Effects of Altitude - PDH Source · • Gage pressure at altitude has a lower operating pressure...
Transcript of Effects of Altitude - PDH Source · • Gage pressure at altitude has a lower operating pressure...
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Copyright Carrier Corporation 2001
Slide 0
Technical Technical Program
Effects of
Altitude
The Carrier Technical
Training World of HVAC
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Copyright Carrier Corporation 2001
Slide 1
OUTLINE• INTRODUCTION
• REVIEW OF ENGINEERING GUIDE
• CENTRIFUGAL FANS
• DERATION METHOD
• DIRECT DRIVE FANS
• ALTITUDE VS. ARID CLIMITE
• CONCLUSION
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Copyright Carrier Corporation 2001
Slide 2
REVIEW OF ENGINEERING GUIDE
• Carrier’s Engineering Guide for
Altitude Effects
• Published 1967
• The first thing I read in 1991
• Effects of altitude.pdf
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Copyright Carrier Corporation 2001
Slide 3
Three Effected Areas
• Psychrometric Properties
• Temperature Levels of Steam Coils
• Air Density
• All effected by increases in altitude
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Copyright Carrier Corporation 2001
Slide 4
Psychrometric Air Properties
• Enthalpy Values
• Increases at higher altitudes
• Dew Point
• Decreases at higher altitudes
• Specific Humidity
• Increases at higher altitudes
• Different Psychrometric Charts are
available for various altitudes
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Copyright Carrier Corporation 2001
Slide 5
2,500 Ft Altitude
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Copyright Carrier Corporation 2001
Slide 6
5,000 Ft Altitude
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Copyright Carrier Corporation 2001
Slide 7
7,500 Ft Altitude
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Copyright Carrier Corporation 2001
Slide 8
Steam Heating Coils
• Higher altitudes reduces heating capacity
• Actual operating pressure is lower at higher
altitudes for the identical gage pressure
• Saturated temperature is therefore lower at
higher altitudes for identical gage pressures.
• Heating coil’s heating performance is therefore
lower for identical gage pressures
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Copyright Carrier Corporation 2001
Slide 9
Air Density
• Air density is lower at higher altitudes
• Most common property effected on HVAC
equipment
• Effect directly correlates to air density
• Table is published on page 12
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Copyright Carrier Corporation 2001
Slide 10
Air Density Ratio Table
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Copyright Carrier Corporation 2001
Slide 11
Air Density
• HVAC systems depends on heating and
cooling the air molecules through the coil or
heat exchanger,
• Higher altitudes have less mass (air
molecules) per CFM
• To provide the same capacity as sea level,
the CFM be increased at a rate inversely
proportional to the ADR
• Many times that is not possible
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Copyright Carrier Corporation 2001
Slide 12
A Practical Guide
• Carrier’s Engineering Guide For Altitude
Effects is a practical guide to determine the
effects (typically negative effects) of
altitude on HVAC systems you are
designing.
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Copyright Carrier Corporation 2001
Slide 13
Centrifugal Fans
• Air density – Yes• RPM Constant (Direct Drive)
» Airflow volume is reduced
» BHP of motor is reduced
• RPM Increased (Belt drive)
» Airflow can be adjusted to equal volume flow as SL
» BHP of motor is reduced
» Divide SL TSP by ADR to calculate equivalent TSP
» Look up in fan curve RPM & BHP. This is the actual RPM
» Multiply BHP by ADR for actual BHP required
• Psychrometrics – No
• Steam Heating - No
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Copyright Carrier Corporation 2001
Slide 14
Direct Drive
Furnace/Fan Coil Fan
Belt Drive
Fan
Direct Drive
Plenum Fan w/ VFD
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Copyright Carrier Corporation 2001
Slide 15
Centrifugal Fans• Fan performance/selection at
altitude overview
• Determine the air density ratio
• Divide required TSP by ADR
• Look up fan performance at this
pseudo point
• This determines the required RPM
• Multiply BHP at pseudo point by
ADR to get actual BHP
• ..\2011\AHU-5000 CFM.pdf
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Copyright Carrier Corporation 2001
Slide 16
Centrifugal Fan Selection
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Copyright Carrier Corporation 2001
Slide 17
Centrifugal Fans• Volume (CFM) Vs. Mass flow
(Lbs/min)
• Previous example was 5000 CFM
• At 6,000 ft altitude, RPM was 1,309
• At sea level, RPM needed was 1,180
• At 6,000 ft, 1,180 RPM can not achieve
3.0” (5,000 CFM @ 2.4”)
• At 1,309 RPM
• Volume flow is 5,000 CFM
• Mass flow is equal to 4,000 CFM @ SL
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Copyright Carrier Corporation 2001
Slide 18
Effects of lower mass flow
• Pros
• Lower BHP to deliver the same volume
• Less energy required to meet required
ventilation rates Getting away with
murder)
• Cons
• Lower delivered cooling capacity of
AHU
» Especially chilled water coils
• Lowers suction temperatures
» Freezing coils
» Wasted energy on latent capavcity
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Copyright Carrier Corporation 2001
Slide 19
Direct Drive Fans
• Direct drive fans at altitude really hurt
• High speed is high speed
• Lowers Volumetric flow (CFM)
• Double Wammy when taking into account Air
Density Ratio (1400 CFM sl on 5 ton)
• Oversize blowers when possible
• Rooftops can’t be done
• Split systems up to 4 tons can (2 ton ACU / 2.5
ton furnace)
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Copyright Carrier Corporation 2001
Slide 20
Effects on Compression
• Air Density – No
• Psychrometrics – No
• Steam Heating – No
• No Effects
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Copyright Carrier Corporation 2001
Slide 21
Water Cooled Condensers
• Air Density – No
• Psychrometrics – No
• Steam Heating – No
• No Effects
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Copyright Carrier Corporation 2001
Slide 22
Air Cooled Condensers
• Air Density – Yes
• Typically prop fans
• Airflow is held constant
• Air mass is decreased @ higher altitudes
• Performance is reduced
• Psychrometrics – No
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 23
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Copyright Carrier Corporation 2001
Slide 24
Evaporative Condensers
• Air Density – No
• Psychrometrics – Yes
• Typically Prop Fans
• Airflow is held constant
• Enthalpy increases at altitude
• An increase in performance is caused
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 25
Evaporative Condensers
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Copyright Carrier Corporation 2001
Slide 26
Chiller Barrells
• Air Density – No
• Psychrometrics – No
• Steam Heating – No
• No Effects
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Copyright Carrier Corporation 2001
Slide 27
Absorption Chillers
• Air Density – No
• Psychrometrics – No
• Steam Heating – Yes
• Gage pressure at altitude has a lower operating
pressure compared to identical gage pressure at
seal level
• Lower actual pressure gives lower performance
• Typically corrected by setting at higher gage
pressure.
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Copyright Carrier Corporation 2001
Slide 28
Absorption Chillers
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Copyright Carrier Corporation 2001
Slide 29
Air Cooled Condensing Units
• Air Density – Yes
• Typically prop fans
• Airflow is held constant
• Air mass is decreased @ higher altitudes
• Performance is reduced
• Compressor / Condenser cross plot reduces the
effects compared to a straight condenser
• Psychrometrics – No
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 30
Air Cooled Condensing Units
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Copyright Carrier Corporation 2001
Slide 31
Air Cooled Chillers
• Air Density – Yes
• Typically prop fans
• Airflow is held constant
• Air mass is decreased @ higher altitudes
• Performance is reduced
• Compressor / Condenser cross plot reduces the
effects compared to a straight condenser
• Psychrometrics – No
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 32
Air Cooled Chillers
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Copyright Carrier Corporation 2001
Slide 33
Chilled Water Coils
• Air Density – Yes
• Centrifugal fans can be adjusted to deliver
identical airflows
• Face areas of coils typically limit increasing
CFM (Increasing to published max helps)
• Coil ratings typically are done by comparing
identical air mass rates for altitude
• Multiply the altitude CFM by the ADR to
obtain seal level CFM rates
• Obtain coil performance from sea level
tables/charts
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Copyright Carrier Corporation 2001
Slide 34
Chilled Water Coils
• Psychrometrics – Yes
• If coil performance includes significant
dehumidification, higher altitudes will release
more moisture and increase the capacity of the
cooling coil performance.
• Less CW flow is required to obtains the same
SL performance.
• If coil is 95% sensible (like our climate), CW
flows are identical
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 35
Chilled Water Coils
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Copyright Carrier Corporation 2001
Slide 36
DX Coils
• Air Density – Yes
• Centrifugal fans can be adjusted to deliver
identical airflows
• Face areas of coils typically limit increasing
CFM (Increasing to published max helps)
• Coil ratings typically are done by comparing
identical air mass rates for altitude
• Multiply the altitude CFM by the ADR to
obtain seal level CFM rates
• Obtain coil performance from sea level
tables/charts
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Copyright Carrier Corporation 2001
Slide 37
DX Coils
• Psychrometrics – Yes
• If coil performance includes significant
dehumidification, higher altitudes will release
more moisture and increase the capacity of the
cooling coil performance.
• Less CW flow is required to obtains the same
SL performance.
• If coil is 95% sensible (like our climate), CW
flows are identical
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 38
DX Coils
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Copyright Carrier Corporation 2001
Slide 39
Cooling Coil Face Velocities
• Air Density – Yes
• Less air molecules to cause condensate water
carry-over
• Increases the published maximum air velocities
• Psychrometrics – No
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 40
Cooling Coil Face Velocities
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Copyright Carrier Corporation 2001
Slide 41
Steam Coils
• Air Density – Yes• Centrifugal fans can be adjusted to deliver identical
airflows
• Air mass is reduced
• Capacity is reduced
• Psychrometrics – No
• Steam Heating – Yes• Gage pressure at altitude has a lower operating pressure
compared to identical gage pressure at seal level
• Lower actual pressure gives lower performance
• Typically corrected by setting at higher gage pressure.
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Copyright Carrier Corporation 2001
Slide 42
Steam Heating Coils
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Copyright Carrier Corporation 2001
Slide 43
Steam Heating Coils
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Copyright Carrier Corporation 2001
Slide 44
Hot Water heating Coils
• Air Density – Yes
• Centrifugal fans typically can be adjusted to
give identical airflow
• Face area of coils typically limit increasing
CFM.
• Less mass flow reduces capacity
• Coil ratings obtained by using correction factor
on performance at seal level
• Psychrometrics – No
• Steam Heating - No
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Copyright Carrier Corporation 2001
Slide 45
Hot Water heating Coils
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Copyright Carrier Corporation 2001
Slide 46
Electric Heaters
• Air Density – Yes
• Capacity is not reduced since the capacity is
based on power consumption of the heating
element (Higher LAT’s)
• Minimum published airflows must be increased
to avoid tripping thermal overloads
• Psychrometrics – No
• Steam Heating – No
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Copyright Carrier Corporation 2001
Slide 47
Electric Heaters
Min Airflow = published min / ADR
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Copyright Carrier Corporation 2001
Slide 48
Gas Heat Exchangers
• Air Density – Yes
• Heat exchanger and flue systems are designed
for constant air volume
• Lower air density causes reduction in
combustible air at higher altitudes
• Reduces capacity 4% / 1,000 FT of elevation
• Psychrometrics – No
• Steam Heating - No
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Copyright Carrier Corporation 2001
Slide 49
Direct Combustion Gas Heat& Power Burners
• Direct Combustion MUA’s and Power Burner
Boiler system state that they do not have any
reduction in output capacity at higher elevations.
• This is true if the natural gas is not de-rated by the
utility company – also called ‘Hot Gas.”
• Most utility companies derate their gas, so
installing contractors do not need to change the
gas orifices.
• Since they do derate the gas, the same 4%/1000 ft
should be used for direct fired and power burned
applications.
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Copyright Carrier Corporation 2001
Slide 50
Room Fan Coils
• Air Density – Yes
• Typically direct drive centrifugal fans – Air
volume is decreased!
• Air mass is decreased (lower CFM & ADR)
• Performance is reduced
• Psychrometrics – No
• Steam Heating - No
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Copyright Carrier Corporation 2001
Slide 51
DXRoom Fan Coils
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Copyright Carrier Corporation 2001
Slide 52
CW Room Fan Coils
![Page 54: Effects of Altitude - PDH Source · • Gage pressure at altitude has a lower operating pressure compared to identical gage pressure at seal level • Lower actual pressure gives](https://reader035.fdocuments.us/reader035/viewer/2022071213/602db0003a1a572c9f189d3b/html5/thumbnails/54.jpg)
Copyright Carrier Corporation 2001
Slide 53
Package Rooftops
• Air Density – Yes• Centrifugal fans typically can be adjusted to give
identical airflow
• Face area of coils typically limit increasing CFM.
• Cooling ratings are typically done by comparing
identical air flow rates for SL at Altitude
• Obtain coil performance from sea level tables/charts
and multiply by correction factors for total and sensible
capacity
![Page 55: Effects of Altitude - PDH Source · • Gage pressure at altitude has a lower operating pressure compared to identical gage pressure at seal level • Lower actual pressure gives](https://reader035.fdocuments.us/reader035/viewer/2022071213/602db0003a1a572c9f189d3b/html5/thumbnails/55.jpg)
Copyright Carrier Corporation 2001
Slide 54
Package Rooftops
![Page 56: Effects of Altitude - PDH Source · • Gage pressure at altitude has a lower operating pressure compared to identical gage pressure at seal level • Lower actual pressure gives](https://reader035.fdocuments.us/reader035/viewer/2022071213/602db0003a1a572c9f189d3b/html5/thumbnails/56.jpg)
Copyright Carrier Corporation 2001
Slide 55
Air Friction Loss
• Air Density – Yes
• Reduces friction loss at same velocities
• Multiply ACFM by ADR to determine SCFM
• Look up SL friction loss in SL table
• The SL friction loss at the SCFM is the actual
loss for the ACFM at altitude
• Psychrometrics – No
• Steam Heating - No