+---
+title: Energy Recovery Ventilators
+category: Mechanical / Air Distribution
+toc_depth: 3
+description: >
+ When to use: Air-to-air energy recovery devices that transfer heat, and optionally moisture, between a building's outdoor (intake) air stream and its exhaust (relief) air stream to reduce the conditioning load imposed by code-required ventilation. Covers packaged rooftop, wall, and ceiling energy recovery ventilators (ERVs and heat recovery ventilators) with integral fans and controls; core-only energy recovery components installed in custom or field-built air handlers and dedicated outdoor air systems (rotary enthalpy and sensible wheels, fixed-plate sensible aluminum cross-flow cores, fixed-plate membrane enthalpy cores, heat-pipe assemblies, and runaround glycol coil loops); the recovery effectiveness, cross-leakage, and frost-control behavior that govern selection; the supply and exhaust fans where integral; filtration; casing; condensate management; and the controls integration including economizer bypass and demand-controlled modulation. Applicable to commercial, institutional, multifamily, and light-industrial buildings where exhaust-air energy recovery is mandated by the energy code or used to reduce ventilation load.
+ Not intended for: The deep-cooling, dehumidification, and reheat sections and overall configuration of a dedicated outdoor air system (see [[sync/dedicated-outdoor-air-systems]]); unitary packaged rooftop units with return-air mixing and integral economizer (see [[sync/packaged-rooftop-units]]); stand-alone supply and exhaust fans not part of a recovery device (see [[sync/hvac-fans]]); supply and exhaust ductwork beyond the unit connections (see [[sync/hvac-ductwork]]); diffusers, grilles, and registers (see [[sync/hvac-air-distribution-devices]]); testing, adjusting, and balancing after installation (see [[sync/testing-adjusting-and-balancing]]); and building automation controls programming and graphics (see [[sync/building-automation-system]]).
+---
+
+# Scope {toc}
+
+## This specification covers factory-rated air-to-air energy recovery devices that exchange heat, and optionally moisture, between a building's outdoor air intake stream and its exhaust air stream to reduce the heating, cooling, and dehumidification load created by code-required ventilation. {note}
+
+## Devices covered include both complete packaged energy recovery ventilators with integral supply and exhaust fans, filters, dampers, and controls, and core-only recovery components furnished for installation within a separate air handler or dedicated outdoor air system. {note}
+
+## Recovery technologies covered are the rotary enthalpy wheel, the rotary sensible wheel, the fixed-plate sensible aluminum cross-flow core, the fixed-plate membrane enthalpy core, the heat-pipe assembly, and the runaround glycol coil loop. {note}
+
+## The distinction between a heat recovery ventilator, which transfers sensible heat only, and an energy recovery ventilator, which transfers both sensible heat and latent moisture, is a controlling selection decision and is not interchangeable terminology in this standard. {note}
+
+## A recovery device exists to pre-condition outdoor air using energy that would otherwise be discarded with the exhaust, so that the downstream cooling and heating equipment is smaller and the annual ventilation energy is lower; the device's certified effectiveness, its cross-stream leakage, and its frost behavior are the central engineering decisions, not accessories. {note}
+
+## Where moisture transfer between the two air streams is unacceptable for reasons of contamination, the recovery device must keep the streams physically separated, which restricts the technology choice and is treated as a hard constraint in this standard rather than a preference. {note}
+
+## Equipment shall be certified or rated in accordance with AHRI 1060, tested in accordance with ASHRAE 84, and selected to satisfy the exhaust-air energy recovery provisions of ASHRAE 90.1 and the air-stream classification and cross-leakage limits of ASHRAE 62.1.
+
+## The boundary of work under this standard is the recovery device and its factory components, from the outdoor air and exhaust air connections through the supply and relief connections for packaged units, or the core inlet and outlet faces for core-only components. {note}
+
+## Supply and exhaust ductwork is covered by [[sync/hvac-ductwork]]; the diffusers, grilles, and registers that distribute the supply air are covered by [[sync/hvac-air-distribution-devices]]; stand-alone fans are covered by [[sync/hvac-fans]]; the dedicated outdoor air system into which a core-only component is installed is covered by [[sync/dedicated-outdoor-air-systems]]; and controls programming, graphics, and trending are covered by [[sync/building-automation-system]]. {note}
+
+# Referenced Standards {toc}
+
+## Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
+
+## Where conflicts exist between referenced standards, the adopted energy and mechanical codes, the equipment manufacturer's instructions, or the contract documents, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
+
+## The energy code and ventilation standard editions adopted by the authority having jurisdiction shall be confirmed before selection, because the energy recovery mandate thresholds and the cross-leakage limits differ between editions. {note}
+
+## Referenced standards list {toc}
+
+| Standard | Title |
+|----------|-------|
+| ANSI/AHRI 1060 (I-P) | Performance Rating of Air-to-Air Exchangers for Energy Recovery Ventilation Equipment |
+| AHRI 1061 (SI) | Performance Rating of Air-to-Air Exchangers for Energy Recovery Ventilation Equipment (SI edition) |
+| ANSI/ASHRAE 84 | Method of Testing Air-to-Air Heat/Energy Exchangers |
+| ANSI/ASHRAE 62.1 | Ventilation and Acceptable Indoor Air Quality |
+| ANSI/ASHRAE/IES 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings |
+| ANSI/ASHRAE 170 | Ventilation of Health Care Facilities |
+| ANSI/AMCA 210 / ASHRAE 51 | Laboratory Methods of Testing Fans for Certified Aerodynamic Performance Rating |
+| ANSI/AMCA 205 | Energy Efficiency Classification for Fans |
+| ANSI/ASHRAE 52.2 | Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size |
+| AHRI Certification Program | Certification Program for Air-to-Air Energy Recovery Ventilation Equipment |
+| NFPA 90A | Standard for the Installation of Air-Conditioning and Ventilating Systems |
+| NFPA 99 | Health Care Facilities Code |
+| UL 1995 | Heating and Cooling Equipment (where accepted by the AHJ) |
+| UL 60335-2-40 | Safety of Household and Similar Electrical Appliances — Particular Requirements for Heat Pumps, Air-Conditioners, and Dehumidifiers |
+| ASHRAE Handbook | HVAC Systems and Equipment, Chapter on Air-to-Air Energy Recovery Equipment |
+
+# Submittals {toc}
+
+## Action Submittals {toc}
+
+### The Contractor shall submit the following for the Engineer's review and acceptance before equipment is ordered.
+
+### Fabrication and procurement shall not proceed until action submittals have been reviewed and returned.
+
+### The certified effectiveness ratings submitted shall be reported at the design supply and exhaust airflows, not at the device's nominal or rated airflow, because effectiveness changes with airflow.
+
+### Submit the following action submittals: {toc}
+
+- Manufacturer's product data for each recovery device, including the recovery technology, model designation, an airflow schematic showing the outdoor, exhaust, supply, and relief streams, and the component schedule
+- AHRI 1060 certified performance ratings for each device, reporting sensible, latent, and total effectiveness at 100% and 75% of the design supply airflow for both the summer and winter rating conditions, the exhaust air transfer ratio (EATR), and the outdoor air correction factor (OACF), all at the design airflows
+- The AHRI certified-product directory listing or equivalent certification reference for each device
+- Air-side pressure drop across the recovery core for both the supply and exhaust streams at the design airflows, for inclusion in the fan selection
+- Fan performance curves at the design operating point per AMCA 210, with power and efficiency and the fan energy index or fan efficiency grade, for packaged units with integral fans
+- A frost-control description identifying the frost-control method, the outdoor air temperature at which it activates, and its effect on ventilation delivery and on net recovery during frost control
+- A written sequence of operation describing normal recovery operation, economizer bypass, frost control, and any demand-controlled ventilation modulation, with the interface points to the [[sync/building-automation-system]]
+- Filter section data with the MERV rating certified per ASHRAE 52.2, initial and final resistance, and frame and seal construction
+- Casing construction details, panel insulation, and, for outdoor units, the weatherproofing and finish system
+- Condensate drain pan and drain connection details for membrane enthalpy cores and for any configuration that condenses in the exhaust stream
+- Electrical data: voltage, phase, minimum circuit ampacity, and maximum overcurrent protection, for units with integral fans or controls
+- The applicable safety listing (UL 1995 or UL 60335-2-40) for packaged units containing a refrigeration circuit
+
+```datasheet
+label: Action Submittals Required
+type: checkbox
+options:
+ - "Product data and unit airflow schematic"
+ - "AHRI 1060 ratings at design airflow (effectiveness, EATR, OACF)"
+ - "AHRI certified-directory listing reference"
+ - "Core air-side pressure drop (supply and exhaust)"
+ - "Fan curves and fan energy index (integral-fan units)"
+ - "Frost-control method and activation description"
+ - "Sequence of operation (recovery, bypass, frost, DCV)"
+ - "Filter MERV certification (ASHRAE 52.2)"
+ - "Casing construction and weatherproofing details"
+ - "Condensate drain pan and connection details"
+ - "Electrical data (integral-fan/controls units)"
+ - "Safety listing for units with refrigeration circuit"
+default: "Product data and unit airflow schematic"
+```
+
+## Closeout Submittals {toc}
+
+### The Contractor shall provide the following at or before substantial completion:
+
+- Operation and maintenance manuals for each device and its major components, organized with a table of contents
+- As-built unit configuration and as-built controls points list reflecting any field modifications
+- Factory test reports for each device, where furnished
+- Startup and commissioning records, including the functional test of economizer bypass, frost control, and any demand-controlled ventilation modulation
+- Energy recovery component maintenance data, including wheel drive belt and seal replacement intervals and purge sector adjustment for rotary devices, and the core cleaning procedure for fixed-plate and membrane cores
+- Filter media installed at substantial completion with MERV certification and installation date tags
+- Warranty documentation from the manufacturer and from any recovery-core sub-supplier
+
+```datasheet
+label: Required Closeout Submittals
+type: checkbox
+options:
+ - "Operation and maintenance manuals"
+ - "As-built configuration and controls points list"
+ - "Factory test reports"
+ - "Startup and commissioning records"
+ - "Energy recovery maintenance data"
+ - "Installed filter media with MERV certification"
+ - "Warranty documentation"
+default: "Operation and maintenance manuals"
+```
+
+## Informational Submittals {toc}
+
+### Submit the following informational submittals for record:
+
+- A psychrometric or tabular analysis showing the entering and leaving conditions of both air streams at the summer and winter design conditions, demonstrating the net load reduction
+- The outdoor air quantity calculation showing how the outdoor air correction factor (OACF) was applied so that the certified intake airflow at the building exterior meets the ventilation requirement
+- Confirmation of the exhaust air stream classification per ASHRAE 62.1 and the corresponding EATR acceptability for the selected device
+
+```datasheet
+label: Informational Submittals Required
+type: checkbox
+options:
+ - "Psychrometric / load-reduction analysis"
+ - "OACF-corrected outdoor air quantity calculation"
+ - "Exhaust air class and EATR acceptability confirmation"
+default: "Psychrometric / load-reduction analysis"
+```
+
+# Quality Assurance {toc}
+
+## Each recovery device shall be a standard cataloged product of a manufacturer regularly engaged in the production of air-to-air energy recovery equipment.
+
+## The recovery component shall be rated under the AHRI Certification Program for Air-to-Air Energy Recovery Ventilation Equipment, and the certified directory listing shall be the enforceable basis of acceptance for effectiveness, EATR, and OACF.
+
+### The AHRI certified directory, not a manufacturer's uncertified catalog page, is the verification of record because the program independently validates the rated effectiveness and leakage values against the ASHRAE 84 test method. {note}
+
+## Where a device or a specific configuration is not listed in the AHRI certified directory, the Contractor shall submit independent laboratory test data conducted per ASHRAE 84 demonstrating equivalent compliance, for the Engineer's acceptance.
+
+## Packaged units that contain a refrigeration circuit shall bear the safety listing applicable to their configuration, either UL 1995 or UL 60335-2-40, as confirmed by the manufacturer.
+
+### Confirm which safety listing applies by the unit configuration, because the listing that governs a packaged recovery unit depends on whether it incorporates a refrigeration circuit and on the listing transition between the two standards. {note}
+
+## Fans furnished as part of a packaged unit shall be rated for aerodynamic performance per AMCA 210 and shall meet the applicable fan efficiency provisions referenced by ASHRAE 90.1.
+
+# Environmental and Service Conditions {toc}
+
+## The design summer and winter outdoor air conditions, and the indoor exhaust air conditions, shall be those of the project location and the served spaces as scheduled, and effectiveness shall be certified at these rating conditions.
+
+## The minimum outdoor air temperature at which the device shall deliver full design ventilation without frost control intervention shall be established, and the frost-control method shall maintain ventilation delivery below that temperature.
+
+### Frost forms when the warm, humid exhaust stream is cooled below its dewpoint and then below freezing within the recovery device, blocking the exhaust passages and degrading or stopping recovery; the temperature at which this begins depends on the indoor humidity and the device type, so the frost-control trigger is a design value, not a fixed constant. {note}
+
+## Outdoor-mounted devices shall be rated for the full range of ambient temperature, wind, rain, and snow loading at the installation location.
+
+## Devices serving exhaust streams that carry grease, corrosive vapors, or high particulate loading shall be of materials and a configuration compatible with that exhaust, or shall be excluded from those streams entirely.
+
+```datasheet
+label: Design Conditions
+type: group
+fields:
+ - label: Summer outdoor air dry-bulb
+ type: range
+ unit: °F
+ min: 85
+ max: 115
+ step: 1
+ default: 95
+ - label: Summer outdoor air wet-bulb (coincident)
+ type: range
+ unit: °F
+ min: 68
+ max: 85
+ step: 1
+ default: 78
+ - label: Winter outdoor air dry-bulb
+ type: range
+ unit: °F
+ min: -20
+ max: 35
+ step: 1
+ default: 5
+ - label: Minimum outdoor temperature for full flow without frost control
+ type: range
+ unit: °F
+ min: -10
+ max: 32
+ step: 1
+ default: 15
+```
+
+# Energy Recovery Performance {toc}
+
+## The recovery device shall be selected and certified to meet or exceed the effectiveness, cross-leakage, and correction-factor values specified below at the design supply and exhaust airflows.
+
+## Effectiveness shall be the AHRI 1060 certified value at the design airflow, reported at both 100% and 75% of design supply airflow, and not the manufacturer's nominal or peak catalog value.
+
+### Effectiveness specified at the device's nominal airflow rather than at the project's design airflow is a recurring selection error, because a device run at an airflow different from its rating point will deliver a different effectiveness; the design airflow is the only airflow that matters. {note}
+
+## A sensible-only device shall be specified where only temperature recovery is intended, and a total (enthalpy) device shall be specified where both temperature and moisture recovery is intended, and the two shall not be substituted for one another without the Engineer's acceptance.
+
+### Confusing a sensible heat recovery ventilator with a total energy recovery ventilator is a common and consequential error; in a humid climate a sensible-only device leaves the entire ventilation latent load to the cooling coil, and in a dry climate a moisture-transferring device may give back humidity that the building is trying to reject. {note}
+
+## The recovery effectiveness shall be the controlling performance value rather than a generic "high-efficiency" label, and the certified value shall be scheduled as a number.
+
+```datasheet
+label: Recovery Type and Effectiveness
+type: group
+fields:
+ - label: Recovery type
+ type: radio
+ options:
+ - "Sensible only (heat recovery ventilator)"
+ - "Total / enthalpy (energy recovery ventilator)"
+ default: "Total / enthalpy (energy recovery ventilator)"
+ - label: Certified sensible effectiveness at design airflow
+ type: range
+ unit: "%"
+ min: 70
+ max: 85
+ step: 1
+ default: 75
+ - label: Certified total (enthalpy) effectiveness at design airflow
+ type: range
+ unit: "%"
+ min: 60
+ max: 80
+ step: 1
+ default: 70
+ - label: Effectiveness reporting points
+ type: radio
+ options:
+ - "100% and 75% of design supply airflow"
+ - "100% of design supply airflow only"
+ default: "100% and 75% of design supply airflow"
+```
+
+## Exhaust Air Transfer and Cross-Leakage {toc}
+
+### The exhaust air transfer ratio (EATR) is the fraction of the exhaust stream that crosses into the supply stream within the device, and it shall be limited to the value acceptable for the served exhaust air class under ASHRAE 62.1. {note}
+
+### The exhaust air transfer ratio shall not exceed the limit established for the served exhaust air stream class, and the certified EATR shall be reported with the effectiveness ratings.
+
+### For a Class 1 exhaust stream, the exhaust air transfer ratio shall not exceed 10%.
+
+### For a Class 2 exhaust stream, the recovered air transfer shall be limited as required to keep recirculated contaminants within acceptable levels for the supply spaces.
+
+### For a Class 3 or Class 4 exhaust stream, energy recovery that transfers any portion of the exhaust into the supply stream shall not be used, and only a device that keeps the two streams physically separated with zero cross-leakage shall be considered.
+
+### Class 3 and Class 4 exhaust streams carry contaminants whose reintroduction into occupied supply air is unacceptable, so recovery from these streams is restricted to separated-stream devices, and rotary wheels, which inherently carry a small amount of exhaust air across on the rotating matrix, are excluded. {note}
+
+### Where zero exhaust-to-supply leakage is required, the recovery device shall be a fixed-plate core, a heat-pipe assembly, or a runaround glycol loop, all of which keep the streams in separate passages.
+
+### Laboratories, operating rooms, isolation rooms, and grease or hazardous exhaust applications require zero exhaust air transfer and shall use only separated-stream recovery devices. {note}
+
+### Rotary enthalpy and sensible wheels shall include a purge sector sized and adjusted to limit carryover from the exhaust to the supply stream, where a wheel is used on an acceptable air class.
+
+### An undersized or unadjusted purge sector allows more exhaust air to be carried across the wheel than the certified EATR assumes, which is why the purge setting is a commissioning item, not a factory-only setting. {note}
+
+```datasheet
+label: Exhaust Air Class and Leakage Limits
+type: group
+fields:
+ - label: Served exhaust air class (ASHRAE 62.1)
+ type: radio
+ options:
+ - "Class 1"
+ - "Class 2"
+ - "Class 3"
+ - "Class 4"
+ default: "Class 1"
+ - label: Maximum exhaust air transfer ratio (EATR)
+ type: range
+ unit: "%"
+ min: 0
+ max: 10
+ step: 1
+ default: 5
+ - label: Zero cross-leakage (separated-stream) required
+ type: radio
+ options:
+ - "No - cross-leakage within class limit acceptable"
+ - "Yes - separated-stream core required"
+ default: "No - cross-leakage within class limit acceptable"
+```
+
+## Outdoor Air Correction Factor {toc}
+
+### The outdoor air correction factor (OACF) is the ratio of the airflow entering the device at the outdoor intake to the airflow leaving toward the supply, and it accounts for leakage and carryover that change the net outdoor air actually delivered. {note}
+
+### The outdoor air correction factor shall not exceed 1.10, and the certified OACF shall be reported with the effectiveness ratings.
+
+### The outdoor air quantity calculation shall apply the certified OACF so that the certified intake airflow at the building exterior is sufficient to deliver the required outdoor air to the spaces after device leakage.
+
+### Omitting the OACF from the outdoor air quantity calculation causes the building to draw less outdoor air than the ventilation requirement demands, because some of the air entering the intake is lost to leakage within the device before it reaches the supply duct. {note}
+
+```datasheet
+label: Outdoor Air Correction Factor
+type: range
+unit: ratio
+min: 1.0
+max: 1.1
+step: 0.01
+default: 1.05
+```
+
+# Device Configuration and Selection {toc}
+
+## The recovery device shall be furnished in the configuration scheduled for its location: a complete packaged energy recovery ventilator with integral fans and controls, a recovery core installed within a separate air handler or dedicated outdoor air system, or a runaround coil pair for remote intake and exhaust locations.
+
+### A packaged unit with integral supply and exhaust fans, filters, and controls is the simplest procurement and is preferred where the intake and exhaust can be brought to a single unit location. {note}
+
+### A core-only component installed in a custom air handler or in a dedicated outdoor air system is used where the recovery section is one part of a larger conditioning unit; see [[sync/dedicated-outdoor-air-systems]] for the surrounding unit. {note}
+
+### A runaround glycol loop is used where the intake and exhaust streams cannot be brought adjacent to one another, because only a circulating fluid, not a shared air path, connects the two coils. {note}
+
+## The recovery core type shall be selected for the application, balancing effectiveness, moisture transfer capability, cross-leakage, pressure drop, and frost behavior.
+
+```datasheet
+label: Device Configuration
+type: radio
+options:
+ - "Packaged rooftop ERV - integral fans and controls"
+ - "Packaged wall/ceiling ERV - integral fans and controls"
+ - "Core-only component for separate AHU or DOAS"
+ - "Runaround glycol coil pair (remote intake/exhaust)"
+default: "Packaged rooftop ERV - integral fans and controls"
+```
+
+```datasheet
+label: Recovery Core Type
+type: radio
+options:
+ - "Rotary enthalpy wheel"
+ - "Rotary sensible wheel"
+ - "Fixed-plate sensible aluminum cross-flow core"
+ - "Fixed-plate membrane enthalpy core"
+ - "Heat-pipe assembly"
+ - "Runaround glycol coil loop"
+default: "Rotary enthalpy wheel"
+```
+
+## Rotary Wheel Devices {toc}
+
+### A rotary enthalpy wheel transfers both sensible heat and latent moisture and offers the highest combined effectiveness, but it carries a small fraction of the exhaust across to the supply and shall be used only where that carryover is acceptable for the air class. {note}
+
+### A rotary wheel shall include a purge sector, variable-speed or modulating wheel drive where capacity control is required, and an accessible drive belt and seal set.
+
+### The wheel rotation shall be confirmed during startup, because a wheel that has stopped or is rotating against a failed drive delivers essentially no recovery while the unit appears to operate normally. {note}
+
+## Fixed-Plate and Heat-Pipe Devices {toc}
+
+### A fixed-plate sensible aluminum cross-flow core transfers heat only and keeps the two air streams in fully separated passages, making it suitable where zero exhaust-to-supply leakage is required. {note}
+
+### A fixed-plate membrane enthalpy core transfers both heat and moisture through a vapor-permeable membrane while keeping the bulk air streams separated, giving low cross-leakage with latent recovery. {note}
+
+### A fixed-plate membrane core shall be furnished with a condensate drain pan and drain connection, because the core condenses moisture during cooling-season operation.
+
+### A heat-pipe assembly transfers sensible heat through a sealed refrigerant tube bundle spanning the two adjacent streams, with the streams fully separated and no moving parts in the air path. {note}
+
+### A heat-pipe assembly serving an application that requires summer and winter operation shall include a tilt or bypass means to control or reverse recovery direction where required by the sequence.
+
+## Runaround Loop Devices {toc}
+
+### A runaround glycol loop places a coil in each of the two air streams and circulates an antifreeze solution between them with a pump, transferring sensible heat only and keeping the streams entirely separate and remote from each other. {note}
+
+### A runaround loop shall be furnished with a circulating pump, an expansion tank, an air separator, and a glycol solution rated for the lowest expected loop temperature.
+
+### A runaround loop is inherently self-protecting against frost because the glycol return temperature to the exhaust coil can be controlled to stay above freezing, which is one reason it is favored where frost would otherwise be severe. {note}
+
+# Frost Control {toc}
+
+## A frost-control method shall be provided and shall be specified by the Engineer rather than left to the Contractor to select in the field.
+
+### Leaving the frost-control sequence to the contractor is a recurring failure, because frost control affects ventilation delivery, net recovery, and equipment protection, and an unspecified method is often omitted entirely until the device frosts in the first cold weather. {note}
+
+## The frost-control method shall be one of preheat of the outdoor air upstream of the core, recovery bypass or cyclic defrost, exhaust-air recirculation, or, for a runaround loop, controlled glycol return temperature.
+
+### Preheat raises the outdoor air temperature so the exhaust never cools below freezing within the core, at the cost of the preheat energy. {note}
+
+### Bypass or cyclic defrost periodically diverts or reduces airflow through the core to let accumulated frost melt, at the cost of reduced ventilation or recovery during the defrost interval. {note}
+
+### Exhaust-air recirculation briefly mixes warm exhaust into the outdoor stream to raise the core inlet temperature during the coldest conditions. {note}
+
+## The frost-control sequence shall identify the outdoor air temperature at which it activates and its effect on ventilation delivery during operation.
+
+```datasheet
+label: Frost Control
+type: group
+fields:
+ - label: Frost-control method
+ type: radio
+ options:
+ - "Outdoor air preheat"
+ - "Recovery bypass / cyclic defrost"
+ - "Exhaust-air recirculation"
+ - "Controlled glycol return temperature (runaround only)"
+ - "None - climate does not require frost control"
+ default: "Recovery bypass / cyclic defrost"
+ - label: Frost-control activation temperature
+ type: range
+ unit: °F
+ min: -10
+ max: 32
+ step: 1
+ default: 10
+```
+
+# Economizer Bypass {toc}
+
+## The recovery device shall include a means to bypass or disable recovery so that it does not impede air-side economizer operation when outdoor conditions are favorable for free cooling.
+
+### ASHRAE 90.1 requires that an energy recovery device not interfere with the economizer; without a bypass, the device would recover heat into the cool incoming air precisely when the building wants that cool air, defeating the economizer. {note}
+
+## The economizer bypass shall be interlocked with the air-side economizer control so that recovery is bypassed or stopped whenever the economizer calls for free cooling.
+
+### A bypass that exists physically but is not interlocked with the economizer control accomplishes nothing, because it will not actuate at the right time; the interlock, not merely the damper or wheel stop, is the requirement. {note}
+
+## For a rotary wheel, the economizer bypass shall be achieved by stopping the wheel; for a fixed-plate or heat-pipe device, it shall be achieved by a face-and-bypass or full-bypass damper.
+
+```datasheet
+label: Economizer Bypass
+type: group
+fields:
+ - label: Bypass method
+ type: radio
+ options:
+ - "Wheel stop (rotary devices)"
+ - "Bypass damper (fixed-plate / heat-pipe)"
+ - "Glycol pump stop / loop bypass (runaround)"
+ default: "Bypass damper (fixed-plate / heat-pipe)"
+ - label: Interlocked with air-side economizer control
+ type: radio
+ options:
+ - "Yes - bypass interlocked with economizer"
+ - "No - economizer not present on served system"
+ default: "Yes - bypass interlocked with economizer"
+```
+
+# Fans {toc}
+
+## Where the device is a packaged unit, the supply and exhaust fans shall be furnished integral to the unit and selected to overcome the external static pressure plus the recovery core pressure drop on each stream.
+
+### The recovery core itself imposes an air-side pressure drop on the order of 0.5 to 1.5 in w.g. per stream, and this loss shall be added to the external static pressure when selecting the fans, because a fan sized only for the duct system will not deliver the design airflow through the loaded core. {note}
+
+## Where the device is a core-only component installed in a separate air handler, the air handler's fans shall be selected to include the recovery core pressure drop on both the supply and exhaust streams.
+
+## Integral fans shall be rated for aerodynamic performance per AMCA 210 and shall meet the fan efficiency provisions referenced by ASHRAE 90.1.
+
+## The supply and exhaust airflows shall be balanced within the maximum imbalance acceptable for the selected device and for the certified effectiveness and leakage values.
+
+### A large imbalance between the supply and exhaust airflows changes the actual effectiveness and the cross-leakage from their certified values and can pressurize or depressurize the building, so the design and balancing shall hold the streams within the device's rated imbalance limit. {note}
+
+```datasheet
+label: Fans and Airflow
+type: group
+fields:
+ - label: Fan arrangement
+ type: radio
+ options:
+ - "Integral supply and exhaust fans (packaged unit)"
+ - "Fans external (core-only in separate AHU)"
+ default: "Integral supply and exhaust fans (packaged unit)"
+ - label: Design supply (outdoor) airflow
+ type: range
+ unit: cfm
+ min: 200
+ max: 20000
+ step: 50
+ default: 2000
+ drawing_ref: true
+ - label: Design exhaust airflow
+ type: range
+ unit: cfm
+ min: 200
+ max: 20000
+ step: 50
+ default: 1900
+ drawing_ref: true
+ - label: Supply external static pressure (excludes core)
+ type: range
+ unit: in w.g.
+ min: 0.25
+ max: 4.0
+ step: 0.05
+ default: 1.0
+ - label: Maximum supply-to-exhaust airflow imbalance
+ type: range
+ unit: "%"
+ min: 0
+ max: 25
+ step: 1
+ default: 10
+```
+
+# Demand-Controlled Modulation {toc}
+
+## Where the served system uses demand-controlled ventilation, the recovery device's fans shall be capable of modulating airflow in response to the ventilation demand signal.
+
+### Demand-controlled ventilation reduces airflow when the space is lightly occupied, which saves fan and conditioning energy, but at very low airflow the core can over-recover and, in a membrane or wheel device, approach conditions where condensation or carryover behavior changes, so the low-flow limit shall be set with these effects in mind. {note}
+
+## A minimum airflow setpoint shall be established below which the device shall not modulate, to preserve acceptable effectiveness and to avoid condensation within the core.
+
+```datasheet
+label: Demand-Controlled Ventilation Modulation
+type: group
+fields:
+ - label: DCV airflow modulation
+ type: radio
+ options:
+ - "Fixed airflow - no modulation"
+ - "Modulating airflow on ventilation demand"
+ default: "Fixed airflow - no modulation"
+ - label: Minimum modulated airflow (% of design)
+ type: range
+ unit: "%"
+ min: 30
+ max: 100
+ step: 5
+ default: 50
+```
+
+# Filtration {toc}
+
+## A filter section shall be provided in the outdoor air stream upstream of the recovery core, and a filter section shall be provided in the exhaust stream upstream of the core.
+
+### Filtering both streams upstream of the core protects the recovery surfaces from fouling, which otherwise degrades effectiveness and, in a wheel, can foul the matrix and the seals. {note}
+
+## The outdoor air filter shall be a minimum of MERV 8, certified per ASHRAE 52.2, with a higher rating where the served spaces or the project require it.
+
+## Filter frames shall seal to the casing to prevent air bypass around the media.
+
+```datasheet
+label: Filtration
+type: group
+fields:
+ - label: Outdoor air filter MERV rating
+ type: select
+ options:
+ - "MERV 8"
+ - "MERV 11"
+ - "MERV 13"
+ default: "MERV 8"
+ - label: Exhaust air filter MERV rating
+ type: select
+ options:
+ - "MERV 8"
+ - "MERV 11"
+ - "MERV 13"
+ default: "MERV 8"
+```
+
+# Casing and Condensate {toc}
+
+## The casing shall be a double-wall insulated construction with a thermal break appropriate to the installation location, and outdoor units shall be weatherproofed and finished for exterior exposure.
+
+## Access doors or removable panels shall be provided for inspection and removal of the recovery core, the filters, and, for rotary devices, the drive components and seals.
+
+## A condensate drain pan and a drain connection shall be provided for any configuration that condenses moisture, including membrane enthalpy cores in cooling operation and any device whose exhaust stream cools below its dewpoint within the unit.
+
+### A missing condensate drain on a membrane enthalpy core is a common omission that leads to water accumulation and microbial growth within the unit during cooling operation, because the core deliberately handles moisture and that moisture must have somewhere to go. {note}
+
+## The drain pan shall be sloped to drain and shall be served by a trap sized for the unit's static pressure.
+
+```datasheet
+label: Casing and Condensate
+type: group
+fields:
+ - label: Casing construction
+ type: radio
+ options:
+ - "Double-wall insulated with thermal break"
+ - "Double-wall insulated (interior unit, no thermal break)"
+ default: "Double-wall insulated with thermal break"
+ - label: Condensate drain provided
+ type: radio
+ options:
+ - "Yes - drain pan and trapped connection"
+ - "No - sensible-only device, no condensation expected"
+ default: "Yes - drain pan and trapped connection"
+ - label: Installation environment
+ type: radio
+ options:
+ - "Outdoor / rooftop - weatherproofed"
+ - "Indoor - mechanical room or ceiling"
+ default: "Outdoor / rooftop - weatherproofed"
+```
+
+# Controls and Integration {toc}
+
+## The device controls shall sequence normal recovery operation, economizer bypass, frost control, and any demand-controlled modulation, and shall provide the monitoring and command points required to integrate with the [[sync/building-automation-system]].
+
+## The controls shall provide status of fan operation, wheel rotation for rotary devices, frost-control activation, and bypass position, as monitored points to the building automation system.
+
+## The sequence of operation shall be submitted and shall define the priority among recovery, economizer bypass, and frost control when their conditions overlap.
+
+### When the outdoor temperature is low enough to call for frost control at the same time the device would otherwise be in economizer bypass, the sequence shall make clear which mode governs, because the two are mutually exclusive and an ambiguous sequence leaves the device oscillating. {note}
+
+# Testing {toc}
+
+## Factory performance certification under AHRI 1060 shall serve as the performance verification for effectiveness, EATR, and OACF, and no field effectiveness test shall be required unless specified.
+
+## Field functional testing shall confirm fan operation, supply and exhaust airflow balance, economizer bypass actuation, frost-control activation, and demand-controlled modulation where provided.
+
+## The supply and exhaust airflows shall be measured and balanced under [[sync/testing-adjusting-and-balancing]] and confirmed to be within the specified imbalance limit.
+
+## For rotary devices, wheel rotation and the purge sector setting shall be verified during startup.
+
+```datasheet
+label: Field Functional Tests
+type: checkbox
+options:
+ - "Supply and exhaust fan operation"
+ - "Supply/exhaust airflow balance within limit"
+ - "Economizer bypass actuation and interlock"
+ - "Frost-control activation"
+ - "Demand-controlled modulation (where provided)"
+ - "Wheel rotation and purge setting (rotary)"
+default: "Supply and exhaust fan operation"
+```
+
+# Installation {toc}
+
+## The device shall be installed level, on the support or curb indicated, with the clearances required for access to the core, filters, and drive components. [[drawing: ERV unit and curb location plan]]
+
+## Outdoor air intakes and exhaust outlets shall be separated and located to prevent short-circuiting of exhaust back into the intake, in accordance with the separation distances of ASHRAE 62.1. [[drawing: intake and exhaust louver locations]]
+
+### Re-entrainment of exhaust into the intake corrupts the outdoor air quality and, on a recovery device, adds to the effective cross-leakage beyond the certified EATR, so the physical separation of intake and exhaust is part of the recovery system's contaminant control. {note}
+
+## Supply, exhaust, outdoor, and relief duct connections shall be made with flexible connectors where required to isolate fan vibration from the ductwork, and ductwork is otherwise covered by [[sync/hvac-ductwork]].
+
+## The condensate drain shall be trapped and routed to an approved point of disposal, and the trap shall be primed at startup.
+
+## Electrical connections to integral fans and controls shall be made in accordance with the manufacturer's electrical data and the unit's nameplate ratings.
+
+## The device shall be installed so that the recovery core can be removed for cleaning or replacement without dismantling adjacent equipment or ductwork.
+
+# Delivery, Storage, and Handling {toc}
+
+## Devices and cores shall be delivered in the manufacturer's packaging with intake, exhaust, and connection openings protected against the entry of dust, debris, and moisture.
+
+## Recovery cores, wheels, and membrane assemblies shall be stored indoors, protected from physical damage and from contamination, until installation.
+
+## Filters shall not be installed until the system is clean and ready for operation, and any construction-phase filters shall be replaced with the specified final filters at substantial completion.
+
+# Warranty {toc}
+
+## The manufacturer shall warrant each device against defects in materials and workmanship for the period scheduled, measured from substantial completion.
+
+## The recovery core or wheel and its drive components shall be covered by the warranty, and any separate sub-supplier warranty on the recovery component shall be passed through to the Owner.
+
+```datasheet
+label: Warranty Period
+type: select
+unit: years
+options:
+ - "1"
+ - "2"
+ - "5"
+default: "1"
+```
+
+# Spare Parts {toc}
+
+## The Contractor shall furnish one complete set of replacement filters for each device, of each size and rating installed, delivered at substantial completion.
+
+## For rotary devices, the Contractor shall furnish one spare drive belt and one set of replacement seals for each wheel.
+
+```datasheet
+label: Spare Parts to Furnish
+type: checkbox
+options:
+ - "One complete set of replacement filters per device"
+ - "One spare wheel drive belt (rotary devices)"
+ - "One set of replacement wheel seals (rotary devices)"
+default: "One complete set of replacement filters per device"
+```