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A Better Package:
Why Save Energy?
The Key to Significant Energy Savings
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Simple Economics: Energy savings is a direct
benefit to a building owner.
Jack Hopkins, P.E.
Principal, Applied Engineering
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Energy Independence: Reducing energy use will
help promote independence for a given country.
Presented to: Association of Energy Engineers
May 13, 2014
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Global Warming: Reducing fossil fuel use will
reduce greenhouse gas emissions.
US Energy Use
HVAC Equipment
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Buildings: 40% of total energy use
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Applied Equipment: 20 to 30% of total
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Buildings: 70% of total electric use
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Unitary or Packaged: 70 to 80% of total
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HVAC: 40% of electric use
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Which is the low-hanging fruit?
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HVAC: 45% of peak electric demand
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Which is being pursued?
A Better Package.key - May 14, 2015
Supply Air Temperature vs.
Supply Air Flow
Statement
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Improvement must come from the most basic
quality level for packaged equipment, as these
units will be selected for the majority of commercial
projects.
Owner vs. Tenant
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What if we start from scratch?
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Packaged units are generally sized on sensible
heat.
Qs = 1.08 x CFM x (TLA - TEA)
Air Handler Design
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What is optimal supply temperature?
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What is optimal airflow?
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Which should govern?
Psychrometric Chart
A Better Package.key - May 14, 2015
Balance of Space Condition
and Coil Performance
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•
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A lower supply air temperature will result in a dryer
space condition for a given space setpoint.
A dryer space condition will also allow comfort to
be maintained at a higher space temperature.
A dryer space condition will usually result in better
indoor air quality.
Physical Factors
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What is required to vary coil discharge temperature
(assume constant flow)?
Supply Air Temperature
Optimization
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Start with 55 degree discharge air
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Unit kW = Fan kW + Comp kW + Cond kW
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Drop to 52 degree discharge air: Unit kW = ?
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Rise to 58 degree discharge air: Unit kW = ?
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What is optimal?
Optimal Supply Air Temp
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Why 55 Degrees?, David Knebel, P.E., circa 1998
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Actual optimal temperature is between 45 and 50
degrees.
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13-15% savings using lower temperature supply air
than 55.
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Even greater savings over equipment with 58
degree discharge
What is required to vary airflow?
A Better Package.key - May 14, 2015
Why Have We Drifted in the
Wrong Direction?
Confirm with Mfr. Software
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Experiment with number of coil rows/fan cfm
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EER up with lower supply air temperature
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Part load efficiencies even greater because:
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Fan savings for lower airflow is continuous
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Compressor penalty is intermittent
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Economics and Competition
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Less expensive to make a bigger fan
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More expensive to make a thicker coil
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Is cost justified?
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Some manufacturers are doing well with this
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Others would follow if market demanded it
Future Issues for Packaged
Equipment
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Building sensible loads are being driven downward
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Better envelopes
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Lower lighting densities
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% of latent to total goes up
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Some packaged equipment can not handle
increased latent loads
Fresh Air Damper Design
A Better Package.key - May 14, 2015
What is This?
Censored!
Slide Plate
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Backward Progress
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Frequently fail in a wide-open position
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Wallpaper falls off!
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Building damage frequently results during the delay
between failure and diagnosis
Poor Rotating Dampers
Poor Rotating Dampers
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2012 IECC: Fresh air dampers within the building
envelope must have AMCA Class I leakage rates
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2012 IECC: No requirements for HVAC unit
dampers
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2010 ASHRAE 90.1: Two values, based on climate
zone. •
All Others: No requirements for HVAC unit dampers
A Better Package.key - May 14, 2015
Proper Rotating Dampers
Proper Rotating Dampers
Proper Fresh Air Dampers
Consequences
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Should be properly sized
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Accurately controlled
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Blade Seals
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Leakage path during unoccupied periods (wastes
energy)
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Can't properly balance fresh air flow
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Economizers: Magnify problems
Edge Seals
A Better Package.key - May 14, 2015
Leakage Standards
Cabinet Leakage
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ASHRAE: None
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IECC: No reference
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ASHRAE 90.1: No reference
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IECC Building Leakage Test: Usually fails through
HVAC unit
Cabinet Improvements
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Prefer double-wall sandwich panels (foam injected)
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Over single-wall metal with foil-faced fiber, taped.
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We need a standard!
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Custom AHU Manufacturers: Less than 1% of rated
airflow. Typically test to less than 1/2%
External Factors
A Better Package.key - May 14, 2015
External Factors
Standards vs. Regulation
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Duct design
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Industry groups: www.advancedrtu.org
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Duct insulation
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Owner groups
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Air distribution
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Still - developers will always be price-driven!
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47? 50? 52? 55?
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Standards (90.1, LEED) only apply to the 1% of
projects!
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DOE vs. ASHRAE
Conclusions
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Energy-based improvements will not only result in
less energy use for new projects, but it will extend
to equipment replacement and building renovation,
arguably a larger market than new construction.
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We must push for a greater commitment if
significant equipment innovation is to occur for the
next generation.
Questions?
A Better Package.key - May 14, 2015