ATEM MODULE 2: MECHANICAL
29
ATEM MODULE 2: MECHANICAL Accredited Texas Energy Manager
Transcript of ATEM MODULE 2: MECHANICAL
ATEM MODULE 2: MECHANICALA c c r e d i t e d T e x a s E n e r g y M a n a g e r
HVAC System Considerations
❯Codes
❯Owner’s requirements
❯System size
-Building shell
- Internal load
-Ventilation load
❯Control
-Operating hours
-Occupancy schedule
-Set points
-Ventilation
❯System type
-Central system
- Individual systems
❯Costs
-First cost
-Floor space cost
-Operating cost
-Owners budget
-Expansion cost
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
HVAC System Considerations
❯Maintenance capabilities
❯Space
-Floor space
-Plenum space
-Furniture placement
❯Maintenance access
- Roofs
- New or existing facility
❯ Impact on future additions
❯Comfort
- Temperature
- Humidity
- Noise
- Ventilation
- Filtration
- Air quality
❯Climate
❯Failure impact
❯Control strategy
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Terms
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
❯BTU
-British thermal unit
-Heat needed to raise temp of 1 lb. of
water 1ºF
❯DX
-Direct expansion
-Air cooled by direct contact w/ refrigerant
in cooling coil
Air Side Terms
❯cfm – cubic feet per minute; measure of air flow
❯Constant air volume – supply air flow rate does not change
❯Multizone – dampers mix hot & cold air to supply several zones from
one unit
❯Reheat – heating coil warms cooling supply air when cooling demand
is low
❯Variable air volume (VAV) – supply air flow rate changes to meet load
demand- Fan coil unit (FCU) – heating and/or cooling coil & fan
- VAV box – regulators supply air volume
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Packaged (RTU)
Types of Systems
Split Central (CHW)
Central (CHW) Systems
❯Advantages
-Large capacity
-Noise isolated/centralized
-Centralized maintenance
-Longer life
-Efficient strategies available
❯Disadvantages
- Higher first cost
- Additional cost for redundancy
- Uses building floor space
- Affects large areas during failure
- More complex system
- Water treatment
- More qualified personnel required
- Higher maintenance cost
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Chiller(s)
CHW System Components
Air Handler
Cooling Tower
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Pumps
More CHW System Components
Terminal Unit Boilers
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
CHW System Diagram
Chiller
P
Cooling Tower Condensed Water
~85F
P
Boiler
AHU AHU
P
Chilled Water~44F
Hot Water~160FWater Cooled
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Multizone Units
One unit serves multiple areas
Split Systems
❯Advantages
- Individual control
-Flexibility promotes energy
efficiency
-Lower first cost
-Less complicated controls
-Failure less disruptive
-Less skilled maintenance required
-Less floor space required than
central systems
-Lower maintenance cost
❯Disadvantages
- Shorter life than central systems
- More systems & components to
service
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Variable Refrigerant Flow (VRF)
❯Applications
-Buildings w/ multiple zones
-Simultaneous heating & cooling desired
❯Equipment
-Single outdoor condensing unit
-Multiple indoor fan coil units
-Connected w/ refrigerant piping
❯Advantages
-High system efficiencies
- Individual zone control
-Less ductwork
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Window Unit
Other System Types
Thru-wall Unit Evaporative Cooler
Ground Source Heat Pumps
❯Refrigerant compressor like air-air system
❯Earth as heat sink/source
❯Well field
-Transfers heat to earth in summer
-Gets heat from earth in winter
-Requires good design for efficient
operation
❯Underground pipe loops filled with
water-antifreeze mixture
-1 well per ton
-Approx. 250’ deep
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
1 ton (cooling) = 12,000 Btu/hr
1 kWh = 3,413 Btu
Conversion Factor
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Calculated at a single operating point
EER =
Example: 3-ton unit
EER = = 10
EER
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Cooling Capacity (Btu/h)
Power Input (Watts)
36,000 Btu/h
3,600 Watts
Other Equipment Efficiencies
❯SEER – Seasonal Energy Efficiency Ratio-Similar to EER
-Efficiency calculated over an entire cooling season
❯COP – Coefficient of Performance-Equivalent of EER for electric heating
❯IPLV – Integrated Part Load Value-Weighted average efficiency at part load values
❯IEER – Integrated Energy Efficiency Ratio-Weighted average efficiency at 4 standard conditions
❯AFUE-Gas fired equipment
-Ratio of Btu out/Btu in
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
IECC – Minimum Efficiencies Common Cooling Equipment
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Size Subcategory Minimum Efficiency
(Btu/h) 2012 2015
< 65,000(5.4 tons)
Split System A/CPackaged A/C
13.0 SEER13.0 SEER
13.0 SEER14.0 SEER
65,000 to 135,000 (5.4 to 11.25 tons)
Split System A/C or Packaged A/C
11.2 EER 11.2 EER
135,000 to 240,000 (11.25 to 20 tons)
Split System A/C or Packaged A/C
11.0 EER 11.0 EER
240,000 to 760,000 (20 to 63.3 tons)
Split System A/C or Packaged A/C
10.0 EER 10.0 EER
< 135,000(11.25 tons)
Ground Source 10.6 EER 10.6 EER
Basic Characteristics of Energy Efficient Systems
❯Proper sizing
❯High system efficiency (SEER, etc.)
❯Operational flexibility
❯Zoning
❯Controls
❯Ability to maintain & service
❯Simplicity
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Ventilation ASHRAE Standard 62.1
❯Minimum outside air requirements
❯Incorporated into codes
❯Continuous ASHRAE review/revisions
❯Basis for ventilation rates
-Room use
-Room size
-Estimated number of occupants
❯Rates can be reduced w/ approved methods
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Outdoor Air & HVAC
❯Separate unit to pre-treat outside air
❯HVAC unts with provisions for high outside air & comfort control- Condenser reheat
› Reduce humidity & maintain comfortable temperature
› Recycles exhaust heat energy
- Two-compressor units
› Small compressor – light loads
› Large compressor – heavy loads
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Air Filters
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
❯Usually place in return air stream
❯Remove dust, pollen, bacteria, etc.
❯Made of fiberglass, cotton, or polyester
❯Efficiency
-MERV rating scale 1 to 16
-Higher ratings mean smaller particles
removed
❯ASHRAE 62 – MERV 6 or better
Bipolar Ionization
❯Air cleaning technology
❯Can be used to reduce outside air
❯Ionization tubes generate + & – ions
❯Ions react with O2 to remove contaminants
-Particulates
-Odors
-Viruses & bacteria
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Refrigerants
❯CFCs
-R-11, R-12, R-113
-Production ceased in 1996
❯HCFCs
-R-22, R-123
-R-22
› Began phaseout in 2010
› 90% reduction in 2015
› Stop production in 2020
› No direct drop-ins
-High Pressures
› New gauges
› Training
❯HFCs
-R-134A, R-404A, R-410A
-Replacements for CFCs and HCFCs
-410A replacing R-22 for DX
equipment
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
Variable Frequency Drives (VFD)
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
❯Control speed of AC motors
❯Applications
-Chillers
-Pump motors
-Large air handlers
❯Benefits
- Match motor speed to demand
- Save energy
- Improve power factor
Variable Frequency Drives (VFD)
❯Affinity Laws- Fans & pumps
- Power varies w/ cube of speed
A c c r e d i t e d T e x a s E n e r g y M a n a g e r
𝑃 𝑠𝑙𝑜𝑤 𝑠𝑝𝑒𝑒𝑑
𝑃 𝑓𝑎𝑠𝑡 𝑠𝑝𝑒𝑒𝑑=
𝑟𝑝𝑚 𝑠𝑙𝑜𝑤 𝑠𝑝𝑒𝑒𝑑
𝑟𝑝𝑚 𝑓𝑎𝑠𝑡 𝑠𝑝𝑒𝑒𝑑
3
=1620
1800
3
= 73%
Reducing motor speed 10%, reduces power 27%
Ashley Williams, MCRP & ATEM
❯ Texas Energy Managers Association
❯ Director of Curriculum and Certification
questions
e n e r g y m a n a g e m e n t p r o g r a m : f u n d a m e n t a l s a n d d e v e l o p m e n t
Texas Energy Managers Association
❯ www.texasema.org
