Air Handler - NHE



Diagnosing HVAC issuesThere are many different possible causes for a HVAC system to not work properly. First it is important to understand the different types of systems that are used for heating and mon heating system types include:Forced air (gas or electric)Steam or hot water-fueled boilersRadiant heatingHeat pumpCommon air conditioning systems include:Central air conditioning systemsDuctless mini splits air conditionersWindow AC unitsHeat pumpsPTAC (Packaged Terminal Air Conditioner)If you are not sure which system you are looking at there are many easy ways to tell such as: Turning on the heat, then checking if the outside unit starts running (Heat Pump)Looking at the labels on the condenser or indoor air handler ?the model number will have an “HP” at the beginning (Heat Pump)Checking for the reversing valve. Inside the condenser if you see a brass-looking device with 3 fittings on one side, you have a heat pump. Don’t see it? Then you have a straight cool air conditioner.Another important thing to know is the terminology of HVAC equipment, tools and processes. Being familiar with these terms will save a lot of time in diagnosing, ordering parts, and fixing issues. Here are some of the common terms used in HVACTerms:Air HandlerThe indoor component of your air conditioner or heating system that moves air through your home.All-In-One SystemAn air conditioning and/or heating system in which all components are located in one cabinet. Used in certain localities and for certain building types, the all-in-one system is installed either beside or on top of your home.Blower MotorA?blower motor?is the component within a home's?HVAC system. The?motor?blows heated air through vents when the heating system is in use. Conversely, some?blower motors?blow cold air when the air conditioning system is in use.BTUBritish thermal unit in scientific terms, it represents the amount of energy required to raise one pound of water one degree Fahrenheit. One BTU is the equivalent of the heat given off by a single wooden kitchen match. For your home, it represents the measure of heat given off when fuel is burned for heating, or the measure of heat extracted from your home for cooling.Capacitor Stores the electrical energy and give this energy again to the circuit when necessary. In other words, it charges and?discharges?the electric charge stored in it. Besides this, it?blocks?the flow of DC and?permits?the flow of pressorThe heart of an air conditioning or heat pump system. It is part of the outdoor unit that pumps refrigerant. The compressor maintains adequate pressure to cause refrigerant to flow in sufficient quantities in order to meet the cooling requirements of the system and your home.Condenser fan motorPart of your HVAC system that is located within the condensing unit. This unit also consists of the compressor and?condenser?coil. ... The?condenser fan motor?is what runs to turn the?fan?blades and blow air across the condenser?coil, where it cools the refrigerant from a hot gas into a liquidCondenser CoilLocated in the outdoor unit, the coil dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid. ContactorMakes and breaks?all power supply lines running to a Load or to repeatedly establish and interrupt an electrical power circuit.ControlA temperature-control device, typically found on a wall inside the home. It consists of a series of sensors and relays that monitor and control the functions of a heating and cooling system. American Standard Heating & Air Conditioning's programmable controls allow you to program different levels of comfort for different times of the day.CyclingRefers to the process of an HVAC system turning on and off. Some systems require less cycling than others, leading to higher energy efficiency and less wear on the system.DamperFound in ductwork, this movable plate opens and closes to control airflow. Dampers are used effectively in zoning to regulate airflow to certain rooms.DuctworkPipes or channels that carry air throughout your home.Flame sensorThe?flame sensor?is a rather simple device located at the burner assembly. It's not much more than a thin, usually bent, metallic rod that sits in front of the?flame stream inside the furnace. The purpose of the?flame sensor?is to confirm to the system that whenever the gas valve is open, a fire is actually present.FurnaceAn indoor heating unit that works in conjunction with an air conditioner or heat pump.GaugesAir conditioning gauges?is used to measure?air conditioner?units pressure within closed-system to evaluate or troubleshoot the central air units.?Gauges manifold?set is the most frequently used item when it comes to refrigerant or pressure. ... The way an?air conditioner gauges work?is by open and closing the hand valve.Heat PumpAn outdoor unit that warms your home in winter and cools your home in summer.Heat stripsWire elements in your unit that are heated by electricity, which in turn, heat?the air that flows over them. Heating air using?heat strips?requires much more energy, but your?heat?pump relies on these?strips?to perform certain tasks, such as defrosting your unit, and EM heat. HVACThe classic acronym for Heating, Ventilation and Air Conditioning. Today, an HVAC system also includes air cleaning and moisture control.Hybrid Comfort SystemA home comfort system that combines a heat pump with a gas furnace (also available in packaged systems). For areas with colder temperatures, combining electric heating (heat pump) with gas heating (furnace) lets you choose from two fuel sources in order to respond to fluctuations in utility costs.Indoor/Outdoor SystemRefers to a comfort system consisting of components in two locations. Common examples include an outside unit, such as an air conditioner, and an indoor unit, such as a furnace with a coil.Indoor CoilThe other, less visible half of your outdoor unit. It's attached to your furnace or air handler. As indoor air flows across it, heat and moisture are drawn out, leaving air that is cool, comfortable and conditioned.Line SetsCopper tubing?lines?used to connect split system air conditioners and heat pumps. Suction?lines?are offered with straight ends or 90-degree bend on one end of the suction?line.Load CalculationA detailed analysis of your home's energy needs conducted by your dealer to help determine which comfort system is best for your home.Matched SystemA heating and cooling system wherein all components are matched in capacity and efficiency. This enables your system to perform at its best, and most efficient, for longer.Outdoor CoilLocated in the outdoor unit, the coil dissipates heat from the refrigerant, changing the refrigerant from vapor to liquid. In American Standard units, the coil is called Spine Fin?.Outdoor UnitThe outdoor portion of a split system, such as an air conditioner or heat pump. May also be a packaged air conditioning and/or heating system in which all components are located in one cabinet.Packaged SystemAn air conditioning and/or heating system in which all components are located in one cabinet. Used in certain localities and for certain building types, the all-in-one system is installed either beside or on top of your home.RefrigerantA substance that produces a cooling effect. It's used in most air conditioning and cooling systems.SEERSeasonal Energy Efficiency Ratio. This is a rating that measures the cooling efficiency of a heat pump or air conditioner. The higher the number, the more efficient the unit.Split SystemRefers to a comfort system consisting of components in two locations. Common examples include an outside unit, such as an air conditioner, and an indoor unit, such as a furnace with a coil.Squirrel CageA centrifugal?fan?is a mechanical device for moving air or other gases. The terms "blower" and "squirrel cage fan", (because it looks like a hamster wheel), are frequently used as synonyms. These?fans?increase the speed and volume of an air stream with the rotating impellers.ThermocoupleA sensor used to measure temperature.?Thermocouples?consist of two wire legs made from different metals. The wires legs are welded together at one end, creating a junction. This junction is where the temperature is measured. When the junction experiences a change in temperature, a voltage is created.ThermostatA temperature-control device, typically found on a wall inside the home. It consists of a series of sensors and relays that monitor and control the functions of a heating and cooling system. American Standard Heating & Air Conditioning's programmable controls allow you to program different levels of comfort for different times of the day.TonA unit of measurement used for determining cooling capacity. One ton is the equivalent of 12,000 BTUs per hour.Two-stage Heating / Two-stage CoolingTwo-stage heating and cooling is considered to be more efficient, because it operates at a low, energy-saving speed most of the time. However, on days when more heating or cooling is required, it switches to the next stage for maximum comfort.Variable-Speed MotorThe fan motor inside higher efficiency indoor and outdoor units is designed to change its speed based on your home's heating and air conditioning requirements. Working in conjunction with your thermostat, it keeps the appropriate-temperature air (e.g., warm air on cold days) circulating throughout your home, reducing temperature variances. The variable-speed motor also increases dehumidification and is quiet because it runs at a lower speed most of the time. Plus, the consistent air circulation eliminates noisy startups and shutdowns.How the systems work:Central air conditioning systems use a closed loop system that circulates refrigerant to cool the air. The refrigerant travels through a compressor valve that subjects it to a great deal of heat and pressure, then into a compressor coil that bleeds off the heat into the outside air. This turns the refrigerant into a liquid state, though it’s still under a lot of pressure. It then moves through an expansion valve and into a series of evaporator coils. As it evaporates, it pulls heat from the surrounding air, cool it. The cool air is then blown with a fan through a system of ducts that distribute it throughout your entire house.The heat pump relies on the same basic system, with two key differences. First, the closed loop in a heat pump is set up such that it can blow hot air into the home instead of outside. This allows it to function as a heater in the winter and an air conditioner in the summer. Secondly, many heat pumps rely on a ductless mini-split system – distributing multiple units throughout the home instead of distributing the air through ducts. Heat pumps are more efficient than central AC, though they struggle a bit when the weather gets particularly cold and they cost more to mon Causes for breakdown:There are countless problems that any of these systems can have to cause the resident discomfort. Here are some of the common issues you may come across.Heating system breakdowns are often caused by:Duct leaks or blockagesBad limiters, fuses, heat stripsWater leaks (Steam or hot water-fueled boilers)Rusted or sediment filled boilersThermostat issues requiring adjustments or thermostat replacementLack of scheduled maintenance inspectionsSimple setting problems, such as a heat pump set to "cool"Clogged air filtersElectrical outage or tripped circuit breakerBlown transformer/ burned or disconnected wiresCoolant low (heat pump)Gas supply issuesCooling system breakdowns are often caused by:Refrigerant leaksEvaporator coil (indoor component) dirty or damagedCompressor (outdoor component) dirty or damagedDuct leaks or blockagesOlder cooling equipment that may benefit from replacementThermostat issues requiring adjustments or replacementNeglected scheduled AC maintenance checkupsSimple setting problems, like a heat pump set to "heat"Clogged air filtersElectric outage or tripped circuit breakerGas line / supply problemAn AC system can malfunction for many reasons:Mechanical parts and contacts can wear outWires can overheat and short out or burn openEquipment can be damaged by impact or vibrationEquipment is operating in conditions it was not meant to operate inTo properly repair an air conditioner, the problem must be solved by identifying and replacing the defective parts. ?By using a systematic approach to troubleshooting, it brings order and helps you logically analyze the problem.A logical and systematic approach to AC repair can be broken down into 7-Steps. Here are the steps:PreparationObservationDefine the problem areaIdentify?possible causesRepair and test1 – PreparationBefore you begin troubleshooting any heat pump or air conditioning system, you must first remember safety. Next, you must gather the information about the equipment you’re working on. It is much easier to analyze a problem if you understand how the system is supposed to work. Locate and review equipment manuals and consult with the resident on the repair history of the system. 2 – ObservationMany air conditioning failures have obvious clues as to their cause. ?Careful observation of the system operation, many times, can identify the fault with very little testing. ?Look for burnt or broken wires, oil in the bottom of the cabinet, swollen capacitors. ?Use your senses, a burnt transformer smells, the sound of the equipment gives you clues. The temperature of components can also help identify problems. Many times the resident will help identify the problem. Do not assume anything.3?–?Get out Your ToolsAt this stage you should have a good idea where to start checking for problems. Step 1 is often used to rule out what isn’t wrong. Study the schematic diagram or follow the manufacturer’s troubleshooting guide. As you test each component, ask yourself, “What does this tell me about the problem?” Note your observations and readings. ?Often times, you can find out what the problem is by identifying what is working right.Tip – Before making a voltage, pressure, or temperature reading – try to predict what it should read from studying the wiring diagram and reviewing refrigeration principles.4 – Identify Possible CausesOnce you have found the problem, it is extremely important to?identify?the cause. Just fixing the problem without identifying the cause will lead you to future unhappy customers. Was it vibration, abrasion, corrosion, lack of maintenance, or age of the component? Identify the cause and take care of it as well.?5 – Repair and Re-testAfter identifying and repairing the faulty component, test and operate the system for a complete cycle. This will make sure you have replaced the proper component and no other components are faulty. It is very?embarrassing?to tell the customer you have fixed their problem, only to be called out the next day because their air?conditioner?isn’t working againWhere to start:Begin your air conditioner troubleshooting at the thermostat by ensuring that the thermostat is on cool and that it is set lower than actual room temperature. This is to ensure that there really is a problem. It may seem silly but it happens more often than not.Next:Is there air coming out of the floor or ceiling registers?If there is not, then, check to see if the fan on the outside unit is running. If the fan on the outside unit is not running either, check to make sure that the breakers for the furnace/air handler and the air conditioner are on.If the breaker is not tripped, then the problem may be your?thermostat, the furnace/air handler?control board, or the wires between the furnace/air handler and the thermostat.If your unit has a condensate pump, check to make sure the reservoir is not full. If the reservoir is full, a limit switch (float switch) will normally stop the air conditioner from running. You will need to repair or replace the pump.If the breaker is tripped, you can reset it by shutting it off and then turning it back on. If it trips again, then check the wiring in the furnace/air handler for signs of damage and repair as necessary.If the blower is running but the fan on the outside unit is not, then continue your air conditioner troubleshooting at the outside unit.Is the fan on the outside unit blowing out hot air?If the blower motor inside is working and the outdoor unit is not, the problem could be capacitor, contactor, If the fan motor is not running, then shut the power off to the unit. Then check all wire connections for signs of damage such as burning and repair as necessary. You should also check the wire connections in the compressor terminal box and repair if necessary.Measuring SuperheatFor many years residential air conditioners used pistons as metering devices, and you will still commonly encounter these systems. The piston looks like a small brass or bronze “bullet,” with a calibrated hole drilled through the center. The size of the hole, along with the pressure drop across the hole, determines how much refrigerant flows through the system.Most of the systems with piston metering devices are charged by the suction superheat method. Manufacturers of these systems typically provide a charging chart or slide rule to properly charge their systems. Sometimes these charts are available from your wholesaler. If you’re fortunate, they may be included inside the service panel of the unit that you’re servicing.Normally the charts will require an indoor wet bulb temperature reading as well as an outdoor dry bulb temperature reading. The indoor wet bulb reading reflects the total heat of the air and, therefore, the total loading on the indoor coil, both sensible?and latent. The outdoor dry bulb temperature will affect how well the system can reject heat to the outdoor air. In the case of the outdoor air there’s no latent heat involved. Once you determine the indoor wet bulb and outdoor dry bulb temperatures, check the manufacturer’s charging chart to determine the proper suction superheat.To measure suction superheat, attach your gauge manifold to the suction service port on the outdoor unit. Do not use the common suction pressure port on a heat pump because the pressure drop through the reversing valve will affect the pressure reading. Take the pressure reading and use a temperature-pressure chart to convert that reading to the saturated temperature of the refrigerant that the system uses. Note that most gauges have the commonly used refrigerants shown on the gauges. This is especially true of the newer digital gauges.Next, attach an accurate digital thermometer to the suction line near the suction gauge port. It’s usually best to insulate the thermometer probe so that it’s not affected by the ambient air. The temperature that you measure should be warmer than the saturated refrigerant temperature. The difference between the saturated suction temperature and the measured suction line temperature is the suction superheat.Add refrigerant to lower the suction superheat. Recover refrigerant to increase the suction superheat. Note that you should never add refrigerant if the superheat is already 5F or less, even if the charging chart shows 0F. You don’t want to overcharge the system if your thermometer or gages are not perfectly accurate. Overcharging can damage the compressor and will also reduce both the capacity and efficiency of the system.Note that if the suction superheat is correct and the suction pressure is low, the system probably has low airflow. Correct the airflow problem and check the charge again.Measuring Sub coolingOn many newer systems, especially high efficiency systems, thermostatic expansion valves (TXVs) are used. Expansion valve systems are normally charged by using the sub cooling method. Liquid sub-cooling is required so that you have only liquid entering the expansion valve with no bubbles present. Vapor bubbles present in the refrigerant will cause low refrigerant flow. Low refrigerant flow will cause a loss of capacity and efficiency in a cooling system.Liquid sub-cooling is normally measured at the liquid line service valve. The manufacturer will usually specify the required sub-cooling on the outdoor unit service panel. It’s usually between 5F and 15F, but always go by the manufacturer’s requirements.To measure liquid sub cooling, attach your gauge manifold to the liquid line service port. If you use a quick-connect fitting on the end of your hose, make sure it’s a low-loss fitting. I’ve seen some quick-connect fittings that allow pressure loss, which can cause inaccuracies in the charging procedure.Take a pressure reading. Use a temperature-pressure chart to convert the pressure to the saturated condensing temperature of the refrigerant.Next, attach an accurate digital thermometer to the liquid line. It’s usually best to insulate the thermometer probe so that it’s not affected by the ambient air. The temperature that you read with the thermometer should be lower than the saturated condensing temperature. The difference between the measured liquid line temperature and the saturated condensing temperature is the liquid sub cooling. Add refrigerant to increase sub cooling. Recover refrigerant to reduce sub cooling.Note that if the sub cooling and superheat are correct, and the suction pressure is low, the system probably has low air flow. Correct the airflow problem and check the charge again.When charging by the sub cooling method, you should be sure to check the suction superheat as well. If the expansion valve goes bad, you can have a very low suction superheat when you have the proper sub cooling. In some cases it’s not possible to achieve the required sub cooling without having a superheat of zero degrees. If you get zero degrees superheat with a TXV, then the TXV is defective and will need to be replaced.The Weigh-in MethodOne other method of charging is the weigh-in method. The weigh-in method can be very accurate if you know the exact length of the refrigerant lines. The outdoor unit usually comes charged with enough refrigerant for the outdoor unit, a standard indoor unit, and 15 or 25 ft. of line set. You must add refrigerant for any line length over what is specified by the manufacturer. You may also have to add or remove refrigerant depending on what indoor unit or indoor coil is used. Even if you charge by weigh-in it’s still a good practice to check the charge using the sub cooling or superheat methods, to ensure that everything is operating properly. ................
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