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THE ONS & OFFS OF ERV EFFECTIVENESS
Josh Quinnell, Ph.D.
Sr. Research Engineer
A Conservation Applied Research & Development Field Study
WelcomeConservation Applied Research & Development
(CARD) Webinar
Mary Sue Lobenstein | R&D Program Administrator
mn.gov/commerce
Minnesota Applied Research & Development Fund
Purpose to help Minnesota utilities achieve 1.5 % energy savings goal by:
• Identifying new technologies or strategies to maximize energy savings;
• Improving effectiveness of energy conservation programs;
• Documenting CO2 reductions from energy conservation programs.
Minnesota Statutes §216B.241, Subd. 1e.
mn.gov/commerce
CARD RFP Spending by Sectorthru mid-FY2017
• 8 Funding Cycles• Nearly 380 proposals• 92 projects funded
mn.gov/commerce
Multi-sector (21) 25.3%
Commercial (36) 37.6%
Residential 1-4 unit (15)
18.7%
Industrial (10) 8.6%
Multifamily 5+ unit (4) 6.6%
Agricultural (6) 3.1%
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Research
Financing Policy
Programs
Discover + Deploy the most effective solutions for a healthy, low-carbon economy
Planning & Consulting
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The Ons & Offs of Energy Recovery
Ventilation Effectiveness
PRESENTER: Josh Quinnell, Ph. D. Senior Research EngineerCenter for Energy & Environment
THE ONS & OFFS OF ERV EFFECTIVENESS
Josh Quinnell, Ph.D.
Sr. Research Engineer
A Conservation Applied Research & Development Field Study
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Today’s Agenda
• Background• What is Air-to-Air Exhaust Energy Recovery?
• Why energy recovery?
• Expectations• Some people are saying “Energy Recovery doesn’t work”
• What are expectations and why do “they” say this?
• Methodology• Characterizing ERVs in Minnesota & in-depth study of representative units
• Results• ERVs in Minnesota
• Energy Savings & Performance
• What types of problems impede energy recovery?
• Recommendations & Conclusions• What do we do with what we have learned?
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Today’s Agenda
• Background
• Expectations
• Methodology
• Results
• Recommendations & Conclusions
Pg. 10
Air-to-air exhaust energy recovery
systems (ERVs)
• ERVs transfer energy between incoming and outgoing
air streams to reduce the energy to condition outside
air
• Energy recovery is subordinate to ventilation flow!
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Energy recovery performance
• 𝐸𝑓𝑓𝑒𝑐𝑡𝑖𝑣𝑒𝑛𝑒𝑠𝑠, ε =𝑅𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝐸𝑛𝑒𝑟𝑔𝑦
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑝𝑜𝑠𝑠𝑖𝑏𝑙𝑒 𝑒𝑛𝑒𝑟𝑔𝑦 𝑟𝑒𝑐𝑜𝑣𝑒𝑟𝑦
• Design parameter
• By itself, not useful for energy savings
• 𝑅𝑒𝑐𝑜𝑣𝑒𝑟𝑦 𝐸𝑛𝑒𝑟𝑔𝑦 𝑅𝑎𝑡𝑖𝑜, 𝑅𝐸𝑅 =𝑅𝑒𝑐𝑜𝑣𝑒𝑟𝑒𝑑 𝐸𝑛𝑒𝑟𝑔𝑦
𝐸𝑛𝑒𝑟𝑔𝑦 𝑢𝑠𝑒𝑑 𝑓𝑜𝑟 𝑅𝑒𝑐𝑜𝑣𝑒𝑟𝑦
• Aligns ERVs with performance metric of heating & cooling eqpt.
• Annualized value represents total energy savings
• Resources:• (2016) ASHRAE HVAC Systems & Equipment Chapter 26,
• (2011) AHRI Guideline V,
• (2014) AHRI Guideline W
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ERV operation varies over the year
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Flow rates through ERVs
• Usually rated and specified at balanced flows, but operated at unbalancedflows
• When supply is greater than exhaust: The largest temperature/humidity changes occur in exhaust stream (common)
• Energy savings is limited by the lower flow rate!
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Energy code (ASHRAE 90.1-2010 / IECC 2012)
% Outdoor Air at Full Design Flow Rate
Zone <30%≥30% &
<40%≥40% &
<50%≥50% &
<60%≥60% &
<70%≥70% &
<80%≥ 80%
Design Supply Fan Airflow rate (cfm)
3-5B, 3-4C NR NR NR NR NR ≥ 5000 ≥ 5000
1-2B, 5C NR NR NR ≥ 26000 ≥ 12000 ≥ 5000 ≥ 4000
6B NR ≥ 11000 ≥ 5500 ≥ 4500 ≥ 3500 ≥ 2500 ≥ 1500
1-6A NR ≥ 5500 ≥ 4500 ≥ 3500 ≥ 2000 ≥ 1000 > 0
7, 8 NR ≥ 2500 ≥ 1000 > 0 > 0 > 0 > 0
• Performance Requirement: 50% (total) effectiveness at design
• Standards Evolution
• 2007: 70% OA and 5,000+ cfm
• 2013: 10% OA
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Today’s Agenda
• Background
• Expectations
• Methodology
• Results
• Recommendations & Conclusions
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What are Energy Recovery Expectations?
¯\_(ツ)_/¯¯\_(ツ)_/¯
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What are Energy Recovery Expectations?
• There are no consistent expectations.
• Performance expectations?
• Reduce design loads on heating & cooling
systems
• Decreases annual energy use to condition
outside air
• It works; not associated with “problems”
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Evidence suggests high rate of problems
63%
67%
55%
62%
31%
22%
10%
11%
6%
11%
35%
32%
0% 20% 40% 60% 80% 100%
PBEEEP
Call backs
Engineers
Owners
MSC
20
10
Reported Issues
Control
Operation
Design &Install
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Today’s Agenda
• Background
• Expectations
• Methodology
• Results
• Recommendations & Conclusions
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Methodology
Objectives:
1. Characterize ERVs in Minnesota
commercial and institutional buildings
2. Detailed study of a representative sample
of ERVs
3. Characterize and improve ERV
performance
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Characterization
• ERV Market Characterization Study for CenterPoint
Energy (2010)
• Public Buildings Enhanced Energy Efficiency Program
(PBEEEP) (2012)
• Limited information from rebated ERV installations
(2007 – 2012)
• Yielded information on 404 ERVs in Minnesota
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Study representative units
• Pick representative units for study• Screen units for a representative sample
• Find units that represent typical MN ERV specifications
• Identify units that may not meet expectations (e.g. have “problems”)
• Monitor them for ~6 months (heating / cooling / swing)• Setup data trending from automation systems
• Install pressure, temperature, and humidity logging equipment
• Conduct airflow and air leakage tests
• Identify & correct issues• Monitor post-implementation performance for savings
estimates
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Today’s Agenda
• Background
• Expectations
• Methodology
• Results
• Recommendations & Conclusions
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Results
Institutional
K-12 Schools
Enthalpy Wheel*
One
Commercial
Higher Ed.
Plate
Two
Other
Membrane
Three+
0% 20% 40% 60% 80% 100%
Institutional BuildingType
Building Type
Unit Type
Units per building
Pg. 29
Sizes
• Characterized units: 3,575,700 cfm of rated capacity
• Units range from 215 cfm to 60,000 cfm
• Lower quartile by size (<3,240 cfm) constitute 5% of
total flow
• Upper quartile (>11,030 cfm) constitute 63% of total
flow
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Representative Units
ERV Manufacturer Type Application SuppliesDesign Supply/ Exhaust Flow
AHRI ε
s1 AIRotor Wheel AHU AHU 5,600 /5,600 70
s2 Semco Wheel DOAS FCU 21,100 / 21,100 78
s3 AIRotor Wheel DOAS VAV 11,800 / 7,400 70
s4 Semco Wheel AHU CAV 33,600 / 33,600 78
s5HeatXChanger Plate AHU VAV 24,000 / 17,000
44/24 (67**)
s6 AIRotor Wheel RTU VAV 5,000 / 5,000 70
s7 Airxchange Wheel RTU AHU 5,600 / 5,600 66
s8 Innergy tech Wheel DOAS VAV 5,500/ 5,500(2) 71
s9 Thermotech Wheel AHU VAV 33,600 / 33,600 73***
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High level savings summary
• Initial Conditions• 3 units were non-functional
• 3 units suspected of major problems were functional
• 1 unit with non-specific concerns was highly functional
• 2 units without concerns were highly functional
• Post-Implementation• 9 units functional
• 2 units with 86% of new savings
• 5 units with 14% new savings
• 2 units with no new savings
Total SavingsPre Post New
$ 40,683 $ 57,851 $ 17,168 + 42%
Savings Profile% Source
88% Gas12% Electric
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Findings
• 75 Issues found on 9 units over 2 seasons
Perception & Expectations
EnergyEfficiency
Minor Issues
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Issues by Category
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Energy Efficiency Issues
~1/3 (24) issues analyzed for energy penalties
Suggests 50% more savings than achieved, but we can only claim savings once!
Heating Penalty
Heating Cost Penalty
Cooling Penalty
Cooling Cost
Penaltytherms/yr $/yr kWh/yr $/yr
Min 16 13 52 6Max 4,721 3,857 5,213 584
Average 1,388 1,134 1,498 168Sum 27,756 22,676 23,963 2,684
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What are some of these issues?
Tag Description CategoryHeating Penalty
Heating Cost
PenaltyTherm $
s1i1 Stuck MAD Part failure 293 239s1i2 High EAT lower limit Operator override 354 289
s1i3 High MAT lower limit Operator override 772 631
s2i1 Backward bypass control Installation issue 2,232 1,824s2i2 Incomplete bypass sequence Control sequence 2,232 1,824
s2i3 Torn canvas Part failure 1,533 1,252s2i4 EAT at purge Installation issue 240 196s2i5 Miswired wheel speed control Installation issue 2,177 1,779
s2i6 No heat valve and wheel staging Installation issue 1,742 1,423
s4i1 Discharge 10F below DAT Setpoint 2,869 2,344s5i1 Reverse damper polarity Operator override 4,721 3,857
s5i2 High EAT lower limit Operator override 4,721 3,857
s5i4 High EAT lower limit Setpoint 167 136s5i5 Warm up schedule Scheduling 425 347s6i2 Failed wheel VFD Part failure 2,452 2,003
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Performance Expectations
• When does energy recovery occur?
• 60% to 80% of recovery between 0ᵒF and 45ᵒF
• <10% of recovery below -5ᵒF or above 85ᵒF
• Little recovery between 45ᵒF and 65ᵒF
Pg. 37
Performance Expectations
• What does energy recovery do?
• Ventilation savings in line with claims
• Primarily reduces heating energy for outside air
• Reduces peak cooling load; downsize cooling to leverage
Pg. 38
Today’s Agenda
• Background
• Expectations
• Methodology
• Results
• Recommendations & Conclusions
Pg. 39
If there were Performance Expectations
Most ERVs in this study would not meet them!
• Units are specified at full capacity and balanced flows
• Exhaust flows are less than supply flows due to point exhaust
systems and other AHUs
• Effectiveness increases; energy recovery decreases
• As-operated flows are different (usually less) than
design (~30% less in this study!)
• Fixed capacity ERVs are installed in variable capacity systems
• ERVs in mixed air units only see fraction of typical capacity
(outside air flow rate fraction)
• Retrofits cause system-wide airflow and building pressure
changes
Pg. 40
Barriers to peak performance
• Lack of familiarity among staff that touch systems
• Technicians & operators rightly/wrongly have learned from
experience
• This is a major barrier when this experience is from poorly or
oddly implemented energy recovery
• No continuous feedback that they are working
• Blinking BAS graphics do not count!
• HVAC systems pick up the slack
• Hard and rare to measure performance
• Problems/behaviors persist; they are normalized
Pg. 41
Good News – It’s easy to validate
Energy Recovery
• Little reason to doubt AHRI rated effectiveness
• Let’s not waste effort validating HX performance
• Validating an ERV does not require Rcx effort
• ERVs on/off at the right times are working!
• Caveat: Flow rates are understood (IAQ, building
pressure)
• Energy penalties are avoided if staff
• 1) Identify when an ERV should be running and
• 2) Assess whether an ERV is running
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Validating working ERVs
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General commissioning guidelines
1. Large ERV systems (10,000 cfm+) must be fully-
commissioned
2. Validated as-operated flows against design flows
3. Control sequences should follow manufacturer
recommendations, deviations must be justified by
project engineers
4. Control intent and detailed sequences should be
specified and as-implemented sequences verified by
an accountable party
5. Cx. agents should set operator expectations
Pg. 45
Targeted Recommendations
• Design Engineers
• Provide more rigorous specifications WRT control of ERVs
• Mechanical and Controls Contractors
• Follow engineer specifications and
• Hold engineers accountable for complete specification,
• Not responsible for making engineering decisions
• Commissioning Agents
• Ensure knowledge transfer on system intent (including control)
• Validate sequencing
• Document as-operated conditions where different than design
• Building Owners / Representatives
• Provide resources for staff to understand systems they administer
• Establish expectations of semi-annual operational checks on ERV systems
Pg. 46
Conclusions
• ERVs meet their AHRI rated performance
• A cost effective addition to all large ventilation systems
• 30% - 90% reduction in heating ventilation load
• 20% - 40% reduction in peak cooling load; equipment downsizing
• Energy recovery typically hindered by practical issues that occur during installation or operation
• Non-functional ERVs go unnoticed
• Staff are not familiar with ERV systems
• ERVs don’t meet expectations due to a large variety of non energy issues
• Rarely performance related issues
• Identifying and resolving specific ERV issues may be time-intensive, but validating a working ERV is easy
• ERV issues are avoided by commissioning and training
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Audience
Question & Answer
CARD Project Resources
CARD Web Page (https://mn.gov/commerce/industries/energy/utilities/cip/applied-research-development/)mn.gov/commerce
For Reports use CARD SearchQuick Link
For Webinars use CARD Webinars & Videos Quick Link
Links to ERV Reports:Final Report
Validation GuideOperations Guide
Thanks for Participating!Upcoming CARD Webinars:
• July 12: Small Embedded Data Center Program Pilot
• July 26: Statewide Commercial Behavior Segmentation & Potential
• August 17: Expanding New Construction Design Assistance Statewide
If you have questions or feedback on the CARD program contact:Mary Sue Lobenstein
mn.gov/commerce
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