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

? ?

?

?

?

?

?

?

?

Questions?