7 th Annual North American Passive House Conference September 27-30, 2012 Denver CO Heat Recovery Ventilation: How do those things really work? Michael LeBeau & Barry Stephens
7th Annual North American Passive House Conference
September 27-30, 2012 Denver CO
Heat Recovery Ventilation:
How do those things really work?
Michael LeBeau
&
Barry Stephens
Session Learning Objectives:
7th Annual North American Passive House Conference
September 27-30, 2012 Denver CO
• The difference between Cross-Flow, Counter-
Flow and Enthalpy Wheel H/ERVs
• Major Components of Heat Recovery Ventilation
• PHI Certification vs HVI Testing, and what that
means to the PHPP
• Design, installation and balancing
(commissioning) for maximum efficiency
Major Components of all HRV’s
• Case and duct connections
• Insulation
• Blowers and motors
• Electronic control circuits
• Defrost or preheat
• Heat Exchanger
• Filters
3
Components of an HRV Device
DC motors
Lowest energy consumption
Heat recovery unit
High heat recovery > 90%
Filters
Control unit /display
5
Duct System
Heat Exchanger Options
• Static Heat Exchanger (HEX) Cores
– HRV or ERV
– Cross-flow
– Counter-flow
• Enthalpy ERV HEX Wheels (extra motor)
6
Four ports – 2 cold, 2 warm
7
Cross-Flow HEX Core
HRV or ERV
8
Counter-Flow HEX Core
HRV or ERV
9
Counter Flow Core Options
10
HRV/ERV Counter-Flow
11
Enthalpy Wheel ERV
12
Apparent Sensible Effectiveness (ASE)
13
• Term used in the CSA C439M standard for
testing HRVs to describe the temperature rise of
the outdoor air passing through an HRV.
• Includes motor heat gain, cross leakage gain
and casing gain.
• Temp rise of outdoor air / temp. difference
between indoor and outdoor air.
• Expressed as a percentage.
Sensible Recovery Efficiency (SRE)
Corrected ASE taking in to account the heat gains from (1) motor heat, (2) cross-flow leakage and (3) casing gain.
CFM Per Watt
• The amount of air moved by the ventilator divided
by the electrical power consumed to run the
blowers, controls and defrost equipment.
15
Exhaust Air Transfer Ratio (HVI)
or
Air Tightness (PHI)
Percentage of air leaking from exhaust air stream to the intake air stream, noted as a percentage.
VENTILATION PERFORMANCE EXT. STATIC NET SUPPLY GROSS AIR FLOW
PRESSURE AIR FLOW SUPPLY EXHAUST
Pa in wg L/s cfm L/s cfm L/s cfm
25 0.1 123 260 123 261 126 266
50 0.2 119 251 119 252 124 262
75 0.3 115 243 115 244 121 255
00 0.4 111 236 112 237 117 247
125 0.5 108 229 109 230 113 239
150 0.6 105 223 105 223 109 230
175 0.7 102 216 102 217 105 223
200 0.8 99 210 99 210 102 217
225 0.9 96 203 96 204 100 212 250 1.0 94 198 94 199 98 208
T1 T2
T3
T4
F 22
Heat exchanger versus energy
exchanger
• Counterflow-heat-exchanger Counterflow energy exchanger
32 F 72 F
41 F 68 F
Counter flow heat-exchanger
≈ 90 %
104 F humid
72 F dry
99 F humid
77 F dry
Counter flow energy-exchanger
≈ 90 %
• Heat exchangers – Cross current flow
– Heat recovered > 90%
• Summer bypass – automatic
– temperature freely adjustable
– Heat exchange
• Ventilators • efficient DC motor
• continuously variable
Solution With HRV/ERV Ventilation
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Questions?