constant
ConstantVolume
Volume Add VAV boxes with reheat; add economizer if
Most costly of conversions.
Multizone,
Will result in highest best system conversion for
not existing
comfort.
comfort.
comfort.
Lower cost than dual Less energy savings as still
Retrofit existing dual duct boxes with new VAV
Less reliable and accurate
Dual Duct, Constant Volume
duct VAV box
havethan
potential
for overcontrols. Fix faulty dampers and seals.
new boxes.
Single Zone, Terminal Reheat, Variable
air volume diffusers; add economizer if
Lower
cost than
replacement.
ventilation of spaces due
Constant Volume
not existing
adding
boxes.
Most energy
Most
costly of of
conversions.
to accuracy
damper
Replace existing dual duct boxes with new VAV
efficient retrofit. Highest energy savings and
Dual Duct, Constant Volume
operation.
boxes and controls.
Will result in highest best system conversion for
Most
energy
comfort.
comfort.
Single Zone, Terminal Reheat, Add VAV boxes upstream of reheat coils; add
efficient
Will saveretrofit.
some
Most costly of conversions.
Constant Volume
economizer if not existing
Will
resultbut
in highest
energy,
may
Reset discharge static pressure based upon
result
in some
Costly conversions. May
comfort.
Induction System, Constant
added zone temperature sensors or feedback
complaints about
have comfort
Lower cost than
Less still
energy
savings as still
Volume
from automation system.
excessive humidity
complaints.
isolating
have potential for overin spacedecks
(lack and
of
Variable air volume diffusers; add economizer if
Multizone, Constant Volume
adding
boxes. May ventilation of spaces due
dehumidification)
not existing
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increase comfort
to accuracy of damper
over existing.
operation.
Take Aways
1. Ensure your design team uses seasonal weather data to
properly size HVAC systems.
2. Periodically check your controls settings to ensure they are set
for the best mix of comfort and efficiency.
3. If it has been a while since you have had a loads analysis and
ventilation study, it can be money well spent as energy savings
can result from minimizing and controlling ventilation rates.
4. When equipment replacement is needed, ensure that HVAC
capacities for its zone/service needs are identified, choose the
most efficient equipment available, and control the
equipment/system in the most efficient manner that
compliments occupant comfort.
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Questions?
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People and ideas you can trust.TM
e
Thank You!
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People and ideas you can trust.TM