Showing results 1 - 198 of 198
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A boiler system can be set up with primary and secondary loops to supply hot water for multiple uses
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A Category I induced draft boiler uses an induced draft fan to pull air through the combustion chamber and to the flue
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A central fan-integrated supply system uses a fresh air intake ducted to the home's central furnace or air handler unit to supply fresh air throughout the home
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A cool room should have low enough heat gains to be easily cooled by a small single-zone cooling system such as a mini-split or a window air-conditioner as shown here
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A direct-vent sealed-combustion fireplace takes its combustion air directly from outside through a dedicated air inlet and vents combustion products directly outside
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A direct-vent sealed-combustion furnace has dedicated pipes for combustion air and exhaust
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A foaming cleaner is used to clean the coils inside this ductless indoor unit; a mini-split bib surrounds the unit to contain overspray and drips
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A foaming sprayer and mini-split bib are required to properly clean this ductless wall-mounted indoor unit
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A ground source heat pump with an open-loop piping system using vertical injection and recharge
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A ground-source heat pump has the same components as a standard air-to-air heat pump except that the liquid-to-refrigerant heat exchanger coil is located inside rather than outside
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A ground-source heat pump with a closed-loop horizontal “Slinky™ “piping arrangement
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A modern single-inlet direct evaporative cooler draws outside air through an 8- to 12-inch media filter
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A nylon draw band and tensioning tool are used to secure the inner coil of the pre-insulated flexible duct
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A nylon draw band and tensioning tool are used to secure the inner liner of the pre-insulated flexible duct
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A permanent awning prevents snow and overflowing ice dams from causing damage to HVAC equipment below.
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A pitot tube can be used to measure velocity pressure in a duct; at least twelve measurements are taken across the duct and velocity pressure is converted to velocity to calculate airflow
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A powered flow hood is used to measure outside air flowing into the inlet terminal of a whole-house ventilation system
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A properly sized cold climate heat pump can meet 100% of a home’s heating load in nearly any location in the United States
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A properly sized high-efficiency heat pump is located in conditioned space in a closet inside the home.
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A single ductless heat pump heats and cools the country’s first DOE Zero Energy Ready certified manufactured home.
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A small, single-zone cooling system such as this ductless mini-split heat pump can be a very effective way to provide emergency cooling with a low power draw on a backup power system.
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After securing the inner coil, cover the draw band and the seam with a generous amount of mastic
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Air handler platforms used as return air plenums can draw air from vented attics and crawlspaces through other connected framing cavities
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An energy recovery ventilator draws in fresh outside air that is filtered and circulated by the central air handler, while stale air from central returns is routed through the ERV to exchange heat before being exhausted outside.
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Anemometers, including the vane style (lower) and hotwire style (upper) are used to measure air velocity to calculate airflow
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Because flue temperatures are cool, intake and exhaust ducts on a Category 4 direct-vent sealed-combustion condensing furnace can be made of PVC
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By plotting the heating capacities at -4°F and 5°F and drawing a line between them, the capacity at 0°F can be estimated
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Calibrations are specific to each airflow station model and size and are needed to convert measured station pressure to airflow
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Category III oil-fired, sealed-combustion boiler configured as a direct-vented appliance that draws its combustion air from outside
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Category III oil-fired, sealed-combustion boiler with the burner assembly cover removed
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Collars that are specifically made for flexible duct have a raised bead to prevent the duct from slipping off
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Concept behind an evaporative cooler – warm air is cooled as the air passes through a wet medium and gives up some of its heat to evaporate the water
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Condensate from this heat pump water heater is routed to a nearby floor drain, shared with the condensate lines from a condensing gas furnace and an air conditioning coil
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Cool air flow is produced when the cooling cycle is energized (set thermostat to “cool”)
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Cooling air temperatures that can be achieved by a direct evaporative cooler at various outdoor conditions
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Cut fiber board with a red V-groove tool and a gray shiplap tool to create mitered corners and a shiplapped edge for duct sections
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Direct-heat risers are bare pipes that heat the space they're in without connected radiators
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Ductless indoor units like this one are controlled individually by handheld remote controllers.
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Equations for calculating duct cross-sectional area for round and rectangular ducts; area is used with measured velocity to calculate airflow
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Evaporative Cooler Sizing in ACH based on wet-bulb temperatures at 1% summer design conditions
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Example expanded performance table from a 1.5-ton air conditioner
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Flowhood is sealed against the irregular surface using pipe insulation along the edge of the hood to complete an airtight seal around the terminal.
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For fireplaces that are not mechanically drafted or direct-vented to outdoors, total net rated exhaust flow of the two largest exhaust fans is .15 CFM per 100 sq. ft. of occupiable space when at full capacity
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Furnaces, boilers, and water heaters located within the home’s pressure boundary are mechanically drafted or direct-vented
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Hand tools for cutting fiber board sheets include a knife, straight edge, and color-coded edge-cutting tools
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Hood capture area that extends out from under the soffit surface must be temporarily sealed.
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If HVAC duct must be installed in an exterior wall, separate it from the exterior with at least R-6 of continuous rigid insulation
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If integrating an ERV/HRV with the heating/cooling duct system, add dedicated ducts for either the supply or return side to prevent short-circuiting of air distribution
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In a Category I gas-fired, natural-draft boiler, the natural draft of the heated flue pulls combustion air through the draft hood into the combustion chamber
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In a typical old style multi-inlet evaporative cooler, the blower fan draws outside air in through multiple media filters and blows it into the home
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In heating mode, split system heat pumps absorb heat from the outside air and “pump” that heat to the indoor air handler unit, which releases it to the inside air.
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Indoor measurement of a whole house mechanical ventilation system with a pressure balancing flowhood provides a sheltered location for measuring airflow
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Install a master vent tree to release air and prevent air binding which blocks steam heat from reaching its destination
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Install supply registers in floors or ceilings to avoid routing ducts through exterior walls
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Iris damper style airflow stations come in different sizes and can be adjusted to control airflow
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It is not recommended to install HVAC systems in enclosed attached garages. However, when HVAC systems are installed in enclosed garages, they must comply with ASHRAE 62.2 duct leakage thresholds.
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Lower-cost local ERVs are usually installed in a ceiling to supply outdoor air to and exhaust air from the room in which they are located
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Metal drain pans under HVAC equipment can corrode over time, especially in humid environments
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National Fuel Gas Code (NFPA 2012) identifies four categories for combustion furnaces and water heaters based on combustion type (sealed or unsealed) and vent pipe temperature
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National HVAC Design Report - Cooling Equipment Selection (Version 3 / 3.1 (Rev. 09))
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Open floor trusses used as return air plenums can draw air from any place connected to that floor
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Proper refrigerant charging is critical to maximizing performance for compression cooling systems
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Pull the insulation and outer liner of the flex duct over the collar to come in full contact with the liner and insulation of the trunk line or fitting and tape in place
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Right - A high-efficiency (95 AFUE) wall-hung gas-fired boiler heats water for the hydro-coil space heating system and also provides a back-up for the solar hot water system.
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Right - All seams in the HVAC equipment and ductwork are sealed with mastic; because the HVAC equipment is in the garage, it is an air-sealed closet.
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Right - An energy recovery ventilation (ERV) brings fresh air into the home while exhausting stale air. Both ducts pass through a heat exchanger where heat from the warmer duct is transferred to the cooler duct.
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Right - An ultra-efficient (COP 5.7) ground source heat pump provides hot water to an air coil in the central air handler which uses a variable-speed electrically commutated fan motor to distribute conditioned air to the home’s ducts.
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Right - The air handler for this geothermal heat pump is located in conditioned space.
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Right - The geothermal heat pump provides hot water for radiant floor heating, domestic hot water, and the air handler for space conditioning upstairs.
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Right - The home’s ground source heat pump preheats water for the air source heat pump water heater.
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Right - The home’s high-efficiency gas boiler provides domestic hot water as well as in-floor radiant heat, while a high-efficiency heat pump provides cooling and a secondary source of heating.
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Right - The precast insulated concrete walls of the basement provide a conditioned space for the high-efficiency (18 SEER, 9.5 HSPF) air-source heat pump, with its variable-speed fan, five-stage compressor, and MERV 11 filter.
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Right - The sealed conditioned crawlspace provides a clean, dry, and temperate environment for the home’s supplemental dehumidifier.
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Right - This evaporative cooler is wall mounted to reduce leak effects and allow for ease of maintenance.
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Right – An insulated space is provided in the home’s attic to house the HVAC equipment.
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Right – The builder has provided homeowners manuals and racks to hold them on the side of the HVAC cabinet in the utility room.
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Right – The corridor in this multistory building is pressurized with outdoor supply air.
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Right – The elevator lobby of this multistory building is pressurized with outdoor air supplied to the space through this ceiling supply register.
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Right – The HVAC unit installed in the insulated attic uses a heat pump to provide heating and cooling while also providing dehumidification and fresh air ventilation.
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Right – This energy recovery ventilator provides fresh air and exhausts stale air through a heat exchanger that recovers heat from the outgoing air in winter and reduces heat from incoming air in the summer to provide ventilation without wasting energy.
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Right – This home’s HVAC system consists of a ground source heat pump that provides heating and cooling with a rated efficiency of 5.0 COP.
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Right – This HVAC condensing unit is elevated on a raised-slab
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Right (decent): For a relatively high-capacity ccASHP sized per Approach 3 or 4 to meet nearly 100% of the heating load, this heat pump’s modulating zone has a decent overlap with the home’s heating load line, reducing short-cycling.
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Right: A well-constructed air handler closet
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Right: Sized per Approach 1, this heat pump will have minimal short-cycling; since sized using Approach 1, it will require backup heat when temp is below 30°F but could still contribute significant heating down to heating design temp (-6°F) and lower
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Right: Sized per Approach 3 or 4, this heat pump’s modulating zone has a large overlap with the home’s heating load line, resulting in minimal short-cycling; the unit may require a small amount of backup heat during the very coldest hours of winter.
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Right: Sized per Approach 3, this heat pump’s modulating zone has a large overlap with the home’s heating load line; it will require backup heating but could still contribute significant heating for all hours of the heating season
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Seal all joints and seams in the metal ductwork with mastic before installing insulation
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Seal seams in fiber board ducts with out-clinching staples, UL-181A-approved tape, and mastic
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Some builders create pan joists by attaching a solid sheet good to the bottom of a floor joist to create a return air pathway
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The AC unit has a drip pan and automatic shutoff in case the condensate drain gets clogged.
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The air handler of the air-to-water heat pump is equipped with a very high efficiency air filter and a damper-controlled fresh air intake.
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The basement is half in and half out of the ground with only 4 feet below grade, which allows for full 36-inch-tall windows that are completely above grade.
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The blower wheel (fan) on this ductless wall-mounted indoor unit has accumulated dust and mold - a common issue for this design.
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The condensate line (amber-colored plastic tube) from the high-efficiency furnace drains into the sewer via the same drain pipe as the clothes washer
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The drain pans sit below the cooling coil to catch condensate and direct it to a drain line
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The ductless air handler of a ductless heat pump can be mounted above the ceiling so that only the register is visible
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The filter access panel on this vertical upflow air handler is located between the return ductwork below and the coils above.
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The grille in the photo on the left brings air into a return air plenum under an air handler platform. As shown in the infrared image on the right, the plenum is not air sealed so hot attic air is being pulled into the air handler closet.
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The high-efficiency air-to-air heat pump is set in an overflow pan with an emergency shut off sensor in case the condensate tube were to clog and cause condensate to fill up the pan.
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The HVAC equipment's condensate drain pan is equipped with a water-level detection device that will shut off the equipment if the water level pan in the pan gets too high
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The mechanical room in the insulated basement houses the water heating equipment, including the storage tank for the solar thermal system and the wall-hung boiler as well as the air handler for the hydro coil and high-efficiency (16 SEER) air conditioner.
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The natural draft and induced draft furnace are both Category I appliances that receive combustion air from the combustion appliance zone
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The NEEP Cold Climate Air Source Heat Pump List allows users to search, sort, and filter for cold climate heat pumps by brand, model, product type, and ducting configuration; an advanced search provides helpful resources for sizing to the heating load
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The passive flow hood (at left) and powered flow hood (right) shown here side by side can be used to measure air flow through outside air intakes, exhaust fans air conditioner supply grills, ERVs, etc.
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The raised hood at the base of the vent stack on this water heater shows that it is an atmospheric vented gas water heater
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The tape is covered with mastic to ensure an airtight seal between the duct and the fitting
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The ultra-efficient air-to-water heat pump draws heat from the outside air to heat inside room air in winter and domestic hot water year-round.
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The ultra-efficient ground source heat pump (COP 4.4) delivers conditioned air throughout the home via ducts; an ERV provides fresh air to the system.
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The very high efficiency (4.7 COP) ground-source heat pump provides hot water to a tank for radiant floor heat and domestic hot water.
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These ERV/HRV configurations are NOT recommended because outdoor air can be sucked back into the ERV/HRV before being distributed to the living space
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These plots compare sizing approaches in terms of the approximate annual heating load a heat pump might carry throughout the year for a hypothetical home in Minneapolis, MN.
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This “high static ducted cassette” heat pump system is similar to a traditional centrally ducted system, serving several areas of a home from one indoor unit
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This ducted mini-split heat pump was installed in the unvented, conditioned attic and ducted with short duct runs to several nearby rooms.
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This ductless wall-hung indoor unit has supplemental air filters (outlined in red), which only filter a portion of the airflow; most of the air bypasses the supplementary filters and only passes through the standard mesh filters.
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This home’s domestic hot water is provided by three systems: solar water heating panels, a heat pump water heater, and an air-to-water heat pump, which also provides hot water to a fan coil.
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This home’s ultra-efficient ground-source heat pump provides hot water for space heating as well as domestic hot water for the 50-gallon storage tank.
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This HRV, installed in a conditioned attic, provides balanced ventilation to the whole home
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This is the compact outside unit for an ultra-efficient air-to-water heat pump (COP 4.1) that provides space heating and domestic hot water.
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This multi-split heat pump system incorporates several indoor units connected to just one outdoor unit; the indoor units include a wall-mounted unit, floor-mounted, ceiling cassette, and mini-air handler.
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This plot shows a heat pump’s minimum and maximum cooling capacities overlaid with a home’s cooling load line, allowing a designer to assess how well-suited the equipment is for the specific home.
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This plot shows a heat pump’s minimum and maximum heating capacities overlaid with a home’s heating load line as well as the annual heating load hours for the home, allowing a designer to assess how well-suited the equipment is for the specific home.
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This plot shows a heat pump’s minimum and maximum heating capacities overlaid with a home’s heating load line, allowing a designer to assess how well-suited the equipment is for the specific home.
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This plot shows a heat pump’s minimum and maximum heating capacities overlaid with a home’s heating load line, allowing a designer to assess how well-suited the equipment is for the specific home.
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This single-zone mini-split ductless heat pump has only one indoor wall-mounted unit and one outdoor unit.
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This traditional centrally ducted heat pump heats and cools the entire home through a network of ducts.
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This upflow air handler for a traditional heat pump has an electric resistance auxiliary heating element located at the top of the unit (circled in red).
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This utility room houses a high-efficiency gas boiler to provide hot water for the radiant floor heating system and faucets. It also has a central air source heat pump and an energy recovery ventilator.
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This wall-hung ductless indoor mini-split heat pump contains a fan, filter, and heating/cooling coil just like a traditional central air handler for a ducted heat pump system
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Three-zone ductless mini-split system consisting of two wall-mounted and one ceiling-mounted indoor ductless units and one outdoor unit
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Three-zone mini-split system consisting of one wall-mounted ductless unit, one ceiling-mounted ductless unit, and one ducted indoor unit, all connected to one outdoor unit
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To attach the flex duct to a main trunk duct or any other connection, the flex duct is pulled over the connecting collar at least 2 inches past the raised bead, then the insulation is pulled back
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Two pieces of flex duct are spliced together with a metal sleeve, nylon draw bands, mastic, metal tape, and more mastic
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Typical coaxial coil (liquid-to-refrigerant heat exchanger) used in a ground-source heat pump
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When HVAC systems are installed in enclosed garages, it is preferable that the equipment is located within an air-sealed room that is connected to the conditioned space.
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When wrapping metal ducts with insulation allow two inches of overlap and staple along the seam with outward clinching staples
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Wrong - ERV heat exchange coils have not been cleaned and have become completely clogged with dirt.
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Wrong – This ductless mini-split heat pump was installed above an exterior door allowing conditioned air to escape when the door is opened, heat transfer through the door, and temperature fluctuations that could impact the unit’s thermostat.
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Wrong – Two combustion appliances are sharing a flue which could lead to backdrafting if one appliance is updated to a direct vent appliance and disconnected from shared chimney.
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Wrong: Sized per Approach 1 or 2, this heat pump’s modulating zone has a small overlap with the home’s heating load line, resulting in a large amount of short-cycling; the unit will require backup heat when the temperature is below 25°F
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Wrong: Sized per Approach 3, there is minimal overlap between this heat pump’s modulating zone and the home’s heating load line, causing excessive short-cycling; it will require backup heat and may not contribute significantly at temperatures below 5°F
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Wrong: Sized per Approach 3, there is small overlap between this heat pump’s modulating zone and the home’s heating load line, resulting in excessive short-cycling; it will require backup heat when the temperature is below 5°F
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Wrong: The door and filter were removed, allowing unfiltered air to enter the air handler leading to premature failure of the system due to dirt accumulation.
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Wrong: This air handling equipment is installed in the garage without isolating the equipment from the garage space
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Wrong: This heat pump is oversized even for Approach 4, and its modulating zone has a small overlap with the home’s heating load line, resulting in a large amount of short-cycling.